Abstract:
A fill and bleed valve for filling a liquid cooling system has a single axially movable plunger, slidable within a central block bore, from a normal operating position to a filling position that opens the cooling system to a supply of coolant. The filling operation is continued until all air is purged from the system. The central block bore also retains a solid fill of coolant, and when shifted back to the normal operating system, no air is introduced into the system.

Description:
TECHNICAL FIELD 
   This invention relates to liquid cooling systems in general, and, in particular, to a fill and bleed valve for such a system used in a liquid cooling system for electronic components. 
   BACKGROUND OF THE INVENTION 
   Electronic components, in particular higher powered computer chips, are becoming more powerful and, consequently, need greater cooling capacity to run properly and durably. Air cooling systems are inherently limited in cooling capacity, and liquid systems, made up of a liquid heat exchanger in close proximity to the component, a pump, and an air to liquid heat exchanger exchanging heat with the ambient, are finding increasing use. Such systems need to be filled, at the time of manufacture, with liquid coolant, meaning that all of the components and lines need to be fully filled and bled of air. Typically, an in line coolant reservoir would be used both to provide a continual supply of make up coolant and to allow air in the system to be continually bled off, much like the reservoirs used in conventional vehicle engine cooling systems. It would be preferable to fill and seal the system air free on a one time basis, with a more compact fill valve, rather than provide a bulky and expensive reservoir. 
   A known fill and bleed valve for a computer chip liquid cooling system uses a set of three rotary valves, one central valve that interrupts the main cooling line, and two rotary fill valves, one to either side of the main shut off valve, that open up a fill inlet and fill outlet port into the system to allow an initial coolant fill to be pumped into, through, and finally out of the system components and lines. Clear lines in the vicinity of the rotary valves provide a visual indication of enough liquid having been pumped in and through the system to displace all entrapped air. That done, the two rotary fill valves can be shut off, and the intermediate main valve re opened. Three separate valves and rotary actions are themselves somewhat bulky and expensive. Furthermore, depending on the level, relative to the fill inlet and outlet points, of the length of system line located between the inlet and outlet points, some air may be trapped and not be totally purged by the fill. 
   SUMMARY OF THE INVENTION 
   The invention provides an improved fill and bleed valve that is simpler, more compact, and which does not potentially trap air that can&#39;t be purged by the fill event. 
   In the preferred embodiment disclosed, a compact valve body interrupts the main system line at a convenient fill point. A central valve body bore, with a closed inner end and an open outer end, opens to a system inlet port and a system outlet port at slightly axially offset points. A pair of axially spaced fill ports also open into the central bore, specifically a fill inlet port located between the system inlet port and the open end of the central bore, and a fill outlet port located between the system outlet port and the closed end of the central bore. A plunger axially movable within the bore, and accessible from the open end of the bore, carries two axially spaced sealing disks. 
   When the plunger is shifted outward to a fill position, the inner disk moves between and divides the two system ports from one another. Concurrently, the outer disk and inner disk together serve to open the fill inlet port and system inlet port to one another. At the same time, the inner disk moves to capture the system and fill outlet ports between it and the closed bottom of the bore, while the outer disk moves to capture the system and fill inlet ports between it and the inner disk. In the valve&#39;s fill position, liquid coolant may be pumped from a supply pool into the system inlet port, flowing into the system inlet port, and then continually through all components and lines of the liquid cooling system, and finally into the system outlet port, out the fill outlet port, and back into the coolant supply pool. This continues until air appears to be purged from the system. Liquid also solidly fills the central bore. 
   When the fill appears to be air free, the plunger is shifted inwardly to a closed or system operating position. Now, the two system ports are re opened to one another, and the two fill ports and divided off from the two system ports, concurrently. The small volume of liquid filling the central valve body bore, from the fill operation, is either squeezed back out into the supply pool or remains in place, without air intrusion. The valve operation requires only the axial push and pull of the plunger, and only the two sealing disks represent potential leak points from the system and out of fill ports. If desired, the fill ports can be easily separately plugged, post fill, if desired. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the valve, partially broken away, during normal operation; 
       FIG. 2  is a view of the valve like  FIG. 1 , but during the initial filling operation; 
       FIG. 3  is a schematic of a liquid cooling system, with a fill and bleed valve according to the invention, during the initial filling operation; 
       FIG. 4  is a schematic of a liquid cooling system, with a fill and bleed valve according to the invention, during ordinary operation; 
       FIG. 5  is a cross section of the valve body, looking up, corresponding to  FIG. 1   
       FIG. 6  is a view like  FIG. 5 , corresponding to  FIG. 2 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring first to  FIG. 4 , a liquid cooling system, indicated generally at  10 , has several coolant line interconnected components, including a pump  12 , so called cold plate  14 , and air to liquid heat exchanger  16 , all of which have liquid coolant (typically a water/glycol mixture) circulating therethrough on a continual basis. The cold plate  14  would be mounted to a computer chip or other heat producing component, which is continually cooled by the system  10 . All components, and the interconnecting lines, need to be filled at the time of assembly, and the coolant fill, ideally, should be solid and air free, so as to avoid pump cavitation and provide maximum efficiency. It is unlikely that significant coolant would be lost, in a well sealed system, but reservoirs have been provided in such systems, in order to provide a means for air bleed from the system. In the subject invention, instead of a reservoir, a fill and bleed valve, indicated generally at  18 , is used to allow for the initial coolant fill, and provides the fill on air free basis, so that a reservoir is unnecessary. The valve  18  is left as a permanent part of the system  10  and could, theoretically, be used again for a system coolant refill, should that become necessary. Ideally, however, the valve would be used on a one time basis, after which it would become redundant. 
   Referring next to  FIGS. 1 and 5 , in the normal running position, valve  18  does no more than pass coolant through it. Valve  18  has a main body  20 , a molded or machined block, with a central bore  22  having a inner closed end  24  and an outer open end  26 . A system outlet port  28  and a circumferentially opposed, discrete system inlet port  30  open through block  20  and into central bore  22 , axially offset from one another by a distance described below. Each system port  28  and  30  is also axially spaced from the bore&#39;s closed and open ends  24  and  26 , so as to leave axial space within bore  22  to accommodate other valve structure. Also opening through block  20  and into central bore  22  are a fill outlet port  32  and a fill inlet port  34 , opening, conveniently, through the same face of block  20 . Fill outlet port  32  is located near the bore closed end  24 , between system outlet port  28  and bore closed end  24 , while fill inlet port  34  is located between system inlet port  30  and bore open end  26 , near the open end  26 . A narrow, coaxial plunger  36  slides within bore  22 , and carries a inner disk  38  and an outer disk  40 , each of which carries an O ring  42  that fits closely within bore  22 , that is, close enough to seal against leakage of the coolant, which is typically not high pressure. In the normal operating position shown, with plunger  36  inserted axially all the way into bore  22 , inner disk  38  resides completely in the axial space between the two outlet ports  28  and  32 , dividing and sealing them one from another, while the outer disk  40  resides in the axial space between the two inlet ports  30  and  34 , also dividing and sealing them from one another. The two system ports  28  and  30  are left totally unblocked and open to one another. It will be noted that the end of plunger  36  engages the bore closed end  24 , providing a natural locater for the normal operating position, while outer disk  40  is nearly flush to the bore open end  26 . As such, outer disk  40  is accessible by a suitable tool, such as a threaded bit (not illustrated), but not freely accessible to purely manual manipulation. Each fill port  32  and  34  is blocked off from any system coolant flow, by the O rings  42 . While the block  20  is sealed against leaks, the two system ports  28  and  30  open freely to one another across central bore  22 . Coolant flows, as shown by the arrows, freely through the entire system  10 , just as if the two system ports  28  and  30  were joined end to end. In that regard, the terms “inlet” and “outlet” for the system ports  28  and  30  are somewhat arbitrary, they simply represent a break in what would otherwise be a continuous flow line, provided to accommodate valve  18 . While valve  18  occupies some space, in general, block  20  is much more compact than a coolant reservoir would be. The normal operating position of valve  18  is the position it would be in for essentially the entire life of the system, but for the initial fill event, described next. 
   Referring next to  FIG. 3 , the system  10  is shown during an initial coolant fill operation, after all components have been assembled, but before it is operating. Valve  18  has been axially retracted to a fill position (detailed below) and coolant is being pumped continually, from a supply pool  44 , into the fill inlet port  34 , continually through the system  10  and all components thereof (pump  12 , cold plate  14 , heat exchanger  16 , and all interconnecting lines) and finally out of fill outlet port  32  and back to the supply pool  44 . This would be done long enough that no significant visible air was being purged from the fill outlet port  32 . Consequently, the fill operation should not have to be done under any significant pressure, or be assisted by a vacuum pull, nor should a separate air bleed valve be needed anywhere, as is often found on hydronic heating systems and the like. Coolant would simply be pumped through until all entrapped air is swept out, and the liquid fill is solid. The internals of valve  18  that allow this to occur are described next. 
   Referring next to  FIGS. 2 and 6 , plunger  36  is retracted axially far enough to move inner disk  38  between the two system ports  28  and  30 , dividing them from one another. As noted above, outer disk  40  could be made tool accessible for this one time operation, as by a threaded shaft and handle threaded into a blind bore in the end of disk  40 , and would be pulled out only so far as to leave its seal ring  42  within the bore  22 , still sealing the bore open end  26 . The proper extent of plunger  36  retraction could be assured by marking the outer disk  40  or providing some other visual or tactile indicator. Conceivably, block  20  could be of a transparent material, as well. Concurrently with the division of the system ports  28  and  30  from one another, the inner disk  38  and bore closed end  24  together open the system outlet port  28  and fill outlet port  32  to one another. Also concurrently, the plunger disks  38  and  40  together open the system inlet port  30  and fill inlet port  34  to another, while outer disk  40  continues to block the otherwise open end of bore  22 . Next, a suitable fill fitting, such as the plate  46  shown would be attached or clamped to the face of block  20 . Individual line fittings  48  and  50  register with the fill ports  32  and  34  respectively. The plate  46  is no more than a convenient mechanism to attach the fill system to the valve  18 , and could be a permanent part thereof, room permitting, with the fittings  48  and  50  simply acting as extensions of the fill ports  32  and  34 . When lines from the coolant supply pool  44  are attached to the fittings  48  and  50 , the fill operation described above is carried out. Coolant entering fill inlet port  34  is forced into system inlet port  30 , through all the system components, back to system outlet port  28 , out of fill outlet port  32  and back to the supply pool  44 . Post fill, plunger  36  is inserted back to its original position, bottoming out on the bore closed end  24 . The system ports  28  and  30  are reopened to each other. Liquid coolant trapped between the plunger inner disk  38  and the bore closed end  24  is not trapped, but is squeezed out of the fill outlet port  32 . Concurrently, coolant trapped between the plunger disks  38  and  40  moves with the plunger  36  in a solid column, with no air intruding, maintaining the air free nature of the system fill. Finally, the plate  46  (if present) is removed. If desired, for a fail safe, the fill ports  32  and  34  could be separately plugged, and the plunger  36  could be locked in place with a suitable tamper proof key or pin. 
   Variations in the disclosed embodiment could be made. The valve block  20  and central bore  22  could comprise a cylindrical pipe section, in effect, closed at one end, and open at the other, with a plunger  36  sliding within. The central bore  22  and disks  38  and  40  need not absolutely be cylindrical in shape, though that is most convenient. As noted, the fill ports  32  and  34  need not open through the same face of block  20 , though that, too, is convenient. Fundamentally, the system ports  28  and  30  must have discrete openings into central bore  22 , but need not be absolutely 180 degrees circumferentially opposed to one another. It is convenient that the be substantially circumferentially opposed, however. Likewise, the system ports  28  and  30  need not be axially offset sufficiently to accommodate the entire thickness of inner disk  38  between them, with no axial overlap of inner disk  38  with either port opening. So long as there is sufficient axial offset to allow the inner disk  38  to divide one system port  28  from the other  30 , the basic concept will still work. Theoretically, the effective axial offset that allows the fill position division of the two system ports  28  and  30  from one another could be partially, or totally, built into the inner disk  38  itself, by cutting away an opposed 180 degrees off of each face of inner disk  38 , rather than by axially offsetting the system ports  28  and  30  from each other. This would require that the inner disk  38  be kept in a preferred angular orientation within the bore  22 , however. In either case, unless the system ports  28  and  30  are axially offset from one another sufficiently to accommodate the entire thickness of inner disk  38 , then some of the area of the ports  28  and  30  opening into bore  22  will be more likely to be blocked during the fill operation, creating an undesirable, though perhaps not debilitating, flow restriction during the fill operation. On the other hand, having the system ports  28  and  30  axially offset from one another more than is absolutely necessary just to accommodate the thickness of inner disk  38  would not be preferred, since the necessity for normal coolant flow to “jog” axially from one system port to the other across the central bore  22  represents some additional flow restriction. The extra length of plunger  36  extending axially from the inner face of inner disk  38 , as noted above, creates a stop to define the normal operating position of valve  18 . That locator could be provided as well by the flush positioning of outer disk  40  to the end of block  20 , allowing plunger  36  to be shorter than disclosed. The outer disk  40  need not be as thick as shown, needing only enough thickness to accommodate its o ring  42 . In that event, a smaller diameter, discrete knob could be created on the end of plunger  36 , outboard of a thinner outer disk  40 , allowing easier manual manipulation of the valve  18 . Post fill, if desired, the fill ports  32  and  34 , while sealed internally by the o rings  42 , could be additionally sealed externally, as by a non illustrated, clamped in place cover or gasket, as a redundant fail safe.