Engine cooling system air venting arrangement with buoyant air purge valve

An engine coolant system contains a thermostat in a horizontally disposed line from the engine and a horizontally disposed air vent or bypass passage located above the thermostat to bleed air from the system. The bypass system contains a buoyant valve having a duckbill-like shape that pivots to one position by buoyancy in response to coolant flow to seal an air vent opening to the radiator, or to a return non-buoyant position permitting the bleed of air; one embodiment providing a valve with a buoyant insert as well as a weight insert; a second embodiment consisting entirely of a material buoyant in the conventional engine coolant.

This invention relates in general to an automotive engine coolant system. 
More particularly, it relates to an air venting arrangement for purging 
the coolant system of air pockets that might inhibit complete filling of 
the cooling system. Still more particularly, it relates to the use and 
location of a buoyant valve in a horizontally disposed air vent passage 
that bypasses the conventional thermostat in a manner to provide complete 
purging of the coolant system of air. 
Automotive engine coolant systems are known in which the thermostat 
contains a bleed air opening to permit venting of air from the coolant 
passage to the radiator to eliminate air pockets in the cylinder head, for 
example. Trapped air can subject the engine parts to substantial 
temperature increases and result in warping or other deleterious effects. 
Some of the known prior systems contain so-called "jiggle pin" type check 
valves, such as is shown, for example, in U.S. Pat. No. 2,810,524, Puster, 
element 212; U.S. Pat. No. 2,829,835, Branson, Element 82; German Pat. No. 
1169723 and British Pat. No. 893671. These small area rivet like pins 
located in the thermostat fall by gravity to a position permitting flow of 
air around the pin to eliminate air pockets in the coolant passages. They 
seat to seal somewhat against the flow of coolant past the thermostat in 
response to the pressure of coolant against the valve. As shown in the 
above references, however, the thermostat is vertically arranged, and any 
air bubble will naturally rise to the top of the coolant and be vented. 
Problems associated with the construction of the above prior art are that 
(1) the thermostat size must be large enough to permit the inclusion of a 
hole and jiggle pin of sufficient size to provide the proper flow 
characteristics; (2) the substitution of the whole thermostat is required 
to change jiggle pin and hole sizes; and (3) the use of a rivet type 
jiggle pin with its rough surfaces does not provide an adequate seal 
against leakage of coolant flow and, therefore, may provide less than 
desirable passenger car heater performance. 
Other forms of air vent check valves and bypass passages are known, as 
illustrated in U.S. Pat. No. 3,973,729, Sliger, and U.S. Pat. No. 
4,011,988, Inagaki, for example. In Sliger, an opening is made in the side 
wall of the thermostat housing for a ball check valve housing, the ball 
falling by gravity to permit venting of air from the coolant passage, and 
being movable by coolant to seat and seal against the passage of coolant 
past the thermostat. The valve and passage are contained within the 
thermostat per se. In Inagaki, the thermostat closure plate requires an 
extension in which is located a thermally responsive bypass valve 20. In 
both of these references, the thermostat is located to operate in 
essentially a vertical direction so that the location of the air vent is 
not of prime importance. British Pat. No. 1,401,396 shows a bypass passage 
containing a jiggle pin that is located not in the thermostat, but in the 
coolant outlet housing, but again this is a vertical installation type 
thermostat. Also of interest is the vent valve in U.S. Pat. No. 2,627,868. 
Here a buoyant valve with a weight at one end rises vertically to block 
the flow of liquid. 
This invention relates to a thermostat of a horizontally movable type; that 
is, one in which the coolant flows past the thermostat in essentially a 
horizontal direction and thereafter changes more or less to a vertical 
direction to connect to tubing leading to the radiator inlet. In this type 
of installation, location of the air vent is of the utmost importance to 
assure a complete purging of the cooling system of air. U.S. Pat. No. 
4,091,991, for example, illustrates a horizontally disposed thermostat 
having a pair of air bypass passages or vents 35 that permit venting of 
air from the coolant flow. In this case, the thermostat is positioned so 
that at least one of the pockets 35 is located at a high position in the 
thermostat to allow air trapped in the coolant to be vented before the 
coolant reaches a level almost to the top of the thermostat. Again, 
however, it will be seen that since the air venting pocket is located in 
the thermostat per se, air can be trapped in the coolant at a level 
between the air pocket and the housing portion vertically above the 
thermostat. 
U.S. Pat. No. 4,300,718, Beyer, is of particular interest in showing an air 
vent bypass passage located vertically above a horizontally disposed 
thermostat. The bypass passage in this case is diagonally disposed and 
supposedly large enough relative to the size of a ball valve retained 
therein to be movable by coolant to a flow blocking position while 
dropping by gravity to a non-flow blocking air bleed position. However, if 
the valve is only slightly smaller than the passage, air pressure also 
could seat the valve, and thereby prevent elimination of the air bubbles. 
Furthermore, once seated, the air pressure forces would tend to keep it 
seated even though the buoyancy changes temporarily because of the 
presence of an air bubble instead of coolant. 
It is an object of the invention, therefore, to provide an engine coolant 
air venting arrangement that eliminates the disadvantages of the known 
horizontally disposed constructions by providing a horizontally disposed 
air venting passage located in the coolant outlet housing and containing a 
buoyant valve in the passage of a construction that permits a maximum 
purging of air from the coolant passages without leakage of coolant itself 
to the radiator. 
It is another object of the invention to provide an air venting arrangement 
of the type described in which the air bypass vent passage contains in one 
embodiment a duckbill-like shaped buoyant valve with a weight, a second 
embodiment having essentially the same shape constructed entirely of 
buoyant material, both embodiments permitting the flow of air into the 
radiator from the coolant passage when the thermostat is closed, but a 
sealing by the valve against the flow of coolant to the radiator.

FIG. 1 shows a portion of an engine and its thermostat housing. Engine 
cooling systems are well known for circulating the flow of coolant from a 
high point of the engine cylinder head to the radiator for return to the 
engine by means of a water pump for further heat exchange. More 
particularly, the engine coolant system usually includes a water or 
coolant outlet housing at the front end of the engine near the top or 
hottest portion of the engine. A thermostat is inserted at this point to 
prevent flow of the coolant into the radiator until a predetermined 
coolant temperature level is obtained. When this happens, the thermostat 
will open and the coolant will circulate through the radiator to be cooled 
by air flow therethrough and then drawn back into the engine by the water 
pump for a further heat exchange action. 
The thermostatic installations generally are of two types. One locates the 
thermostat in the end of a vertical conduit so as to be movable vertically 
to open or close the passage. Air trapped in the coolant behind the 
thermostat generally escapes through a constant leak type hole in the 
thermostat or through a jiggle pin type valve previously described above, 
there being little hindrance to the passage of air since the passage is at 
the same level as the thermostat seal surface. The second form of 
installation and one with which this invention is concerned is one in 
which a horizontally movable thermostat is provided that connects to a 
right angled passage leading to the radiator. In this instance, any air 
trapped behind the thermostat may remain so trapped if not enough 
circulation can occur and more importantly if an air vent is not provided 
that is sufficiently higher than the coolant level. 
This invention is directed to an arrangement to assure an efficient 
operation of the horizontal type thermostat by the efficient venting of 
air from the coolant system. More particularly, FIG. 1 shows an end of a 
shell type coolant outlet housing 10. It is attached to one end of the 
engine cylinder head over the end of a coolant discharge passage 12 
located at the uppermost portion of the head. The other end, not shown, of 
housing 10 is adapted to be connected by a flexible tubular hose or 
similar conduit, also not shown, to the inlet or upper portion of a 
conventional radiator. 
As viewed in FIG. 1, the passages 12 and 14 are horizontally disposed, the 
passage 14 receiving therein a known type of horizontally movable 
thermostat 16. 
Turning to the invention, the cylinder head is provided with an air vent 
bypass passage 18. It has an inlet portion 20 located vertically above the 
outermost vertical point of passage 12 with which thermostat 16 
communicates. Passage 18 is connected by tubing 23 upwardly to a portion 
of the larger hose, not shown, connected to the radiator. Such a 
construction permits any air trapped in this portion of the coolant 
passage upstream of thermostat 16 to be vented into the connecting hose 
and therefrom into the radiator due to its location at a vertical point 
higher than the highest inlet portion of the coolant flow passage. Passage 
12 in this case is shown with pockets 22 that result from the process of 
casting of the cylinder head. Air trapped in passage 12 migrates to these 
pockets 22 and therefore must be driven therefrom to be vented through 
passage 18. This is done by allowing sufficient circulation of flow of air 
and coolant. 
The venting of the air through passage 18 is controlled in this case by a 
buoyant check valve 24 enclosed in a cylindrical valve housing 26. The 
valve housing has an air opening 28 at one end of a controlled size also 
forming a valve seat for sealing of the opening when the end 30 of valve 
24 is forced up against it by the coolant. The housing 26 is crimped at 
its left hand end 31 as seen in FIG. 1 to a diameter smaller than valve 24 
to retain the valve in the valve housing. The valve otherwise is freely 
movable within the valve housing in a manner now to be described. 
Referring to FIGS. 2 and 3, the valve 24 initially is formed from a 
cylindrical piece of material with a balled or semi-spherical end 30. A 
longitudinally extending wedge of the rod is then removed forming two 
symmetrically shaped portions 36 and 37 on opposite sides of the 
longitudinal centerline 40 of the valve. The two side portions 36 and 37 
then are collapsed to in effect form an overall duckbill-like shape to the 
valve. The smaller end 30 is then machined at right angles to the sides to 
form two flat end faces 38 and 39. The larger end 36 also is machined to 
remove a circular segment of the balled end leaving a flat valve face 34. 
The upper or more vertical portion 36 is provided with a buoyant insert 42 
adjacent the face 38, the lower portion 37 containing a weight insert 44 
adjacent face 39. This provides moments of force about the center point 46 
for the semi-circular end portion 32 on the valve. The buoyancy of the 
valve and the pressure differential against it thus pivots it about point 
46 on surface 48 in response to flow of coolant into bypass passage 18, 
from the position shown in FIG. 3 to the valve seated position shown in 
FIG. 1. 
The force of the buoyancy of valve 24 in the coolant times the moment arm 
distance to centerpoint 46 will provide a clockwise movement about point 
46 to pivot the flat face 34 of the valve from the air bleed position 
shown in FIG. 3 to the flow blocking position shown in FIG. 1. In this 
position, the semi-spherical surface adjacent the face 34 provides a line 
contact seat against the edge of the valve seat defined by opening 28. As 
the coolant level drops or the flow is interrupted by an air bubble, the 
upward buoyancy force is replaced by the downward force of the weight 44 
times the distance to point 46 creating a moment causing the valve to 
pivot in a counterclockwise direction about 46 to return the valve to the 
FIG. 3 air bleed position. It will be clear that this construction also 
provides a self-righting advantage so that the valve is always positioned 
correctly to function in the manner desired and will not rotate. 
The operation is believed to be clear from the above description and a 
consideration of the drawings. However, in brief, below a predetermined 
temperature level, coolant flow past thermostat 16 will be blocked upon 
the seating of the thermostat except for the usual controlled bypass flow 
to the heater block, not shown. The air contained in pockets 22 now can 
escape through the bypass passage 18 past valve 24, which will have fallen 
away from opening 28 to permit the air to pass through the bypass passage 
to the radiator. By the time the air pockets have been eliminated, the 
coolant flow will have begun to reach the outermost diameter of the 
thermostatic housing. Further increases in the level of the coolant then 
will pivot the valve 24 to seat against the opening 28 and seal against 
leakage of any flow of coolant towards the radiator. Therefore, so long as 
thermostat 16 remains closed, no coolant flow through passage 18 will 
occur. 
FIGS. 4-6 show an alternative embodiment. In this case, the valve 24' is 
constructed or machined of a similar shape as that in FIGS. 1-3 entirely 
of a buoyant material, such as from polypropelene stock, which is buoyant 
in a glycol solution. No inserts or weights are necessary as the buoyancy 
and pressure differential forces acting on the valve will orient the valve 
into the upright position of FIG. 5 if initially installed as shown in 
FIG. 4 rotated out of the upright position. The valve per se again has a 
duckbill-like shape with, in this case, a concave shaped face 34' that 
mates with a spherically formed valve seat having an opening 28'. In all 
other respects, the valve 24' of FIGS. 4-6 pivots and moves in essentially 
the same manner as the valve 24 of FIGS. 1-3. 
From the above, it will be seen that the invention provides an engine 
coolant air venting arrangement that assures a greater elimination of air 
pockets in the coolant than previous constructions and, therefore, 
provides a greater protection to engine parts from overheating. It will be 
seen that the above is provided by an air bypass passage that is located 
above the highest point of the coolant passage so that air pockets 
existing in the coolant can be properly vented. It will further be seen 
that a buoyant check valve in a bypass passage is employed to permit the 
egress of air from the coolant while preventing leakage of coolant towards 
the radiator through the passage, which would be detrimental to the 
efficiency of the vehicle heater system. 
While the invention has been shown and described in its preferred 
embodiments, it will be clear to those skilled in the arts to which it 
pertains that many changes and modifications may be made thereto without 
departing from the scope of the invention.