Water box and expansion chamber assembly

In a heat exchanger, e.g. a radiator for a motor vehicle, the water box (10) and the expansion chamber (11) are made in a single plastic moulding, and are divided by a common wall (12) having at least one orifice for liquid communication therebetween. The expansion chamber tapers from a wider bottom to a narrower top. The narrower top has a filler cap, while the wider bottom is closed by an add-on cover.

The present invention relates to a water box and expansion chamber assembly 
for a heat exchanger such as the radiator in the cooling circuit of a 
motor vehicle. The water box and the expansion chamber are obtained by 
moulding and they share a common wall which separates one from the other, 
and which includes a communication orifice, and optionally a degassing 
orifice. 
BACKGROUND OF THE INVENTION 
Such an assembly is known in which the water box and the expansion chamber 
are disposed generally vertically with the upper part of the expansion 
chamber being provided with a liquid filler orifice suitable for receiving 
a stopper that includes a set of over pressure and under pressure release 
valves. The cross section of the expansion chamber tapers going down from 
the top in order to facilitate with drawing a molding core, andd the said 
communication orifice is at or near the bottom of the expansion chamber. 
This known arrangement suffers from various drawbacks. Firstly, the stopper 
for closing the top of the expansion chamber must either have at least the 
same area as the largest cross section of the expansion chamber, which 
means that outsize stoppers have to be used with expansion chambers of 
ordinary size, or else some kind of funnel shaped cover must be fitted to 
the top of the expansion chamber, or else the expansion chamber must be 
re-designed to be of smaller cross section than usual in order to receive 
a normally sized stopper. Secondly, it is inconvenient for the small end 
of the expansion chamber's taper to be the end near to its communication 
orifice with the water box, since under these circumstances, a shortage of 
water in the radiator then causes the water level to drop more quickly in 
said end of the expansion chamber, and it may drop right down to the said 
communication orifice. 
Further, the relatively small cross section at the bottom end of the 
expansion chamber causes liquid to circulate more quickly in this zone, 
which leads to there being an increased danger of air bubbles going into 
the radiator via the communication orifice, and hence to poorly de-gassed 
liquid circulating therein. 
Preferred embodiments of the present invention reduce these drawbacks. 
SUMMARY OF THE INVENTION 
The present invention provides a water box and expansion chamber assembly 
for a heat exchanger including at least one heat conveying liquid, e.g. 
the radiator of a motor vehicle, wherein the water box and the expansion 
chamber are made by moulding with a common dividing wall having an orifice 
for liquid communication between the expansion chamber and the water box, 
the cross section of the expansion chamber increasing gradually from one 
end thereof to the other, the smaller end of the expansion chamber being 
terminated by a filler orifice, and the larger end of the expansion 
chamber being closed by an add-on cover. 
Thus, the invention makes it possible for the cross section of the 
expansion chamber to be independent from the area of its filler orifice, 
which means that the expansion chamber can be closed using a stopper of 
standard size, and that the filler orifice may be disposed in any 
convenient manner relative to the axis of the expansion chamber. 
At the same time, since the expansion chamber tapers from a relatively 
large bottom to a relatively small top, a shortage of water in the heat 
exchange circuit leads to a relatively slow drop of liquid level in the 
lower part of the expansion chamber, so the liquid flows more slowly, so 
there is less risk off air bubbles being entrained into the radiator, and 
hence de-gassing is improved. 
The add-on cover may be designed to perform various extra functions, e.g. 
it may have a fixing peg or finger on its outside surface; it may be 
shaped to receive a liquid level detector to indicate when the expansion 
chamber is short of liquid; it may include bleeder means; or it may 
include a stopper with valves for setting a safe pressure level inside the 
expansion chamber.

MORE DETAILED DESCRIPTION 
The water box and expansion chamber assembly shown in FIG. 1 is moulded in 
a single piece of plastic. The expansion chamber 11 is tubular and of 
substantially circular cross section, and the water box 10 is separated 
therefrom by a wall 12 having a degassing orifice 13 near its top and an 
orifice 14 near its bottom for communication between the water box 10 and 
the expansion chamber 11. 
In this embodiment the assembly is intended for generally vertical 
disposition, i.e. the longitudinal axis 15 of the expansion chamber 11 is 
substantially vertical. However, the assembly could be designed for 
horizontal use. 
The top 16 of the expansion chamber 11 constitutes a filler orifice, and 
its ouside surface is threaded to receive a conventional stopper of the 
kind that is generally provided with a set of under pressure and over 
pressure release valves. The filler orifice projects above the top of the 
water box 10 and may be mounted off the axis 15 (as shown), with a joggle 
17 bridging the gap. The expansion chamber is gently flared from a 
relatively smaller top 16 to a larger bottom 18 which is closed and sealed 
by a cover 19 fixed thereto in any suitable manner. The increasing cross 
section of the expansion chamber 11 makes it easy to mould the assembly in 
plastic, using a tapering mould core that is removed after the plastic has 
set via said end 18. 
As indicated above, having a wider bottom to an expansion chamber favours 
the retention of a minimal quantity of liquid in the expansion chamber, 
and improves degassing, i.e. the separation of bubbles of air from the 
water in the expansion chamber, by reducing a rate at which liquid flows 
in the lower part of the expansion chamber and by avoiding air bubbles 
being sucked through the orifice 14 into the radiator. 
In the embodiment shown in FIG. 1, the cover 19 which closes the bottom 18 
of the expansion chamber 11 includes a fixing peg or finger 20 projecting 
from the outside face 21 of the cover 19. 
In the embodiment shown in FIG. 2, the cover 30 which closes the bottom 18 
of the expansion chamber 11 serves as a support for a detector to detect 
when there is too little liquid in the expansion chamber. The detector 
comprises a float 31 and a magnetically controlled electric switch 32 such 
as a reed switch capsule. 
The reed switch bulb 32 is lodged in tubular sleeve 33 which is closed at 
35 not far from its top end, and which projects up into the expansion 
chamber 11 in a funnel-like manner from the cover 30. The spring blades 36 
inside the bulb 32 are connected by conductors 37 to contact blades 38 
mounted on a part 39 which is lodged in the tubular sleeve 33. 
The float 31 carries a permanent magnet 40, and is annular in shape, being 
threaded over the top of the sleeve 33, in such a manner as to be 
vertically slidable therealong. Its movement is limited by lower stops 41 
and upper stops 42 which form a rim at the top of the sleeve 33. The top 
of the sleeve is split so that the float ring can be snap fitted on the 
sleeve 33. 
So long as the expansion chamber is filled with liquid to a normal depth, 
the float is held against the upper stops 42, but when the level drops 
sufficiently, the ring float 31 will drop until its magnet 40 changes the 
state of the contacts in the reed switch capsule 32, thereby generating an 
alarm signal. Clearly the contacts could be either normally closed or 
normally open; all that matters is that they should change to another 
condition when the level of liquid is abnormal. 
In the embodiment shown in FIG. 3, the bottom 51 of the expansion chamber 
50 includes a heat exchanger outlet tube 52, and the wall 53 separating 
the expansion chamber from the water box 54 includes a communication 
orifice 55 opposite the end of the outlet tube 52. 
The cover 56 closing the bottom 51 of the expansion chamber 50 comprises an 
upper disk 57 and a lower disk 58 which are interconnected by a vertical 
axial tube 59. The top of the tube 59 is closed by the upper disk 57, 
while the bottom of the tube 59 opens out through the lower disk 58. A 
cylindrical plug 60 is screwed into the bottom of the tube 59 to close 
both the bottom of the tube 59 and a side opening 61 located in the tube 
wall near to its bottom. The upper disk has an orifice 62 passing 
therethrough which is smaller than the bore of the outlet pipe 52 or the 
orifice 55 passing through the dividing wall 53. 
In normal operation, the orifice 61 is closed by the stopper 60 which also 
seals the bottom of the tube 59 by means of a sealing ring 63. Liquid 
leaving the water box 54 passes through the orifice 55, flows round the 
tube 59, and passes on to the outlet tube 52. The orifice 62 in the upper 
disk 57 of the cover 56 allows the expansion chamber to operate normally. 
To empty the heat exchanger, all that needs to be done is to unscrew the 
stopper 60, and the liquid contained in the heat exchanger then flows into 
the tube 59 via the orifice 61 and on out of the system via the bottom of 
the tube. 
In the embodiment shown in FIG. 4, the cover 70 which closes the bottom 71 
of the expansion chamber 72 is screwed to the bottom and seals it by means 
of a sealing ring 73. The cover 70 is generally cylindrical, being of 
circular cross section and comprising a lower disk 74 and an upper disk 75 
interconnected by a tubular skirt 76. The upper disk 75 presses against an 
internal shoulder 77 in the expansion chamber 72 via a sealing ring 78. 
The upper disk 75 is provided with a central orifice 79 which is closed by 
a flexible valve disk 80 made of rubber or the like and resting on the 
upper surface of the upper disk 75. The upper surface of the flexible 
valve disk 80 is reinforced by a metal disk 81, and a spring 82 presses 
down thereon from a bridge member 83 which is firmly attached to the upper 
disk 75. 
In the figure, the bridge member 83 is in the form of an upsidedown 
cylindrical bowl with a rim made fast to the upper disk 75 and with holes 
84 for liquid to flow through. Any other form of bridge that provides a 
fixed point to which to secure the spring 82 and also allows liquid to 
flow into the expansion chamber from the orifice 80 would also be 
suitable. 
There is a hole through the center of the valve disk 80 and its reinforcing 
metal 81, and the hole is closed by a valve disk 86 which is resiliently 
urged upwards against the lower surface of the valve disk 80 by means of a 
rod 85 passing through the central hole and a spring 88 acting between the 
other end 87 of the rod 85 and the upper surface of the reinforcing disk 
81. 
The skirt 76 of the cover 70 has a circumferentially extending slot 89 
substantially opposite an orifice 90 in the wall 91 dividing the expansion 
chamber 72 and the water box 92 in the assembly. 
The set of over pressure and under pressure valves which has just been 
described works as follows: 
If the pressure in the expansion chamber 72 is higher than the pressure in 
the water box 92, the resulting downwards force on the valve disks will 
tend to move the valve disk 86 downwards. Once the force applied to the 
valve disk 86 by the pressure difference exceeds the force applied thereto 
by the spring 88, the valve disk 86 will move downwards, opening the 
central hole in the valve disk 80, thereby establishing communication from 
the expansion chamber into the water box. 
In the contrary case, the resultant force on the valve disks is upwards, 
and once said force overcomes the force of the spring 82 the valve disk 80 
will lift off the upper cover disk 75 and liquid will flow from the water 
box into the expansion chamber via the orifice 79 and the orifices 84. 
Naturally, in this embodiment, the expansion chamber 72 does not include a 
degassing orifice through the top of the dividing wall 91, and its top end 
is not closed by a stopper having over pressure and under pressure release 
valves, but by a simple stopper having a vent to provide communication 
with the ambient air.