Abstrict A condenser (10) with a return header tank (14) has a receiver
or reservoir canister (22) physically attached along side the return
header tank (14), and open thereto through a discrete upper inlet
(20) and lower outlet (21). The bottom of canister (22) is closed
by an end cap (34) that is, preferably, welded or brazed in place.
Before end cap (34) is attached, a tube of desiccant material (24)
is installed and located within canister (22) by a standoff (26)
comprised of a tight fitting, notched, disk shaped base (28) and
narrow central post (30) which is comparable in length to the height
of the inlet (20) above the lower end cap (34). The tight fit allows
the tube (24) to be inserted up into the canister (22), well away
from the bottom of canister (22) and free of heat damage as the
end cap (34) is attached. Later, in operation, the central post
(30) keeps the tube (24) located clear of the inlet (20) and outlet
(21).
Claims What is claimed is:
1. A condenser (10) having a generally vertically oriented return
header tank (14) on one side with a separator (18) dividing it into
an upper section (U) and a lower section (L), and a generally cylindrical
reservoir canister (22) attached beside return header tank (14)
having an inlet (20) into the return header tank upper section (U)
and an outlet (21) into the return tank lower section (L), said
canister (22) also having a lower end closure (34), characterised
in that,
said canister (22) includes a desiccant material container (24)
located therewithin by a standoff (26) having a generally circular,
disk shaped base (28) with edge cutouts (32), said base (28) making
an interference fit with the inside of canister (22) and being fixed
to the lower end of material container (24), said standoff also
having a central post (30) that is fixed to base (28), and which
is substantially narrower than the inside of canister (22), and
substantially as long as the axial height of inlet (20) above the
lower end closure (34),
whereby base (28) serves to locate desiccant material container
(24) away from lower end closure (34) during installation, and,
during operation, post (30) and base (28) serve to maintain the
desiccant material container (24) away from the inlet (20) and outlet
(21), while leaving the inlet (20) and outlet (21) unblocked, by
virtue of the length and width of post (30).
Description TECHNICAL FIELD
This invention relates to air conditioning systems in general,
and specifically to an improved desiccant installation for a condenser
having an attached receiver.
BACKGROUND OF THE INVENTION
Automotive air conditioning systems typically include either an
accumulator canister or a receiver canister that serve as a refrigerant
reservoir. An accumulator is located just before the compressor,
and allow only (or substantially only) refrigerant vapor to be drawn
off of the top before compression, with liquid settling at the bottom.
Receiver canisters are located just after the condenser, and are
intend to allow only (or substantially) only liquid refrigerant
to be drawn off the bottom for the refrigerant expansion valve.
A canister of either type also provides a convenient location for
a container of desiccant material, usually a bag or pouch of mesh
material, which absorbs water vapor from the liquid refrigerant
reservoir. Either an accumulator or a receiver usually has ample
room within it for the desiccant, and some kind of pre existing
piping arrangement within it from which the desiccant bag can be
conveniently suspended. The desiccant works better if suspended
within, rather than resting free on the bottom of, the canister,
and is also less subject to damage in the event that a bottom closure
is later welded to the canister. A typical example of such an arrangement
may be seen in U.S. Pat. No. 4354362 where an internal pipe provides
a practical suspension post for a desiccant container.
A relatively recent trend is the attached or so called "integral"
receiver, in which a reservoir canister is incorporated structurally
onto, on into, the return header tank of a so called cross flow
condenser design. A cross flow or "headered" condenser
typically has a main pass, within which gas condenses to liquid,
and a sub cooling section, within which liquid refrigerant is further
cooled. An example may be seen in U.S. Pat. No. 5537839. The reservoir
runs along the side of the return tank, and two openings or short
pipes near the base of the return tank connect the main pass condenser
tubes to the reservoir canister. The two openings are separate or
discrete, so that all condensed refrigerant entering the return
tank from the main pass is forced to flow through the upper opening
and into the reservoir canister, where it forms a rising or falling
reserve liquid column (depending on conditions). From the reservoir
canister, liquid refrigerant can flow into the discrete lower opening
and into the sub cooling section, and ultimately to the expansion
valve. Generally, and preferably, the reservoir canister or tank
section is no more than an empty vessel, with no internal structure
suitable for suspending a desiccant cylinder or pouch. One exception
may be seen in U.S. Pat. No. 5159821. There, refrigerant is forced
centrally up into the reservoir canister in a fountain like central
pipe, which also provides a convenient suspension pole for the desiccant
cylinder. This is an undesirably complex and expensive structure,
however.
More typically, the desiccant would simply rest where gravity would
take it anyway, on the inside of the base of the reservoir canister,
and this is the situation disclosed in U.S. Pat. No. 5537839
already noted above. This puts the desiccant container both in a
position where it could be damaged by welding or brazing on a bottom
closure, and in a position where it is axially coextensive with,
and could clog or block, the discrete openings between the reservoir
canister and the return manifold. The patent recognizes this issue
by providing a separate bottom threaded plug for installing the
desiccant container. There is also provided an additional internal
cage like structure to confine the desiccant away from the openings.
That same structure retains the desiccant so that it is in line
with the openings, and therefore at least theoretically capable
of blocking them. Furthermore, the cage like structure represents
a potential threat to the structural integrity of the desiccant
container, which is generally a cloth or plastic open mesh, especially
when subjected to vibration and bouncing in operation. Both the
threaded plug and the retention cage also require additional cost
and manufacturing steps.
SUMMARY OF THE INVENTION
An improved desiccant installation for a condenser with an integral
receiver is provided in accordance with claim 1.
In the embodiment disclosed, a refrigerant condenser of the cross
flow, headered type has an inlet header on one side, a return header
on the other, and an upper or main pass section of flow tubes divided
from a smaller sub cooler section by a separator located near the
bottom of the return tank. Alongside the return tank, a simple cylindrical
reservoir canister is structurally attached by any suitably solid
and compact means. The main pass empties into the return header,
which then empties into the reservoir canister through a discrete
inlet just above the separator. From the reservoir canister, the
liquid refrigerant empties back into the return tank through an
outlet and then into the sub cooler section. There is no inner structure
within the reservoir canister beyond the smooth inner wall, and
it is preferably enclosed at top and bottom by a simple cap that
is brazed or welded in place, giving a simple and reliable seal.
A cylindrical, open mesh container of desiccant material has a
diameter that gives it a small radial clearance from the inner wall
of the reservoir canister, and an axial length which, if it were
allowed to rest on the bottom of the reservoir canister, would put
it in line with both the inlet and outlet, and liable to block free
flow through them. However, this is prevented by a standoff structure
that consists of a narrow, centrally located bottom post and an
upper, disk shaped base. The post is longer than the height of the
inlet above the bottom end cap of the reservoir canister, and the
base has an outer diameter that makes a tight interference fit with
the inner wall of the reservoir canister. Therefor, the standoff
structure can be used to insert the desiccant into the reservoir
canister before the bottom end cap is sealed in place. The desiccant
can be inserted past and beyond the inlet and outlet openings, where
it will remain, at least temporarily, until after the bottom cap
is welded in place, safe from heat damage. In later operation, the
interference fit will help prevent vibration and damage of the desiccant
tube within the canister, and even if the desiccant should sink
downwards, the desiccant itself will never rest on the bottom of
the canister, or block the inlet and outlet, because of the dimensions
of the post. Cut outs are provided in the edge of the disk to allow
liquid refrigerant to freely flow up or down past the disk.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the invention will appear from the
following written description, and from the drawings, in which:
FIG. 1 is a schematic view of the type of condenser in which the
invention is installed;
FIG. 2 is a perspective view of a desiccant tube and standoff;
FIG. 3 is a perspective view of just the standoff structure;
FIG. 4 a view showing a cross section of the reservoir canister
with the desiccant tube-standoff unit aligned therewith;
FIG. 5 is a view like FIG. 4 showing the unit over inserted prior
to canister closure;
FIG. 6 is a view like FIG. 5 showing the canister closure welding,
process with the desiccant container held in a protected position;
FIG. 7 shows the location of the unit within the reservoir canister
after an equilibrium position has been reached during operation.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring first to FIG. 1 a condenser 10 of the cross flow, headered
type has an inlet/outlet header tank 12 on one side, and a return
header tank 14 on the other, each of which is divided into discrete
upper (U) and lower (L) sections by separators 16 and 18 respectively.
Heated, compressed refrigerant vapor enters the upper section (U)
of header tank 12 above separator 16 and flows across and through
the flow tubes in the main pass section (not illustrated in detail).
In the main pass, refrigerant is condensed to liquid form and flows
into the upper section (U) of return tank 14 above the separator
18. From there, all liquid refrigerant is forced, by the separator
18 to flow through an upper inlet 20 and into an attached reservoir
canister 22 where it backs up into a reserve column of varying
height. From the reserve column, liquid refrigerant can flow down
and through a lower outlet 21 into lower section (L) of return
tank (14) and ultimately into a sub cooler section of condenser
10 comprised of those flow tubes located below the two separators
16 and 18. In the sub cooler section, liquid refrigerant is further
cooled, below the temperature necessary to simply condense it, and
flows finally back into the lower section (L) of header tank 12.
No desiccant structure is illustrated within canister 22 in FIG.
1 but that is described next.
Referring next to FIG. 2 a desiccant container comprises a simple,
elongated cylindrical tube 24 of mesh material, which has an open
weave with a fill of conventional granular desiccant material contained
within. Tube 24 is heat sealed or otherwise closed at the top, and,
at the bottom, is preferably fixed to a standoff, indicated generally
at 26. Standoff 26 is an integral structure, which may be formed
of any suitable heat and refrigerant resistant material. A disk
shaped base 28 at the top is supported on a narrow, solid central
post 30 of axial length X1. Base 28 is four lobed, with a circular
outer edge of diameter of D1 broken into four equal arcs by four
cut outs 32. In the embodiment disclosed, tube 24 is preferably
fixed centrally to the upper surface of base 28 by glue, sonic welding
or other technique to create a unit that can be handled during installation
as, and operate later as, a single component.
Referring next to FIGS. 4 and 5 reservoir canister 22 is shown
prior to having its open lower end closed by an end cap 34. The
upper end has already been closed by an upper end cap 36. As disclosed,
at this point in the manufacture, the entire condenser 10 would
have been run through the braze oven, and be complete, but for the
installation of the desiccant containing tube 24 and the lower end
cap 34. However, it could be that neither end cap 34 or 36 is in
place, or, the lower end cap 34 could be in place, but not the upper
end cap 36. The invention will accommodate any of those possible
scenarios. Next, as shown in FIG. 5 the tube 24 is inserted into
the inside of canister 22 through the open lower end, by pushing
up on the standoff 26. This could be done easily by hand, or automated,
since the post 30 and base 28 are easily grabbed and manipulated,
and are not subject to damage, as the material of the tube 24 would
be. The tube 24-standoff 26 unit is pushed in until the arcuate
edges of base 28 tightly engage the inner wall of canister 22 with
an interference fit. The inner wall of canister 22 has a diameter
D2 that is sufficiently smaller than diameter D2 to assure that
snug fit. The unit is pushed to the point shown in FIG. 5 where
the end of the tube 24 is clear of the upper end cap 36 and the
bottom of post 30 is clear of the bottom of canister 22. It will
remain in that position, at least temporarily, by virtue of the
interference fit.
Referring next to FIGS. 6 and 7 Once the tube 24-standoff 26 unit
has been pushed into canister 22 the bottom end cap 34 is welded
into place by welding tool 38. In the location shown, the tube 24
and even the bottom of post 30 are well clear of the heat produced
by the bottom closure process. The cap 34 provides a very inexpensive
and secure closure and seal, as compared to a threaded plug, or
other closure that is installed without heat. Later, in operation,
the tube 24-standoff 26 unit can sink down under the force of gravity
and vibration, as shown in FIG. 7 until the bottom of post 30 rests
on the bottom end cap 34. However, the height of the upper inlet
20 above the bottom end cap 34 indicated at X2 is comparable to
or less than the length X1 of the post 30. Post 30 then, is sufficient
to keep the tube 24 supported on base 28 above and clear of the
inlet and outlet 20 and 21 at all times during operation, so that
flow in or out will not be impeded. Once flow has entered the canister
22 below the base 28 it can flow freely up (or back down) through
the cut outs 32 and around (and through) the mesh material of the
tube 24. In addition, the surface of the tube 24 is kept away from
the sharp edges of the openings 20 and 21 where it could be damaged,
and is exposed only to the smooth, upper inner surface of canister
22 where it is far less subject to damage. Furthermore, fixing
the bottom of tube 24 to the base 28 helps to keep the tube 24
which has some inherent stiffness, radially centered and away from
the wall of canister 22 preserving a radial clearance for refrigerant
flow. So doing also prevents tube 24 from bouncing axially up and
down within canister 22 in operation.
Variations in the disclosed embodiment could be made. The base
28 need not be directly attached to the bottom of tube 24 nor the
post 30 directly attached to base 28 and the two would still act
as a locater and standoff. The standoff function alone could be
provided, most simply, just by a post 30 of sufficient length (long
enough to keep the tube 24 off of the bottom of the canister 22).
A disk shaped structure like base 28 would be needed to allow the
bottom of tube 24 to rest on post 30 without damage, while still
being open to refrigerant flow past the base 28. That disk like
structure could be integral to, or even a part of the bottom of,
tube 24 however, and could be open to refrigerant flow by virtue
of being a meshed structure or the like, instead of having the cut
outs 32. Having a discrete structure, like base 28 anchored to
the bottom of tube 24 rather than just resting freely on top of
it, provides the additional advantages noted above of keeping the
tube 24 axially and radially located, in addition to just keeping
it off of and away from the bottom cap 34 and clear of the ports
20 and 21. |