Abstrict A canister is attached to a header tank and includes an upper inlet
and a lower outlet. Before end cap is brazed to close the bottom
of canister, a tube of desiccant material is installed into the
canister by a standoff. The standoff includes a disk shaped base
and narrow central post which is comparable in length to the height
of the inlet above the lower end cap. This is followed by inserting
a spur of a higher melting temperature into the canister into a
position and extending radially from the post and into an interference
fit with the interior wall of the canister that is tighter than
the interference fit between the base and the canister.
Claims What is claimed is:
1. A condenser assembly comprising; a generally vertically oriented
return header tank, a generally cylindrical reservoir canister attached
beside said return header tank and having an inlet into said return
header tank and an outlet into said return tank lower section (L),
said canister having an interior wall and including a lower end
closure, a desiccant material container disposed within said interior
wall of said canister, a standoff disposed within said interior
wall of said canister and includes a central post that is substantially
narrower than the cross section of the space defined by said interior
wall of canister and as long as the axial height of inlet above
the lower end closure for maintaining the desiccant material container
disposed above said inlet and said outlet while leaving said inlet
and said outlet unblocked by virtue of the length and width of said
post, a spur supported on and extending radially from said post
and making an interference fit with the interior wall of said canister,
said spur being of a material different than the material of said
standoff.
2. An assembly as set forth in claim 1 wherein said standoff is
made of an organic polymeric material and said spur is made of an
organic polymeric material that has a higher melting temperature
than the organic polymeric material of said standoff.
3. An assembly as set forth in claim 1 wherein said standoff includes
a disk shaped base supported on said upper end of said post, said
spur being spaced axially along said post below said base and having
a frictional interference fit with said interior wall of said canister.
4. An assembly as set forth in claim 3 wherein said base is integral
with said post.
5. An assembly as set forth in claim 3 including a frictional interference
fit between said base and said interior wall which is less than
the interference fit between said spur and said interior wall.
6. An assembly as set forth in claim 5 including a mechanical connection
between said spur and said post.
7. An assembly as set forth in claim 6 wherein said spur includes
a plurality of radially extending spokes and a ring interconnecting
said spokes.
8. An assembly as set forth in claim 7 wherein said post defines
an annular groove and said spokes have inner ends disposed in said
groove to define said mechanical connection.
9. An assembly as set forth in claim 8 wherein said spokes have
outer ends in said frictional engagement with said interior wall.
10. An assembly as set forth in claim 9 wherein said ring is spaced
radially from both of said ends of said spokes.
11. An assembly as set forth in claim 10 wherein said spokes each
have a relieved corner for facilitating insertion of said spur into
said canister.
12. A method of disposing a desiccant material container within
the interior wall of a canister having an inlet and an outlet, said
method comprising the steps of; inserting a desiccant material container
followed by a standoff into the interior wall of the canister inserting
a spur into the canister and along the standoff into a position
supported on and extending radially from the standoff and into an
interference fit with the interior wall of the canister.
13. A method as set forth in claim 12 further defined as inserting
a spur of a material different than the material of the standoff.
14. A method as set forth in claim 12 further defined as inserting
a standoff made of an organic polymeric material and inserting a
spur made of an organic polymeric material that has a higher melting
temperature than the organic polymeric material of the standoff.
15. A method as set forth in claim 12 further defined as inserting
a standoff that includes a post and a disk shaped base supported
on the upper end of the post to support the desiccant material container,
and inserting the spur to a position spaced axially along the post
below the base and into a frictional interference fit with the interior
wall of the canister.
16. A method as set forth in claim 15 further defined as inserting
a standoff with the base being integral with the post.
17. A method as set forth in claim 15 further defined as forming
a frictional interference fit between the base and the interior
wall which is less than the interference fit between the spur and
the interior wall.
18. A method as set forth in claim 17 including establishing a
mechanical connection between the spur and the post.
19. A method as set forth in claim 18 including inserting a spur
having a plurality of radially extending spokes and a ring interconnecting
the spokes.
20. A method as set forth in claim 19 further defined as inserting
the inner ends of the spokes into the post to define the mechanical
connection.
21. A method as set forth in claim 20 further defined as disposing
the outer ends of the spokes in the frictional engagement with the
interior wall.
22. A method as set forth in claim 21 wherein the inserting of
the spur is further defined as rotating the spokes about the ring
into a cone and moving the inner ends of the spokes along the post
and rotating the outer ends of the spokes about the inner ends to
mechanically engage the inner ends with the post as the spokes are
moved into a radial plane.
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 allows 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, into 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 any 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. However, this is an undesirably complex and expensive
structure.
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 the above mentioned U.S.
Pat. No. 5537839. 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.
Yet a further improvement is set forth in U.S. Pat. No. 6170287
assigned to the assignee of the subject invention and including
some, but not all, of the inventors named herein. This patent discloses
a simple cylindrical reservoir canister alongside the return tank.
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.
This is prevented under the invention of the '287 patent 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. Therefore, 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.
The one-piece standoff prevents the desiccant bag from blocking
the communication ports and is made of a material that allows ultrasonic
welding of the polyester bag containing the desiccant. As alluded
to above, the interference fit between the standoff and the interior
wall of the cylindrical canister keeps the bag away from the heat
generated by brazing or welding the end cap to the end of the canister.
It is important that this interference fit require a high insertion
force and not be degraded to the extent that desiccant bag can move
within the canister after the end caps are brazed or welded in place.
Such undesirable movement of the desiccant bag results in a rattle.
The material selected for the standoff must meet the temperature
criteria for ultrasonic welding to the polyester bag for the desiccant
bag while at the same time resisting degradation from the welding
or brazing of the end cap to the canister. The material of the standoff
must balance between the welding to the desiccant bag and the heat
deflection from welding or brazing the end cap to close the canister.
A poor weld of the canister bag to the standoff can result in the
bag detaching from the standoff in assembly and degradation of the
interference fit between the standoff and the canister from excessive
heat can result in rattle of the desiccant bag within the canister.
SUMMARY OF THE INVENTION
An improved standoff for desiccant in a condenser reservoir of
automotive air conditioning system is provided by the subject invention.
In accordance with the subject invention, a desiccant material
container is inserted within the interior wall of a canister having
an inlet and an outlet along with a standoff. Thereafter, a spur
is inserted into the canister and along the standoff into a position
supported on and extending radially from the standoff and into an
interference fit with the interior wall of the canister.
The spur may be of a material different than the material of the
standoff whereby the spur withstands a higher temperature than the
standoff. Accordingly, the subject invention facilitates a maximum
and secure bond between the standoff and the desiccant bag while
at the same time the spur maintains the integrity of the interference
fit between the standoff and the canister after welding or brazing
of the end cap to the canister to minimize rattle after prolonged
use. This can be accomplished while at the same time reducing the
insertion force required to insert the standoff and desiccant bag
into the canister. In other words, the interference fit need not
be over tight to allow for degradation from the heat of securing
the end cap to the canister.
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 an exploded view showing a cross section of the reservoir
canister with the desiccant tube-standoff aligned therewith;
FIG. 5 is a view like FIG. 4 showing the standoff inserted prior
to insertion of the spur and 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;
and
FIG. 8 shows the spur being moved into mechanical connection with
the post of the standoff.
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 on one side, and a return header
tank on the other, each of which is divided into discrete upper
(U) and lower (L) sections by separators and respectively. Heated,
compressed refrigerant vapor enters the upper section (U) of header
tank, above separator, 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 (L) of return tank, above the separator. From there,
all liquid refrigerant is forced, by the separator, to flow through
an upper inlet and into an attached reservoir canister, 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,
into lower section (L) of return tank and ultimately into a sub
cooler section of condenser, comprised of those flow tubes located
below the two separators. 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. No desiccant structure is illustrated within the interior
wall of the canister in FIG. 1 but that is described next.
Referring next to FIG. 2 a desiccant container comprises a simple,
elongated cylindrical tube of mesh material, which has an open weave
with a fill of conventional granular desiccant material contained
within. Tube is heat-sealed or otherwise closed at the top, and,
at the bottom, is preferably fixed to a standoff, generally shown.
The standoff is disposed within the interior wall of the canister
and includes a central post that is substantially narrower than
the cross section of the space defined by the interior wall of the
canister. A disk shaped base is disposed on the upper end of the
solid central post and is in a frictional interference fit with
the interior wall of the canister.
The post extends from the top thereof through an axial length X1
to a lower end, the axial length X1 being as long as the axial height
of inlet above the lower end closure for maintaining the desiccant
material container disposed above the inlet and the outlet while
leaving the inlet and the outlet unblocked by virtue of the length
and width of the post.
The base is four lobed, with a circular outer edge of diameter
of D1 broken into four equal arcs by four cut outs. In the embodiment
disclosed, the desiccant tube is preferably fixed centrally to the
upper surface of base 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. The standoff is preferably
made of polyester for easy welding to the polyester desiccant bag
or tube. The standoff could also be made of nylon or any other material
suitable for a strong adhesion to the bag.
A spur is supported on and extends radially from the post and makes
an interference fit with the interior wall of the canister. The
spur is of a material different than the material of the standoff.
More specifically, the material of the spur is made of an organic
polymeric (plastic) material that has a higher melting temperature
than the organic polymeric (plastic) material of which the standoff
is made, as by injection molding. The material of the spur is a
high melting plastic that has a heat deflection temperature in excess
of 400.degree. F. Both materials will be refrigerant resistant.
The disk shaped base is integral with and supported on the upper
end of the post and the spur is spaced axially along the post below
the base. The base has a frictional interference fit with the interior
wall of the canister.
The spur includes a plurality of radially extending spokes and
a ring interconnecting the spokes. The post defines an annular groove
and the spokes have inner ends disposed in the groove to define
a mechanical connection between the spur and the post. The groove
could be in the form of a plurality of annularly spaced notches
instead of a groove continuously extending about the post. In other
words, dividing the groove into discrete notches to receive the
ends of the spokes results in the same mechanical connection. The
spokes have outer ends that are in frictional engagement with the
interior wall of the canister. However, the frictional interference
fit between the base and the interior wall is less than the interference
fit between the spokes of the spur and the interior wall.
The ring is spaced radially from both of the ends of the spokes
whereby it is disposed approximately midway along the length of
the spokes. The spokes each have a relieved corner for facilitating
insertion of the spur into the canister.
Referring to FIG. 4 the reservoir canister is shown prior to the
insertion of the spur and having its open lower end closed by an
end cap. An upper end cap has already closed the upper end. As disclosed,
at this point in the manufacture, the entire condenser would have
been run through the braze oven, and be complete, but for the installation
of the desiccant containing tube and the lower end cap. However,
it could be that neither end cap is in place, or, the lower end
cap could be in place, but not the upper end cap. The invention
will accommodate any of those possible scenarios. Next, as shown
in FIG. 5 the tube is inserted into the interior wall of the canister,
through the open lower end, by pushing up on the standoff. This
could be done easily by hand, or automated, since the post and base
are easily grabbed and manipulated, and are not subject to damage,
as the material of the tube would be. The tube standoff unit is
pushed in until the arcuate edges of base tightly engage the interior
wall of canister with an interference fit. The interior wall of
canister has a diameter D2 that is sufficiently smaller than diameter
D1 to assure that snug frictional interference fit. The unit is
pushed to the point shown in FIG. 5 where the end of the tube is
clear of the upper end cap, and the bottom of post is clear of the
bottom of canister. It will remain in that position, at least temporarily,
by virtue of the interference fit. This interference fit between
the base and the canister need only be sufficient to hold the post
in this pre-assembled position until the tighter interference fit
of the spur is attained. This facilitates a lower insertion force
than in previous assemblies.
As best illustrated in FIG. 8 the spur is molded in a flat configuration
as shown in phantom at the bottom of FIG. 8 with the ring spaced
sufficiently from the inner ends of the spokes to allow the spokes
to rotate in a radial plane about the ring to an open position,
as shown in phantom in the middle of FIG. 8. While the post is being
held against movement, as it is in the inserted position of FIG.
5 the spur, while in the open position, is moved into the open
bottom of the canister and along the post. A tool may be utilized
to insert the spur that grips the post and reacts against the inner
ends of the spokes to push the spur open and into the canister until
the spokes reach the groove. The spur is inserted into the canister
as the inner ends of the spokes slide along the post and reach the
groove whereupon the spokes are released with the inner ends thereof
disposed in the groove to form a mechanical connection between the
spur and the post. In other words, when the spokes are released,
the inherent resiliency of the spur returns it to the flat configuration
thereby urging or biasing the inner ends of the spokes into the
groove.
Referring next to FIG. 6 once the tube, standoff and spur have
been positioned in the canister, the bottom end cap is welded into
place by welding tool. In the location shown, the tube, and the
bottom of the post, are well clear of the heat produced by the bottom
closure process. The bottom cap provides a very inexpensive and
secure closure and seal, as compared to a threaded plug, or other
closure that is installed without heat.
Although the stronger interference fit between the spur 33 and
the canister should prevent rattle, during operation, the spur may
slide downwardly in the canister to allow the tube and standoff
to sink down under the force of gravity and vibration until the
bottom end of the post rests upon the bottom end cap, as shown in
FIG. 7. However, the height of the upper inlet above the bottom
end cap, indicated at X2 is comparable to or less than the length
X1 of the post. The post, then, is of sufficient axial length to
keep the tube, supported on base, above and clear of the inlet and
outlet at all times during operation, so that flow in or out will
not be impeded. Once flow has entered the canister below the base,
it can flow freely up (or back down) through the spokes of the spur
and the cut outs of the base, and around (and through) the mesh
material of the tube. In addition, the surface of the tube is kept
away from the sharp edges of the openings, where it could be damaged,
and is exposed only to the smooth, upper inner surface of canister,
where it is far less subject to damage. Furthermore, fixing the
bottom of tube to the base helps to keep the tube, which has some
inherent stiffness, radially centered and away from the wall of
canister, preserving a radial clearance for refrigerant flow. So
doing also prevents tube from bouncing axially up and down within
canister in operation.
Variations in the disclosed embodiment could be made. The base
need not be directly attached to the bottom of tube, nor the post
directly attached to base, and the two would still act as a locator
and standoff. The standoff function alone could be provided, most
simply, just by a post of sufficient length (long enough to keep
the tube off of the bottom of the canister). A disk shaped structure
like base allows the bottom of tube to rest on post without damage,
while still being open to refrigerant flow past the base. That disk
like structure could be integral to, or even a part of the bottom
of, tube, however, and could be open to refrigerant flow by virtue
of being a meshed structure or the like, instead of having the cut
outs. Having a discrete structure, like base, anchored to the bottom
of tube, rather than just resting freely on top of it, provides
the additional advantages noted above of keeping the tube axially
and radially located, in addition to just keeping it off of and
away from the bottom cap and clear of the ports.
The invention therefore provides a method of disposing a desiccant
material container within the interior wall of a canister having
an inlet and an outlet. The method includes the steps of inserting
a desiccant material container followed by a standoff into the interior
wall of the canister, as illustrated in FIG. 5. As shown in FIG.
8 this is followed by inserting a spur into the canister and along
the standoff into a position supported on and extending radially
from the standoff and into an interference fit with the interior
wall of the canister.
As alluded to above, the spur is preferably of a material different
than the material of the standoff. More specifically, the spur is
made of an organic polymeric material that has a higher melting
temperature than the organic polymeric material of the standoff.
After the standoff and desiccant container are in the canister,
the spur is inserted into a position spaced axially along the post
below the base and into a frictional interference fit with the interior
wall of the canister. More specifically, the frictional interference.fit
between the base and the interior wall is formed to be less than
the interference fit between the spur and the interior wall.
As illustrated in FIG. 8 the insertion of the spur is further
defined as rotating the spokes about the ring into a cone and moving
the inner ends of the spokes along the post and rotating the outer
ends of the spokes about the inner ends to mechanically engage the
inner ends with the post as the spokes are moved into a radial plane.
Inserting the inner ends of the spokes into a groove or the like
establishes the mechanical connection with the post. As the inner
ends of the spokes engage the groove, the outer ends of the spokes
continue to move along the post about the inner ends thereof until
the spur again becomes flat and the outer ends of the spokes are
in the frictional engagement with the interior wall. |