Abstrict A pressure vessel housing that can be brazed and leak tested before
adding desiccant material, eliminating the risk of damaging desiccant
bags during assembly. The desiccant is added to the housing of the
pressure vessel through an existing inlet opening in the top of
the accumulator housing, thereby eliminating the potential for damage
to the desiccant and the desiccant container while maintaining the
integrity of the housing because no additional openings in the housing
are required to access the desiccant material. A screen permanently
mounted inside the pressure vessel supports the loose desiccant
material and another screen removably attached to the inlet opening
provides access to the loose desiccant material housed within the
pressure vessel. A method of making the pressure vessel allows the
accumulator assembly to be leak tested before the desiccant is added,
reducing scrap and allowing repair of accumulator assemblies.
Claims What is claimed is:
1. A pressure vessel comprising:
a fully enclosed elongate housing having an inlet opening, an outlet
opening and an interior surface defining an enclosed chamber;
an inlet tube extending through said inlet opening of said housing
and having a discharge end within said housing;
an outlet tube extending through said outlet opening of said housing
and having an inlet end spaced below said inlet tube discharge end;
a baffle member having an outer periphery, said outlet tube extending
through and secured to said baffle member, said baffle member positioned
within said housing and below said discharge end of said inlet tube
and above said inlet end of said outlet tube;
a baffle screen having first and second peripheries, said first
periphery of said baffle screen circumscribing and fixed to said
outer periphery of said baffle member, said second periphery of
said baffle screen circumscribing and fixed to said interior surface
of said housing, whereby said baffle member and said baffle screen
divide said enclosed chamber into an upper chamber and a lower chamber;
means for fastening said baffle screen to said interior chamber
of said housing;
an inlet screen secured to said inlet opening; and
a loose desiccant material disposed within said upper chamber of
said housing, said baffle screen for supporting said loose desiccant
material in said upper chamber and preventing said loose desiccant
material from entering said lower chamber, said inlet screen for
preventing said loose desiccant material from entering said inlet
tube.
2. The pressure vessel as claimed in claim 1 wherein said housing
is an elongate cylindrical tube closed at each end by centrifugal
spinning.
3. The pressure vessel as claimed in claim 2 wherein said housing
is an aluminum alloy.
4. The pressure vessel as claimed in claim 1 wherein said baffle
screen is a thermoplastic.
5. The pressure vessel as claimed in claim 4 wherein said means
for fastening said baffle screen to said interior chamber of said
housing further comprises means for thermally conforming said baffle
screen to said interior chamber of said housing under action of
centrifugal force and conductive heat generated during spin closing
of said housing.
6. A method of making a pressure vessel comprising the steps of:
closing one end of an open ended cylindrical tube leaving an open
end;
drilling inlet and outlet openings into said closed end;
inserting and brazing an inlet tube to said inlet opening;
attaching a baffle member to an outlet tube;
fastening a baffle screen around an outer periphery of said baffle
member;
inserting said outlet tube, baffle member and baffle screen through
said open end of said cylindrical tube into said outlet opening;
brazing said outlet tube to said outlet opening;
fastening said baffle screen to the interior wall of said cylindrical
tube;
closing said remaining open end of said cylindrical tube by centrifugal
spinning creating an enclosed chamber divided into upper and lower
chambers by said baffle member and baffle screen;
inserting loose desiccant material through said inlet tube into
said upper chamber of said housing; and
attaching a removable inlet screen to said inlet opening.
7. A method of making a pressure vessel as claimed in claim 6 wherein
said step of fastening a baffle screen around said baffle member
further comprises fastening a baffle screen made of thermoplastic.
8. A method of making a pressure vessel as claimed in claim 7 wherein
said step of fastening said baffle screen to said cylindrical tube
further comprises fastening said baffle screen to said cylindrical
tube by fusing said baffle screen to said cylindrical tube by centrifugal
force and conductive heat generated from spin closing said remaining
open end of said cylindrical tube.
Description BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an accumulator or receiver dryer and
a method of making the same, for use in an automobile air conditioning
system. More particularly, the present invention relates to packaging
replaceable desiccant in an accumulator or receiver dryer.
2. Description of the Prior Art
In air conditioning systems, and particularly those for automotive
applications, the accumulator is typically located at the outlet
end of the evaporator. Its purpose is to filter out any particulates
in the refrigerant fluid and remove any moisture present in the
refrigerant vapor. A desiccant material is placed within the accumulator
housing specifically for the purpose of removing the unwanted moisture
from the refrigerant vapor.
During assembly of the accumulator, it is important to avoid saturating
the desiccant material. Handling the desiccant material during the
assembly process introduces the potential for saturation from exposure
to humidity of air in the assembly area. Therefore, handling should
be kept to a minimum.
A fully sealed unitary housing is a desirable feature of an accumulator.
A one-piece construction without joints that may leak is an objective
of accumulator assemblies. The simplicity of a unitary housing is
also an important feature, which reduces costs and improves reliability.
Such a unitary housing can be accomplished by spin welding closed
the accumulator housing as taught by U.S. Pat. No. 4675971 to
Masserang.
In known accumulator assemblies and methods of making same, the
desiccant material is added to the housing prior to welding and
leak testing the accumulator assembly. This known method introduces
the risk of saturating the desiccant, and results in a high scrap
rate and material cost for damage the desiccant bag incurs during
brazing and testing operations.
In addition, with known devices and methods of making these devices,
field repair and rework are not practical. Repairs consist of removing
the defective device and replacing the entire accumulator or receiver
unit.
There are accumulators for air-conditioning systems which sealingly
connect a separate desiccant container in the bottom of the accumulator
housing prior to permanently assembling the accumulator. The desiccant
remains serviceable through the bottom of the housing. This system
is disclosed in U.S. Pat. Nos. 4276756 and 4291548 to Livesay.
The Livesay references disclose an access opening in the bottom
of the housing that opens into the interior of a desiccant container.
A separate, empty desiccant container is placed inside the accumulator
housing. A U-shaped tube is placed inside the housing. The empty
desiccant container is received in the bight portion of the U-shaped
tube.
The desiccant container has an open lower end that communicates
with the opening in the bottom of the housing. An annular seal attachment
sealingly attaches the lower end of the desiccant container through
the open lower end thereof. A detachable closure cooperates with
the closure fitting to close the access opening in the housing.
The desiccant container is filled after the housing has been permanently
assembled by inverting the container and gravity feeding desiccant
material. U.S. Pat. No. 4291548 discloses a desiccant container
that is a foldable bag that can be inserted through the opening
in the bottom of the housing.
U.S. Pat. No. 4838040 to Freeman discloses a receiver dryer in
which the housing has a readily openable lid held in place by quick
disconnect clamps. The lid can be removed to allow a desiccant canister
to be inserted inside the housing. To ensure adequate sealing, the
housing has an annular O-ring. The separate lid has an overhang
that seals against the O-ring of the housing. Additionally, the
lid has an internally depending sleeve segment that is provided
with another O-ring. The two O-rings are necessary to completely
seal the housing against leakage. The lid is secured in place by
a quick disconnect clamping band.
Accumulators must maintain high standards during testing. Therefore,
a one-piece or unitary design is desired for the housing. The number
of access openings and weld joints should be kept to a minimum for
the housing to withstand the demanding impact, leak and burst test
requirements. A drawback associated with prior art arrangements
that provide access to the desiccant material is the need for a
separate access opening. Additional openings disrupt the integrity
of the accumulator or receiver dryer housing. Any opening in the
housing introduces the potential for leaks, so a minimum number
of openings is desirable.
A leak proof housing can be manufactured by spin welding a unitary
housing into a closed configuration. Therefore, the number of components
and attachments inside the accumulator housing should be kept to
a minimum to reduce the risk of components breaking loose during
the spin weld process. The accumulator disclosed in Livesay and
the receiver dryer disclosed in Freeman require several additional
components to accomplish accessibility to the desiccant material
making spin welding impractical. In addition, if the devices disclosed
by Livesay or Freeman cannot be closed by spin welding without defeating
their innovative design feature of a separate opening to provide
access to the desiccant.
In Livesay, not only is an additional opening required, but a separate
desiccant container to hold the desiccant material is necessary.
A sealing attachment between the container and the housing is necessary
to maintain the desiccant container's position within the housing,
and a closure member is necessary to prevent desiccant material
from escaping the container.
The receiver dryer disclosed by Freeman also requires significant
additional structure. A separate lid, two O-rings, a clamping band
and a separate desiccant container are all necessary additional
components for access to the desiccant material. Additionally, the
sealing attachment between the desiccant container and the casing
disclosed by Freeman must be extremely reliable to avoid desiccant
material from escaping the desiccant container and contaminating
the interior of the casing.
The location of the desiccant within the housing is an important
aspect of an accumulator design. Ideally, the desiccant is located
near the top of the housing. Locating the desiccant near the top
of the housing ensures all vapor components of the refrigerant pass
through the desiccant thereby improving the accumulator's performance.
In operation, the liquid refrigerant settles in the bottom of the
accumulator housing. Positioning the desiccant in the bottom of
the housing introduces the risk of saturating the desiccant material.
In addition, all of the vapor inside the accumulator housing is
not forced through the desiccant. The vapor that remains near the
top of the housing never reaches the desiccant material and may
contain unwanted moisture as a result. The Livesay references disclose
locating the desiccant in the bottom of the housing, which is not
desirable for optimum accumulator performance.
What is needed is an accumulator housing that can be accessed for
inserting or removing desiccant material, having a minimum of components
and without separate access openings that compromise the integrity
of the housing.
SUMMARY OF THE INVENTION
The present invention embodies a housing that can be brazed and
leak tested before the desiccant is added, eliminating the risk
of damaging desiccant bags during assembly. A loose desiccant material
is added directly to the housing of the present invention through
an existing inlet opening in the top of the accumulator housing.
The loose desiccant material can be added after the accumulator
is completely assembled and tested.
The potential for damage to the desiccant and the desiccant container
are completely eliminated. The integrity of the housing is not compromised
as no additional openings in the housing are required to access
the desiccant material. The desiccant material is ideally located
in the top portion of the housing.
The present invention employs a screen permanently mounted inside
the pressure vessel that supports the loose desiccant material.
Another screen, removably attached to the inlet opening, provides
access to the loose desiccant material housed within the pressure
vessel.
A method of making the present invention allows the accumulator
assembly to be leak tested before the desiccant is added. This reduces
scrap and allows repair of accumulator assemblies.
The method includes spin welding closed a cylindrical tube; attaching
an inlet tube to the closed end of the cylindrical tube; assembling
an outlet tube, baffle member, and baffle screen; inserting the
outlet tube assembly inside the cylindrical tube; attaching the
outlet tube to the closed end of the cylindrical tube; spin closing
the remaining open end of the cylindrical tube; adding loose desiccant
through the inlet tube; and inserting a removable screen to the
inlet opening.
In one embodiment, the baffle screen is made of a thermoplastic
material. The baffle screen is thermally bonded to the vessel's
housing by centrifugal force and heat generated during the spin
welding process.
The removable inlet screen facilitates field repair and rework
of the accumulator assembly. It is not necessary to replace the
entire accumulator assembly merely because the desiccant material
needs to be replaced. The inlet screen can be removed, the accumulator
can be emptied of old desiccant material, new material can be added
through the inlet opening, and the screen replaced.
It is an object of the present invention to add loose desiccant
material to the housing after assembly, brazing, and leak testing
of the housing.
It is another object of the present invention to provide access
to the desiccant material without jeopardizing the integrity of
the housing.
It is yet another object of the present invention to provide access
to the desiccant material without removing the housing from the
overall air-conditioning system, enabling field repair.
It is a further object of the present invention to position the
desiccant material in the top of the housing to ensure adequate
drying of refrigerant vapor.
These objects, features, and advantages of the present invention
will become readily apparent from the following detailed description
of the preferred embodiment when taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view shown in partial cross section of a prior
art accumulator;
FIG. 2 is a cross-sectional view taken along line II--II of FIG.
1;
FIG. 3 is a side view shown in partial cross section of an accumulator
of the present invention; and
FIG. 4 is a cross-sectional view taken along line IV--IV of FIG.
3 showing the detail of the baffle screen and inlet screen of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1 there is a schematic of a generally conventional
vehicular air-conditioning accumulator 100. The structure of the
prior art accumulator 100 includes a cylindrical tubular housing
110 that is closed at both ends. Typically, the housing 110 is closed
by a spin welding process being conventional in the art as taught,
for example, by U.S. Pat. No. 4675971 to Masserang, or mig welding
a center joint as known by one skilled in the art.
The prior art accumulator 100 includes an inlet opening 120 and
an outlet opening 140 in the top of the accumulator housing 110
providing access to the interior of the housing 110. An inlet tube
130 is brazed or welded to the inlet opening 120 of the accumulator
housing 110. An outlet tube 150 is included which receives additional
structure efore it is permanently affixed to the outlet opening
140 of the accumulator housing 110.
Typically, the outlet tube 150 has a U-shaped configuration. A
bight portion 155 of the outlet tube 150 is located in the lower
region of the accumulator housing 110. A first leg 151 of the outlet
tube 150 supports a baffle 160 or deflector plate, which is permanently
fixed to the outlet tube 150 by brazing or welding. A second leg
152 of the outlet tube 150 is shorter than its first leg 151 and
its end located underneath the baffle 160. The outlet tube assembly
is welded or brazed to the accumulator housing 110 at the outlet
opening 140 in the top of the accumulator housing 110.
A desiccant bag 170 or other container holding a desiccant material
180 is attached to the outlet tube 150 prior to the outlet tube
150 being permanently attached to the top of the accumulator housing
110. Usually the desiccant bag 170 is supported in the bight portion
155 of the outlet tube 150.
The baffle 160 is permanently affixed to the interior walls of
the accumulator housing 110. Usually, this is done by tack welding
the baffle 160 to the interior of the housing 110 at several locations
around the perimeter of the baffle 160 or by an interference fit
between tabs 161 on the outer periphery of the baffle 160 and the
interior walls of the accumulator housing 110.
It is critical for proper operation of the accumulator that the
desiccant bag 170 or container is not damaged while permanently
attaching the baffle 160 to the housing 110 yet it is a common
occurrence which cannot be detected until after the impact and burst
tests are completed. If a damaged desiccant bag is discovered, the
entire accumulator 100 is scrapped, which is costly.
The outlet tube 150 is permanently attached to the accumulator
housing 110. Typically it is brazed or welded. The brazing process
used to attach the baffle 160 and outlet tube 150 introduces significant
risks to the desiccant material 180. The desiccant 180 can be damaged
by the heat generated by the welding or brazing process.
The remaining open end of the accumulator 100 is closed. After
the accumulator 100 is fully assembled, the unit is tested. Any
failures at this stage usually result in irreparable damage to the
desiccant bag 170 and the entire unit 100 must be scrapped because
there is no way to access the interior of the accumulator housing
110.
Repair and rework are not options using this method of manufacture.
The structure of prior art accumulators 100 is not consistent with
accessing the desiccant material 180 without destroying the integrity
of the accumulator housing 110.
FIG. 3 is an accumulator 200 of the present invention that is similar
to prior art accumulators except for the elimination of a separate
desiccant bag 170 or container and the relocation of the desiccant
material within the accumulator. Like components of the prior art
accumulator of FIGS. 1 and 2 are labeled with the same reference
numerals increased to 200. The present invention allows a method
of manufacture that eliminates the need for a separate desiccant
bag 170 thereby eliminating the risk of damage thereto and costly
scrap of to the complete accumulator assembly. Additionally, the
accumulator 200 of the present invention allows access to the desiccant
material 280 without affecting the integrity of the accumulator
housing 210.
The majority of components of the accumulator 200 of the present
invention are the same as those of prior art accumulators 100. The
housing 210 is spun weld closed as in prior art accumulators 100.
The inlet tube 230 configuration is the same as prior art accumulators
100. The shape and positioning of the outlet tube 250 is also the
same as prior art accumulators. The baffle 260 shape and position
of the baffle 260 are also the same as in prior art accumulators
100.
The accumulator 200 of the present invention is modified from prior
art accumulators 100 by including a screen 290 positioned between
the periphery of the baffle 260 and the interior wall of the housing
210. While the shape, position and attachment of the baffle 260
to the outlet tube 250 is the same as prior art accumulators, the
present invention includes the baffle screen 290 that surrounds
the periphery of the baffle or deflector plate 260. The baffle screen
290 effectively separates the interior of the housing 210 into an
upper chamber 211 and a lower chamber 212. The baffle screen 290
supports loose desiccant material, and therefore must have pores
292 which are small enough to prevent any desiccant material 280
from escaping into the lower chamber 212 of the housing 210. The
pores 292 are large enough so as not to interfere with the flow
of refrigerant fluid into the lower chamber 212 of the housing 210.
The baffle screen 290 can be attached to the outer periphery of
the baffle 260 by any means sufficient to permanently affix the
baffle screen 290 to the baffle 260. Some of the methods will be
discussed in detail below. It is imperative that loose desiccant
material 280 not escape into the lower chamber 212 of the housing
210.
The baffle screen 290 must be attached to the inner wall of the
housing 210. The same method used to attach the baffle screen 290
to the baffle 260 could be employed to attach the baffle screen
2902 to the interior wall of the housing 210. The periphery of the
baffle screen 290 must be completely sealed against the interior
wall of the housing 210 as it is sealed to the periphery of the
baffle 260 to prevent any loose desiccant material 280 from escaping.
In one embodiment of the present invention, the baffle screen 290
is initially temporarily fastened to the interior of the housing
210 by an interference fit, or tack welding. The baffle screen 290
is permanently bonded to the interior of the housing by heat generated
during the welding process used to close the housing 210. The baffle
screen 290 can be made of a thermoplastic or a material containing
sintered thermoplastic pellets. Under centrifugal force and heat
generated during the welding process, the thermoplastic material
of the baffle screen 290 bonds to the interior of the housing 210.
The baffle screen 290 and baffle 260 combination divide the interior
of the housing 210 into the upper and lower chambers 211 and 212.
The baffle screen 290 effectively supports the loose desiccant material
280 and prevents it from escaping into the lower chamber 212 of
the housing 210. The baffle screen 290 neither prohibits nor interferes
with the flow of refrigerant from the upper chamber 211 into the
lower chamber 212 of the housing 210.
The inlet tube 230 is permanently affixed to the inlet opening
220 in the top of the accumulator housing 210 just as in prior art
accumulators 100. However, the present invention includes an inlet
screen 221 that covers the inner diameter of the inlet opening 220.
The purpose of the inlet screen 221 is the same as that of the baffle
screen 290 surrounding the baffle 260. The inlet screen 221 does
not prohibit free flow of refrigerant, yet the loose desiccant material
280 is prevented from escaping the interior of the accumulator housing.
The inlet screen 221 covering the inner diameter of the inlet opening
220 need not be permanently affixed, and it is in fact desirable
to maintain the removability of this screen 221 by mounting the
inlet screen 221 against a shoulder on the inlet tube or in any
convenient manner providing the inlet screen 221 is removable after
installing same in the inlet tube 230. The inlet screen 221 can
be removed for emptying and refilling the upper chamber 211 of the
housing, facilitating field repair and rework.
Finally, as mentioned above, loose desiccant material 280 is located
in the upper chamber 212 of the accumulator housing 210. The loose
desiccant material 280 is prevented from entering the lower chamber
212 of the accumulator housing 210 by the baffle 260 and the baffle
screen 290. Likewise, the inlet screen 221 prevents the loose desiccant
material 280 from escaping through the inlet opening 220. The accumulator
200 of the present invention includes introducing loose desiccant
material 280 through the inlet opening 220 of the accumulator 200.
Once the desiccant material 280 is added, the inlet screen 221 is
placed over the inner diameter of the inlet opening 220.
One advantage of the present invention is readily apparent. The
desiccant material 280 need not be added to the assembly until after
the accumulator 200 is completely assembled and pressure and leak
tested. This eliminates unnecessary handling of the desiccant material
280 and eliminates potential harm to the desiccant material 280
during the assembly and testing process. Additionally, the entire
accumulator assembly 200 minus the desiccant material 280 can
be leak, impulse and proof tested, repaired, reworked, and retested
before any desiccant material 280 is added. The ability to repair
and rework units saves scrapping a fully assembled unit lowering
manufacturing costs.
Another advantage is that the desiccant material 280 can be accessed
in the field. It is now possible to perform field repairs and maintenance
procedures that were not possible before. It is no longer necessary
to replace accumulators 200 that could not be repaired simply because
of inaccessibility to the desiccant material 280.
The following steps are included in the method of making an accumulator
200 of the present invention;
closing one end of the housing, such as by welding as taught in
U.S. Pat. No. 4675971 or another welding process known by one
of ordinary skill in the art;
drilling inlet and outlet openings in the closed end of the housing
to the same size as the outer diameter of the inlet and outlet tubes;
inserting the inlet tube into the inlet opening and brazing the
tube to the top end wall of the housing;
axially inserting the baffle over a leg of the outlet tube and
fastening the baffle thereto;
temporarily fastening the baffle screen around the outer periphery
of the baffle by a mechanical fastener;
inserting the outlet tube, baffle, and baffle screen through the
open end of the accumulator housing;
brazing the outlet tube to the housing;
fastening, by brazing or otherwise, the baffle to the interior
wall of the housing;
temporarily fastening the baffle screen to the interior wall of
the housing by means of mechanical fasteners;
closing the remaining open end of the accumulator housing, by spin
welding to generate enough heat to thermally and centrifugally bond
the baffle screen to both the baffle and the interior wall of the
housing;
introducing loose desiccant material through the inlet tube into
the upper chamber of the outlet housing; and
removably fastening an inlet screen within the inner diameter of
the inlet tube over the inlet opening of the accumulator housing.
While the preferred embodiment of the present invention is to thermally
bond the baffle screen to the interior of the housing, any alternative
method of attachment may also be employed to obtain the same results,
such as welding or adhesive bonding.
Although a particular embodiment of the present invention has been
illustrated in the accompanying drawings and described in the foregoing
detailed description, it is to be understood that the present invention
is not to be limited to just the embodiments disclosed. For example,
the baffle screen could be adhesively bonded to the baffle and interior
wall of the accumulator housing and the remaining end of the housing
closed by means other than spin welding. Another example involves
relying on the permanent bond between the interior wall of the housing,
the baffle screen and the baffle to maintain the baffle's position
within the accumulator housing and eliminating the step of fastening
the baffle to the outlet tube. Numerous rearrangements, modifications
and substitutions are possible, without departing from the scope
of the claims hereafter. |