U.S. patent application number 11/128755 was filed with the patent office on 2005-12-08 for method and apparatus for cleaning containers.
Invention is credited to Bexten, Dan, Norby, Jerry.
Application Number | 20050268944 11/128755 |
Document ID | / |
Family ID | 34637054 |
Filed Date | 2005-12-08 |
United States Patent
Application |
20050268944 |
Kind Code |
A1 |
Bexten, Dan ; et
al. |
December 8, 2005 |
Method and apparatus for cleaning containers
Abstract
A machine for cleaning containers such as flat media carriers
has inside and outside arrays of nozzles arranged to spray a
cleaning solution onto containers supported on a spinning rotor in
a chamber. The cleaning solution, a mixture of water and a
detergent or surfactant, is prepared by drawing out surfactant from
a surfactant bulk storage vessel with a metering pump. The flow
rate of the water is measured by a flow meter and in combination
with the metering pump, a proper amount of surfactant is injected
into the water line to produce a mixture with a desired surfactant
concentration for removing contaminants. The mixture is injected
into the water line at a mixing control valve to ensure that the
water and surfactant are thoroughly mixed before being injected
into the media carrier.
Inventors: |
Bexten, Dan; (Kalispell,
MT) ; Norby, Jerry; (Kalispell, MT) |
Correspondence
Address: |
PERKINS COIE LLP/SEMITOOL
PO BOX 1208
SEATTLE
WA
98111-1208
US
|
Family ID: |
34637054 |
Appl. No.: |
11/128755 |
Filed: |
May 13, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11128755 |
May 13, 2005 |
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10043716 |
Jan 9, 2002 |
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6904920 |
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10043716 |
Jan 9, 2002 |
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09905030 |
Jul 12, 2001 |
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09905030 |
Jul 12, 2001 |
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09113440 |
Jul 10, 1998 |
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6432214 |
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09905030 |
Jul 12, 2001 |
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09658395 |
Sep 8, 2000 |
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6797076 |
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Current U.S.
Class: |
134/22.1 ;
134/33; 134/34 |
Current CPC
Class: |
B08B 3/02 20130101; H01L
21/67051 20130101; H01L 21/6704 20130101; B08B 9/093 20130101; B08B
9/0861 20130101 |
Class at
Publication: |
134/022.1 ;
134/033; 134/034 |
International
Class: |
B08B 009/00 |
Claims
What is claimed is:
1. A method for cleaning flat media carriers, comprising: spinning
the carriers about a spin axis; pumping surfactant out of a storage
vessel; mixing the surfactant with a predetermined amount of water
to obtain a mixture of surfactant and water; and spraying the
mixture of surfactant and water onto the carriers.
2. The method of claim 1 with the pumping performed via a flow
metering pump, further including setting a flow rate of the flow
metering pump to achieve a desired concentration of surfactant in
the mixture of surfactant and water.
3. The method of claim 1 with the mixing performed via a mixing
control valve.
4. The method of claim 3 further including measuring the amount of
water flowing into the mixing control valve.
5. The method of claim 3 further including adjusting the amount of
surfactant pumped out of the storage vessel based on the measured
amount of water flowing into the mixing control valve.
6. The method of claim 1 further including stopping the rotor and
then spinning the rotor in a reverse direction.
7. The method of claim 1 further including spraying the mixture of
surfactant and water in a radial inwardly direction from a first
outer spray manifold, and also spraying the mixture of surfactant
and water in a radial outwardly direction, from a second inner
spray manifold.
8. A method for removing contaminants from flat media carriers,
comprising: loading the carriers onto a rotor within a flat media
carrier cleaning machine; spinning the rotor; spraying a
water/surfactant mixture onto the carriers via an inlet line by:
injecting water into the inlet line; measuring the flow of water
entering the inlet line; pumping surfactant from a storage vessel
into the inlet line using a flow metering pump; mixing the
surfactant and water to obtain a surfactant/water mixture; and
setting flow rate of the flow metering pump to achieve a desired
concentration of surfactant for the surfactant/water mixture.
9. The method of claim 8 further comprising discontinuing pumping
surfactant; and rinsing the carriers by spraying the carriers only
with water.
10. The method of claim 9 further comprising discontinuing
injecting of water into the inlet line; and drying the carriers by
spraying the carriers with a dry gas.
11. The method of claim 10 wherein the dry gas comprises nitrogen
or air.
12. The method of claim 8 wherein the water comprises de-ionized
water.
13. The method of claim 8 further comprising spinning the rotor at
from 1-50 rpm while spraying the mixture toward the carriers.
14. The method of claim 8 further comprising adjusting flow rate of
surfactant being pumped into the inlet line by adjusting operation
of the metering pump.
15. The method of claim 8 wherein the surfactant and water are
injected into the inlet line via a mixing control valve.
16. A method for cleaning one or more containers, comprising:
spinning the rotor; supplying DI water to the mixer at a known flow
rate; pumping surfactant from a storage vessel to a mixer via a
flow metering pump; adjusting the amount of surfactant pumped out
of the storage vessel based on the flow rate of water flowing into
the mixer; mixing the surfactant with water at the mixer, to obtain
a mixture of surfactant and water; and spraying the mixture of
surfactant and water onto the containers.
Description
[0001] This Application is a Divisional of U.S. patent application
Ser. No. 10/043,716, filed Jan. 9, 2002, and now pending, which is
a Continuation of U.S. patent application Ser. No. 09/905,030,
filed Jul. 12, 2001, and now abandoned, which is a
Continuation-in-Part of:
[0002] U.S. patent application Ser. No. 09/113,440, filed Jul. 10,
1998, now U.S. Pat. No. 6,432,214; and U.S. patent application Ser.
No. 09/658,395, filed Sep. 8, 2000, now U.S. Pat. No.
6,797,076.
FIELD OF THE INVENTION
[0003] The field of the present invention relates to cleaning
apparatus for rinsing and drying containers and carriers used to
hold and process semiconductor wafers, substrates, flat panel
displays and other flat media.
BACKGROUND OF THE INVENTION
[0004] Flat media, such as silicon or other semiconductor wafers,
substrates, photomasks, flat panel displays, data disks, and
similar articles require extremely low contamination levels. Even
minute contaminants can cause defects. Accordingly, it is necessary
to maintain a high level of cleanliness during all or nearly all
stages of production of these types of flat media. The flat media
described may be referred to below as "wafers", although it will be
understood that "wafers" means any form of flat media.
[0005] Wafers are typically processed in batches. For example, in
manufacturing semiconductor chips, for use in computers,
telephones, televisions, and other electronic products, silicon
wafers will undergo many batch processing steps, such as oxidation,
photolithography, diffusion, chemical vapor deposition,
metallization and etching. Batch handling may occur throughout the
entire production process, or for one or more processing steps or
related handling operations. Batch processing of this type almost
always utilizes some type of carrier or container to hold the
wafers being processed.
[0006] A wafer carrier or container holds a group of wafers. The
wafer carriers can be of various designs, and may be more
specifically referred to as a wafer boat. In many applications,
they are made of a suitable polymeric material, e.g., polypropylene
or TEFLON.RTM. fluoropolymer. The sides and sometimes the bottom of
the wafer boat have receiving slots formed to receive and hold the
wafers in a spaced array with the faces of the wafers adjacent to
one another. Typically, the central axes of the wafers are aligned.
The wafers are slid into the carrier or container, such as from the
side or above, and are removed by sliding them outwardly. The
receiving slots are shallow so that the wafer is engaged only at
the peripheral edges and along a thin marginal band extending
inwardly from the periphery.
[0007] Wafer carriers can also be provided in the form of a
protective case or box in which the wafers are held and are sealed
against contamination during travel within the processing facility.
Wafer carriers of this type are frequently designed to hold a wafer
boat having a complementary design. The complementary relationship
of the protective wafer carrier box and the wafer carrier boat
allow the boat and supported wafers to be fully enclosed and
securely held in place during transport. The term "carrier"
referred to below means a carrier, a container, with or without a
lid, or a wafer boat.
[0008] At certain stages in the manufacturing process, the wafer
carriers must be cleaned. Cleaning them is difficult because they
typically have features which include slots, grooves or apertures,
and inside corners which can trap contaminants. The difficulty in
cleaning is enhanced by the extremely low contamination levels
which are required for processing the wafers.
[0009] Accordingly, cleaning of wafer carriers remains a difficult,
time consuming and relatively costly procedure. Sticky-back labels,
fingerprints, dust, metal particles, photoresist and organic
chemicals may also contaminate the wafer carriers.
[0010] Various machines have been made and used for cleaning wafer
carriers. In these machines, the carriers are mounted on a rotor
and spin within a chamber, while cleaning solutions are sprayed
onto the carriers. The spinning movement minimizes process time and
also helps in drying the carriers. In certain applications,
surfactant is introduced and mixed with de-ionized water, at a
concentration of approximately 1:10,000. Used in this way, a
surfactant acts as a wetting agent which helps to remove loosely
adhered particles. Typically the surfactant is used only once and
then discarded as waste.
[0011] The surfactant is typically held in a vessel from which it
must be transferred into the wafer carriers during the cleaning
process. Since the surfactant stream is applied in such small flow
volume so as to produce the desired small concentration level, it
is difficult to control volume flow of the surfactant into the
carriers. In one system as described in U.S. patent application
Ser. No. 09/113,440, surfactant is pumped from the bulk storage
vessel into a holding tank where it is diluted to a desired level.
The diluted surfactant solution is then drawn out of the holding
tank by a venturi into the water stream where it is mixed or
aspirated with the water. The water and surfactant mixture is then
directed to the rinsing manifold ready for injection into the wafer
carrier.
[0012] Accordingly, it is an object of the invention to provide an
improved machine for cleaning carriers and containers for flat
media.
SUMMARY OF THE INVENTION
[0013] Apparatus for cleaning flat media carriers includes a rotor
rotatably mounted within a chamber. Nozzles within the chamber are
arranged to spray a washing mixture of water and a detergent or
surfactant onto carriers supported on the rotor. The washing
mixture is prepared by drawing out surfactant directly from a
surfactant bulk storage vessel by means of a metering pump. The
flow rate of the water is measured by a flow meter and in
combination with the metering pump, a proper amount of surfactant
is injected into the water line to produce a mixture with a desired
surfactant concentration for removing contaminants.
[0014] In a second aspect of the invention, the surfactant solution
is injected into the water line at or upstream of an inline mixing
control valve to ensure that the water and surfactant are
thoroughly mixed before being injected into the wafer carrier.
[0015] In a third aspect of the invention, where the wafer carrier
is provided with multiple rinse manifolds for spraying the carrier,
a flow meter is provided in the water inlet line for each manifold
and a separate metering pump is provided for injecting surfactant
into each water line to ensure that a proper amount of surfactant
is injected into each water line to produce a mixture with a
desired surfactant concentration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Other objects and features will become apparent from the
following detailed description taken in connection with the
accompanying drawings. However, the drawings are provided for
purpose of illustration only, and are not intended as a definition
of the limits of the invention.
[0017] In the drawings, wherein the same reference numbers denote
the same elements throughout the several views:
[0018] FIG. 1 is a front, top and right side perspective view of
the present cleaning apparatus.
[0019] FIG. 2 is a back, top and left side perspective view
thereof.
[0020] FIG. 3 is a front, top and right side perspective view of
the apparatus shown in FIGS. 1 and 2, with the covers removed.
[0021] FIG. 4 is a back, top and left side view thereof.
[0022] FIG. 5 is a back, top and left side perspective view with
various components removed for purposes of illustration.
[0023] FIG. 6 is a front, top and right side perspective view of
certain major components of the apparatus shown in FIGS. 1-5.
[0024] FIG. 7 is a perspective view of the rotor removed from the
chamber.
[0025] FIG. 8 is a plan view thereof.
[0026] FIG. 9 is a section perspective view illustrating air
movement through the apparatus.
[0027] FIGS. 10, 10A, and 10B are a schematic diagram showing fluid
flow and interconnections in the present machine.
[0028] FIG. 11 is a left front side perspective view of a preferred
configuration for the pumping and control valve system of FIG.
10.
[0029] FIG. 12 is a rear right side perspective view of the
configuration of FIG. 11.
[0030] FIG. 13 is a schematically illustrated top view showing
orientations of spray manifolds and nozzles.
DETAILED DESCRIPTION OF THE DRAWINGS
[0031] Turning now in detail to the drawings, FIGS. 1 and 2
illustrate a carrier cleaning machine 10 having a frame 12 and
housing panels 14 forming an enclosure. A back door 16 and front
door 16A are provided on the front and back surfaces of the machine
10. The machine 10 is generally installed in a clean room, of the
type used in manufacturing semiconductors. An air filter enclosure
18 is located above the front door 16A, and contains a filter which
filters clean room air. An exhaust duct 26 extends out of the top
of the machine 10, at the back right corner, and is ordinarily
connected to a facility or building exhaust duct.
[0032] Referring to FIGS. 3, 6 and 9, a cylindrical chamber 24 is
supported within the frame 12. The chamber 24 has cylindrical side
walls 25 and is closed off on the top and bottom by a top plate 36
and a bottom plate 38. The top plate 36, has a central opening 37
so that air passing through the filter box 18 can flow into and
downwardly through the chamber 24. An exhaust plenum 50 at the
lower back and right side of the chamber 24 connects to the exhaust
duct 26, for moving air out of the chamber 24. A drain opening 39
at a low point of the chamber 24, in the exhaust plenum 50 drains
fluids out of the chamber.
[0033] Referring to FIGS. 5, 9 and 13, outer rinse manifolds 28
(R1-R4), each having e.g., 12 spray nozzles, are positioned around
the outside circumference of the chamber 24, on the chamber
cylindrical side walls 25. The outer rinse manifolds 28 may be
located on the outside of the cylindrical side walls 25, as shown
in FIGS. 4-6 and 10, or may be on the inside surface of the
cylindrical side walls 25, so long as the rinse spray nozzles 30 on
the outer rinse manifolds 28 are appropriately positioned to spray
the work pieces, i.e., the wafer carriers.
[0034] Inner rinse manifolds 29 are positioned near the center of
the chamber 24, with each inner rinse manifold (R5-R8) having a
plurality of rinse spray nozzles 30 oriented to spray outwardly
onto the work pieces (i.e., wafer carriers, containers or
lids).
[0035] Similarly, outer dry manifolds 64 (D5-D8), each having a
plurality of dry spray nozzles 66, are spaced apart around the
circumference of the chamber 24, on the chamber cylindrical side
walls 25. Inner dry manifolds 65 (D1-D4), each also having a
plurality of dry spray nozzles 66 are positioned near the center of
the chamber 24. A preferred orientation of the dry manifolds
(D1-D8) and the rinse manifolds (R1-R8) is shown in FIG. 13.
[0036] Referring momentarily to FIG. 10, the outer dry manifolds 64
are connected via a distribution manifold 61 and then by fluid
lines 63 to a supply 120 of pressurized gas such as air or nitrogen
via control valve 63a. Similarly, the inner dry manifolds 65 are
connected via a distribution manifold 68 and then by fluid lines 67
to a pressurized gas supply 130 via control valve 67a. The outer
rinse manifolds 28 are connected via a distribution manifold 141
then by fluid lines 140 to a control valve 170 and a source 110 of
de-ionized (DI) water. The inner rinse manifolds 29 are connected
via a distribution manifold 151 and then by fluid lines 150 to a
control valve 180 and the DI-water source 110. Pressurized gas
lines are also connected to the spray manifolds, for purging, via
the control valves 170, 180. A boost pump 46 increases the water
pressure of the DI-water from the external source 110 to the rinse
manifolds 28 and 29.
[0037] The control valves 170, 180 are preferably mixing control
valves which ensure that the surfactant is thoroughly mixed with
the DI-water.
[0038] Referring to FIGS. 3-6, and 10-12, a surfactant tank or
bottle 35 is connected to surfactant metering pumps 48 and 49 via a
fluid line 190. The surfactant metering pump 48 is connected to the
mixing control valve 170 via fluid lines 192. Pump 48 pumps
surfactant from the tank or bottle 35 into the control valve 170
where it is mixed with the DI water for injection into the outer
rinse manifolds 28 via fluid lines 140. The surfactant metering
pump 49 is connected to the control valve 180 via fluid lines 194.
Pump 49 pumps surfactant from the tank or bottle 35 into the
control mixing valve 180 where it is mixed with the DI water for
injection into the inner rinse manifolds 29 via fluid lines
150.
[0039] The drain opening 39 at the bottom of the chamber 24 leads
to a diverter 90 which connects the drain opening 39 to either a
reclaim tank 42 or to a facility waste drain 92.
[0040] On the surfactant side, a return line 142 from fluid line
192 proximate the mixing control valve 170 provides for priming of
surfactant (under the control of control valve 145) back to vessel
35; and a return line 152 from fluid line 194 proximate the mixing
control valve 180 provides for priming of surfactant (under the
control of control valve 155) back to vessel 35. On the DI-water
side, a recirculation line 147 from fluid line 115 proximate the
mixing control valve 170 provides for recirculation of DI-water;
and a recirculation line 157 from fluid line 117 proximate the
mixing control valve 180 provides for recirculation of DI-water.
The recirculation lines 147 and 157 provide a flow of water through
the tool even when the tool is idle to prevent bacteria formation
in lines and valves.
[0041] Referring momentarily to FIG. 9, air heaters 58 are provided
within an air inlet plenum 56 behind the air filter box 18 and over
the center or inlet opening 37 leading into the top of the chamber
24. Blanket heaters 55 are also provided around the top of the
chamber 24. A computer/controller 112 is linked to and controls the
various pumps, valves, heaters, and flow sensors.
[0042] Referring to FIGS. 6-9, a rotor 70 is rotatably supported
within the chamber 24 on a base 104. The rotor has a top ring 72
and a bottom ring 74 connected by a frame work 75. Ladders 76 are
pivotally supported on upper and lower ladder supports 82 extending
radially outwardly from the top ring 72 and the bottom ring 74.
Each ladder 76 has a plurality of compartments 78 for holding
containers or carriers 85, or container lids 87, as shown in FIG.
9. The configuration of the ladders 76 and the design of the
compartments 78 on the ladders 76 are adapted for the specific
sizes and types of carriers, containers, and lids to be cleaned.
The entire rotor 70 is rotatably supported on a center column 100
and a rotor axle 106 within the center column 100. A rotor drive
motor 102 spins the rotor 70. The detailed design features of the
rotor 70, center column 100 and rotor axle 106 are well known, and
are described in U.S. Pat. No. 5,224,503, incorporated herein by
reference. Alternately, the tool may be constructed with
non-rotating ladders.
[0043] In use, the machine 10 is typically installed in a silicon
wafer or other flat media manufacturing facility. As the wafers are
moved through various processing steps, the carriers 85 become
contaminated, and must be cleaned before wafers are replaced into
the carriers. The door 16 or 16A of the machine 10 is opened. The
rotor 70 is turned or indexed until a ladder 76 is aligned with the
door. The ladder 76 is then turned 180.degree. so that the empty
compartments 78 can be accessed through the door 16. The carriers
85 are loaded into the compartments 78 and the ladder is turned
back to its original position, so that the compartments 78 are
facing to the inside of the chamber 24. The ladders 76 are
preferably provided with a latch or detent to lock the ladders into
the closed or operating position, with the compartments 78 facing
the inside of the chamber 24. The next ladder 76 is then brought
into alignment with the door, for loading, by turning the rotor 70
(by hand or via control of the rotor drive motor 102). Loading
continues until all of the ladders 76 are filled.
[0044] A facilities panel 40 on the machine 10, as shown in FIG. 6,
has connections to input de-ionized water and gas, e.g., nitrogen
or air into the machine 10, and a connection for the waste drain
92, as well as gauges and valves for measuring and controlling
fluid/gas flow.
[0045] The surfactant tank 35 is supplied with a detergent or
surfactant, for example, Valtron DP 94001 (a high pH alkaline
detergent) a preferred surfactant for removing photoresist. The
term "surfactant" as used in this application means a surfactant or
a detergent. The controller 112, via appropriate control of valves
and pumps, delivers DI-water and surfactant into the mixing control
valves 170, 180 to make a desired DI-water/surfactant mixture for
injection into each of the rinse manifolds 28, 29. The DI-water
boost pump 46 boosts the water pressure in the supply line 114 to
deliver DI-water to both mixing control valve 170 and mixing
control valve 180. A flow meter 116 is disposed in the fluid line
upstream of the outer rinse mixing control valve 170 to measure the
flow of DI-water being supplied thereto. Similarly, a flow meter
118 is disposed in the fluid line upstream of the inner rinse
mixing control valve 180 to measure the flow of DI-water being
supplied thereto.
[0046] The system is initially calibrated by using information from
the flow meter 116 in combination with controls on the metering
pump 48 to set a reasonably precise surfactant concentration for
the DI-water/surfactant mixture for injection into the outer rinse
manifolds 28. Similarly, the system is calibrated by using
information from the flow meter 118 in combination controls on the
metering pump 49 to set a reasonably precise surfactant
concentration for the DI-water/surfactant mixture for injection
into the inner rinse manifolds 29. Preferably, the solution is
1:10000 surfactant, with the balance being DI-water, for each of
the manifolds, but having separate flow control/metering, the
surfactant concentration levels may be individually set.
[0047] The metering pumps 48, 49 are preferably a type of positive
displacement pump, such as a diaphragm pump. The flow rate of such
a diaphragm pump may be adjusted by adjusting the pump stroke
(which sets the pumping volume per stroke) and/or the pump speed
(strokes per minute). The pumps are preferably set at a relatively
high speed so that surfactant is delivered into the system at a
less pulsed/intermittent manner.
[0048] The system operator may adjust the surfactant/DI-water
concentration by adjusting the pump stroke (which sets the pumping
volume per stroke) and/or the pump speed (strokes per minute).
[0049] Though the system may be operated by having a preset pumping
rate for the metering pumps 48, 49 and surfactant/DI-water
concentration, an electronic control system may be implemented,
using inputs from flow meters 116, 118 and electronic control of
the pumping rates of the metering pumps.
[0050] A low-level sensor 35a may be provided on the surfactant
vessel 35 for alerting that the fluid level in the vessel is low
and needs replacement. The sensor 35a may either be a liquid sensor
inside the vessel, or capacitive sensor located outside the vessel,
or some other suitable device. The sensor may just determine when
the level has reached a particular (low) level, indicating time for
surfactant replacement, or certain types of sensors may provide a
signal corresponding to surfactant level. For example, the tray 35b
(see FIG. 11) in which the vessel 35 is inserted may comprise a
load cell supporting the surfactant vessel 35 to provide the weight
of the vessel 35 with the change in weight of the vessel as
determined by the load cell providing an indication of fluid
level.
[0051] The controller 112 controls the rotor drive motor 102,
causing the rotor 70 to spin in a first direction, at a low speed,
e.g., 1-50 rpm. Via control of the pumps 46, 48, 49 and valves 170,
180, the DI-water/surfactant solution is sprayed onto the carriers
85 on the spinning rotor.
[0052] After a sufficient duration e.g., 3-10 minutes, the rotor 70
reverses direction while the surfactant solution spraying
continues, for improved spray coverage. The inner rinse manifolds
29, located inside of the rotor 70, spray radially outwardly from
the center of the chamber 24. The outer rinse manifolds 28, located
around the chamber cylindrical side walls 25 spray radially
inwardly toward the chamber center. This dual spray action,
combined with bi-directional rotation of the rotor 70, provides
virtually complete coverage of all surfaces of the containers
85.
[0053] After completion of application of the surfactant solution,
the manifolds are purged by gas or nitrogen flowing through check
valves 143, 153 and the control valves 170, 180 as shown in FIG.
10.
[0054] During the surfactant wash cycle, the diverter valve 90 is
positioned to direct fluid to the facility waste drain 92.
Typically, as the machine 10 begins the rinse cycle, the diverter
90 remains in position to connect the drain opening 39 to the
facility waste drain 92. DI-water is sprayed onto the carriers 85
from all of the rinse manifolds (R1-R8), with the rotor 70 spinning
in a first direction, and then reversing and spinning in the
opposite direction, e.g., at from 1-50 rpm, preferably about 6 rpm.
The heaters 58 are then turned on, and the rotor accelerated up to
e.g., 300 rpm, so that water droplets on the containers 85 are
centrifugally flung off of the containers, and the containers are
dried. The blanket heaters 55 are located on the outside of the top
of the chamber 24 and are on continuously, for warming the top of
the chamber. The DI rinse water goes out the waste drain 92.
[0055] If desired, for example in a water circulation mode where
DI-water (without surfactant) is circulated through the chamber,
the diverter valve 90 may be switched to a closed position.
[0056] While the machine 10 is useful for cleaning various
contaminants, the specific cleaning parameters, such as duration of
surfactant, rinse water, and air/gas spray, rotation speeds and
sequences, heater operation, surfactant concentration, etc., may be
varied somewhat to achieve optimum results, with different
containers and contaminants, as would be apparent to one skilled in
the art from the descriptions herein.
[0057] Surfactants are generally not flammable or explosive, and do
not have the same environmental disadvantages associated with
solvents. On the other hand, surfactants can be very expensive,
e.g., $40/gallon. Using the metering pumps to produce a precise and
consistent concentration of surfactant for the DI-water/surfactant
mixture, the system conserves surfactant. The system may also use
the surfactant reclaimation techniques of U.S. Pat. No. 6,432,214
hereby incorporated by reference.
[0058] Thus, a novel cleaning machine and method has been shown and
described. Various changes can, of course, be made without
departing from the spirit and scope of the invention. The
invention, therefore, should not be restricted, except to the
following claims and their equivalents.
* * * * *