Aspirator liquid blending device using multiple restrictors

An improved aspirator device for the accurate blending of an additive liquid such as a liquid concentrate with a pressurized stream of a main liquid such as water. The improvement involves the use of a metering means composed of at least two plastic injection molded restrictors in serial communication. Each restrictor has, as its smallest diameter fluid passage, a hollow bore of from about 0.005 inches to 0.010 inches in diameter and from about 0.005 inches to 0.010 inches in length wherein the dimensions of each hollow bore are such to provide a volume:volume dilution ratio of the additive liquid to the main liquid of from about 1:500 to 1:2,500.

TECHNICAL FIELD 
This invention relates to an improved aspirator device for accurately 
blending small quantities of a first liquid with a second liquid using a 
metering device to control the flow of the first liquid that comprises at 
least two molded plastic liquid flow restrictors. 
BACKGROUND ART 
Aspirator devices which rely on the venturi effect to create a vacuum and 
draw a first liquid into a second pressurized liquid flowing past an 
orifice are well known in the art. For example, Published PCT Patent 
Application No. WO 91/16138 to Horvath et al. teaches a precision-ratioed 
fluid-mixing device and system that uses an aspirator device to meter a 
quantity of a liquid concentrate such as a cleaner liquid disinfectant 
into a pressurized stream of water from a household water plumbing line to 
obtain a ready-to-use aqueous cleaning or disinfecting solution. Horvath 
et al. use a combination of two orificed metering elements which together 
limit the flow of the concentrate into the pressurized stream of water. 
One such metering orifice is located in the aspirator itself (cylindrical 
orifice 230 of nominal diameter 0.080 inches) and the other is a removable 
metering element located in the diptube extending into the container 
holding the liquid concentrate. Horvath et al. teach that the nominal 
diameter of the orificed inlet 188 in the removable metering element could 
range between 0.006 inches to 0.071 inches. 
A commercial system of the type described in the Horvath et al. patent 
application has been sold since 1991 under the brand name of SOLUTIONS 
CENTER.TM. by the S. C. Johnson Professional Products Division of S. C. 
Johnson & Son, Inc. of Racine, Wis. The SOLUTIONS CENTER.TM. system also 
uses a combination of two metering elements, but one metering element of 
either about 0.048 inches or 0.103 inches in diameter is molded into the 
top of an apertured plug pressed into the neck of the plastic concentrate 
container. A removable metering element located in the diptube extends 
into the container from the apertured plug and is serially connected to 
the other metering element in the plug. The removable metering element 
used depends upon the product to be dispensed and thus the dilution ratio 
desired. The orifices in the removable metering elements range from 0.005 
inches to 0.045 inches in diameter. The apertured plug is connected to a 
tube leading to the venturi in the aspirator device so that the contents 
of the liquid concentrate container are drawn into the flowing stream of 
water when a valve is opened by pressing a button to start the flow of 
water through the aspirator. Since the concentrate container (additive 
liquid) has both metering orifices, the user simply attaches a concentrate 
container to the system and does not have to select a metering orifice to 
obtain a properly diluted solution. 
Another example of commonly known aspirator device is a garden hose-end 
sprayer which is used to apply lawn fertilizers and insecticides. One 
example of such a device is shown in U.S. Pat. No. 4,068,681 to McNair et 
al. McNair et al. teach a hose-end sprayer that has a reservoir container 
that is filled with a dry dissolvable solid lawn chemical. The reservoir 
container is attached to the device and automatically fills with water 
when water flows through the hose. A diptube in the container is connected 
to an aspirator that has an upper orifice and a closed opposite end 
containing a series of small orifices. The device also has a water bypass 
line which permits water to be forced into the reservoir container that is 
filled with the solid chemical. During filling of the reservoir container, 
the pressure of the water coming through the aspirator forces water 
backwards through the diptube into the reservoir container and out through 
the small orifices located in the bottom of the diptube. The result is a 
series of high velocity water streams that agitate the dry chemical in the 
bottom of the container and assist in dissolving the chemical in the water 
being admitted. 
The improvement described by McNair et al. relates to a valve system 
located in the upper part of the reservoir container. Once the container 
is filled with water, the valve closes to stop the escape of air from the 
container through the valve. A small amount of water is forced into an 
opening that then reverses the flow of water through the diptube. A small 
amount of the dissolved chemical is drawn through the small orifices in 
the bottom of the diptube and up through the diptube to a metering orifice 
into the main water stream by way of the venturi effect. The metering 
function appears to be handled by the orifice near the aspirator rather 
than by the small orifices at the opposite bottom end of the diptube. 
Further metering can also be accomplished by another metering jet. 
U.S. Pat. No. 4,058,296 to Wetherby teaches the use of check valves in the 
bottom of the diptube in an aspirator device to prevent backflow of the 
pressurized liquid into a liquid concentrate into the liquid concentrate 
container. Column 1, lines 18-43 cites as prior art a certain mixing 
apparatus that uses a bypass conduit arrangement in combination with, 
among other things, a series of conduit restrictions. No reference is 
given to any specific patent that might describe such a system. Such 
references may be to U.S. Pat. Nos. 3,104,823 and 3,181,797 to Hayes that 
describe aspirator devices for blending liquids which use restrictors in 
the form of bushings. The restrictors are said to provide a pressure drop 
in the conduit system that is divided into two separate paths comprising a 
main conduit and a bypass conduit. These bushings or restrictors are used 
to divide up the flow of the diluted concentrate provided by the aspirator 
devices. 
For reasons of economy and efficiency, it is becoming more and more 
desirable to use dilution systems that use highly concentrated liquids 
that require high dilution ratios such as from about 1:500 to 1:2,500 
parts by volume of the concentrate liquid to the main liquid such as 
water. Accurate dilutions are important to avoid the waste of concentrate 
that inevitably occurs when the liquid concentrate is manually measured 
out into a quantity of main liquid such as water. Use of too much 
concentrate can also have detrimental effects such by leaving unwanted 
residues of the active ingredients on surfaces being treated. For example, 
a volume dilution ratio of 1:256 requires the careful measurement of 0.5 
ounces of concentrate and dissolving that concentrate in 1 gallon of 
water. To achieve a volume dilution ratio of 1:512, 0.25 ounces of 
concentrate must be added to a gallon of water. If only a quart of diluted 
liquid is desired, then the quantity of concentrate to be measured is very 
small indeed. This is simply not convenient for a maintenance user and 
waste of the concentrate is almost inevitable. 
An even more important consideration is when a sanitizer or disinfectant 
liquid is being prepared. Accurate dilution of the concentrate is critical 
to obtain a solution which will have the required disinfecting properties. 
If the solution is too dilute, then bacteria will not be adequately 
removed by the solution. That can create problems in a hospital or other 
institutional setting where proper removal of bacteria is important. Since 
inaccurate dilutions can create problems, conscientious maintenance 
personnel tend to use too much concentrate which results in waste of the 
concentrate. 
Molded plastic components that are often made by injection molding are 
often used in aspirator devices of the above type for reasons of economy 
and simplicity of manufacture. High dilution ratio devices require the use 
of restrictors containing very small orifices. There is a limit as to the 
diameter and length ("land") of an orifice that can be injection molded 
because the pin used to form the orifice can be warped or broken as 
plastic is injected at high pressure if the diameter of pin is too small 
for its length to handle the pressure. Generally, orifices of smaller than 
about 0.005 inches in diameter with land lengths longer than the diameter 
cannot be injection molded from plastic. The land length is important to 
the dilution ratio of liquid concentrate to main liquid. The viscosity of 
the liquid concentrate affects its flow through the orifice in the 
restrictor. Generally, a longer land length is needed for higher liquid 
dilution ratios, but this is not technically feasible for a single 
restrictor because of molding technology limitations. A practical dilution 
ratio limit for a single restrictor is about 1:750. 
Use of additional operations such as laser drilling to create the desired 
orifice in a plastic restrictor is often not effective because the heat of 
the laser melts the plastic and makes creates an undesirable variability 
in the diameter and land length of the plastic restrictor. Drilling with 
fine drills is so labor intensive and time consuming that it is typically 
not economical to commercially make restrictors by such a method. 
Thus, there is still a need for an improved aspirator device for blending 
two liquids that can accurately provide volume dilution ratios of a liquid 
concentrate to a main liquid such as water of from about 1:500 to 1:2,500. 
SUMMARY DISCLOSURE OF THE INVENTION 
One object of the present invention is to provide an improved aspirator 
device for accurately blending, by way of the venturi effect, an additive 
liquid such as a liquid concentrate with a pressurized main liquid at a 
volume dilution ratio of from about 1:500 to 1:2,500. Another object is to 
provide such a device where the metering means used to achieve such 
dilutions is readily manufactured from plastic materials using 
conventional molding procedures, preferably injection molding procedures. 
Yet another object of the present invention is to provide an improved 
aspirator device where the metering means is fully contained within a 
liquid concentrate container so that the desired dilution ratios are 
achieved simply by attaching the concentrate container to the aspirator 
device without further measurement or intervention needed by the user. It 
is a further object of the present invention to provide a metering means 
composed of two or more plastic injection molded restrictors in serial 
communication having readily injection moldable orifices with a diameter 
and land length that operate together to provide accurate high dilution 
ratios. 
These and other objects of the present invention are provided by an 
aspirator device for accurately blending a pressurized main liquid passing 
through an aspirator with a metered quantity of an additive liquid 
contained within a reservoir wherein passage of main liquid through the 
aspirator causes the additive liquid to be drawn into the main liquid by 
way of venturi action from the reservoir through a metering means, the 
improvement characterized by the metering means comprising at least two 
molded plastic liquid flow restrictors that are in serial flow 
communication with the additive liquid, each such restrictor having as its 
smallest diameter fluid passage a hollow bore of from about 0.005 inches 
to 0.010 inches in diameter and up to about 0.010 inches in length wherein 
the length does not substantially exceed the diameter and the amount of 
main fluid flowing through the aspirator and the dimensions of each hollow 
bore are such as to provide a volume:volume dilution ratio of the additive 
liquid to the main liquid of from about 1:500 to 1:2,500.

BEST MODE OF CARRYING OUT THE INVENTION 
In the drawings, like features are referred to by like reference numerals. 
Referring to the drawings, FIG. 1 is a simplified cross-sectional view of 
aspirator device 10 which comprises a conventional aspirator 12 composed 
of tube 14 having entry chamber 20 and exit chamber 28 with channel 18 
positioned between chambers 20 and 28 where channel 18 has a smaller 
diameter than chambers 20 and 28. A pressurized liquid such as water from 
a water main enters entry chamber 20 by means of a rubber or plastic hose 
21 or other conduit that is affixed to chamber 20 in a conventional manner 
such as by a threaded pipe connection, friction fitting, solvent bonding 
or a clamping arrangement. A conventional shutoff valve (not shown) is 
used to start and stop the flow of pressurized liquid through aspirator 
12. 
The pressurized water flows in the direction of arrow 22 and increases in 
velocity as it passes through narrower channel 18 containing additive tube 
24. As a result of the venturi effect, the movement of the water passing 
over tube 24 creates a vacuum in passage 16 of tube 24 which draws 
additive liquid 26--which may be a liquid concentrate--through passage 16 
in the direction of arrow 25. Additive liquid 26 is drawn into channel 18 
where it mixes with the water passing through channel 18 into exit chamber 
28 to form an accurately diluted water solution of additive liquid 26. 
That solution flows out of aspirator 12 in the direction of arrow 29 
through a rubber or plastic exit hose 27 or other conduit for use. 
To reach channel 18, additive liquid 26 flows through a series of passages 
through neck 32 of reservoir container 34 which stores additive liquid 26. 
Tube 24 is connected to diptube 30 that contains three restrictors 36, 
36', 36" with flanges 38, 38' (see FIG. 2) that have a slightly larger 
diameter than the inside diameter of passage 40 in diptube 30. Tube 14 may 
be conventionally attached to neck 32 by means of a screw cap, plug or 
other connection means. FIG. 1 shows cap 31 which is fixed over neck 32 in 
a sealing fashion such as by means of screw threads (not shown). 
More preferably, a conventional check valve 15 is connected to tube 24 
between tube 24 and diptube 30, as shown, or alternatively mounted as part 
of diptube 30 (not shown), which permits additive liquid to flow in the 
direction of arrow 25. However, check valve 15 prevents pressurized liquid 
in chamber 18 from traveling opposite the direction of arrow 25 back into 
container 34 which would dilute additive liquid 26 and result in a 
solution with an incorrect volume dilution ratio. As shown, check valve 15 
is mounted on cap 31 and tube 17 serves to provide a connection between 
check valve 15 and diptube 30. Diptube 30 is made of a flexible plastic 
such as polyethylene or polypropylene so that flange 38 forms a seal 
between the outer edge 42 of flanges 38 and wall 35 of passage 40 in 
diptube 30. Container 34 may be made of a plastic such as polyethylene, 
polypropylene or other suitable plastics. 
Neck 32 of container 34 is sealed by means of a plastic friction fit plug 
33 which permits check valve 15 and tube 17 to be joined together in a 
sealing fashion. Cap 31 can be removed so that a new container 34 of 
additive liquid 26 can be substituted when the additive liquid from a 
previously attached container 34 is depleted or if a different additive 
liquid is to be dispensed from aspirator device 10. 
Thus, additive liquid 26 is drawn into chamber 18 through passage 16, check 
valve 15, passage 19, and passage 40 as well as through orifices 44, 44', 
44" of restrictors 36, 36', 36". Restrictors 36, 36', 36" serve to meter 
the flow of additive liquid 26 from reservoir container 34 through screen 
46 on screen holder 48 affixed to end 41 located at the bottom of diptube 
30. Holder 48 contains bottom openings 50 which permit additive liquid 26 
to pass into the bottom of holder 48 through screen 46 into passage 40 and 
ultimately into channel 18. A screen is preferred to prevent small 
crystals or other materials from plugging fine orifices 44, 44', 44". The 
size of the screen opening may have an effect on the volume dilution 
ratios obtained by restricting the flow of additive liquid 26. This should 
be taken into consideration when making the improved aspirator device of 
the present invention. 
Outside air passes through vent 53 in cap 31 into open space 54 between cap 
31 and plug 33 and finally through vent 52 in plug 33 into container 34. 
Air is admitted to container 34 as additive liquid 26 is drawn into the 
main liquid stream in chamber 18. This prevents the formation of a vacuum 
in container 34 that could affect the dilution ratios obtained by reducing 
the flow of additive liquid 26 into the main liquid. 
The Horvath et al. precision-ratioed fluid-mixing device and system noted 
above gives an example of an aspirator device to which the present 
invention could be applied. The Horvath et al. PCT Patent Application 
derives priority from U.S. Ser. No. 07/513,401 filed on Apr. 23, 1990 now 
abandoned which is hereby incorporated by reference to teach an aspirator 
device and system which would be improved by the use of the present 
invention. 
FIG. 2 is a cross-sectional view of restrictor 36--restrictors 36' and 36" 
have the same configuration where reference numerals with an apostrophe 
("'") correspond to the same reference numerals in FIG. 2. FIG. 2 better 
shows the internal details of restrictor 36 that include hollow 
cylindrical bore or orifice 44 having diameter D1 and land L1, longer 
cylindrical bore or passage 37 having diameter D2 and land L2, and shorter 
cylindrical bore or passage 39 having diameter D3 and land L3. To achieve 
the objectives of the present invention, a small diameter orifice is used 
wherein D1 is from about 0.005 inches to 0.010 inches in diameter. A 
typical tolerance on small restrictor orifice diameters is .+-.0.0002 
inches. To injection mold such a small diameter orifice, the length of the 
land formed by a corresponding pin in the mold is typically no greater 
than the diameter of the bore or orifice. Thus, the length of L1 is no 
more than about 0.010 inches, but does not exceed the length of D1 due to 
molding considerations relating to the use of the small diameter pins 
needed to form such an orifice. 
Orifice 44 is formed by using a mold pin with portions that together form 
orifice 44, angled passage 43 and longer passage 37. A separate mold pin 
is used to form shorter passage 39. These two mold pins come together and 
meet when the mold is closed to form restrictor 36. Wall 45 preferably has 
a 45.degree. angle relative to the central long axis of orifice 44 to 
obtain optimum molding of orifice 44. The diameters D2 and D3 of passages 
37 and 39 are preferably significantly larger than the diameter D1 of 
orifice 44 so that orifice 44 acts to control the liquid flow rate and 
thus, the dilution ratio of additive liquid 26 to the main liquid passing 
through channel 18. For convenience, D2 and D3 typically have the same 
diameter. Typically, L2 and L3 are longer than L1 and L2 is longer than 
L3. The values of L2 and L3 can also affect the dilution ratio obtained 
depending upon the viscosity of the additive liquid. 
The orientation of the restrictor 36 in diptube 30 can affect the dilution 
ratios obtained. To obtain more accurate dilution ratios, each restrictor 
36 should be inserted into passage 40 of tube 30 such that longer passage 
37 faces toward end 41 of tube 30. 
Although restrictors 36, 36' and 36" may be placed anywhere along passages 
16, 19 or 40, more accurate dilution ratios are obtained, especially when 
higher dilution ratios are desired, when each restrictor 36 used is in 
close proximity to the other restrictors as shown in FIG. 1. "Close 
proximity" means that each restrictor 36 is positioned so as to be nearly 
touching the next restrictor 36. Once a steady state flow of main liquid 
stream has been established, the placement of each restrictor 36 will not 
have a significant effect on the dilution ratio. However, when small 
amounts of solution are desired, the placement of each restrictor 36 in 
close proximity to the next one tends to reduce any viscosity effects on 
the start of the flow of additive liquid 26 into the main liquid stream 
and thus provides a more accurately diluted solution of additive liquid 
26. 
Restrictor 36 can be made from any plastic material which can be molded, 
particularly by injection molding, such as polyethylene, polypropylene or 
polysulfone. Polypropylene is presently preferred because of its solvent 
resistance to common cleaning and maintenance chemicals. 
The dimensions of tube 14 and channel 18 are selected in conjunction with 
the size of orifice 44 and the number of restrictors 36 to be used to 
obtain the desired volume dilution ratio, also taking into consideration 
the passage diameters and land lengths of present in each restrictor 36. 
It is also contemplated that the orifice 44 used in one restrictor need 
not have the same diameter and land length as the orifice 44 used in the 
second orifice. That provides more flexibility in obtaining the desired 
volume dilution ratio of additive liquid to main liquid. If desired, three 
or more restrictors could be used to achieve the desired volume dilution 
ratio as will be shown in the following Examples. 
Likewise, an orifice, such as one having a nominal diameter of 0.080 inches 
could be placed in plug 33 to which diptube 30 is attached. Such an 
orifice could also be in the aspirator 12 itself at the point where tube 
14 meets chamber 18 (the latter in the manner shown in the Horvath et al. 
patent application noted above). In any event, there must be at least two 
restrictors of the type described herein present in the aspirator device 
of the present invention. In that case, the orifice in the plug or 
aspirator combines with the orifices present in the restrictors to achieve 
the desired volume dilution ratio. 
INDUSTRIAL APPLICABILITY 
The improved aspirator device of the present invention is particularly 
useful in conjunction with the accurate delivery of diluted solutions made 
from highly concentrated liquids. Such solutions can be used as 
disinfectants, hard surface cleaners for floors, windows and the like, 
degreasers, mildewcide, fungicide and insecticide solutions, floor 
polishes, and the like. 
EXAMPLES 1-3 
These Examples show the ability of the restrictors of the present invention 
to achieve accurate volume dilution ratios when used in a commercial S.C. 
Johnson Professional SOLUTIONS CENTER.TM. aspirator blending system. In 
these Examples, the aspirator used the SOLUTIONS CENTER.TM. system was 
part no. 10034004 commercially obtained from Hydro Systems Company of 
Cincinnati, Ohio which was connected to a standard utility water supply 
line. The water pressure reaching the aspirator was adjusted by a 
regulator to be 40 pounds per square inch gauge with a flow rate through 
the aspirator of 3.6 gallons per minute. A flexible tube containing a 
check valve was connected by way of a conventional screw cap to a 
reservoir container of the type sold by S. C. Johnson Professional for use 
with the SOLUTIONS CENTER.TM.. That container had a plastic plug in the 
neck of the container which contained an orifice of 0.043 inches in 
diameter. The plastic diptube connected to the plug had the same 
appearance as shown in FIG. 1 although a different number of restrictors 
as indicated in each Example. The additive liquid used was J-512 
Sanitizer, a sanitizer product concentrate commercially available from S. 
C. Johnson Professional Division of S. C. Johnson & Son, Inc. 
In these Examples, one, two or three restrictors of the type shown in FIG. 
2 were used where the nominal value of D1 was 0.006 inches and the nominal 
value of L1 was 0.040 inches, and the remaining passages in the restrictor 
had nominal values of D2=0.050 inches, D3=0.050 inches, L2=0.245 inches, 
and L3=0.100 inches. 
The results of the testing are shown in Table I. Each Example was composed 
of three Runs (A, B and C). The volume dilution ratio of the solution 
obtained from each Run was measured by taking a five gallon sample of 
solution from the aspirator device and determining the volume dilution 
ratio by weight difference based on the amount of water and additive 
liquid used. The calculated volume dilution ratios obtained are reported 
in Table I. 
Example 1 is a comparative Example that uses one restrictor of the type 
described above. Examples 2 (using two of the same size of restrictors) 
and 3 (using three of the same size of restrictors) show the ability of 
two or three, respectively, restrictors to achieve much higher volume 
dilution ratios with reasonably good accuracy without the need to use a 
single restrictor with a much smaller orifice. 
TABLE I 
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Example Run A Run B Run C 
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1 1:1299 1:1288 1:1346 
2 1:1918 1:1882 1:1882 
3 1:2504 1:2478 1:2469 
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Other modifications and variations of the improved aspirator device of the 
present invention will become apparent to those of ordinary skill in the 
art from the examination of the above specification and drawings. Thus, 
other variations of the improved aspirator device of the present invention 
may be made which fall within the scope of the appended claims, even 
though such variations were not specifically discussed above.