A FOAM-GENERATING DEVICE FOR A
The present invention resides in a foam generating and dispensing device and, more par-ticularly, to a foam generating device for a manu-ally operated atomizing dispenser having the capacity to spray a foamable liquid as a foam.
,Foam generating and dispensing devices are wll known in the art. The demand for these devices has heretofore been satisfied almost exclusively by the disposable, self-contained aerosol dispensers, due to their convenience and adaptability to a wide variety of products and ,15 foaming conditions. However, the continued use of such self-contained aerosol dispensers is presently being re-evaluated, due in part to recently espoused environmental concerns over the effects of some of the chemical propellants used therein and in part to changing economic conditions. Accordingly, workers in the art have embarked upon a search for ,an acceptable replacement for the aerosol foam dispensers.
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-2-Generally, those replacement deviceswhich have been proposed are of the type which include a collapsible bottle and a foam-forming cap assembly. The foam-forming cap assembly typically includes a homogenizing element of sponge-like material providing minute tortuous passages in which a flow of foamable liquid and air from the container is mixed to provide foam.
Exemplary devices of this type are described in US Patent No. 3,985,271; US Patent No. 3,973,701;
US Patent No. 3,937,364; and US Patent No. 3,572,590.
In such devices, the mixture of air and liquid loses considerable velocity as it passes through the homo-genizing element. Consequently, such devices unde-sirably have only limited "reach", i.e., theyrequire the use to dispense the foam in near proximity to the surface upon which the foam will be deposited.
Furthermore, because the user must apply his efforts to expel both liquid and air simultaneously, appreci-able energy is wasted in forming and dispensing ; the foam. Still further, such devices are unecono-mical inasmuch as they require that the bottle be -~ only partially filled with a foamable liquid so that the necessary internal air supply is avail-able for foam formation.
Consequently, attempts have been made to convert a conventional manually-operated atomizing dispenser (or "pump sprayer" as they are often called) to a foam-forming device, thereby ~0 overcoming some of the disadvantages of the "col-lapsible bottle" foamers. Specifically, it has been appreciated that (a) a pump sprayer is highly efficient, i.e., the user's efforts are directed ' .
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V~8 to expelling only liquid, thereby minimizing the labor involved in its operation, and (b) it has considerable "reach", i.e., the liquid can be pro-jected over a considerable distance. Nevertheless, it is believed that foam-generating pump sprayers have heretofore not met with success. For what-ever reason, it would appear that pump sprayers (which have replaced the aerosol dispenser in numerous other applications) have not been made adaptable to the generation and dispensation of a foam of commercially acceptable quality.
Accordingly, it is an object of the pre-sent invention to provide a foam generating and dispensing device for a hand-held, manually operated dispenser which requires only minimal effort to operate which has considerable reach, which can spray a foam of commercially acceptable quality, and which can be economically produced by con-ventional fabrication techniques. It is also an object of this invention to provide a pump sprayer or manually operated atomizing dispenser having the capacity to spray a foamable liquid as a foam.
The present invention provides a foam generating device for a hand-held, foam-spraying apparatus comprising a manually operated dispen-sing pump, including an atomizing nozzle, for drawing a foamable liquid from a container and ejecting it as a spray into the atmosphere through the atomizing nozzle, said foam generating device being operatively associated with the dispensing pump for producing foam from the spray without substantially modifying the predetermined spray j ~, ..... , . . , ~ . .
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'7 pattern and comprising a screen retained in the path of the spray, and means for introducing air into the spray so that the spray is permitted to foam upon contact with the screen, said foam gen-erating device permitting substantially all thespray to pass therethrough without contact except by the screen.
The device generates foam on the surface of the screen using air external to the dispensing pump. Consequently, the user's labor is miminized since the amount of liquid expelled in the form of a foam is directly proportional to the effort con-tributed, there being no wasted energy due to the compression of air as in the "collapsible bottle"
; Additionally, minimal velocity is lost by the spray as it is converted to foam in the device since substantially all the spray passes through the foam generating device without con-tact except by the surface of the screen. Accord-ingly, the reach of the spraying apparatus utilizing the present foam generating device is considerably increased compared to the "collapsible bottle"
Furthermore, the foam generating device of the present invention provides a foam of com-mercially acceptable quality, i.e., it is relatively dry and stable and has little tendency to drip when deposited on a vertical surface. Consequently, the device is eminently suited for spray-foaming household cleaners and the like.
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Still further, the foam generator of the present invention is very economical to produce ; since, in some instances, it can be readily con-structed with only minimal modification for use on a pre-existing pump sprayer.
Fig. 1 is a side elevation view, showing the foam generating device in cross-section attached to a conventional manually operated foam-spraying apparatus.
Fig. 2 is a front elevation view of the foam generating device of Fig. 1.
~ ig. 3 is a cross-sectional side elevation view of another embodiment of a foam generating device.
Fig. 4 is a side elevation view, par-tially in cross-section, of another embodiment of a foam generating device attached to a conventional ^ hand-held dispensing pump.
Fig. 5 is a front elevation view of the foam generating device of Fig. 4.
`~ Referring to Figs. 1 and 2, a manually operated dispensing pump 10 is detachably con-nected by a conventional threaded coupling 11 to a container 12 for receiving a foamable liquid therein. It is not a requirement of this inven-~ tion that the dispensing pump be connected to - the container, though such is desirable to enhance l mobility. Generally, a conventional hand-held ..
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,; ~ ' ' . ' ~0 dispensing pump/containter combination, such as is currently marketed for household use, is pre-ferred. Regardless of the particular form chosen, it is understood that fluid communication will be provided between the dispensing pump and the foam-able liquid, e.g., through a dip tube 13 (shown in phantom), so that the dispensing pump is able to draw liquid from the container.
As used herein, the term "foamable liquid"
is meant to include any liquid having the capacity to form a foam when dispensed by the foam-spraying apparatus of the present invention. Generally, such liquids will exhibit the following properties:
surface tension in the range of 20 to 45 dyne/cm, preferably 25 to 35 dyne/cm; density in the range of 0.8 to 1.2 g/cc, preferably 0.98 to 1.05 g/cc;
and viscosity in the range of 0.9 to 1.7 centi-- stokes, preferably 1.1 to 1.4 centistokes.
The dispensing pump may generally be of any conventional construction, so long as it in-cludes an atomizing nozzle 14. The term "atomi-zing nozzle" as used herein is intended to be generic to a mechanism for providing a fine spray of liquid through a single or a plurality of orifices.
Such dispensing pumps are generally provided with a compression mechanism, e.g., a piston 15 and an actuator 16, to force the liquid from the container through the atomizing nozzle with sufficient velocity to form the spray. Suitable dispensing pumps will preferably provide a spray having a velocity in the range of 15 to 21 meters/sec. through an orifice having a diamenter in the the range of from 0.3 to ~ A .
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0.65 mm and a land length in the range of from 0.25 to 0.6 mm. Exemplary dispensing pumps which may be used in the present invention include the AFA 7510 sprayer manufactured by the AFA Corpo-ration and the Canyon CS sprayer manufactured by theCanyon Corporation.
The foam dispensing device of the pre-sent invention includes a bell-shaped housing 20 which is provided with a screen 21. The housing is operatively attached to the dispensing pump by a suitable mechanism such as a snap-fit mech-anism which consists of a peripheral projection 22 which extends from the atomizing nozzle and a complimentary annular groove 23 defined by the inner surface of the housing 20. The housing 20 functions to retain the screen 21 in the path of the spray at a predetermined distance d from the - atomizing nozzle, i.e., the distance from the point at which the spray is ejected from the dispensing pump into the atmosphere (which point will typically coincide with the location of the nozzle face 24).
~ In order to generate a high quality foam, dista@ce ; d will generally be in the range of from 0.8 to 4 mm, preferably in the range of from 2 to 3 mm.
Furthermore, the screen size will generally be in the range of from 60 to 200 mesh (U.S. Sieve Series), preferably in the range of from 100 to 180 mesh.
; Screens having a smaller mesh size than that indi- ~-cated will severely reduce spray velocity and cause ~0 excessive dribbling, whereas screens having a larger mesh size will permit spray to pass there-through without sufficient foaming. The screen can be made of any material which is inert to the .
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)7'~l3 ._ foamable liquid which will be dispensed. Because of their low cost and characteristically flat surface conformations, plastic screens, such as those made from polyethylene or polypropylene, are preferred. Furthermore, such plastic screens are eminently suited for sonic or electronic welding, thus providing a convenient method of attaching the screen to housing 20, should the housing be constructed of a similar plastic material. Other methods of attachment, such as by a suitable adhesive or press-fit mechanism, can also be used.
' The foam generating dèvice also includes means for introducing air into the spray so that the spray is permitted to foam upon contact with the screen. One method of accomplishing this is to construct housing 20 so that the diameter of the opening therein is larger than the diameter i of the spray pattern at the point which it inter-;~ 20 cepts the screen, whereby air is permitted to enter the foam generating device from the front.
This will be better understood by referring to Fig. 2, which shows the screen diameter s of the spray pattern as it intercepts the screen 21 (depicted by shading) and the diameter o of the opening of housing 20. Another method is exempli-fied by Fig. 3, wherein housing 20' defines pass-ageways 25 which permit air to flow into the spray through the wall of the foam-forming means.
Either of these methods, or a combination thereof, may be used. In either method, however, the foam generating device should be constructed so as to provide the proper amount of air for good foam , . . . .
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formation. Specifically, if too little air is avail-able, some of the spray will pass through the screen without foaming, thereby resulting in an undesirably wet foam being ejected from the foam-spraying appara-tus.
It is a requirement of the foam generating device of the present invention that substantially all the spray pass therethrough without contacting any surface except the surface of the screen.
Mechanical breakup of the spray, such as by im-pinging upon the walls of housing 20, should be minimized, since such will cause the reduction of spray velocity and result in undesirable dribbling from the foam-spraying apparatus.
It will be appreciated that the foam generating device of the present invention is cap-able of numerous embodiments. For example, it may be constructed so as to be detachable from the -dispensing pump, as exemplified by Figs. 1 to 3, or it may be permanently integrated with the dispens-ing pump, as exemplified by Figs 4 and 5. In Fig. 4, the foam generating device comprises an integral box-like member 30, which protrudes outwardly from a dispensing pump 10' adjacent to the atomizing nozzle. The box-like member includes a flap 31, retaining a screen 21, and defines suitable air passages 35 at a position rearward of the flap. -Flap 31 is connected to the box-like member by a hinge 32 so that the flap can be pivoted 270 from a foam generating position, wherein the screen is retained in the path of the spray, to a position where no foam is generated (shown in phantom).
Suitable locking pins 33 and 34 snap-fit into mating - ' ' ' . : ' :, ' , .' . . ,, . ' :, : , - . . . : . .
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recaptacles defined by the box-like member 30 and the upper surface of the dispensing pump 10', re-spectively, to enable the user to lock flap 31 in the desired operating position.
, 5 The type of dispensing pump to be used in the present foam-spraying apparatus is not crit-; ical. For example, the dispensing pump can be a finger-actuated, vertically-oriented mechanism as ` well as the hand-actuated, horizontally-oriented mech-; 10 anism like that shown in Figs. 1 and 4. Addition-, ally, the form of the screen can be varied within the scope of the functional requirements suggested earlier. For example, the screen may be arcuate in cross-section, e.g., protruding away from the atomizing nozzle, and the openings of the screen can be of any desired configuration, i.e., the ~- openings need not be s~uare.
Example In order to demonstrate the effective-~'~ 20 ness of the foam-forming apparatus of the present invention, experiments were performed by testing ~ two commercially available dispensing pumps, i.e., ';f1 the AFA 7510 sprayer and the Canyon CS sprayer, ;~ with and without the foam generating device de-picted in Figs. 1 and 2. The foam generating device included a 100 mesh (U.S. Sieve Series) nylon screen ' spaced a distance d of 3 to 4 mm from the atomi-zing nozzle and had an opening o of about 10 mm.
For comparison, an AFA 5910 sprayer was tested with and without an AFA 5912BA foaming attachment.
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- 1()90748 A foamable liquid cleaner having a sur-face tension of 31.2 dyne/cm, a density of 1.02 g/cc, and a viscosity of 1.37 centistokes was used in all tests.
The results of these experiments are shown in Table 1. It can be seen that the AFA
5912BA foaming attachment severely modified the predetermined spray pattern and rendered the dis-pensing pump relatively hard to operate.
In contrast, the foam generating device ;
of the present invention did not substantially modify the predetermined spray pattern nor did it substantially affect the amount of effort required ~-to operate the dispensing pump. In addition, the present foam generating device was able to produce a very good quality foam - much like that produced by a typical aerosol dispenser.
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