Foam may be technically defined as a physical mixture of a compressible fluid and an incompressible fluid in such a manner that bubbles are formed. The degree of mixing and work put into the system determines the size and dispersion of bubbles. A lather is a specific form of foam with uniformly small bubbles that is recognized for its penetration and cleaning ability on soiled surfaces. Lathering generally requires considerable mechanical working of a foamable material. For example, a bar of soap or liquid soap can be mixed with water in the hands and worked for 10 seconds or so to produce an effective lather.
Alternatives to manually working bar and liquid soaps may become popular because of the convenience offered in reducing the time and energy required to generate a lather. Aerosol foam generators, for example, mix a propellant with a foamable liquid to produce a rich foam. However, aerosols are increasingly unpopular because of their cost and negative environmental impact.
Another, more cost effective, alternative to generating and dispensing a foam is to use hand held squeeze bottle dispensers. Inexpensive squeeze bottle foam dispensers have been developed by a number of individuals. Squeeze-bottle foamers, such as those described in Boehm et al. U.S. Pat. No. 3,422,993, Wright U.S. Pat. Nos. 3,937,364, 4,018,364, and 4,531,659, use hand squeezing force and a deformable squeeze bottle to mix air with a foamable liquid inside the bottle and then force the mixture through a porous homogenizer to generate small bubbles.
Unfortunately, currently existing squeeze bottle foam dispensers have several drawbacks. The most troubling drawback involves inconsistency in the foam's characteristics. One reason for foam inconsistency is that some individuals squeeze the foam dispensers with a great deal of force which results in a high squeeze rate and high bottle pressure while others squeeze more gingerly resulting in a relatively low squeeze rate and bottle pressure. This variation in the squeeze rate and the pressure developed within the bottle results in variation in the consistency and overall quality of the foam dispensed. As a result a poor runny foam is frequently produced rather than the desired lather.
Additionally, there are several drawbacks which are a direct result of the storage and operation of current squeeze bottle foam dispensers in an upright orientation. The upright orientation necessitates spouts which extend horizontally or downwardly because foam is normally dispensed into an upward-facing palm. These spouts have a certain length. Often a considerable amount of foam remains throughout the length of the spout after dispensing and condenses in time. This condensate either drips out of the spout as a liquid or forms a residue which gradually plugs up the spout. Other problems which result from the upright operating and storage orientation include the inability to dispense a foam if the bottle is tilted such that the diptube is no longer submerged, and the difficulty in dispensing any foamable liquid located below the diptube as the bottle becomes empty.