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Description  |
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BACKGROUND OF THE INVENTION
This invention relates to compositions useful for cleaning electrical
contact surfaces. More particularly, the invention is directed to methods
and compositions for maximizing electrical contact between contacting
metal surfaces, particularly between the battery contacts in electrical
devices such as portable lights, calculators, mechanized toys and games
and the like.
It is well known that the exposed surfaces of most metals tend to attract
oxygen atoms, leading to the formation of metal oxides on the exposed
surface. It also is known that the spontaneous growth of such an oxide
film on an exposed metal surface can force its way between two contacting
surfaces, particularly when contact pressure between the two metals is
light, such as between disposable batteries and their spring mount
electrical contacts. Because metal oxides are poor conductors
(non-conductors or, at best, semi-conductors), an interfering oxide film
between electrical contact surfaces can reduce the area over which good
electrical contact can be made, progressively degrading and eventually
precluding electrical conduction.
It is an object of this invention to provide a composition and method for
cleaning metal contact surfaces so as to effectively establish and
maintain maximal electrical contact between electrically conducting
surfaces, and to protect these surfaces from subsequent oxidation. It is
another object of this invention to provide an inexpensive, reuseable
device for applying the composition of the invention to terminals of
disposable batteries and for carrying out a preferred embodiment of the
method of this invention.
These and other objects and features of the invention will be apparent from
the description, drawings, and claims which follow.
SUMMARY OF THE INVENTION
The invention provides a composition comprising a mixture or solution of a
volatile metal cleaning agent and an oxidation occluding agent. The
composition is useful for restoring and preserving maximal electrical
contact between two metal surfaces when applied to one or both surfaces.
The composition is applied to the metal surface preferably simultaneously
with or after the surface has been abraded. The action of abrading the
metal contact surface serves to dissociate metal oxides and/or other
contaminants from the metal surface. The volatile cleaning agent displaces
the abraded material from the metal surface, and the oxidation occluding
agent forms a protective coating over the cleaned metal surface,
substantially inhibiting reoxidation of the exposed metal. The composition
of the invention allows electrical contacts to be cleaned quickly, easily
and safely, and without the need for granular abrasives.
Metal cleaning agents which can be used in the present composition include
any volatile solvents which are compatible with the oxidation occluding
agent of choice. Volatile organic solvents such as hydrocarbon solvents
are preferred for this purpose. Hydrocarbon solvents which are
particularly preferred include one or more terpene solvents, such as for
example, limonene.
Oxidation occluding agents which can be used include those compatible with
the desired cleaning agent, and which are capable of forming a protective
coating on the metal contact surface. Currently preferred occluding agents
include waxes which may be made up of one or more different wax
components. For example, useful waxes include synthetic waxes; ester-type
waxes such as carnauba wax and candelilla wax; hydrocarbon waxes such as
beeswax, and natural or synthetic paraffins.
The composition may further contain additives, including fragrances and/or
coloring agents. For example, coloring agents capable of coloring the
treated electrical contact surfaces may be added, thereby allowing the
user to identify the metal surface as treated.
By varying the components of the composition and their concentrations, the
composition may be a waxy solid, paste, or liquid. When the composition is
a solid or paste, it can be applied to the metal contact surface with a
cloth or other material. The cloth preferably has a rough or abrasive
surface so that when it is used to apply the composition, it
simultaneously abrades, cleans and coats the surface. If the composition
is liquid, it is first absorbed into a porous or wicking material which is
capable of absorbing the liquid and retaining it therein, and which
preferably acts as an abrasive. The metal surface then is rubbed with the
impregnated material to abrade the metal surface and to simultaneously
apply the absorbed liquid composition to the surface, thereby abrading,
cleaning and protecting the contact surface in a single step. It will be
apparent to those skilled in the art that the metal contact surface also
can be abraded by rubbing the surface with a sufficiently stiff abrasive
material prior to the application of the composition of this invention.
In a particularly preferred embodiment of the invention, the composition is
applied to a battery terminal and/or its mating contact in a
battery-powered light, calculator, electronic camera or the like, by means
of a specially designed applicator device. The device comprises a housing
defining a reservoir for holding the composition of the invention in
liquid form, a wick which is in communication with the reservoir and is
itself rubbing surface protruding from the housing, and a removable cap
means which interfits with the housing, surrounds the wick and rubbing
surface, and serves to prevent evaporation of the volatile cleaning agent
from the wick. Preferably, this cap is adapted to fit over the wick and
the reservoir. The cap also may be adapted to interfit with a hole in the
end of the housing opposite the wick to prevent misplacement when the
device is in use.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other objects of this invention, the various features
thereof, as well as the invention itself, may be more fully understood
from the following description, when read together with the accompanying
drawings, in which:
FIG. 1 is a longitudinal cross section of a preferred embodiment of the
applicator of the invention, and
FIG. 2 is a perspective view of the applicator of the invention ready for
use.
Like-referenced characters in the respective drawn figures indicate
corresponding parts.
DETAILED DESCRIPTION OF THE INVENTION
The composition of the present invention cleans electrical contact surfaces
and protects the surfaces from oxidation thereby maintaining maximal
electrical contact. The composition comprises a volatile cleaning agent
capable of removing from the metal surface metal oxides and other
contaminants which have been dissociated from the metal contact surface by
abrasion, and an oxidation occluding agent capable of forming a protective
coating over the contact surface, thereby inhibiting reoxidation and the
build-up of insulative oxides on the cleaned metal surface.
The volatile cleaning agent can be any agent which is compatible with the
oxidation occluding agent and which has a sufficiently low vapor pressure
that the solvent evaporates shortly after application. Preferably, the
cleaning agent also serves as a vehicle for application of the oxidation
occluding agent and is mutually miscible with the occluding agent.
Volatile organic solvents such as hydrocarbon solvents are useful as
cleaning agents. Particularly preferred hydrocarbon solvents include one
or more terpene solvents. A mixture of solvents having different
evaporation rates may be used to adjust the rapidity with which the
solvent evaporates from the composition during its application.
Terpenes are organic materials which are found in nature in the essential
oils of many plants. Terpenes have carbon skeletons made up of isoprene
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units joined together in a regular, head-to-tail configuration. Terpene
compounds include, for example, limonene, citronellol, T-terpinene,
isoborneol, camphene and squalene. Terpenes can be monocyclic (e.g.,
dipentene), dicyclic (e.g., pinene) or acyclic (e.g., myrcene). Terpenes
which are particularly useful include limonene and mixtures including
limonene. Limonene (C.sub.10 H.sub.16) occurs naturally in oils found in
lemons, caraway and oranges, for example. Terpene solvents are
biodegradable and non-toxic.
The oxidation occluding agent can be any agent that is compatible with the
cleaning solvent, and which can be applied readily to a contact surface by
rubbing. It should be adherent to metal surfaces, capable of forming a
coating on the metal surface and relatively nonvolatile. The coating
formed by the occluding agent should be a substantially continuous coating
or film on the metal surface capable of protecting the exposed metal
surface from atmospheric oxygen and contaminants without interfering with
electrical conduction. It need not itself be an electrical conductor.
Waxes, oils and mixtures thereof are particularly useful as oxidation
occluding agents for use in the composition of this invention. The
occluding agent may contain one or more waxes and/or oils depending on the
desired form of the composition, and on the type of cleaning solvent used.
Useful waxes include hydrocarbon waxes such as beeswax and paraffins
(natural or synthetic); ester-type waxes such as carnauba and candelilla
waxes; and synthetic waxes such as polyethylene waxes. Useful oils
include, for example, mineral oil and drying oils such as tung oil and
linseed oil.
A formula for a composition made in accordance with the principles of the
present invention and establishing the range of the constituents is as
follows (all percentages are by weight unless otherwise indicated):
______________________________________
volatile cleaning agent
20-99%
oxidation occluding agent
1.0-80%
______________________________________
The composition preferably comprises from about 10% to about 50% occluding
agent, with the balance being comprised of the volatile cleaning agent.
It will be readily understood that the above formula may be varied
appreciably, depending, for example on the nature of the components used,
and on the desired form of the final product. For example, in one
embodiment of the invention, the composition may be formulated as a paste.
Here, the preferred amounts of oxidation occluding agent to cleaning agent
is about 67% occluding agent to about 33% cleaning agent. The paste may be
prepared, for example, by blending the occluding agent (e.g., a wax or
mixture of oils and waxes) in the cleaning agent solvent at a temperature
above the melting point of the wax and below the boiling point of the
solvent. Upon cooling, the wax precipitates from the solution and forms a
matrix of amorphous crystal-like structures which entrap the solvent. A
small amount of the paste then may be applied to a battery contact
terminal surface and/or the mating battery terminals of an electrical
device with a cloth or other flexible material. The action of rubbing the
paste on the metal surface with the cloth releases the solvent from the
wax matrix, allowing it to clean the metal surface. The rubbing or
abrading action serves to distribute the wax over the contact surface in a
thin continuous coating.
Where a fluid composition is desired, a smaller ratio of occluding agent to
solvent is suggested (e.g., about 25% occluding agent to about 75%
cleaning agent). Optionally, a combination of occluding agents can be
used, preferably a combination comprising one or more waxes and oils. For
example, an oil to enhance fluidity and reduce viscosity may be used in
combination with a "soft" wax to provide a durable coating. Mineral oil is
preferred for this purpose. Preferred component ratios for liquid
formulations are about 33% occluding agent about to 67% cleaning agent,
however, higher amounts of occluding agent can be used as long as the
composition is still wickable. A fluid composition may be formed
essentially in the same way as a paste composition, by, for example,
combining the occluding agent with the solvent at an elevated temperature,
preferably stirring the solution as it cools to maintain a single phase
solution.
In addition to the two essential components, the composition may contain
various additives, including fragrances and/or coloring agents capable of
staining or coloring-treating metal surfaces.
The composition of this invention is used in a method for enhancing and
maintaining electrical contact between two or more contact surfaces,
typically battery terminals and their mating contacts in a battery-powered
device. The method is carried out by abrading one or more of the surfaces,
preferably by rubbing the surface with a cloth or other fibrous material
of sufficient stiffness to dislocate any metal oxides, dust and grit
associated with the contact surface. The surface then is cleaned and
protected by applying and rubbing the composition of this invention on the
abraded surface. As indicated earlier, the steps of abrading the metal and
applying the composition may be, and preferably are, performed as a single
step. The treated contact surface then is placed in contact with its
reciprocal contact surface. Cleaning and coating the exposed contact
surface serves both to establish a good electrical connection and to
reduce substantially the opportunity for subsequent metal oxide formation,
thereby maximizing and helping to maintain electrical contact between the
surfaces.
In another aspect, the invention is embodied as an applicator device 5
shown in the drawing. The device may be better understood by referring to
FIG. 1, wherein a generally cylindrical, hollow housing 8, easily
hand-held, defines a wicking reservoir 10 which contains the composition
of this invention 11 in liquid form. Housing 8 defines a hole 9 in its
base and a sealing surface 7 adapted to interfit with a cap 14. The
reservoir 10 further contains a porous wicking material 12 capable of
absorbing and retaining the composition among its porous interstices. The
wicking material 12 comprises a material of sufficient stiffness such
that, when rubbed against a metal contact surface, it is capable of
abrading the surface sufficiently to dislocate any associated metal
oxides. Wick 12 may be fabricated from synthetic and/or natural felts,
intertangled cellulosic fibers, and similar known wicking materials. Wick
12 preferably is made of polyester felt. The housing and other parts
preferably are molded plastic such as, for example, high density
polyethylene. Wick 12 protrudes from the housing 8 and terminates at a
rubbing surface 13, here defined by a flat, bevel cut end of wick 12. The
applicator further comprises a removable cap 14 capable of substantially
preventing evaporation of the volatile solvent when interfitted with the
housing about the protruding wick 12 at sealing surface 7. In a
particularly preferred embodiment of the device, the removable cap is
adapted to be held in the hole 9 in the base of the housing 8 when not in
use. The method of the invention may be practiced conveniently by removing
cap 14, manually rubbing the contact to be treated with rubbing surface
13, and then replacing the cap until the next use.
EQUIVALENTS
The invention may be embodied in other specific forms without departing
from the spirit or essential characteristics thereof. The present
embodiments are therefore to be considered in all respects as illustrative
and not restrictive, the scope of the invention being indicated by the
appended claims rather than by the foregoing description, and all changes
which come within the meaning and range of equivalency of the claims are
therefore intended to be embraced therein.
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