U.S. patent number 3,870,039 [Application Number 05/324,667] was granted by the patent office on 1975-03-11 for fractionated liquid jet.
This patent grant is currently assigned to Les Produits Associes. Invention is credited to Pierre Jean Jousson, Michel Antoine Cesar Moret.
United States Patent |
3,870,039 |
Moret , et al. |
March 11, 1975 |
Fractionated liquid jet
Abstract
A method and apparatus for fractionating liquid jets into a
plurality of unitary, discrete liquid droplets for successively
impacting a selected area, for example in the oral cavity, for
stimulating the gum tissues and for cleaning the teeth and
interdental spaces. Such a system for the practice of body care,
for example, oral hygiene, generally comprises a reservoir for the
liquid to be fractionated, a nozzle member for directing the
fractionated jet against the area to be stimulated and cleaned, a
pump for supplying the liquid under pressure from the reservoir to
the nozzle member, and a suitable conduit for transferring the
liquid from the reservoir to the pump and from the pump to the
nozzle member. In a first embodiment, means are provided for
producing vibrations and transferring the vibrations to the nozzle
member to cause the liquid jet to divide into a plurality of
unitary, discrete liquid droplets after exiting from the nozzle
member. The parameters for the production of such liquid droplets
are disclosed and include the ejection velocity of the jet, the
fluid flow velocity through the nozzle, the nozzle opening
diameter, the frequency of pulsation, the diameter of the formed
droplets, and the distance from the tip at which the liquid
droplets are completely formed and separated. The effect of the
rugosity of the nozzle, the surface tension of the fluid, and the
efficiency of the system are also disclosed. In a second
embodiment, the physical construction of the nozzle effectively
fractionates the jet and comprises an obturating member disposed in
the free end of the nozzle member which includes a plurality of
passages located therethrough. The cross-sectional area of each of
the passages is much smaller than the adjacent liquid conduit of
the nozzle member.
Inventors: |
Moret; Michel Antoine Cesar
(Geneva, CH), Jousson; Pierre Jean (Geneva,
CH) |
Assignee: |
Les Produits Associes (LPA SA,
Geneve, CH)
|
Family
ID: |
23264573 |
Appl.
No.: |
05/324,667 |
Filed: |
January 18, 1973 |
Current U.S.
Class: |
601/162;
601/161 |
Current CPC
Class: |
B05B
1/08 (20130101); A61C 17/028 (20130101) |
Current International
Class: |
A61C
17/00 (20060101); A61C 17/028 (20060101); B05B
1/08 (20060101); B05B 1/02 (20060101); A61h
009/00 () |
Field of
Search: |
;128/66,24A,62A |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Trapp; Lawrence W.
Attorney, Agent or Firm: Lane, Aitken, Dunner &
Ziems
Claims
What is claimed is:
1. An apparatus for body care comprising means for storing a
liquid, nozzle means for projecting the liquid at an ejection
velocity within a predetermined range to a selected area, said
nozzle means including a nozzle having an opening having a diameter
in the range of about 0.2 to about 1.1 mm, means for supplying the
liquid under pressure from said storing means to said nozzle means,
and means for fractionating the liquid at a frequency in the range
of about 200 to about 5,000 cps into a plurality of unitary,
discrete liquid droplets for successively impacting said selected
area with said plurality of unitary, discrete liquid droplets,
wherein said droplets are further characterized in that each of
said droplets successively percusses said selected area at an
impact rate substantially equal to the number of droplets produced
by said fractionating means per unit of time, said droplets having
a diameter when formed which is larger than the diameter of the
opening in the nozzle.
2. The apparatus as set forth in claim 1 wherein said nozzle means
projects said liquid at an ejection velocity in the range of about
2 to about 7 m/sec.
3. The apparatus as set forth in claim 1 wherein the number of
droplets produced by said nozzle means is equal to the
fractionating frequency.
4. The apparatus as set forth in claim 1 wherein said fractionating
means comprises means for transmitting said vibrations to said
liquid within said nozzle means whereby the liquid divides into
said plurality of unitary, discrete liquid droplets after exit from
said nozzle means.
5. The apparatus as defined in claim 1 wherein said fractionating
means for producing said unitary, discrete liquid droplets is
included in a portion of said nozzle means.
6. The apparatus as defined in claim 1 wherein said nozzle defines
a passage for the conduction of said liquid therethrough, one end
of said passage being connected to said supplying means for
receiving said liquid under pressure and further including means
disposed in said other end of said passage for fractionating said
liquid into a plurality of unitary, discrete liquid droplets.
7. The apparatus as defined in claim 6 wherein said fractionating
means includes an obturating member for fractionating said liquid
into said plurality of unitary, discrete liquid droplets, said
obturating member defining at least one passage therethrough, the
cross-sectional area of said passage in said obturating member
being small compared to the cross-sectional area of said passage in
said nozzle member.
8. The apparatus as set forth in claim 7 wherein the diameter of
said passage in said obturating member is on the order of about 0.2
to about 0.5 mm and the diameter of said passage in said nozzle
member is on the order of about 1.5 to about 2.0 mm.
9. The apparatus as defined in claim 8 wherein said obturating
member defines a plurality of passages therethrough, the
cross-sectional area of each of said passages being small compared
to the cross-sectional area of said passage in said nozzle
member.
10. The apparatus as set forth in claim 9 wherein the diameter of
each of said passages in said obturating member is on the order of
about 0.2 to about 0.5 mm and the diameter of said passage in said
nozzle member is on the order of about 1.5 to about 2.0 mm.
11. The apparatus as set forth in claim 1 wherein said droplets
ultimately assume an approximately spherical shape after exit from
said nozzle within a distance of about 3 to about 90 times the
nozzle opening diameter.
12. The apparatus as set forth in claim 11 wherein each of the
spherical droplets has substantially the same diameter.
13. The apparatus as set forth in claim 1 wherein said nozzle means
projects said liquid at an ejection velocity in the range of about
2 to about 7 m/s and having a practical minimum governed by the
formula:
v = 2.5f .phi..sub.j
where
v = velocity
f = frequency of vibration
.phi..sub.j = diameter of liquid jet
14. The apparatus as set forth in claim 1 wherein the velocity of
said liquid through said nozzle has a Reynolds number less than
about 2.500.
15. In a system for the practice of oral hygiene which is capable
of cleaning the teeth and interdental spaces and stimulating the
gum tissues of the type which comprises means for storing a liquid
to be projected into the oral cavity of the user; nozzle means,
including a nozzle having an opening having a diameter in the range
of about 0.2 to about 1.1 mm, for projecting said liquid at an
ejection velocity within a predetermined range into said oral
cavity; and means for providing said liquid under pressure from
said storing means to said nozzle means, the improvement
comrpising:
means for fractionating the projected liquid at a frequency in the
range of about 200 to about 5,000 cps into a plurality of unitary,
discrete liquid droplets for successively impacting a selected area
within said oral cavity with said plurality of unitary, discrete
liquid droplets, wherein said droplets are characterized as
substantially entirely composed of said fluid and substantially
free from voids within each of said droplets, and wherein said
droplets in said plurality of said droplets are further
characterized in that each of said droplets successively percusses
said selected area at an impact rate substantially equal to the
number of droplets produced by said fractionating means per unit of
time, said droplets having a diameter when formed which is larger
than the diameter of the opening in the nozzle.
16. The apparatus as set forth in claim 15 wherein said nozzle
means projects said liquid at an ejection velocity in the range of
about 2 to about 7 m/sec.
17. The apparatus as set forth in claim 15 wherein the number of
droplets produced by said nozzle means is equal to the
fractionating frequency.
18. A method for the practice of body hygiene comprising the steps
of:
providing a source of liquid under pressure to be projected at an
ejection velocity within a predetermined range from an opening in a
nozzle having a diameter in the range of about 0.2 to about 1.1 mm
against a selected area of the body of the user,
fractionating said liquid at a frequency in the range of about 200
to about 5,000 cps into a plurality of unitary, discrete liquid
droplets having a diameter when formed, which is larger than the
diameter of the opening in the nozzle, for successively impacting
said selected area with said plurality of unitary, discrete liquid
droplets, wherein said droplets are characterized as substantially
entirely composed of said fluid and substantially free from voids
within each of said droplets, and wherein said droplets in said
plurality of droplets are further characterized in that each of
said droplets successively percusses said selected area at an
impact rate substantially equal to the number of droplets produced
by the step of fractionating per unit of time, and
projecting the fractionated liquid against said selected area.
19. The method as defined in claim 18 wherein said body hygiene is
oral hygiene and said selected area is an area within the oral
cavity of the user.
20. The method as set forth in claim 18 wherein the step of
projecting is further defined as projecting the fractionated liquid
at an ejection velocity in the range of about 2 to about 7
m/sec.
21. The method as set forth in claim 18 wherein the step of
fractionating is further characterized in that the nuber of
droplets produced by said nozzle is equal to the fractionating
frequency.
22. The method as set forth in claim 18 wherein the step of
fractionating includes the steps of generating vibrations in said
frequency range and transmitting said vibrations to said liquid
within said nozzle means whereby the liquid divides into a
plurality of unitary, discrete liquid droplets after exit from said
nozzle.
23. The method as defined in claim 18 wherein the step of
fractionating is further defined by the step of causing said liquid
to flow from a passage having a first cross-section to a passage
having a second cross-section which is small compared to said first
cross-section.
24. The method as set forth in claim 18 wherein the step of
projecting includes the step of projecting said liquid by an
ejection velocity in the range of about 2 to about 7 m/s and having
a practical minimum governed by the formula:
v = 2.5f .phi..sub.j
where
v = velocity
f = frequency
.phi..sub.j = diameter of liquid jet
25. The method as set forth in claim 18 wherein the step of
fractionating includes the step of passing the liquid through an
opening having a Reynolds number less than about 2.500.
Description
CROSS-REFERENCE TO A RELATED APPLICATION
The subject matter of this application is related to the subject
matter disclosed and claimed in United States patent application
Ser. No. 227,640, filed Feb. 17, 1972, which is a continuation of
Ser. No. 887,586, filed Dec. 23, 1969, both now abandoned, both
assigned to the assignee of this application.
BACKGROUND OF THE INVENTION
This invention relates to a method and apparatus adapted to provide
body care and especially suited for oral hygiene. More
particularly, this invention relates to a method and apparatus for
fractionating liquid jets into a plurality of unitary, discrete,
liquid droplets for successively impacting a selected area, for
example, the oral cavity, to stimulate the gum tissues and to clean
the teeth and interdental spaces. Still more particularly, this
invention relates to the characteristics of such a method and
apparatus in terms of the theoretical and practical limits of the
precise parameters involved for the production of such liquid
droplets.
In the prior art, a number of methods and apparatuses for caring
for the body with a flow of fluid have been developed. Devices are
known for cleansing and massaging the external bodily surfaces of
both animals and humans, ranging from such simple fluid lavage
devices as the well-known showerhead and whirlpool baths to more
specialized fluid massage techniques and devices. For
particularized body care, specialized methods and devices have been
developed including, by way of example, vaginal and anal douching
apparatuses, and wound lavage devices. It is thus a broad aim of
this invention to provide a method and apparatus broadly directed
to body care by the use of a liquid jet which has been fractionated
into a plurality of unitary, discrete liquid droplets.
In the art of oral hygiene, it has long been a problem to find an
effective and sufficient solution to the problem of cleaning the
teeth and massaging the gum tissues while also cleaning interdental
spaces. Perhaps the best known solution rests in the conventional
manually operated toothbrush, a device which has proved highly
ineffective in cleaning the interdental spaces and massaging the
gums for a number of reasons, including the lack of vigor of the
user and the time involved to achieve even a partially effective
gum massage and interdental cleaning. Where additional apparatus
has been used for interdental cleaning and gum massaging, such as a
protrusion on the handle of the toothbrush, or toothpick-like
devices, the result has been similarly ineffective for the reasons
stated above, as well as because of the requirement that the
interdental cleaning and gum massage takes on the character of a
separate and distinct operation beyond that of merely brushing the
teeth. Accordingly, the prior art has proposed a number of
appliances for dental care which are intended for cleaning the
interdental spaces as well as massaging the gums of the users, but
also achieving an effective cleaning of the teeth. For example, the
British Pat. No. 382,430 and the corresponding U.S. Pat. No.
1,995,424 to K. E. L. Guinness, in particular, describe an
appliance especially aimed for use by dentists which comprises the
combination of a nozzle projecting a liquid onto the teeth and/or
gums of the patients, a reservoir for the liquid to be projected,
and a device for pumping the liquid intermittently from the
reservoir to the nozzle to form a jet of liquid which is pulsed at
a frequency of about 3,300 or 3,600 pulsations per minute.
An apparent improvement of this device has also been described in
U.S. Pat. No. 3,227,158 to J. W. Mattingly. This improvement
consists substantially of the limitation of the jet pulsation
frequency to values on the order of 1,200 to 1,600 pulsations per
minute to accommodate the relaxation time of the mucous membranes
of the gums which are subjected to the impact of the pulsating, but
continuous jet. The relaxation time is that time which is necessary
for the gum tissues to recover to their normal state after having
been locally compressed by the jet and was there considered to be
determined with a view toward optimizing the massaging effect on
the gum tissues.
Whereas these appliances have apparently effectively allowed
massaging the gums at a more or less efficacious manner, none of
them has, however, provided a radical solution of the problem,
faced by humans at least daily, of cleaning the teeth and the
interdental spaces of the mouth.
Thus, whereas a jet of liquid delivered by one or the other of the
above described appliances is of a pulsed nature and consequently
produces on the teeth surfaces to be cleaned a continuous jet of
liquid pulsed at a frequency corresponding to that of the
pulsations with which the jet is actuated, the disaggregation by
the jet of the deposits which may cover the surfaces occurs only
very slowly and in a generally unsatisfactory manner even when a
very large amount of liquid is projected onto those surfaces.
It has also been noted in this connection that when a liquid thread
segment, having a mass corresponding to that emitted by a nozzle
during the period of one pulsation of the jet, is projected onto a
surface covered with a deposit, the disaggregation of that deposit
does not practically occur except in the impact zone of the liquid
thread segment and then only at the instant when the impact occurs
since the mass of liquid which arrives thereafter on the deposit
simply flows over the deposit to erode only the peripheral parts of
the deposit. Thus, the phenomenon of the buffer zone largely
defeats the disaggregating impact of the later-arriving fluid. For
these purposes, the buffer zone can be defined as the damping
phenomenon on the impact surface caused by an incident liquid jet
as the result of the residual fluid film which remains present on
the impact surface.
Since the issuance of the patents previously mentioned, appliances
for effecting only a mechanical or pneumatic massage of the gums,
and toothbrushes with increasingly perfected action, have also been
proposed. For example, an electric toothbrush identified by the
trademark Broxodent includes an oscillatory motor which confers a
particular effectiveness to the brush, especially with regard to
cleaning the teeth, and to a lesser extent, the interdental spaces,
while somewhat massaging the gums.
Moreover, certain other devices have been proposed which represent
a compromise between the pulsed jet appliances previously described
and the toothbrushes having mechanically driven brushes. These
devices comprise a reservoir for liquid, a pump feeding a flexible
conduit from this reservoir, and a handle arranged at the free end
of the conduit for removably supporting either a nozzle or a small
vibrating brush, the latter being intended to palliate the problems
mentioned above. For example, the use of this device generally
requires a long and fastidious operation, especially if the device
in question is used in turn by various members of a family each
having his own nozzle and small brush. The user thus must remove
the brush or nozzle of another family member from the apparatus,
fit his nozzle thereon, clean his teeth by jet projection, remove
the nozzle, and replace it by his own brush to conclude the
cleaning, then rinse this brush and perhaps rinse the nozzle. In
addition to these practical drawbacks, this device has another
undesirable feature which is primarily economic, namely the wear of
the small brushes which have to be periodically replaced.
Accordingly, it is an object of this invention to provide a method
and apparatus for body care and especially for oral hygiene, which
obviates the problems of the prior art.
It is another object of this invention to provide a method and
apparatus for fractionating liquid jets into a plurality of
unitary, discrete liquid droplets for use in body care, and
especially for use in oral hygiene for stimulating the gum tissues
and for cleaning the teeth and interdental spaces.
It is a more specific object of this invention to provide, in one
embodiment thereof, means for imparting vibrations to a nozzle for
transmitting liquid from a reservoir under pressure thus to
fractionate the jet into a plurality of liquid masses.
It is an additional object of this invention, and another
embodiment thereof, to provide a nozzle structure which is capable
of producing a plurality of unitary, discrete liquid droplets
without requiring means for imparting a vibration to the
nozzle.
It is still another object of this invention to consider the effect
of various parameters such as the ejection velocity of the jet, the
velocity of fluid flow through the nozzle, the nozzle diameter, the
frequency of vibration, and the like, on the production of a
plurality of such droplets for successively impacting a selected
area to be massaged and/or cleaned.
It is an additional object of this invention to consider, in
addition to the parameters mentioned above, the effect of nozzle
rugosity, the effect of buffer zone damping, and the relative
efficiency of certain body care devices.
These and other objects of this invention will become apparent from
the written description of the invention which follows, taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE INVENTION
This invention, directed to overcoming the problems of the prior
art and to achieving the aforementioned objects, comprises a method
and apparatus for fractionating liquid jets into a plurality of
discrete, unitary liquid droplets which, when projected onto an
area of the body stimulate and clean that area. In particular, such
liquid droplets, when projected on the teeth and/or gums of the
user, stimulate the gum tissues and clean the teeth and interdental
spaces. Such a system for the practice of oral hygiene generally
comprises a reservoir for the liquid, such as water or water and a
suitable mouthwash, nozzle means for projecting a liquid to a
desired location in the mouth of the user, and means for supplying
the liquid under pressure from the reservoir to the nozzle member.
According to the invention, means are provided for fractionating
the liquid into a plurality of discrete unitary liquid droplets
which are substantially free from voids within each of the droplets
for successively impacting the area to be cleaned and/or
stimulated. In a first embodiment, means are provided for
generating a vibration and for transmitting the vibrations to a
nozzle means where the vibrations are imparted to the liquid
passing therethrough to cause the liquid to divide into a plurality
of discrete, unitary liquid droplets after exiting from the nozzle
means. The useful diameters of nozzle to produce such droplets are
included in a range between about 0.2 and about 1.1 mm, and
preferably between about 0.4 and 0.6 mm. The frequency of vibration
is generally greater than about 200 cps to assure a minimum
efficacy and less than about 5,000 cps to avoid cavitation in the
fluid so that the droplets are substantially free from voids within
each of the droplets. The diameter of the formed droplets is larger
than the diameter of the nozzle opening from which they are issued,
a factor which is opposite to that possessed by liquid droplets
from jets produced by ultrasonic vibrations in which the diameter
of the jet is smaller than the diameter of the opening. The
ejection velocity of the jet is at least about 2 m/s which provides
a certain efficacy and, at maximum, is about 7 m/s in the best
cases. The ejection velocity is generally limited by the turbulence
of the jet so that the ejection velocity is preferably in the range
between about 2 and about 5 m/s. The liquid droplets thus formed
according to the invention are entirely formed and separated when
they are at a distance from the tip of the opening of the nozzle
ranging from about 3 times to about 90 times the diameter of the
nozzle, and this distance appears to be proportional to the
ejection speed of the liquid. The droplets produced according to
the invention from a nozzle having a diameter of 0.2 mm for a
preferred frequency of 500 cps and an ejection velocity of 5 m/sec
have a surface pressure of 3.82 g/cm.sup.2 and a weight of 0.239 mg
(for water) for droplets having a diameter of 0.77 mm. Under the
same conditions of frequency and ejection velocity, droplets from a
nozzle having a diameter of 1.1 mm have a diameter of 2.6 mm, a
surface pressure of 1.13 g/cm.sup.2 and a weight of 9.2 mg. The
development of these parameters, both calculated and observed, is
discussed in greater detail hereinafter in this description of the
invention.
In a second embodiment, the construction of the nozzle member and
the nozzle means causes the jet to be fractionated. An obturating
member is disposed in the free end of the nozzle member and
includes a plurality of passages therethrough. Since the
cross-sectional area of each of the passages in the obturating
member is much smaller than the adjacent liquid conduit in the
nozzle member, an aberration of the streamline of the liquid is
established which causes the liquid to fractionate into unitary,
discrete liquid droplets after the liquid exits from the free end
of the nozzle member.
The effect of the damping on the later-arriving liquid by liquid
resting on the surface of impact is largely overcome by the
successive impacting of the fractionated liquid jet according to
the invention. The impact rate is substantially equal to the number
of droplets produced by the fractionating means per unit of
time.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 illustrates a first embodiment of a body care device
suitable for use for oral hygiene according to the present
invention;
FIG. 2 is a partial view of the nozzle tip which illustrates at a
highly magnified scale the manner by which the liquid jet is
fractionated into a plurality of unitary, discrete liquid droplets
at the outlet of the nozzle of the device;
FIG. 3 is a summary of the characteristics of the droplets and
parameters of the device for producing such droplets according to
the invention;
FIG. 4 is a table comparing a number of characteristics of the
droplets produced from 0.2 and 1.1 mm nozzle diameters, under
specific conditions of frequency and ejection velocity;
FIG. 5 shows a second embodiment of an appliance for body care
according to the invention;
FIG. 6 is a partial longitudinal sectional view, not in scale,
taken along line 6--6 of FIG. 5;
FIG. 7 is a sectional view taken along line 7--7 of FIG. 6;
FIG. 8 shows a detailed sectional view of the nozzle shown in FIG.
6 which illustrates the manner by which the liquid jet is
fractionated at the outlet of the nozzle or according to the second
embodiment;
FIG. 9 illustratively shows the application of a pulsed, continuous
liquid jet to dental residues;
FIG. 10 illustratively depicts the application of a fractionated
liquid jet produced according to the invention to dental residues
and illustrates the manner in which the buffer zone effect has been
overcome; and
FIG. 11 is a photographic illustration of the buffer zone for the
case of a single jet of pulsated fluid compared to the plurality of
jets providing a plurality of unitary, discrete liquid droplets
according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIG. 1, the apparatus of the first embodiment of the invention
comprises a reservoir 10 which contains a mass of liquid 11 which
may be water, a solution of analgesic, mouthwash, toothpaste or the
like in water, or another suitable fluid. A conduit 12 is connected
to an opening in the wall of the reservoir 10 to conduct the liquid
11 to a pump 13. Pressurized liquid is provided from the outlet of
the pump 13 to the inlet 14 of a nozzle 15 through the conduit 16.
Preferably, the conduit is flexible to permit the user to
manipulate the nozzle 15.
The nozzle 15 may be produced in a number of shapes and sizes
depending on the ultimate end use. The nozzle 15 is connected to a
source 17 of vibrations and both are contained in a suitable casing
18, designated illustratively in phantom outline in FIG. 1,
designed to permit the user to guide the flow of liquid 20 which
exudes from the tip 21 of the nozzle 15 to the desired location on
the body, for example, to a selected area in the mouth.
The vibrator 17 is energized by periodic electrical signals
produced by an electronic vibration generator 22 which is amplified
by an amplifier 23. The preferred frequency range for the signal
frequency is on the order of about 200 to about 5,000 cps. One
specific example of the type of generator contemplated for use in
this invention is electro-magnetic vibrators.
When the generator 22 is off, and if the tip of a nozzle 15 has an
opening having a circular cross section, the flow through this
nozzle is cylindrical and equilibrated for its generally effective
length under the action of its internal cohesion strength. This
equilibrium is, however, relatively precarious and can be broken as
soon as the jet 20 is subject to any perturbation produced at its
origin, e.g., at the outlet of the nozzle 15. Particularly, it has
been known that when a jet is submitted near its origin to
relatively high frequency vibration, the form of the jet is
altered. The alteration in jet form is exponentially increasing
from the outlet of a nozzle 15.
If the frequency of vibration applied to the liquid 20 is constant,
the flow of liquid from the outlet of the nozzle 15 is altered in
such a manner that the flow profile of the liquid 20 exhibits a
plurality of spaced contractions which increase in magnitude with
an increase in distance from the tip 21 of the nozzle 15. Thus, as
can best be seen in FIG. 2, the streamline of liquid 20 from the
tip 21 is characterized by a plurality of contractions 25 which
increase in magnitude until the jet of liquid breaks into a
plurality of unitary, discrete liquid droplets 26. Primarily
because of the surface tension of a liquid, the masses 26
ultimately assume the shape of a generally spherical liquid droplet
27. As will be discussed, the plurality of liquid droplets 27 are
effectively used for cleansing the selected area on the body, for
example, the dental surfaces to be cleaned.
A number of parameters relating to the physical characteristics of
the nozzle, the frequency of vibration, the fluid flow
characteristics, and the like, are of interest in producing the
liquid droplets contemplated by this invention by means of
electro-magnetic vibrators. These parameters are herein set forth
based upon the emperical studies of the applicants with reference
to their theoretical basis.
Ejection Velocity
While there is theoretically no limit in a vacuum with a perfect
nozzle opening, i.e., one without rugosity, and a laminar flow of
liquid therethrough, for a maximum ejection velocity, the minimum
ejection velocity is of interest. The minimum ejection velocity of
the liquid jet for a given nozzle diameter and a predetermined
vibrator frequency can be calculated in order to produce a maximum
number of liquid droplets (which are adjacent to one another and do
not touch). A jet of fluid having an ejection velocity of less than
that indicated herein will not produce discrete liquid droplets,
and the liquid will no longer be fractionated.
The theoretical minimum ejection velocity for the jet 20 is given
by the following formula which expresses the geometric
transformation of a cylinder to a sphere:
v.sub.min = 1.22f .phi..sub.j
where v is the velocity of the jet in cm/s, f is the frequency of
the vibrator in Hz or cps, and .phi..sub.j is the diameter of the
liquid jet in cm.
However, practical trials have shown that the actual minimum
velocity for a jet to produce a maximum number of liquid droplets
which are adjacent to one another but not touching is about twice
as high as the theoretical minimum ejection velocity for a number
of reasons. When formed, the liquid droplets are generally oval
along the longitudinal axis, as shown by the droplets 26 in FIG. 2.
This factor mitigates against the theoretically perfect production
of adjacent spherical droplets 27. Moreover, because of the
superficial or surface tension of the fluid, the liquid droplets in
formation and still joined (as shown between the contractions 25)
must separate from each other by a certain distance so that the
cylinder of water joining them has a striction sufficient enough to
provoke their rupture and separation. This factor indicates that a
greater distance between droplets is necessary than that indicated
by the theoretical value. Moreover, the rugosity of the nozzle
produces at the surface of the liquid droplets in formation a
certain heterogeneousness which artifically increases their
diameter thus making it easier for the droplets to join together
again if they are not sufficiently far from one another.
Thus, the practical formula for the minimum ejection velocity is
given by:
v.sub.min = 2.5f .phi..sub.j
Fluid Flow Velocity
In addition to the ejection velocity which is the same as the fluid
flow velocity at the point of exit from the nozzle 21, the fluid
flow velocity must be such that a laminar, rather than a turbulent
flow is produced. Since it is known that a fluid flow becomes
turbulent when the Reynolds number is greater than 2.500 for a tube
with a polished inner surface, it has been determined that the
limit of liquid velocity possessing laminar flow has a maximum
value of about 4 m/s for a nozzle opening of 0.2 mm diameter and a
maximum value of about 7 m/s for a nozzle opening of 1.1 mm
diameter. It has been observed practically that the jet can only be
disequilibrated by the vibrations of the nozzle to form liquid
droplets in the case when the flow is laminar.
Those limits can be verified by the use of the Reynolds formula.
The Reynolds formula is:
.pi.e = (v.phi..sub.j /.nu.)
where v is the flow velocity in c/s, j.sub..phi. is the diameter of
the fluid cross section in cm, and .nu. is the kinematic viscosity
coefficient which, for water at 20.degree.C is 0.01 cm.sup.2
/s.
Since fluid flow becomes turbulent when the Reynolds number is
greater than 2.500 for a tube with polished inner surfaces,
calculation with the above formula shows that with a mean diameter
of 0.6 mm, the flow becomes turbulent with a velocity of about 4
m/s. Thus, since the jet can only be disequilibrated by vibrations
to form discrete liquid droplets when the flow is laminar, and the
nozzle diameters may range from 0.2 to about 1.1 mm, as will be
discussed hereafter, the practical limits for liquid velocity are
in the range of about 4 to about 7 m/s.
Diameter of Nozzle Opening
It has been found that if the diameter of the nozzle opening is
greater than about 1.1 mm, it is no longer possible to form stable
liquid droplets because the droplets become "too soft" due to their
mass which is too heavy relative to the surface tension on one
hand, and due to the ease with which the fluid droplets are
deformed when they come in contact with the air.
Thus, it has been found that the minimum nozzle opening diameter to
produce discrete liquid droplets is between about 0.15 and about
0.20 mm because in this area the relative rugosity of the nozzle
opening becomes important. The relative rugosity of the nozzle
opening is defined by the ratio of the opening rugosity, in
micro-inches or micro-meters, to the diameter of the opening. At
such diameters, the roughness of the inner part of the diameter,
measured by the rugosity, becomes preponderant and the jet tends to
break down into a mist rather than produce the liquid droplets.
In order to better define the difference between the relative
hardness of a liquid droplet which is formed from the nozzle
opening having a diameter of 1.1 mm and a droplet from a nozzle
opening having a diameter of 0.2 mm, the ratio of the relative
hardness of the droplets can be calculated. The diameter of the
liquid droplets formed after exit from the outlet of a nozzle is
given by the relation:
.phi..sub.liquid droplets = 2 [(3/4.pi. ) (.alpha..sup.. S.sup..
v/f)].sup.1/3
where f is the vibration frequency of the nozzle, S is the
cross-sectional area of the nozzle opening, .alpha. is the
contraction coefficient of the opening, and v is the velocity of
the jet.
Practical trials and calculations have determined that the
contraction coefficient of the opening is about 0.97 for a nozzle
opening having a diameter of about 1.1 and about 0.92 mm for a
nozzle opening of about 0.2 mm. Thus, for the particular case of a
jet having an ejection velocity of 5 m/s, and a vibration frequency
of 500 cps, liquid droplets each having a diameter of 2.6 mm are
produced from a nozzle opening having a diameter of 1.1 mm while
liquid droplets each having a diameter of 0.77 mm are produced from
a nozzle opening of 0.2 mm.
The surface pressure p acting on a droplet of liquid due to the
surface tension of the liquid can be calculated by the formula:
p = (4T/.phi.)
where T is the surface tension equal to 72 dynes/cm for water in
contact with air, and .phi. is the diameter of the droplets in
cm.
Thus, for a nozzle opening having a diameter of 1.1 mm and
producing liquid droplets each having a diameter of 2.6 mm as
indicated above, the surface pressure is 1.13 g/cm.sup.2 whereas
for a nozzle opening having a diameter of 0.20 mm and producing
liquid droplets each having a diameter of 0.77 mm as shown above,
the surface tension is 3.82 g/cm.sup.2.
From the foregoing, it is apparent that by diminishing the section
of the nozzle opening by more than 30 times (from a nozzle with a
diameter of 1.1 mm to a nozzle with a diameter of 0.2 mm), and
keeping the other parameters exactly the same for both nozzles,
i.e., the ejection velocity and fractionating frequency are the
same, the cross-sectional area of the liquid droplets is reduced by
10.4 times. Furthermore, the flow rate of the small opening is
about 40 times smaller than that of the large opening which thus
illustrates the superiority of a jet having a small diameter,
particularly in those instances where the jet is used for oral
lavage where it is desired to minimize fluid flow in the mouth of
the user. This feature is a significant advantage of the invention
when used for oral hygiene.
In order to take into consideration all parameters relating to the
difference of the relative hardness between the two droplets
considered in the above examples, the respective weights of the
droplets must be introduced.
The weight of a spherical droplet is defined by the equation:
W = (4/3) .pi.r.sup.3 .rho.
where .rho. is 1 g/cm.sup.3 for water.
Calculation with this formula shows that each of the droplets
having a diameter of 2.6 mm produced from a nozzle opening having a
diameter of 1.1 mm has a weight of 9.2 mg, while each of the
droplets having a diameter of 0.77 mm produced from a nozzle
opening having a diameter of 0.20 mm has a weight of only 0.239 mg.
If the ratio between the weights of these two droplets is
calculated, it is found that each of the droplets produced from the
nozzle opening having a diameter of 1.1 mm is 38.5 times heavier
than each of the droplets produced by the nozzle opening having a
diameter of 0.2 mm.
Furthermore, the surface tension, which tends to maintain each of
the droplets in its spherical form, is 3.4 times smaller in the
case of a droplet produced by the nozzle opening having a 1.1 mm
diameter than in the case of a droplet produced by a nozzle opening
having a 0.2 mm diameter. Thus, each of the droplets having a
diameter of 2.6 mm is 130 times softer and more vulnerable than
each of the droplets having a diameter of 0.77 mm, with the same
ejection velocity and fractionating frequency.
Vibration Frequency
The frequency of vibration to produce the subject liquid droplets
is within the range of about 200 cycles per second to about 5,000
cycles per second. Practical trials have shown that for a water jet
produced from a nozzle having a diameter of 1.1 mm, it was not
possible to exceed a vibration frequency of about 500 cycles per
second to obtain a fractionation of the jet because the damping of
the vibration transmission through the water is proportional to the
vibration frequency and to the water mass, and thus, to the nozzle
diameter.
It has also been found that the droplets which were more easily
formed in the higher range of frequencies and velocities were
produced when the diameter of the nozzle opening was in the range
between 0.4 and 0.6 mm. This occurred because with such diameters,
the droplets were on one hand not "too soft" and, on the other
hand, not preponderantly influenced by the nozzle opening
rugosity.
Formation Distance
The distance measured from the tip of the nozzle where the droplets
are entirely formed and separated from each other were found in
practical tests to be extremely variable and to depend on many
factors. However, this distance seemed to increase proportionally
with the ejection velocity of the liquid. This distance was
measured between less than 3 times the diameter of the nozzle
opening and up to 90 times this diameter in extreme cases.
The droplets may also be produced from a jet subjected to
acoustical vibrations or to hydraulic pressure vibrations in the
frequency range disclosed.
The parameters discussed above are tabulated in FIGS. 3 and 4.
FIGS. 5-8 illustrate a second embodiment of the invention. In FIG.
5, as in FIG. 1, the overall system for the practice of dental
hygiene comprises a reservoir 10 containing a liquid 11, a pump 13
and suitable conduits 12 and 16 for conducting the liquid from the
reservoir to the pump and from the pump to the nozzle member 50. As
will be seen, the construction of the nozzle member 50 causes the
fractionation of the liquid jet 60 into a plurality of unitary,
discrete liquid droplets according to the invention.
An obturating member 55 is disposed in the opening 51 defined by
the tip 52 of the nozzle member 50, which surrounds the free end of
the passage 58. The member 55 consists, for example, of a small
cylindrical block of synthetic material having in the central
portion thereof a plurality of longitudinal micropassages 57 which
are arranged equidistantly in a circular locus about the center of
the member 55.
These micropassages 57 preferably have a diameter which is much
less than that of the adjacent passage 58, for example, on the
order of 0.2 to 0.5 mm, while the adjacent passage 58 has a
diameter on the order of 1.5 to 2.0 mm.
As in the case of nozzle member 15 in FIG. 1, if the nozzle member
50 does not include member 55, the jet produced by this nozzle is
generally cylindrical, in equilibrium along its entire effective
length under the action of its internal cohesive forces.
If the liquid jet is subjected to a perturbation, as discussed in
connection with FIG. 1, the equilibrium of the jet may be
destroyed. This occurs in the apparatus shown in FIGS. 5-8 due to
the presence of the obturating member 55. At the outlet of the
micropassages 57, the various produced jets 60 are divided
gradually into a plurality of discrete, unitary liquid droplets
61.
The slight liquid take-off 62 which occurs at the inlet of each
micropassage 57 gives rise to an instability in the remainder of
the micropassage, which is of sufficient magnitude to create this
fractionation. Moreover, the sudden change of cross-section which
the liquid coming from the pump 13 encounters at the level of the
upstream face of the obturating member 55 is the source of
reflections and refractions of pressure waves within the liquid in
the passage 58, as well as within the liquid in each micropassage
57. Thus, this structure causes an oscillatory pressure phenomenon,
the frequency of which corresponds to that of the production of
droplets 61 and which seems to be inversely proportional to the
length of the micropassages.
It is to be noted, in particular, that when the micropassages 57
have a diameter of 0.2 mm and a length of 8 mm, for example,
divided jets with 20,000 droplets per minute have been obtained,
while with micropassages 57 of the same cross section, but having
twice the length, i.e., 16 mm the number of droplets becomes
essentially equal to 10,000 per minute.
Each of the jets produced by the appliance is thus divided into a
series of liquid "projectiles" having a somewhat spherical shape,
the effect of which has turned out to be particularly important
with regard to cleaning the teeth and the interdental spaces, as
was discussed in connection with FIGS. 3 and 4.
The parameters discussed in connection with FIGS. 1 and 2 have been
confirmed by a laboratory experimentation apparatus comprising a
nozzle from which a pressurized water jet with a continuous flow
was produced. The jet was fractionated into discrete liquid
droplets by means of a thin rotating disc provided with equally
spaced indentations along the periphery of the disc and driven by
an electric motor. By this apparatus, the jet having an adjustable
ejection velocity was fractionated by an adjustable fractionating
frequency. The desired fractionating frequency was obtained by the
modification of the rpm of the motor and, if necessary, changing
the number of indentations on the disc.
Cleaning trials have shown that the greater a jet is fractionated
the better its cleaning action, all other conditions being similar.
In this respect, it was noted that a fractionated jet was even more
effective than a continuous jet using twice as much water.
In FIG. 9, the food residue 31 is shown as being contacted by the
continuous portion of a pulsed jet 32 of liquid such as one which
would be produced by devices described earlier in this
specification. FIG. 10, on the other hand, shows the food residue
31 being successively impacted by a plurality of discrete, unitary
liquid droplets which are produced according to the invention.
In the case of FIG. 9, the solid jet 32 partially disaggregates the
central part of the food residue 31 only during its initial impact,
while the water flow which arrives later and strikes the food
residue 31 is considerably slowed because the water which arrived
earlier and has formed a water film 33, acts as a buffer between
the residue 31 to be disaggregated and the jet 32. Thus, the water
flows across the surface of the food residue 31 in a superficial
manner and its disaggregating action is restricted primarily to an
erosion of the peripheral areas of the residue.
As shown in FIG. 10, the disaggregating process is improved because
each liquid mass successively percusses the food residue 31 without
formation of a buffering water film. Thus, there are as many
impacts per time unit as there are produced drops. Accordingly, a
high efficiency of disaggregation of food residues is achieved.
Moreover, the explosion effect at each impact, of each droplet is
added to that of crushing the droplet on the deposit, thus
contributing to further improvement of the efficiency with which
the jet disaggregates the deposit.
Thus, the cleaning effected in the case of the projection of a
plurality of liquid droplets is far better than the cleaning
obtained by a pulsated jet projection, even at a rate of 3,000
pulsations per minute for the same rate of liquid discharge from a
single nozzle. Similarly, for the same washing quality, the
quantity of liquid employed in using a device according to the
invention, is far less than that necessary by the presently
marketed devices. It is also clear that the washing time will also
be reduced accordingly.
The efficiency of the above described device is such that it is
possible not only to remove the small residues from the teeth but
also the large deposits covering the entire surface of each tooth.
In particular, the food particles wedged in the interdental spaces
which are very difficult to reach even with the more efficient
electric toothbrush are effectively removed with the method and
apparatus of the invention.
It is also apparent that the devices according to the invention can
also be used to provide an efficient massaging of the gums in
addition to their described cleaning functions. This is
accomplished by adding a pulsation at an appropriate frequency to
the liquid column supplying the nozzle 15. Thus, it is possible,
for example to equip such a device with a pump 13 having a
discontinuous operation, for example a piston pump, able to supply
the nozzle 15, and which is pulsated at a suitable frequency,
partially determined by the relaxation time of the gum mucous
tissue. When a pulsation is added to the liquid, the vibrator 17
produces a fractionated jet as previously described.
By way of further explanation, the buffer zone can be defined as
the damping phenomenon on the incident liquid jet by the residual
film sill present on the impact surface. To show its effect,
spraying trials have been made against a transparent pane of glass
which permitted examination of the buffer zone through the glass.
By means of a stroboscopic light, the phenomenon was clearly
visualized as shown in FIG. 11.
In FIG. 11, the buffer zone is shown on the left hand side thereof
for the case of a single pulsated jet of liquid compared with a 6
micro-jet nozzle according to the invention pulsated at the same
frequency for visualization, as shown on the right hand side of the
photograph of FIG. 11.
From FIG. 11, it is clearly shown that the jet on the left has a
buffer zone much thicker than the jet on the right because the
whiter the aspect of the water on the photograph, the thicker the
film of water. At the level of the impact of the jet, shown by the
whiter dot in the center of the left hand portion of the
photograph, it appears that this dot which should be absolutely
white in the case of direct contact of the fluid with the glass
surface is blurred, which proves that the jet is strongly damped or
buffered. On the contrary, in the case of the nozzle with 6 jets
according to the invention, as shown on the right hand portion of
the photograph, it can be observed that outside the jets, within
the zone which resembles the orange-like sections, there is
practically no buffer zone since those portions are black.
Furthermore, at the impact point of the six jets, six very white
dots are visable, which proves that each of the six reaches the
glass surface with full energy and without interference by a
buffering water film. This photographic illustration confirms FIGS.
9 and 10.
The invention may be embodied in other specific forms without
departing from its spirit or essential characteristics. 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 claims rather than by the foregoing description,
and all changes which come within the meaning and range of the
equivalents of the claims are therefore intended to be embraced
therein.
* * * * *