Note: Descriptions are shown in the official language in which they were submitted.
CA 02560405 2010-07-26
SPRAY HEAD FOR ATTACHMENT TO AN AEROSOL SPRAY UNIT
FIELD
The present invention relates to an aerosol spray head, an aerosol spray unit
comprising the aerosol spray head and a process for spraying pressurised
product.
BACKGROUND
One conventional approach to dispensing a product onto a target application
surface is via atomisation of that product. One way of achieving atomisation
is to
combine the product with a propellant (compressed gas) in a pressurized unit
having a
dispensing valve fluidly connected to a dispensing outlet. On opening the
dispensing
valve, the product is forced thereduough and dispensed via the outlet in an
atomized form
onto the target application surface.
The present inventors have established, however, that current atomization
technology generally does not deliver a satisfactory product distribution onto
the target
area. In particular, the distribution is observed to be uneven, with, for
example, increased
deposition occurring in the centre and correspondingly reduced deposition
towards the
extremities of the target site. In addition to the uneven spread of active
agent and resulting
uneven achievement of benefit across the target site, increased deposition in
one area, for
example the centre, may additionally result in the formation of unsightly
residues and
unpleasant cooling in that region of the consumer's skin, due to the increased
amounts of
product deposited there and increased amounts propellant evaporating at that
location.
In addition to the above-mentioned shortcomings, a single outlet spray head
also
places physical limitations on the composition which may be sprayed. In
particular, high
viscosity compositions may not be practically sprayed, because insufficient
energy may
be retained in such a fluid under typical pressurisation conditions for it to
become
sufficiently atomised on leaving the spray outlet.
With reference to US 3,767,125, a multi-outlet spray head is proposed for
spraying dry powder aerosols.
With reference to US 5,516,045, an alternative multi-outlet spray head is
disclosed, especially for spraying hair lacquer.
It would be advantageous to provide a spray head which overcomes the
disadvantages of spray heads disclosed in the prior art.
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Summary
According to a first aspect of the invention a spray head for attachment to an
aerosol container containing pressurised product is provided, the spray head
comprising
conduit means, more than one separate spray outlet and a splitting chamber (4)
for diverting
the flow to the spray outlets, wherein the conduit means (2) comprise inlet
means for
attachment to a valve stem of the aerosol spray unit and conduit outlet means
which are
in direct fluid communication with the splitting chamber, wherein the
splitting chamber is
in fluid communication with the spray outlets and wherein, for each spray
outlet, the
ratio, Ll/L2, of the distance (Li) between the conduit outlet means and the
spray outlet to
the distance (L2) between the inlet means and the spray outlet is from 0.01 to
0.6.
According to a second aspect of the invention, an pressurised aerosol spray
unit is
provided, having a spray head as defined in the first aspect of the invention.
According to a third aspect of the invention, a portable pressurised aerosol
spray
unit is provided, having a spray head as defined in the first aspect of the
invention.
According to a fourth aspect of the invention, a process for spraying a
pressurised
product is provided, comprising the steps of spraying said product through a
spray head
according to the first aspect of the invention, such that the product has a
Reynolds
Number of at least 1000 as it leaves said spray outlets.
These and other features, aspects, and advantages of the present invention
will
become evident to those skilled in the art from a reading of the present
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
While the specification concludes with claims which particularly point out and
distinctly claim the invention, it is believed the present invention will be
better
understood from the following description of preferred embodiments taken in
conjunction
with the accompanying drawings, in which like reference numerals identify
identical
elements and in which:
Fig. 1 is a cross-sectional view of a spray head according to the invention
Fig. 2 is an enlarged cross-sectional view of the important parts of a spray
head
according to the invention.
DETAILED DESCRIPTION
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While the specification concludes with claims which particularly point out and
distinctly claim the invention, it is believed the present invention will be
better
understood from the following description.
All weights, measurements and concentrations herein are measured at 250C on
the
composition in its entirety, unless otherwise specified.
Unless otherwise indicated, all percentages of compositions referred to herein
are
weight percentages of the total composition (i.e. the sum of all components
present) and
all ratios are weight ratios.
As has been discussed, a limitation of traditional aerosol spray head
configurations is that they may produce an uneven distribution of product on
the target
site. In addition, the viscosity of the product to be sprayed may be
practically constrained
to remain below a certain level.
By introducing instability into the fluid flow at an early stage it is
possible to
atomize products with greater viscosities and, at the same time, improve the
product
distribution on the target site. The replacement of a single spray outlet by
multiple outlets
may assist in introducing that instability, because, for a given volume flow
of product, the
size of the shear interface (i.e. the total outlet perimeter size) is greater
for multiple
outlets than for a single outlet. Without wishing to be bound by theory, it is
believed that
this measure may prevent the formation of a smooth film structure just outside
the outlet
where the product commences its trajectory to the target site. The
disadvantage of a
smooth film structure is that it may propagate a relatively coarse atomization
in the final
stage before the product reaches the target site, with the drops at the center
of the spray
being larger than those near the periphery. It is in the final stage of the
spray formation
where an instability in the system may help disintegrate the product into
ligaments and
then further into drops to form a highly atomised spray and an improved drop
distribution.
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WO 2005/095000 4 PCT/US2005/010459
In addition, in a multi-outlet system, it is observed that, following the
split in the
flow to channel fluid to the separate orifices, changes to the separate flows
may occur
such that there may be differences, for example, in viscosity or other
parameters, between
what is sprayed from one outlet and what is sprayed from the other or others.
If there are
differences between the individual sprays immediately after they leave their
respective
spray outlets, then that may translate into differences in product
distribution at the target
site. Without wishing to be bound by theory, it is believed that these changes
may be
brought about by manufacturing limitations. In other words, it is very
difficult to ensure
that the ducts along which the separate flows travel are identical. To counter
this, it has
been found to be beneficial to locate the point at which the flow splits to
travel to the two
or more separate spray outlets close to the spray outlets such that most of
the flow within
the spray head occurs prior to the split. To be more specific and as set out
above, it has
been found that it is beneficial to design the spray head (1) such that the
ratio, L 1/L2, for
each spray outlet (3), of the distance (L1) between the conduit outlet means
and the spray
outlet (3) to the distance between the inlet means (5) and the spray outlet
(3) is from 0.01
to 0.6, preferably from 0.015 to 0.4 and more preferably from 0.02 to 0.4.
In the event that the conduit and/or ducts leading to the spray outlets have a
non-
constant cross-sectional area such that either or both of Li and L2 may vary
depending
on the line of measurement, then the measurements must be made along the
centre line
connecting the centres of the inlet means (5), the conduit outlet means and
the respective
spray outlet (3).
In one preferred embodiment, at least one of the spray outlets has a ratio
Li/L2
which is different from the other or others. In another preferred embodiment,
all the spray
outlets have the same ratio Li/L2.
Advantageously, at least one of the spray outlets and preferably all of the
spray
outlets are non-circular. Employing non-circular spray outlets may
additionally assist in
introducing early instability into the flow, thereby improving distribution at
the target
site.
As used herein, the term "circle" means a closed plane curve every point of
which
is equidistant from a fixed point within the curve and the word "circular"
shall be
interpreted accordingly.
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WO 2005/095000 5 PCT/US2005/010459
The spray outlets (3) may have any non-circular shape, but advantageously have
a
cross-sectional shape selected from the group consisting of polygonal, semi-
circular,
crescent, stellate and mixtures thereof. If polygonal, then each polygonal
cross-sectional
shape may advantageously be selected from the group consisting of polygons
having
from three to ten sides. Preferably, the polygons are selected from the group
consisting of
triangular, rectangular, pentagonal, hexagonal and mixtures thereof.
The spray head (1) according to the invention may have any number of spray
outlets (3) above two, but preferably has from 2 to 36 and more preferably
from 3 to 12
spray outlets (3).
According to a second aspect of the invention, an aerosol spray unit (10) is
provided comprising a pressurised product to be dispensed and having a spray
head (1)
according to the first aspect of the invention.
As used herein, the term "spray unit" means a pressurised aerosol canister,
comprising a valve, the valve stem (11) of which extends from the canister,
typically at the
top. Such canisters typically have a volume up to 1000m1, though more
typically below
200m1 and are typically pressurised at 103kPa to 552 kPa (15 to 80psi), more
typically
less than 414 kPa (60psi).
As used herein, the term "product" means all components of the composition or
mixture contained within the spray unit, including all active agents, all
carrier materials
and all propellant.
Preferably, the product to be dispensed is a cosmetic product, more preferably
it is
selected from the group consisting of antiperspirants, deodorants and mixtures
thereof.
If the product to be dispensed is an antiperspirant, then it may comprise
antiperspirant active particulates and a carrier such that the antiperspirant
active
particulates are not soluble in the carrier. Alternatively, the antiperspirant
active may be
solubilised in the carrier.
According to a third aspect of the invention, a portable aerosol spray unit
(10) is
provided comprising a pressurised product to be dispensed and a spray head (1)
according to the first aspect of the invention..
As used herein, the term "portable" used in relation to an aerosol spray unit
means
that it may readily be transported in one hand by a single adult person of
ordinary
strength.
CA 02560405 2011-06-16
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According to a fourth aspect of the invention, a process for spraying a
pressurised
product is provided comprising the steps of spraying said product through a
spray head
having at least two separate spray outlets (3), wherein at least one of the
spray outlets (3)
has a non-circular cross-section, such that the product has a Reynolds Number
of at least
3000 as it leaves said spray outlets (3).
It is understood that the examples and embodiments described herein are for
illustrative purposes only and that various modifications or changes in light
thereof will
be suggested to one skilled in the art without departing from the scope of the
present
invention.
The citation of all documents is, in relevant part, not to be construed as an
admission
that it is prior art with respect to the present invention. To the extent that
any meaning or
definition of a term in this written document conflicts with any meaning or
definition of
the term in a cited document, the meaning or definition assigned to the term
in this written
document shall govern
While particular embodiments of the present invention have been illustrated
and
described, it would be obvious to those skilled in the art that various other
changes and
modifications can be made without departing from the spirit and scope of the
invention.
It is therefore intended to cover in the appended claims all such changes and
modifications that are within the scope of this invention.
