U.S. patent application number 11/141050 was filed with the patent office on 2006-12-21 for product coating method and apparatus.
Invention is credited to Peter King.
Application Number | 20060286220 11/141050 |
Document ID | / |
Family ID | 37573637 |
Filed Date | 2006-12-21 |
United States Patent
Application |
20060286220 |
Kind Code |
A1 |
King; Peter |
December 21, 2006 |
Product coating method and apparatus
Abstract
A method and apparatus for coating a product is provided, the
method comprising delivering the product to a top end of an
inclined chute, the chute comprising at least one mesh portion
provided in its conveying surface; allowing the product to fall
along the conveying surface; and when the product passes over the
at least one mesh portion during its fall, spraying the product
with a coating.
Inventors: |
King; Peter; (Oxford,
GB) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
37573637 |
Appl. No.: |
11/141050 |
Filed: |
June 1, 2005 |
Current U.S.
Class: |
426/235 |
Current CPC
Class: |
A21C 15/002 20130101;
A23P 20/12 20160801; B05B 5/08 20130101; B05B 5/1683 20130101; B05B
7/1445 20130101; A23P 20/18 20160801; B05B 5/057 20130101 |
Class at
Publication: |
426/235 |
International
Class: |
B65B 3/04 20060101
B65B003/04 |
Claims
1. A method of coating a product, the method comprising: delivering
the product to a top end of an inclined chute, the chute comprising
at least one mesh portion provided in its conveying surface;
allowing the product to fall along the conveying surface; and when
the product passes over the at least one mesh portion during its
fall, spraying the product with a coating.
2. A method according to claim 1, wherein the coating is subjected
to at least one pressurised gas stream, whereby the coating is
sprayed towards the at least one mesh portion.
3. A method according to claim 1, comprising the step of applying
an electric field in order to charge the coating.
4. A method according to claim 3, wherein the at least one mesh
portion is held at a potential, so that the charged coating is
attracted to the mesh.
5. A method according to claim 1, comprising the step of vibrating
the conveying surface, thereby encouraging the product to fall.
6. A method according to claim 1, wherein the conveying surface is
provided with corrugations along its length, thereby encouraging
the product to fall along the conveying surface.
7. Apparatus for coating a product, the apparatus comprising: an
inclined chute comprising at least one mesh portion provided in its
conveying surface; and means for spraying a coating onto the
product when the product is in contact with the at least one mesh
portion.
8. Apparatus according to claim 7, wherein the means for spraying
comprises: a gas jet nozzle; means for coupling a source of
pressurised gas to the gas jet nozzle; and means for introducing
the coating adjacent to the gas jet nozzle; wherein in use gas
ejected from the nozzle impinges on the coating, thereby creating a
coating spray.
9. Apparatus according to claim 7, wherein the means for spraying
further comprises: an electrode attached to or located adjacent to
the nozzle; and means for charging the electrode; wherein in use
the electrode provides an electric field which is used to charge
the coating.
10. Apparatus according to claim 7 and comprising means for
vibrating the inclined chute.
11. Apparatus according to claim 7, wherein the conveying surface
is provided with corrugations along its length.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method and apparatus for
the coating of products and is applicable in particular, though not
necessarily, to a method and apparatus for coating food
products.
BACKGROUND TO THE INVENTION
[0002] There exist a wide variety of products which require to be
coated with a substance (e.g. powder, liquid, suspension, etc)
during their preparation. For example, snack foods such as potato
crisps and corn chips are usually coated with a flavouring. It is
generally desirable to be able to achieve a uniform and
controllable coating over the entire surface of a product. It is
also desirable to be able to minimise wastage of the coating, and
to reduce the dispersion of the coating into the environment around
the products.
[0003] A traditional method used for coating snack foods involves
the use of a rotating drum which has its axis at a slight tilt to
the horizontal. Products introduced into one end of the drum tend
to travel to the other end as the drum rotates. Flavouring in the
form of a powder is delivered via an inclined chute to a location
within the drum so that the flavouring is sprinkled onto the
products to be coated. Whilst this technique tends to result in an
acceptable level of coating uniformity, it is not ideal, with
flavour concentration varying between product pieces and across the
surfaces of individual pieces. Further, the drum itself is an
expensive piece of equipment, and environmentally unfriendly. When
it is required to change the coating substance to be used, it is
likely that the drum will have to be cleaned or replaced due to
contamination with the first coating substance. This results in
decreased productivity due to downtime.
[0004] It has been recognised that coating uniformity may be
improved by placing a charge on the powder grains, using for
example a wire electrode located in the transit path of the
product. If the product delivery mechanism, e.g. the rotating drum,
is grounded, the products to be coated will also tend to be
grounded as they pass under the flavouring delivery mechanism.
Charged flavouring grains will be attracted to the products in a
generally uniform manner, in turn resulting in a generally uniform
coating. Such a process is described in our co-pending British
Patent Application No. GB 0204786.8.
[0005] A known electrostatic coating apparatus comprises a venturi
tube through which the coating substance is forced by a pressurised
gas. Upon emerging from an exit nozzle, the substance passes over a
charging electrode. A blockage problem can arise as the coating
substance builds up within the venturi tube, particularly where the
surrounding environment is hot and possibly humid (this is often
the case in a food production facility). A further potential
problem is that the coating substance is not broken down into
sufficiently small grains by the delivery system. Such blockage
results in production downtime, increasing operating costs and
decreasing productivity.
[0006] GB 2,177,585 describes an apparatus for coating food
products in which the falling product is subjected to a stream of
charged coating from an electrostatic sprayer. The product is
collected in a wire basket connected to an earthed funnel, the
funnel carrying away excess coating. The funnel may, over time,
become blocked with excess coating, leading to production downtime
whilst the funnel is cleaned or changed. As the product falls
through the stream of coating and impacts upon the basket, there is
the possibility of damage to the product, especially if the product
is fragile. Once the basket has been filled with coated product,
the basket has to be emptied, requiring a pause in production.
Further, the wire basket is earthed whilst the falling product is
isolated, resulting in the charged coating being attracted to the
basket in preference to the product, causing it to adhere to the
basket.
SUMMARY OF THE INVENTION
[0007] According to a first aspect of the present invention, there
is provided a method of coating a product, the method comprising
delivering the product to a top end of an inclined chute, the chute
comprising at least one mesh portion provided in its conveying
surface; allowing the product to fall along the conveying surface;
and when the product passes over the at least one mesh portion
during its fall, spraying the product with a coating.
[0008] The present invention is applicable in particular to the
coating of snack food products with a dry, powdered flavouring.
However, the invention may also be used to coat other products
including, but not limited to, pharmaceuticals. The invention may
also be used to coat products with substances other than dry
powdered substances including, for example, liquids, suspensions
and slurries.
[0009] An advantage of the present invention is that the food
product comes in direct physical contact with the earthed wire
mesh, the food product consequently also being earthed. The charged
coating material will then be attracted to the food product
directly, in contrast with the described prior art.
[0010] Preferably, the coating is subjected to at least one
pressurised gas stream, whereby the coating is sprayed towards the
at least one mesh portion. More preferably, the method further
includes the step of applying an electric field in order to charge
the coating.
[0011] The at least one mesh portion may be coupled to a potential,
whereby the charged coating is attracted to the mesh.
[0012] Preferably, the conveying surface is vibrated, thereby
encouraging the product to fall.
[0013] The conveying surface may be provided with corrugations
along its length, thereby encouraging the product to fall along the
conveying surface.
[0014] According to a second aspect of the present invention, there
is provided apparatus for coating a product, the apparatus
comprising an inclined chute comprising at least one mesh portion
provided in its conveying surface; and means for spraying a coating
onto the product when the product is in contact with the at least
one mesh portion.
[0015] The means for spraying may comprise a gas jet nozzle; means
for coupling a source of pressurised gas to the gas jet nozzle; and
means for introducing the coating adjacent to the gas jet nozzle;
wherein in use gas ejected from the nozzle impinges on the coating,
thereby creating a coating spray.
[0016] The means for spraying may further comprise an electrode
attached to or located adjacent to the nozzle; and means for
charging the electrode; wherein in use the electrode provides an
electric field which is used to charge the coating.
[0017] Preferably, the apparatus further comprises means for
vibrating the inclined chute.
[0018] The conveying surface may be provided with corrugations
along its length
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 illustrates in perspective view apparatus for coating
a product in accordance with a first embodiment of the present
invention;
[0020] FIG. 2 illustrates a nozzle and nozzle mounting member of
the apparatus of FIG. 1;
[0021] FIG. 3 is a flow diagram showing a method of coating a
product;
[0022] FIG. 4 illustrates apparatus for coating a product in
accordance with a further embodiment of the present invention;
and
[0023] FIG. 5 illustrates apparatus for coating a product in
accordance with a still further embodiment of the present
invention.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS
[0024] There is illustrated in FIG. 1 apparatus for coating a
product with a coating in accordance with a first embodiment of the
present invention. A product delivery mechanism comprises a first
inclined chute 10, a second inclined chute 12, and a third inclined
chute 14. The first chute is connected to the second chute, and the
second chute is connected to the third chute, thereby providing a
continuous conveyor for products to be coated. The second chute 12
is inclined at an angle to the horizontal greater than the angle of
the first chute 10 to the horizontal. A wire mesh 16 is provided on
the second chute 12, flush with the top of the second chute 12,
replacing a portion of the second chute and providing passage
therethrough for particles smaller than the grid separation of the
mesh 16. The wire mesh 16 may be made from any suitable metal. A
motor 18 is attached to the three chutes, the motor causing the
chutes to vibrate. A hopper 20 is provided beneath the wire mesh
16.
[0025] Located on top of a support frame (not shown in FIG. 1) is a
hopper 1 into which is loaded a dry, powdered coating 2. An opening
in the base of the hopper 1 is coupled to a screw conveyor 3 which
comprises a screw mounted within a cylindrical tube. The screw is
rotated within the cylindrical tube by a suitable motor. An end of
the screw conveyor 3 leads into a vertically oriented feed tube 4,
the open lower end of which is located directly above an inclined
supply chute 5. Coupled to an underside of the supply chute 5 is a
vibration motor 6 arranged to vibrate the supply chute at a
relatively high frequency but with a relatively small amplitude.
The motor 6 may be for example a model FoodTech FTO1 supplied by
FMC.
[0026] The lower or exit end of the supply chute 5 projects towards
the wire mesh 16, the exit end having a width of about 25 to 75 mm.
A nozzle mounting 7 is located beneath the lower end of the supply
chute 5, and is illustrated in more detail in FIG. 2. The nozzle
mounting 7 comprises a single moulded piece of plastics material,
having a generally cylindrical passage 42 passing therethrough,
close to one end of the mounting 7. The passage is designed to
receive a complimentary shaped and sized nozzle 44 which, once
inserted into the passage 42, can be secured therein with a screw,
clip, or similar fastening.
[0027] Fixed into the mounting 7 is a short needle electrode 48,
located in the passage just beneath the mouth of the nozzle. The
electrode 48 is coupled via a conductor 49 to a high voltage
charging circuit (for example a cascade arrangement). In use, the
electrode is charged up to a voltage of around 85 KV. An end of the
nozzle 44 is coupled via a hose 46 to a source of pressurised air
(not shown in the figures). The nozzle mounting and the various
components attached thereto are designed to withstand the high
ambient levels of heat and moisture, and to be suitable for use on
a food production line. A suitable control unit is used to control
the pressure of air supplied to the nozzle and the voltage applied
to the electrode. The nozzle mounting is substantially as described
in the above-referenced co-pending British Patent Application.
[0028] Having explained the structure of the apparatus with
reference to FIGS. 1 and 2, the operation of the apparatus will now
be described. With the hopper 1 loaded with coating 2, the screw
conveyor 3 is operated to drive the coating 2 into the top of the
feed pipe 4. Powder drops through the pipe 4 and lands on the
supply chute 5. Due to the inclined angle of the supply chute and
the vibration of the supply chute by the motor 6, the coating 2 is
conveyed along the chute to its exit end. It will be appreciated
that vibration of the powder within the supply chute will result in
some dispersion of the powder, i.e. larger lumps will tend to be
broken up into smaller lumps or grains.
[0029] As the coating 2 reaches the exit end of the supply chute 5,
it will spill over the edge and will begin falling under gravity.
Directly beneath the exit end of the supply chute, pressurised air
is forced through the nozzle 7 and passes through the electric
field created by the charged electrode 48. The air becomes charged
as it passes through this field. The charged air then impacts on
the coating 2, tending to disperse the powder and to break up
particles into micro sizes (i.e. 45-75 microns in diameter). The
coating particles also become charged when subjected to the
electric field created by the charged electrode 48. It is noted
that smaller particles (i.e. of micron sizes) accept a charge more
easily than larger particles.
[0030] In the case where the coating is a liquid or slurry, it may
be preferable to use a pump and a misting nozzle to generate the
coating spray rather than using pressurised air from the gas jet
nozzle as described above.
[0031] Products 8 to be coated are conveyed along the first chute
10 and move onto the second chute 12, where they fall under gravity
and with the aid of vibration from the motor 18, passing over the
wire mesh 16. The wire mesh 16 is connected to earth potential and
therefore when the products 8 come into electrical contact with the
mesh either directly or indirectly, the products 8 are also
connected to earth potential. The dispersed, charged coating 2
accelerates towards the wire mesh 16 and the products in contact
with the wire mesh. As the charged coating meets those products in
contact with the mesh, it becomes attached to the surface of the
products. Any excess coating will pass through the wire mesh and be
collected in the hopper 20 and may be conveyed back to the hopper 1
for reuse without disrupting the coating process. Preferably, the
chutes 10, 12, 14 are made from an insulating material, for
example, plastic, to prevent them from attracting the coating.
Coated products continue to pass along the second chute 12, and
then continue to pass along the third chute 14, from which they are
removed and packaged. The method described above is further
illustrated in the flow diagram of FIG. 3.
[0032] A further embodiment of the present invention is illustrated
in FIG. 4, where the third chute 14 further comprises a second wire
mesh 16' and a second hopper 20', substantially similar to wire
mesh 16 and hopper 20 of the first embodiment. The products coated
whilst in contact with the first mesh 16 also pass over the second
mesh 16', at which point any loose coating 2 travelling along the
chutes 12, 14 may be collected in the second hopper 20'. This
minimises wastage of the coating since any excess may be reused,
and furthermore there will be less production downtime since the
chutes 12, 14 will not be contaminated with such high levels of the
coating. It will be appreciated that the second mesh 16' and second
hopper 20' may be provided at any point along the chutes 12, 14
after the first wire mesh 16, and also that any number of
additional mesh/hopper combinations may be provided.
[0033] A further embodiment of the present invention is illustrated
in FIG. 5, where the second chute 12 is corrugated, with the
corrugations 30 perpendicular to the general direction of motion of
products along the second chute 12. All other aspects of this
embodiment are substantially identical to those of the first
embodiment. The corrugations 30 of the second chute 12 encourage
the products to tumble as they pass the wire mesh 16. This improves
the coating of the products with the coating 2.
[0034] It will be appreciated that the apparatus and method
described above do not require any small aperture components, e.g.
Venturi tubes, slots, or holes, through which the flavouring powder
must pass. There is therefore little likelihood of components
becoming blocked, resulting in less downtime and higher
productivity.
[0035] It will be appreciated by the person of skill in the art
that various modifications may be made to the above-described
embodiments without departing from the scope of the present
invention. For example, where larger amounts of flavouring must be
delivered to the product to be coated, a wider chute or multiple
chutes, arranged side by side, may be used. A corresponding set of
nozzles may be employed to charge and disperse the flavouring.
Alternatively, a wide mouthed knife nozzle may be used.
* * * * *