[0001] The present application relates to an apparatus for application of high build coatings
such as plaster and stucco.
[0002] Many industries, such as the construction and aerospace industries, have a need to
apply high build coatings. High build coatings are coatings with a finished thickness
from about 0.060" (1.5 mm) to 2.000" (51 mm) and densities ranging from approximately
2 lbs/cubic foot to 100 lbs/cubic foot (32 to 1600 kg/m
3). Plaster and stucco are examples of two high build coatings which are frequently
used in the construction industry for aesthetic and structural purposes, as well as
for fireproofing. Plaster and stucco coatings are mixtures of hygroscopic binders,
fillers and water. Plaster is typically an interior coating based on gypsum, while
stucco is traditionally an exterior coating which is usually based on portland cement,
but also has been made with other hygroscopic materials such as gypsum. The fillers
are typically materials such as cork, vermiculite, glass fibres, styrofoam beads,
phenolic microballoons, glass microballoons, and cellulose fibres.
[0003] Traditional application techniques required manual mixing of the plaster and/or stucco
in a barrel or pot, with the mixed material being applied manually. Manual application
had many disadvantages including a short pot-life of the material and the labour required
to apply the material.
[0004] Because thicknesses up to about 2.00" (51 mm) are regularly required for high build
coatings, spray systems have been developed to apply high build coatings more quickly
than manual application allows. Prior art spray systems generally include a bin or
hopper for holding a dry material which typically includes the hygroscopic material
and a filler, a nozzle for wetting the dry material, a flexible conduit extending
between the bin and the nozzle and an apparatus for generating a motive force to move
the dry material from the bin or hopper through the conduit and out the nozzle. The
prior art spray system may include two bins, one for holding the hygroscopic binder
and one for the filler material, and a mixing device for combining the dry materials
either prior to entry into the conduit or along the conduit, after entry.
[0005] Such prior art spray systems feed the dry material to the nozzle, which then wets
the dry material, and ejects the wetted material onto the substrate thereby coating
it. Typically the dry material comprises the hygroscopic material and a filler. Properties
of the coating deposited are dependent on water control, the degree of wetting, uniformity
of the hygroscopic material/filler distribution and filling timing.
[0006] In an alternative construction, as shown in CH 563511 (Guidicelli and Gianelli),
a wet cement mixture is forced into a spray nozzle through a tube. The wet mixture
is atomized by compressed air in a first part of the nozzle, and then mixed with atomized
hardening liquid in a second part of the nozzle, before being sprayed onto a substrate.
[0007] One problem associated with typical prior art spray systems stems from the means
used to generate the motive force. Two such means are a compressor and an eductor
connected to the bin. The compressor forces the dry material out of the bin through
the conduit and nozzle using pressurized air. The eductor creates a low pressure upstream
of the eductor that draws the dry material out of the bin.
[0008] The means for generating the motive force can be placed at the upstream end of the
conduit or the downstream end of the conduit. Eductors and compressors placed at the
upstream end of the conduit push the dry material through the conduit. The problem
with pushing the dry material through the conduit is that line losses are experienced,
material separation according to particle size occurs, and fall-out occurs, all of
which results in a non-uniform mixture passing through the nozzle which consequently
inhibits wetting of the dry material and therefore decreases the properties of the
coating.
[0009] To solve the problems of upstream eductors and compressors, eductors have been placed
at the downstream end of the conduit, such as the granular material emitting means
shown in U.S. Patent No. 3,788,555. The granular material emitting means comprises
an elongated, substantially tubular main body portion and an elongated tubular branch
portion. The axis of the bore of the branch portion intersects the axis of the bore
of the main body portion at an acute angle of about 30° to about 80°, with 30° to
60° being preferable. One end of the bore of the branch portion is connected to a
suitable source of fluid under pressure and one end of the tubular main body portion
is connected to granular material reservoir through a conduit. During operation, the
fluid under pressure flows through the branch portion and the acute angle is sufficient
to cause the flow of the fluid to provide an area of reduced pressure upstream of
the junction between the bore of the main body portion and the bore of the branch
portion. This reduced pressure tends to cause the granular material to be withdrawn
from the reservoir, entrained in the fluid, and carried through the conduit to the
main body portion and out of the granular emitting means.
[0010] The downstream eductor of the aforementioned patent has the benefit of pulling the
granular material all the way up the conduit, thus no line losses, material separation
or fallout should be experienced. However, the downstream eductor above has two problems
with respect to applying high build coatings. The granular materials for use with
the granular emitting device are perlite, clay, sand, talc, mica, calcium carbonate,
calcium silicate, glass beads, plastic spheres and the like. These materials all weigh
less than the hygroscopic materials necessary to form high build coatings; therefore,
the motive force requirements necessary for the granular emitting means are less than
those necessary for forming high build coatings.
[0011] Another problem associated with the spray apparatus disclosed in the aforementioned
patent is that convergent nozzles are used to mix the granular material with a plural
component material, such as a resin and a curing agent external to the spray apparatus.
The use of convergent mixing external to the spray apparatus is necessary in the Harrison
patent because the resin and curing agent turn from liquid to solid upon contact with
the atmosphere; therefore mixing outside the spray apparatus is necessary to prevent
clogging of the apparatus. However, it is desired that high build materials be mixed
within the nozzle in order to optimize wetting and exercise greater control of pressure,
turbulence and impingement angles.
[0012] A need therefore exists for a spray apparatus to apply coatings of hygroscopic material
and filler, which exerts sufficient motive force on dry material to move it and which
maintains this force throughout the length of the conduit, while substantially uniformly
wetting the dry material within the nozzle.
[0013] The present application provides for a spray system including a conveyance device
which moves the dry material through a conduit and uniformly wets the dry material
within a nozzle. There is disclosed a spray system for application of a wetted dry
material is provided, the spray system including: a nozzle, the nozzle having a liquid
inlet through which a liquid enters and a conveyance device attached to the nozzle.
The conveyance device includes an outer enclosure which has an air inlet through which
compressed air enters and an inner enclosure disposed substantially within the outer
enclosure, the inner and outer enclosure defining an air manifold therebetween. The
inner enclosure includes a longitudinally extending inner bore and an array of bores
disposed therethrough, the array of bores providing fluid communication of the compressed
air between the air manifold and the inner bore. Each of the bores in the array has
an internal diameter, the internal diameter being sufficient to allow the compressed
air to flow from the air manifold through the inner bore, thereby producing a vacuum
within the inner bore. The vacuum produced is of sufficient strength to transport
a predetermined volume of the dry material through the inner bore to the nozzle where
the dry material is wetted by the liquid, the vacuum also being sufficient to propel
the wetted dry material from the nozzle onto a substrate in order to coat the substrate
with the wetted dry material.
[0014] Thus in broad terms, the invention provides a spray apparatus comprising a conveyance
device, said device including an inner enclosure and an outer enclosure, the outer
enclosure being disposed around the inner enclosure to form an elongate air manifold
between the enclosures, the elongate manifold having an inlet for compressed air,
and a plurality of axially spaced bores being provided in a wall of the inner enclosure
to allow fluid communication between said inner enclosure and said air manifold, said
bores being angularly oriented relative to a longitudinal axis of the enclosures to
create a vacuum in said inner enclosure when air flows through said bores, said vacuum
serving to force the material through said device, said device also having a material
inlet and a material outlet, said apparatus also comprising a nozzle with a liquid
inlet, such that in use material to be sprayed can pass through the material inlet
and the material outlet and be wetted as it passes through the nozzle.
[0015] A preferred embodiment of the invention will now be described by way of example only
and with reference to the accompanying drawings, in which:
Fig. 1 is a perspective view of one embodiment of a spray system according to the
present application shown in the operating mode;
Fig. 2 is a perspective partially broken away and partially in section view of the
spray apparatus of Fig. 1; and
Fig. 3 is a front view of the spray apparatus of Fig. 1, shown in operative mode.
[0016] Referring now in specific detail to the drawings, with like reference numerals identifying
similar or identical elements, referring initially to Fig. 1, there is illustrated
a perspective view of one embodiment of a spray system 10 of the present application
shown in the operating mode. Spray system 10 applies wetted dry material droplets
15 onto a substrate 16 in the form of coating 14 and includes a spray apparatus 12
and a dry material feed assembly 18. Spray apparatus 12 preferably includes a nozzle
26 connected to a conveyance device 28. The dry material feed assembly 18 preferably
includes a bin 20, which holds a dry material 24, and a conduit 22 for delivering
the dry material from bin 20 to spray apparatus 12. As used herein, the term "dry"
material refers to any material utilized with spray apparatus 12, prior to the material
being wetted by a liquid delivered through nozzle 26.
[0017] With continued reference to Fig. 1, nozzle 26 includes an aperture (not shown) connected
to a liquid inlet 30 for entry of a liquid into the nozzle, and includes an outlet
32 through which the wetted dry material droplets 15 exit. In the present embodiment
liquid delivery hose 40 connects the liquid inlet 30 to a liquid supply 42.
[0018] Conveyance device 28 includes a dry material inlet 34 connected to conduit 22 and
a dry material outlet 36. Dry material outlet 36 is located downstream of dry material
inlet 34 and is connected to nozzle 26. The conveyance device 28 further includes
an aperture (not shown) connected to an air inlet 38 for entry of compressed air into
the conveyance device. Air inlet 38 is connected to an air hose 44 at one end thereof,
the air hose connecting the air inlet 38 to an air supply 46. The air supply 46 used
is a conventional industrial air compressor capable of producing between about 125
to 150 psig (0.86 to 1.03 MPa) air. The compressor should be designed for continuous
operation, therefore, the compressor should have active cooling and lubrication. The
preferred air compressors offer air-cooling and moisture removal from the compressed
air through blow-down and desiccation, with point-of-use filters to further remove
moisture and oil vapours from the compressed air. Two such compressors are manufactured
by Ingersall-Rand and by Champion Corp, under the names HP-100 and HRA 30-12, respectively.
The conveyance device 28 provides uniform conveyance of the dry material 24 from bin
20 to the dry material inlet 34, mixing currents (not shown) to aid in production
of wetted dry material droplets 15, and uniform discharge of the wetted dry material
droplets 15 from the outlet 32.
[0019] With continuing reference to Fig. 1, dry material feed assembly 18 includes conduit
22 which is connected at a first end to conveyance device 28 and is connected at a
second end, opposite the first end, to bin 20. Conduit 22 is preferably connected
at its first end to an inner enclosure 62 of conveyance apparatus 28 by a stub extension
(not shown). The conduit, stub extension and inner enclosure all have complementary
inner and outer diameters to aid in the delivery of dry material from the conduit
to the conveyance device. Alternatively, conduit 22 may be connected to inner enclosure
62 by a screw fitting, by machined recesses that accept thin sleeves which form protruding
stubs, or any other conventional attachment method. Conduit 22 is connected at its
second end to bin 20. The conduit is preferably connected to bin 20 by a hose clamp
fitting, but alternatively may be connected in any manner which will provide communication
between the bin and conduit without leakage of dry material and which will not reduce
the inside diameter of the conduit so as to create a check point.
[0020] The bin 20 or hopper to hold the dry material 24 preferably includes sloped side
walls and a mechanical agitator (not shown) to break up any dry material which may
become caked or stuck together, prior to the dry material entering conduit 22. The
sloped walls preferably are angled at about 60° to about 70° in order to minimize
channelling of the dry material 24 while maximizing the useful volume of the dry material.
In addition to having sloped side walls the bin 20 also preferably feeds to a single
screw or twin screw discharge which provides a reasonably uniform discharge of the
dry material from the bin 20 to conduit 22. The mechanical agitator, the bin 20 and
the single or twin screw discharge are all conventional designs, readily available
to one skilled in the art from a variety of sources including Acrison, Inc of Moonachie,
NJ.
[0021] With continuing reference to Fig. 1, conduit 22 is preferably flexible and includes
a relatively smooth bore (not shown) disposed therethrough. In the present embodiment,
the inner diameter of the bore is preferably in the range of 1 to 2 inches (25 to
51 mm), with approximately 1.625 inches (41 mm) especially preferred. The diameter
of the bore is determined by several factors including, but not limited to; the type
of material to be transported, the ability of the air compressor to provide sufficient
air volume and pressure to transport the material and the cost to do so.
[0022] Conduit 22 may be constructed from a variety of thermoplastic materials, as long
as the material utilized provides sufficient strength to preclude collapse of the
conduit under the vacuum which is utilized for conveyance of the dry material 24 from
the bin 20 to the nozzle 26. The preferred conduit material is also low in cost since
this element can be subject to high wear. Preferred conduit materials include, but
are not limited to, clear fibre-reinforced polyethylene, polybutylene or polybutadiene
tubing. Various other materials may be employed, depending upon the preference of
the designer. Some factors to consider during selection are functionality, cost, ease
of manufacture, durability and the type of material to be coated onto the substrate.
[0023] Referring now to Fig. 2, there is illustrated a perspective view partially broken
away and partially in section of the spray apparatus 12. Nozzle 26 further includes
connector 48 attached to dry material outlet 36 of conveyance apparatus 28. Connector
48 includes an upstream first section 50 adjacent the dry material outlet 36, a downstream
second section 52 adjacent outlet 32 and a nozzle ring 54 welded therebetween. In
the present embodiment the first section, the second section and the nozzle ring are
preferably cylindrical and define a longitudinal axis "X" as shown in Fig. 2. Alternatively,
connector 48 may be formed as a single member and may also be formed in a variety
of shapes. Nozzle ring 54 preferably includes a plurality of circumferentially disposed
injection holes, represented by the injection hole 55. The injection holes are most
preferably distributed in a plane perpendicular to the longitudinal axis "X", at an
equal radial distance from the longitudinal axis in order to maximize wetting of the
dry material.
[0024] Nozzle 26 further includes a liquid enclosure 56 spaced apart from nozzle ring 54.
Liquid enclosure 56 is preferably circumferentially disposed about the nozzle ring
and partially disposed about first and second sections 50 and 52 adjacent the nozzle
ring. The liquid enclosure 56 defines a liquid manifold 58 disposed between the liquid
enclosure and the nozzle ring. Liquid enclosure 56 is preferably fitted about connector
48 by a interference fit and the seams are preferably sealed by foil or putty to prevent
leakage through the liquid manifold 58. However, any method can be used to join these
elements provided that the liquid does not leak through the liquid manifold 58.
[0025] With continuing reference to Fig. 2, the conveyance device 28 further includes an
outer enclosure 60 substantially disposed about inner enclosure 62 thereby providing
essentially an airtight air manifold 64 between the outer and inner enclosures. In
the present embodiment, the outer and the inner enclosures are preferably cylindrical
and are made of aluminum, although other shapes and materials may be utilized. Aluminum
is the preferred material because it is inexpensive, easy to drill, easy to machine
and facilitates attachment of the two enclosures by welding. Other materials that
may be used are plastic, steel or any high strength low wear alloys with or without
ceramic liners.
[0026] In the embodiment of Fig. 2, inner enclosure 62 includes an elongated tubular member
66 which has a longitudinally extending inner bore 68 disposed therethrough, bore
68 defining a longitudinal axis "Y", such that dry material inlet 34 and the dry material
outlet 16 are spaced apart along the longitudinal axis "Y". In the present embodiment
inner bore 68 has a continuous diameter. Inner enclosure 62 further includes an array
of bores, represented by bore 74, disposed through tubular member 66, about the circumference
thereof, in a random pattern. The array of bores extends substantially along the length
of inner enclosure 62, the length being represented in the present embodiment as L
a. Bores 74 provide fluid communication of the compressed air between the air manifold
64 and the inner bore 68 as represented by the air flow arrow F
a.
[0027] Air manifold 64 functions to evenly distribute the compressed air to all of the bores;
dampens any fluctuations in air flow due to pressure surges, dry material surges or
plugged bores; and functions to provide uniform distribution of the vacuum, as described
further below, and uniform mixing within the inner bore.
[0028] Each of the bores 74 includes an internal diameter "d", and is disposed at an angle
α with respect to the longitudinal axis Y. The internal diameter d must be sufficient
to allow the compressed air to flow from the air manifold 64 through bores 74, into
inner bore 68 and out the dry material outlet 36, thereby producing a vacuum sufficient
to transport a predetermined volume of the dry material to the nozzle outlet at a
predetermined velocity, otherwise known as throughput. In addition, the vacuum must
also be sufficient to propel the dry material and the liquid from the nozzle onto
the substrate (not shown). Bore angle α provides directional flow of the dry material
toward the dry material outlet and is preferably angled to create mixing currents
as the dry material is moved toward the dry material outlet 36. In the present embodiment
the directional flow of the dry material is illustrated by the dry material flow arrow
F
d. The mixing currents, or vortex effect, is represented by the flow line F
v.
[0029] It is preferred that the bore angle α be less than 90 degrees because if the bore
angle is too large, the directional guidance and the vortex effect will be reduced,
consequently reducing the discharge rate from the nozzle and the turbulence of the
flow F
v. Likewise, if the angle is too small the effectiveness of the directional guidance
and the efficiency of mixing and discharge will be dampened. Therefore, it is preferred
that the bore angle be between about 15° and 45°, and it is most preferred that the
bore angle be about 30°.
[0030] The number of bores will vary depending on the desired throughput. For example, a
throughput of approximately 12 cu. ft/hr (0.34 m
3/hr) requires approximately 56 bores. Likewise, the spacing of the bores also depends
on the desired throughput. The bores are preferably disposed in a random pattern,
for maximization at the vortex effect which facilitates wetting of the dry material
as described hereinbelow.
[0031] With continued reference to Fig. 2, outer enclosure 60 is connected to air inlet
38, upstream from nozzle 26. It is preferred that the inlet be positioned non-orthogonally
with respect to the longitudinal axis Y so that tangential entry of the compressed
air into the air manifold 64 is provided. Thus the air inlet is preferably disposed
at an angle φ with respect to the longitudinal axis "Y". In the present embodiment
φ is approximately 35 to 45 degrees.
[0032] Referring now to Fig. 3, there is illustrated a front view of the spray apparatus
12 of the present application, shown in operative mode. Injection holes 55 extend
through nozzle ring 54 and create a liquid screen 78 when the liquid flows through
the injection holes 55, the liquid screen extending across the cross-sectional area
of the nozzle ring 54. In the present embodiment there are 14 injection holes, with
a separation angle of approximately 25° between each of he holes which is appropriate
for connector 48 which, in the present embodiment has an inner diameter of about 1"
(25 mm) to about 2.5" (64 mm). The number and optimum placement of the injection holes
would depend on the diameter, type of dry material, flow rate of the liquid, flow
rate of dry material, and liquid pressure. The injection hole size should, however,
be small enough to produce desired discharge stream characteristics of the wetted
material to a first order, or acceptable, degree of satisfaction. In this embodiment
the injection holes are round, however other shapes may be used with different results.
Liquid screen 78 provides for a high velocity of impingement of the liquid with the
dry material, creates very fine streams of the liquid and enough misting to ensure
that all of the dry material is at least wetted prior to ejection. Ideally the mixing
regime is turbulent whereas the discharge stream of material has more laminar flow
characteristics.
[0033] The operation of spray apparatus 12 will now be described with reference to Figs.
1-3. Spray apparatus 12 can be held by an operator or the spray apparatus can be mounted
using conventional mounting methods to move in the x-y plane on a pedestal robot of
the type known by those of ordinary skill in the art. The substrate 16 to be coated
may be any one of a variety of substrates having a variety of surface roughness. Surface
roughness refers to the peak to valley heights and the average distance or period
of the peak to valley transition on the substrate surface, and is preferred in the
present application to improve adhesion of the coating to the substrate. The preferred
substrate has a surface roughness is in the range of approximately .005" to .125"
(0.13 mm to 3.18 mm), peak to valley surface roughness, as is known in the art. Some
examples of substrates with which the system can be utilized include, but are not
limited to, cinder blocks, poured concrete, chicken wire, rough stone, plywood, straw
bales, styrofoam, stacked tires, cellulose batting, and rough-backed fibreglass composite.
Regardless of the substrate utilized, the orientation of the substrate may be horizontal,
vertical, overhead or somewhere in between.
[0034] The dry material selected preferably has a specific gravity in the range of about
0.25 (as for cork/cellulose) to about 8.00 (as for ceramics/metals). The particle
size of the dry material can range from 25 microns to 0.25 inches (6.4 mm) depending
on the specific gravity of the dry material, the length of the conduit, and the motive
pneumatic power provided by the air supply. In the present embodiment a cement/filler
mixture is used as the dry material, however, a gypsum/filler mixture can also be
utilized.
[0035] Referring now to Figs 2 and 3, the liquid supply for the present embodiment provides
water with a viscosity of 1 cps to produce a cement or coating. Any other liquid with
a comparable viscosity can be used with the nozzle 26 of this embodiment. The water
in the present embodiment is flowed at a pressure in the range of approximately 20
to 65 psig (140 to 450 kPa), so that as the water passes through the liquid screen
78 a combination of turbulent diverging streams and mist is created. Water flows from
liquid supply 42 through delivery hose 40 into liquid manifold 58 of nozzle 26, as
described above. The liquid manifold 58 aids in evening out pressure variations for
each of the injection holes 55, by being completely filled with liquid during operation.
The water pressure should be monitored by using a flow meter or actual measurements
to ensure that adequate water flow for proper impingement/wetting of the dry material
occurs.
[0036] Referring now to Figs 1 and 2, air flows from the air supply 46 through the air hose
44 and through the air inlet 38 and into the air manifold 64. The air pressure at
the inlet 38 is dependent on the specific gravity of the dry material used, the coating
rate (i.e. rate at which a particular area is covered at a certain thickness) and
the relative standoff distance S, between the nozzle and the substrate. In the present
embodiment the working range for the standoff distance is approximately 12 to about
30 inches (30.5 to 76 cm). Alternative stand-off distances are acceptable as long
as a uniform spray pattern cross-section is achieved with acceptable taper of the
coating thickness at the outer extremities. Reduced thickness at the periphery is
to be expected but should be within acceptable limits as established for the particular
application, as is known in the art.
[0037] If the air pressure at the air inlet is too strong there can be dramatic divergence
of the powder when it leaves the nozzle outlet, thus causing poor adhesion to the
substrate and excess scatter in the work area. Conversely, if the air pressure at
the air inlet is too weak then there will be an insufficient vacuum created for the
transfer of the dry material from the bin 20 to the dry material outlet 36. Thus,
the air pressure should minimize divergence while producing a sufficient vacuum to
achieve an acceptable flow rate. The nominal pressure range from the air supply to
the air inlet is about 25 psig to about 110 psig (170 - 760 kPa). Pressure in the
air manifold preferably ranges from 10 psig to about 50 psig (69 - 345 kPa).
[0038] The air from the air inlet 38 enters the air manifold 64 at a velocity that is dependent
on the pressure at the air inlet, the diameter of the air inlet and the total cross-sectional
area of the air manifold. The air velocity should be sufficient to create a back-pressure
in the air manifold which increases airflow out of the manifold, such velocity resulting
in a rise in the air manifold dynamic pressure. The air velocity should also be high
enough to create a sufficient vacuum to transport the dry material. In the present
embodiment the air velocity is in the range of approximately 50 to 500 feet per second
(15.2 - 152 m/s) which is sufficient to achieve the aforementioned effects.
[0039] The air flows from the air inlet 38, into the air manifold 64, through bores 74,
into the inner bore 68 and out the dry material outlet 36. The air flow from the air
inlet which has a diameter of approximately .45" to about .50" (11.4 - 12.7 mm) through
the small diameter bores 74 which are all angled in the same direction as shown in
Fig. 2, creates a low pressure area behind the air entering the inner bore 68 which
in turn creates the vacuum within the inner bore 68 that effectively draws the dry
material from the bin 20 up the conduit 22 and into the conveyance device 28. The
vacuum achieved by the air flow is weak, about 5-15 inches of water or 0.4-1.2 inches
of mercury (1.3 - 3.9 kPa); however, this is strong enough to draw the dry material
because of the pressure differential between the bin and the conduit and the entraining
current of the air. If the length of the conduit increases the air volume and/or velocity
will have to increase to create the same vacuum due to line losses and the mass in
the line.
[0040] The dry material, once it flows into the dry material inlet 34, flows adjacent the
bores 60. The dry material flow F
d increases in velocity or accelerates, along L
a and swirls because of the vortex effect created by the angle α of the bores, as described
above. The swirling created by the vortex effect F
v separates the dry material particles, consequently aiding in wetting of the dry material,
because it increases the dry material surface exposed to the liquid downstream. The
pressure at the dry material inlet in the present embodiment is about 26-27 inches
of mercury (88 - 91.4 kPa). Alternate pressures at the dry material inlet are possible
as long as a satisfactory coating is achieved.
[0041] The accelerated and separated dry material particles are drawn through the dry material
outlet 36 and into the nozzle 26. Referring to Figs. 2 and 3, the dry material flows
through the liquid screen 78 created by the flow of the liquid through the holes 55
and nozzle ring 54. As the material flows out of the nozzle outlet it emerges as a
uniform stream of wetted dry material droplets 15 with sufficient velocity to provide
good "splat" formation on impact with the substrate, i.e. sufficient flattening of
the coating droplets as they impact the substrate, with minimum rebound. The formation
of the wetted dry material droplets occurs as the dry material is mixed with the water
at the liquid screen and in the turbulent flow immediately downstream of the nozzle
outlet 36. The wetted dry material droplets are hygroscopic particles of dry material
that have surface adsorbed the liquid. These wetted dry material droplets will adsorb
the liquid and contact the substrate 16. The combination of velocity of the wetted
dry material droplets and standoff combine to adhere the droplets to the substrate
forming the coating 14. In time the coating cures to form concrete.
[0042] Wetting of the droplets can be modified and improved by adjusting the surface to
volume ratio of the dry material to the liquid, water impingement, duration of exposure
to the liquid between the liquid screen and substrate and by adjusting the turbulence
within the inner chamber and at the nozzle outlet.
[0043] The dry material to water ratio is carefully monitored by a flow meter and controlled
by operator controlled valves in order to obtain the desired wetted droplets and hence
properties of the concrete, (i.e. compressive strength and density). Proper mixing
is verified by product testing, but is assumed based on consumption (retention) of
the materials converged as a unit mass (minimum waste). The amount of waste will increase
as the mixture ratio deviates above or below the nominal. This waste is generated
by material bouncing off or sloughing off the substrate which indicates a less than
desirable mixture. On a vertical surface the adherence and build rate indicate the
quality of mixing. In addition to the above, there may also be on-line control provided
by a flow controller, a motion controller, a thickness monitor or the like.
[0044] Thickness building occurs by traversing the substrate in a sweeping, horizontal or
vertical motion. The rate of thickness building with vary with the materials used.
For example, on a vertical surface with a standoff of 24 inches (61 cm) and a swath,
or width, of about 4" (10.2 cm) a cork/cement mixture was sprayed at 4 feet per second
(1.22 m/s) with a thickness per pass of 0.125" (3.175 mm) and a transfer efficiency
of about 80% (i.e. coating sticking). This yielded a deposition rate of approximately
48 sq. feet (4.46 m
2) per minute at a thickness of 0.125" (3.175 mm) or 12 sq. feet (1.11 m
2) per minute at a thickness of 0.5" (12.7 mm).
[0045] The spray system of the present application as described hereinabove provides for
uniform conveyance of the dry material because the motive force created by the vacuum
to move the dry material is substantially equal throughout the conduit. In addition,
a conveyance device is provided which improves wetting of the dry material by creating
a vortex effect which separates the dry material in an inexpensive manner, without
moving parts. The present apparatus also eliminates concerns of pot-life, waste and
product uniformity by wetting the dry material close to the nozzle outlet.
[0046] Another advantage of the present system is that it utilizes a relatively low vacuum
because the point of wetting is located downstream, therefore the conveyance device
moves the dry powder, not a more viscous and adherent liquid/powder mixture that would
require a stronger vacuum.
[0047] Other advantages of the present apparatus include inexpensive construction, ease
of manufacture, ease of use and cleaning, highly adjustable spray rates, ease of control
of water-to-cement ratio, uniform coating thickness and greater deposition rates,
improved strength of the cement product, decreasing rebound, and the ability to blend
many dry materials with the conveyance device.
[0048] While a particular invention has been described with reference to an illustrated
embodiment, this description is not meant to be construed in a limiting sense. It
is understood that although the present invention has been described in a preferred
embodiment, various modifications of the illustrative embodiment, as well as additional
embodiments of the invention, will be apparent to persons skilled in the art upon
reference of this description without departing from the scope of the invention, as
recited in the claims appended hereto.
1. A spray apparatus (12) comprising a conveyance device (28), said device including
an inner enclosure (62) and an outer enclosure (60), the outer enclosure (60) being
disposed around the inner enclosure (62) to form an elongate air manifold (64) between
the enclosures, the elongate manifold having an inlet (38) for compressed air, and
a plurality of axially spaced bores (74) being provided in a wall of the inner enclosure
(62) to allow fluid communication between said inner enclosure (62) and said air manifold
(64), said bores being angularly oriented relative to a longitudinal axis of the enclosures
to create a vacuum in said inner enclosure when air flows through said bores, said
vacuum serving to force the material through said device, said device also having
a material inlet (34) and a material outlet (36), said apparatus also comprising a
nozzle (26) with a liquid inlet (30), such that in use material to be sprayed can
pass through the material inlet (34) and the material outlet (36) and be wetted as
it passes through the nozzle (26).
2. A spray apparatus (12) as claimed in claim 1 for application of a wetted dry material
(15), wherein said air inlet (38) through which compressed air enters is provided
in said outer enclosure; and wherein said inner enclosure (62) includes an elongated
tubular member (66) having a longitudinally extending inner bore (68) disposed therethrough,
said bore defining said longitudinal axis, said material inlet (34) being disposed
along said longitudinal axis (Y), and said material outlet (36) being spaced apart
from said dry material inlet (34) along said longitudinal axis (Y), said dry material
outlet (36) being in communication with said nozzle (26); and wherein each of said
bores (74) has an internal diameter (d), said internal diameter (d) being sufficient
to allow said compressed air to flow from said air manifold (64) through said inner
bore (68), thereby producing a vacuum sufficient to transport a predetermined volume
of said dry material through said inner bore (68) to said dry material outlet (36)
and into said nozzle (26) where said dry material is wetted by said liquid, said vacuum
also being sufficient to propel said wetted dry material from said nozzle (26) onto
a substrate (S) in order to coat said substrate (S) with said wetted dry material
(15).
3. The spray apparatus of claim 2, wherein said array of bores (74) are disposed at an
angle (α) with respect to said longitudinal axis (Y).
4. The spray apparatus of claim 3, wherein said bore angle (α) provides directional flow
of said dry material through said inner bore (68), toward the dry material outlet
(16), said bore angle (α) also creating mixing currents.
5. The spray apparatus of either of Claims 3 and 4, wherein said angle (α) is between
about 15° to about 45°.
6. The spray apparatus of any of claims 2 to 5, wherein said nozzle (26) further includes
a nozzle ring (54), said nozzle ring (54) having a plurality of injection holes (55)
disposed therethrough.
7. The spray apparatus of Claim 6, wherein said nozzle further includes a liquid enclosure
(56) spaced from said nozzle ring (54).
8. The spray apparatus of Claim 7, wherein the space disposed between said liquid enclosure
(56) and said nozzle ring (54) defines a liquid manifold (58).
9. The spray apparatus of Claim 8, wherein liquid passing from the liquid manifold (58)
through said injection holes (55) forms a liquid screen.
10. The spray apparatus of any claims 2 to 9, wherein said air inlet (38) is disposed
at an angle (φ) with respect to said longitudinal axis (Y).
11. The spray apparatus of Claim 10, wherein said angle (φ) is between about 35° to about
45°.
1. Spritzvorrichtung (12) mit einer Fördereinrichtung (28), die eine innere Hülle (62)
und eine äußere Hülle (60) aufweist, wobei die äußere Hülle (60) um die innere Hülle
(62) herum angeordnet ist, um einen länglichen Luftverteiler (64) zwischen den Hüllen
zu bilden, wobei der längliche Verteiler einen Einlass (38) für Druckluft aufweist
und wobei eine Mehrzahl von axial voneinander beabstandeten Bohrungen (74) in einer
Wandung der inneren Hülle (62) ausgebildet ist, um eine Fluidverbindung zwischen der
inneren Hülle (62) und dem Luftverteiler (64) zu ermöglichen, wobei die Bohrungen
relativ zu einer Längsachse der Hüllen in einem Winkel orientiert sind, um einen Unterdruck
in der inneren Hülle zu erzeugen, wenn Luft durch die Bohrungen hindurch strömt, wobei
der Unterdruck für eine zwangsweise Beförderung des Materials durch die Einrichtung
dient, wobei die Einrichtung ferner einen Materialeinlass (34) und einen Materialauslass
(36) aufweist, wobei die Vorrichtung ferner eine Düse (26) mit einem Flüssigkeitseinlass
(30) aufweist, so dass im Gebrauch zu spritzendes Material durch den Materialeinlass
(34) und durch den Materialauslass (36) passieren kann und bei seiner Passage durch
die Düse (26) befeuchtet werden kann.
2. Spritzvorrichtung (12) nach Anspruch 1 zur Aufbringung eines befeuchteten Trockenmaterials
(15), wobei der Lufteinlass (38), durch den Druckluft eintritt, in der äußeren Hülle
(62) vorgesehen ist; und wobei die innere Hülle (62) ein längliches rohrförmiges Element
(66) mit einem darin angeordneten, sich in Längsrichtung erstreckenden Innenhohlraum
(68) aufweist, der die Längsachse bildet, wobei der Materialeinlass (34) längs der
Längsachse (Y) angeordnet ist und der Materialauslass (36) von dem Trockenmaterialeinlass
(34) entlang der Längsachse (Y) beabstandet ist, wobei der Trockenmaterialauslass
(36) mit der Düse (26) in Verbindung steht; und wobei jede der Bohrungen (74) einen
Innendurchmesser (d) aufweist, der ausreichend ist, um ein Strömen der Druckluft von
dem Luftverteiler (64) durch den Innenhohlraum (68) zu ermöglichen, um dadurch einen
Unterdruck zu erzeugen, der ausreichend ist, um ein vorbestimmtes Volumen des Trockenmaterials
durch die Innenbohrung (68) zu dem Trockenmaterialauslass (36) sowie in die Düse (26)
hinein zu transportieren, wo das Trockenmaterial von der Flüssigkeit befeuchtet wird,
wobei der Unterdruck ferner ausreichend ist, um das befeuchtete Trokkenmaterial von
der Düse (26) auf ein Substrat (S) voranzutreiben, um das Substrat (S) mit dem befeuchteten
Trockenmaterial (15) zu beschichten.
3. Spritzvorrichtung nach Anspruch 2,
wobei die Anordnung von Bohrungen (74) in einem Winkel (α) in Bezug auf die Längsachse
(Y) angeordnet ist.
4. Spritzvorrichtung nach Anspruch 3,
wobei der Bohrungswinkel (α) eine gerichtete Strömung des Trockenmaterials durch den
Innenhohlraum (68) in Richtung auf den Trockenmaterialauslass (16) schafft, wobei
der Bohrungswinkel (α) ferner Mischströme erzeugt.
5. Spritzvorrichtung nach einem der Ansprüche 3 und 4,
wobei der Winkel (α) ca. 15° bis ca. 45° beträgt.
6. Spritzvorrichtung nach einem der Ansprüche 2 bis 5,
wobei die Düse (26) ferner einen Düsenring (54) aufweist, wobei der Düsenring (54)
eine Mehrzahl von darin angeordneten Einspritzöffnungen (55) aufweist.
7. Spritzvorrichtung nach Anspruch 6,
wobei die Düse ferner eine Flüssigkeits-Umschließung (56) aufweist, die von dem Düsenring
(54) beabstandet ist.
8. Spritzvorrichtung nach Anspruch 7,
wobei der zwischen der Flüssigkeits-Umschließung (56) und dem Düsenring (54) angeordnete
Raum einen Flüssigkeitsverteiler (58) bildet.
9. Spritzvorrichtung nach Anspruch 8,
wobei von dem Flüssigkeitsverteiler (58) durch die Einspritzöffnungen (55) strömende
Flüssigkeit einen Flüssigkeitsschleier bildet.
10. Spritzvorrichtung nach einem der Ansprüche 2 bis 9,
wobei der Lufteinlass (38) in einem Winkel (φ) in Bezug auf die Längsachse (Y) angeordnet
ist.
11. Spritzvorrichtung nach Anspruch 10,
wobei der Winkel (φ) ca. 35° bis ca. 45° beträgt.
1. Appareil de pulvérisation (12) comprenant un dispositif de transport (28), ledit dispositif
comprenant une enceinte interne (62) et une enceinte externe (60), l'enceinte externe
(60) étant disposée autour de l'enceinte interne (62) pour former un collecteur d'air
allongé (64) entre les enceintes, le collecteur allongé ayant un orifice d'entrée
(38) pour de l'air comprimé, et une pluralité d'alésages (74) axialement espacés étant
disposée dans une paroi de l'enceinte interne (62) pour permettre une communication
fluidique entre ladite enceinte interne (62) et ledit collecteur d'air (64), lesdits
alésages étant angulairement orientés par rapport à un axe longitudinal des enceintes
pour créer un vide dans ladite enceinte interne lorsque de l'air s'écoule à travers
lesdits alésages, ledit vide servant à forcer la matière à travers ledit dispositif,
ledit dispositif comportant également un orifice d'entrée (34) de matière et un orifice
de sortie (36) de matière, ledit appareil comprenant également une buse (26) avec
un orifice d'entrée de liquide (30), de sorte qu'en utilisation, la matière à pulvériser
peut passer à travers l'orifice d'entrée (34) de matière et l'orifice de sortie (36)
de matière (36) et peut être mouillée à mesure qu'elle passe à travers la buse (26).
2. Appareil de pulvérisation (12) selon la revendication 1 pour application d'une matière
sèche mouillée (15), dans lequel ledit orifice d'entrée d'air (38) à travers lequel
de l'air comprimé entre est disposé dans ladite enceinte externe ; et dans lequel
ladite enceinte interne (62) comporte un élément tubulaire allongé (66) ayant un alésage
interne (68) s'étendant longitudinalement disposé entre ceux-ci, ledit alésage définissant
ledit axe longitudinal, ledit orifice d'entrée de matière (34) étant disposé suivant
ledit axe longitudinal (Y) et ledit orifice de sortie (36) de matière étant espacé
dudit orifice d'entrée (34) de matière sèche le long dudit axe longitudinal (Y), ledit
orifice de sortie (36) de matière sèche étant en communication avec ladite buse (26)
; et dans lequel chacun desdits alésages (74) a un diamètre interne (d), ledit diamètre
interne (d) étant suffisant pour permettre audit air comprimé de s'écouler depuis
ledit collecteur d'air (64) à travers ledit alésage interne (68), produisant, par
cet effet, un vide suffisant pour transporter un volume prédéterminé de ladite matière
sèche à travers ledit alésage interne (68) vers ledit orifice de sortie (36) de matière
sèche et dans ladite buse (26) où ladite matière sèche est mouillée par ledit liquide,
ledit vide étant également suffisant pour propulser ladite matière sèche mouillée
à partir de ladite buse (26) sur un substrat (S) afin de revêtir ledit substrat (S)
de ladite matière sèche mouillée (15).
3. Appareil de pulvérisation selon la revendication 2, dans lequel ladite rangée d'alésages
(74) est disposée selon un angle (α) par rapport audit axe longitudinal (Y).
4. Appareil de pulvérisation selon la revendication 3, dans lequel ledit angle (α) d'alésage
procure un écoulement directionnel de ladite matière sèche à travers ledit alésage
interne (68), vers l'orifice de sortie (16) de la matière sèche, ledit angle (α) d'alésage
créant également des courants de mélange.
5. Appareil de pulvérisation selon l'une quelconque des revendications 3 et 4, dans lequel
ledit angle (α) se situe entre environ 15° à environ 45°.
6. Appareil de pulvérisation selon l'une quelconque des revendications 2 à 5, dans lequel
ladite buse (26) comporte, en outre, une bague (54) de buse, ladite bague (54) de
buse ayant une pluralité de trous d'injection (55) disposée à travers celle-ci.
7. Appareil de pulvérisation selon la revendication 6, dans lequel ladite buse comporte,
en outre, une enceinte liquide (56) espacée de ladite bague (54) de buse.
8. Appareil de pulvérisation selon la revendication 7, dans lequel l'espace disposé entre
ladite enceinte liquide (56) et ladite bague (54) de buse définit un collecteur liquide
(58).
9. Appareil de pulvérisation selon la revendication 8, dans lequel le liquide passant
du collecteur liquide (58) à travers lesdits trous d'injection (55) forme un écran
liquide.
10. Appareil de pulvérisation selon l'une quelconque des revendications 2 à 9, dans lequel
ledit orifice d'entrée d'air (38) est disposé selon un angle (φ) par rapport audit
axe longitudinal (Y).
11. Appareil de pulvérisation selon la revendication 10, dans lequel ledit angle (φ) est
entre environ 35° à environ 45°.