U.S. patent application number 10/550769 was filed with the patent office on 2006-06-01 for nozzles.
Invention is credited to Mitchell Joe Dodson.
Application Number | 20060113400 10/550769 |
Document ID | / |
Family ID | 31500674 |
Filed Date | 2006-06-01 |
United States Patent
Application |
20060113400 |
Kind Code |
A1 |
Dodson; Mitchell Joe |
June 1, 2006 |
Nozzles
Abstract
A nozzle (10) for producing a flat spray pattern, the nozzle
comprising a fluid passageway terminating in an end wall having an
outlet aperture (20), the fluid passageway having at least one
deflector (3, 4) that deflects the fluid towards the aperture; and
adjustable means (21,22) to vary the cross-section of the aperture,
and Snowmaking equipment comprising at least one nozzzle of the
above kind, the nozzle being inclined upwardly to, in use, project
a plume of waterdroplets the nozzle being positioned adjacent a jet
of compressed air, the variation in the cross-section of the
aperture reflecting the characteristics of the plume.
Inventors: |
Dodson; Mitchell Joe;
(Tawonga South, AU) |
Correspondence
Address: |
HOFFMANN & BARON, LLP
6900 JERICHO TURNPIKE
SYOSSET
NY
11791
US
|
Family ID: |
31500674 |
Appl. No.: |
10/550769 |
Filed: |
March 2, 2004 |
PCT Filed: |
March 2, 2004 |
PCT NO: |
PCT/AU04/00433 |
371 Date: |
September 27, 2005 |
Current U.S.
Class: |
239/14.2 ;
239/418; 239/502; 239/505; 239/513; 239/520; 239/521 |
Current CPC
Class: |
B05B 15/62 20180201;
B05B 1/046 20130101; F25C 2303/0481 20130101; B05B 7/0807 20130101;
B05B 1/30 20130101; B05B 15/622 20180201; F25C 3/04 20130101 |
Class at
Publication: |
239/014.2 ;
239/502; 239/505; 239/513; 239/520; 239/521; 239/418 |
International
Class: |
F25C 3/04 20060101
F25C003/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 3, 2003 |
AU |
2003901631 |
Claims
1. A nozzle for producing a flat spray pattern, the nozzle
comprising a fluid passageway terminating in an end wall having an
outlet aperture, the fluid passageway having at least one deflector
that deflects the fluid towards the aperture; and adjustable means
to vary the cross section of the aperture.
2. The nozzle according to claim 1, wherein the fluid passageway
has two deflectors in the form of wall portions that converge
towards the aperture.
3. The nozzle according to claim 1, wherein the means to vary the
cross section of the aperture comprises displaceable shutters that
move from opposite sides of the aperture to decrease or increase
the cross section of the aperture.
4. The nozzle according to claim 1, wherein the end wall is
furnished by a cross member that extends across the end of the
fluid passageway, the cross member supporting axially displaceable
pins adapted to move across the aperture to decrease or increase
the cross section of the aperture.
5. The nozzle according to claim 4, wherein means is provided to
control the axial displacement of the pins.
6. The nozzle according to claim 4, wherein in adjusting the cross
section of the aperture the pins move the same distance in opposing
directions.
7. The nozzle according to claim 4, wherein the fluid passageway
and cross member are circular.
8. The nozzle according to claim 7, wherein the diameter of the
fluid passageway is the same as the diameter of the cross
member.
9. The nozzle according to claim 1, wherein each pin is coupled to
an internally threaded block, a shaft being in threaded engagement
with each block whereby rotation of the shaft causes movement of
the blocks to displace the pins in opposite axial directions.
10. A nozzle for producing a flat spray pattern, the nozzle
comprising a T-piece, the leg of which is a pipe defining a fluid
passageway and the head of the T being a pipe positioned across the
end of the fluid passageway, an aperture is positioned in the head
of the T-piece axially aligned with the fluid passageway, the head
pipe defining two deflectors that converge towards the aperture,
and a pin terminating in a planar end face is positioned at each
end of the head of the T-piece to be displaceable along the T-piece
so that the end faces of the pin can move across the aperture to
vary the cross section of the aperture.
11. The nozzle according to claim 10, wherein the pins are in screw
threaded engagement with the head of the T-piece so that axial
displacement of the pins across the aperture is effected by
rotation of the pins.
12. Snowmaking equipment comprising at least one nozzle according
to claim 1, the nozzle being inclined upwardly to, in use, project
a plume of water droplets, the nozzle being positioned adjacent a
jet of compressed air, the variation in the cross section of the
aperture reflecting the characteristics of the plume.
13. Snowmaking equipment comprising at least one flat jet water
nozzle inclined upwardly to, in use, project a plume of water
droplets, the nozzle being positioned adjacent a jet of compressed
air, the nozzle having an outlet aperture, and means to vary the
cross section of the aperture to adjust the characteristics of the
plume to suit the ambient conditions.
14. The snowmaking equipment according to claim 12, wherein the jet
of compressed air is placed downstream of the nozzle.
15. The snowmaking equipment according to claim 14, wherein the jet
of compressed air comprises an array of apertures.
16. The snowmaking equipment according to claim 15, wherein the
width of the jet equates to the width of the plume of the water
droplets.
17. The snowmaking equipment according to claim 12, wherein the
plume of water droplets escaping from the nozzle is directed
tangentially against the underside of the air jet.
18. The snowmaking equipment according to claim 12, wherein four
flat jet water nozzles are positioned spaced apart in a horizontal
plane, the spacing of the nozzles equating to the maximum width of
each plume.
19. The snowmaking equipment according to claim 12 wherein the
water nozzle, nozzles and jet or jets of compressed air are
supported on a head, the head being pivotally inclined to a self
standing mast.
20. The snowmaking equipment according to claim 19 wherein the mast
is rotatable about a vertical axis.
21. The snowmaking equipment according to claim 19, wherein the
head is vertically adjustable relative to the mast whilst maintain
the angle of inclination of the water nozzle and air jet.
22. The snowmaking equipment according to claim 19, wherein the
head includes four nozzles spaced so that the plumes meet at their
widest points.
23-24. (canceled)
Description
FIELD OF THE INVENTION
[0001] This invention relates to nozzles and more particularly to
flat jet nozzles especially, but not exclusively, for use in
snowmaking equipment. The invention also relates to snowmaking
equipment.
BACKGROUND OF THE INVENTION
[0002] There are many types, designs and configurations of nozzles
that are particularly used in industrial situations for the
spraying of fluids. Nozzles of this kind are used in the
irrigation, cleaning, painting and fire extinguishing industries.
Spraying systems incorporating nozzles of this kind have wide
ranging industrial applications. Nozzles are also used in
snowmaking equipment and the nozzle that is the subject of this
invention has its primary use in snowmaking equipment.
[0003] Flat jet nozzles that produce a flat spray pattern are
known. They distribute liquid as a flat or sheet type spray. Some
use elliptical orifices with the axis of the spray pattern being a
continuation of the axis of the inlet pipe connection. Others use a
deflector, the deflecting surface diverting the spray pattern away
from the axis of the inlet pipe connection. There are a number of
different nozzles that provide a flat spray pattern. Variations of
these nozzles provide considerable variations in the spray pattern.
The adjustability of nozzles of this kind is usually confined to
variation in the liquid pressure.
[0004] There are a number of parameters that contribute to
successful snowmaking. The constant fluctuations in these
parameters means that efficient snowmaking equipment needs to be
continually adjustable to ensure optimum efficiency. The
adjustability and resultant efficiency is critical to successful
snowmaking and often critical to the economics of a ski resort.
[0005] It is the issues surrounding the design of nozzles that
produce a flat spray pattern and the issues of snowmaking equipment
that have brought about the present invention and its
derivatives.
SUMMARY OF THE INVENTION
[0006] In accordance with one aspect of the present invention there
is provided a nozzle for producing a flat spray pattern, the nozzle
comprising a fluid passageway terminating in an end wall having an
outlet aperture, the fluid passageway having at least one deflector
that deflects the fluid towards the aperture; and adjustable means
to vary the cross section of the aperture.
[0007] Preferably, the fluid passageway has at least two wall
portions that converge towards the aperture. The means to vary the
cross section of the aperture may comprise displaceable shutters
that move from opposite sides of the aperture to close off or
increase the aperture of the cross section.
[0008] Preferably, the end wall is furnished by a cross member that
extends across the end of the fluid passageway, the tube supporting
axially displaceable pins adapted to move across the aperture to
decrease or increase the cross section of the aperture.
[0009] In a preferred embodiment means is provided to control the
axial displacement of the pins.
[0010] In a preferred embodiment the nozzle comprises a T-piece,
the leg of which is a pipe defining a fluid passageway and the head
of the T being a pipe positioned across the end of the fluid
passageway, an aperture is positioned in the head of the T-piece
axially aligned with the fluid passageway, and a pin terminating in
a planar face is positioned at each end of the head of the T-piece
to be displaceable along the T-piece so that the end faces of the
pin can move across the aperture to vary the cross section of the
aperture.
[0011] In the preferred embodiment the fluid passageway and cross
member are circular and the diameter of the fluid passageway is the
same as the diameter of the cross member. It is also preferable
that in adjusting the cross section of the aperture the pins move
the same distance in opposing directions.
[0012] According to a further aspect of the present invention there
is provided snowmaking equipment comprising at least one flat jet
water nozzle inclined upwardly to, in use, project a plume of water
droplets, the nozzle being positioned adjacent a jet of compressed
air, the nozzle having an outlet aperture, and means to vary the
cross section of the aperture to adjust the characteristics of the
plume to suit the ambient conditions.
[0013] Preferably, the jet of compressed air is placed downstream
of the nozzle. The jet of compressed air preferably comprises an
array of apertures. The width of which equates to the width of the
plume at the air jet.
[0014] Preferably, four flat jet water nozzles are positioned
spaced apart in a horizontal plane, the spacing of the nozzles
equating to the maximum width of each plume.
[0015] In accordance with a still further aspect of the present
invention there is provided snowmaking equipment comprising a
rotatable mast that supports a head, the head comprising at least
two spaced apart flat jet water nozzles, each nozzle having an
outlet aperture, each nozzle being positioned adjacent a jet of
compressed air and means to vary the cross section of each aperture
to vary the output of each nozzle.
[0016] Preferably, the head is vertically adjustable whilst
maintaining the angle of inclination of water and air nozzles. In a
preferred embodiment, the plume of water droplets escaping from
each nozzle is directed tangentially against the underside of the
air jet. The air jet preferably has an array of a plurality of
spaced outlet apertures, the width of the array being substantially
the same as the width of the plume at the air jet.
[0017] Preferably, the head includes four nozzles spaced so that
the plumes meet at their widest points.
DESCRIPTION OF THE DRAWINGS
[0018] Embodiments of the present invention will now be described
by way of example only in which:
[0019] FIG. 1 is a perspective view of snowmaking equipment,
[0020] FIG. 2 is a side elevational view of the snowmaking
equipment in three different vertical positions,
[0021] FIG. 3 is a plan view of the snowmaking equipment,
[0022] FIG. 4 is a side elevational view of the snowmaking
equipment when supported on an uneven inclined surface,
[0023] FIG. 5 is a detailed perspective view of the head of the
snowmaking equipment shown in FIG. 1,
[0024] FIGS. 6a, 6b and 6c are cross sectional views taken along
the lines 6-6 of FIG. 5 showing a water jet and air nozzle in three
different relative positions,
[0025] FIG. 7 is an enlarged cross sectional view of part of the
head enclosed by the circle 7 in FIG. 5,
[0026] FIG. 7a is a cross sectional view of two adjacent nozzles
illustrating a means of adjusting the nozzles,
[0027] FIGS. 8a and 8b are cross sectional views taken along the
lines 8-8 of FIG. 7 showing the outlet of the water jet in two
positions,
[0028] FIG. 9 is a cross sectional view taken along the lines x and
showing the physical association of a water jet with an air
jet,
[0029] FIG. 10 is a cross sectional view illustrating the
association of a plume of water contacting the air jet,
[0030] FIG. 11 is a perspective underside view of the air jet,
[0031] FIG. 12 is a perspective view of a head for snowmaking
equipment of a second embodiment,
[0032] FIG. 13 is a plan view of the head,
[0033] FIGS. 14a and 14b are plan views of the head illustrating
movement of mechanisms to adjust flat jet nozzles,
[0034] FIG. 15 is an enlarged perspective view within the area 15
of FIG. 13 illustrating the adjustment mechanism of the flat jet
nozzle, and
[0035] FIG. 16 is an enlarged perspective view within the area 16
of FIG. 13 illustrating the relationship between the flat jet water
nozzle and air nozzle.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] The preferred embodiments that are illustrated in the
accompanying drawings relate to snowmaking equipment that
incorporates an adjustable flat jet nozzle. The invention covers
both the nozzle per se applicable to many spraying industries as
well as snowmaking equipment that incorporates a nozzle, it is
however understood that the snowmaking equipment has many other
features that contribute to its improved design and operation.
[0037] The nozzle 10 is shown in detail in FIGS. 7 and 8. Although
it is shown in association with snowmaking equipment it is
understood that this nozzle is applicable to many fields totally
unrelated to snowmaking. The nozzle has applicability in any
industrial spraying application where there is a need for a
variable flat jet nozzle.
[0038] As shown in FIGS. 7 to 10 of the accompanying drawings, an
adjustable nozzle 10 comprises a T-piece 11, the leg 12 of which is
a cylindrical fluid passageway that is secured to a rectangular
mounting plate 13. Welded across the end of the leg 12 is a piece
of cylindrical pipe 15 with a circular outlet aperture 20
positioned co-axially with the axis of the fluid passageway. The
pipe is hollow to accommodate a pair of cylindrical pins 21, 22.
Each pin is cylindrical and terminates in a planar face 23 at one
end. An O-ring 24 is located in a groove on the exterior of the pin
spaced from but close to the face 23. The other end of the pin is
provided with an external thread 26 that is arranged to be a screw
fit within a threaded sleeve 30 which is in turn welded to a radial
flange 31 that joins a larger hollow sleeve 32 that operates as a
pin guide. As shown in FIG. 10, the circular cross section of the
T-piece head 15 provides two converging surfaces 3 and 4 that cause
water flowing towards the aperture 20 to converge towards the
aperture. The planar ends 23 of the pins 21, 22 operate to vary the
cross section of the aperture 20. As the pins move in the pipe the
ends progressively close off the aperture 20 as shown in FIGS. 8a
and 8b.
[0039] In other options the T-piece head (not shown) could be of
triangular cross section with opposed sides converging towards the
aperture. A square tube with the aperture in one corner also
provides the two converging walls.
[0040] In other embodiment the head could be a rectangular block
with an elongate groove with an aperture in the base of the groove.
The pins are in block form to slide in the groove. The adjacent end
of the pins are bevelled to define converging surfaces with the
straight edges of the pins being adjacent the aperture to define an
adjustable slit across the aperture.
[0041] The nozzle described above provides a flat spray profile.
The exact profile varies in dependence with the position of the
pins 21, 22 in the aperture 20.
[0042] Displacement of the pin guides 32 causes displacement of the
pins 21, 22 to vary the cross section of the aperture 20. If the
pin guides are coupled to a suitable servo mechanism the nozzle can
have a constantly variable output depending on the position of the
pins. Ideally, each pin moves by the same amount in opposite
directions.
[0043] The nozzle has the advantage that its output can be varied
whilst maintaining full input fluid pressure. This differs from
most flat jet nozzles where the adjustability is either by
variation of the input fluid pressure or by changing the nozzle
aperture by replacing the end of the nozzle.
[0044] Although in the preferred embodiment the outlet aperture 20
of the nozzle is circular, it is understood that other shapes are
envisaged. A larger diameter aperture provides a small spray angle
whilst a smaller aperture diameter increases the spray angle. A
wide slot on the other hand provides a very wide spray angle. The
fluid flow can be increased by increasing the width of the aperture
20 by moving the pins apart 21, 22. Conversely, a decrease in fluid
flow is achieved by moving the pins 21, 22 together. Preferably,
the pressure always remains constant, namely at its maximum. Use at
maximum pressure results in higher velocity and smaller spray
particle size. The closer the pins are together results in small
spray particles and less fluid flow which is ideal for
snowmaking.
[0045] Although the variable flat nozzle 10 described above is
specifically designed for use with snowmaking equipment, it is
understood that this nozzle could be used in a wide range of other
industrial applications. The adjustability of the nozzle could be
manual through use of a spanner, Allen key or similar such tool to
displace the pins or through more automated means by driving the
pin guides as shown in FIG. 7.
[0046] FIGS. 1 to 11 illustrate snowmaking equipment S utilising a
bank of four nozzles 10 of the kind described above. As shown in
FIG. 3, the nozzles 10 are mounted spaced apart so that the plumes
of water particles that are ejected from the nozzles meet at their
maximum width.
[0047] As shown in FIG. 5, the snowmaking equipment S comprises a
mast M that is pivotally rotated about an adjustable base structure
B that comprises three legs 51, 52, 53 mounted on adjustable skids
55 that extend outwardly by about 2 metres and are equally spaced
around a common pitch circle. The legs 51, 52, 53 support an
adjustable triangular bracing structure 60 on which the mast M is
rotatably mounted. The mast comprises a vertical column 61 that is
mounted centrally of the base structure B, the vertical column 61
has a rearwardly trailing arm 62 that terminates in a mounting
bracket 63 that in turn pivotally supports two closely spaced
parallelogram linkages 64, 65. The parallelogram linkages 64, 65
pivotally supports a head assembly H that is in the form of a pair
of triangular support frames 66, 67 that are rigidly secured to the
spray head H.
[0048] The spray head H is shown in FIG. 5 and essentially
comprises an elongate water pipe 71 referred to as a manifold that
has projecting therefrom four adjustable nozzle assemblies 10 of
the kind described above and shown in FIGS. 7 to 9. Each nozzle 10
is also associated with a compressed air jet 75 as shown in FIG. 5.
The jets 75 are interconnected by pipe 76 and fed by a common
source of compressed air. The array of nozzles 10 and air jets 75
support a rectangular wind vane 74 shown in FIGS. 1 and 3. The
compressed air and water are supplied to the head H by flexible
pipes that run down the mast M to the ground as shown in FIG.
4.
[0049] The parallelogram linkages 64, 65 are in a parallel closely
spaced configuration. Each parallelogram linkages 64, 65 as shown
in FIG. 4 comprises two elongate arms 68, 69 that are pivoted at
one end to the mounting bracket 63 on the mast M and the triangular
frame 66 or 67 on the spray head H at the other end. The
parallelogram linkage has the opportunity of assuming a variety of
vertical positions as shown in FIG. 2. At the highest position the
arms 68, 69 extend vertically whilst at a lowest position the arms
68, 69 are slightly extended below the horizontal. In each case the
triangular support for the jet assemblies remains at the same angle
to the horizontal. The triangular frames 66, 67 can be covered in
sheet material to act as a subsidiary wind vane to the primary vane
74. The parallelogram linkages are attached to trailing arm 80 that
is coupled to a spring 81 that is in turn attached to rearwardly
extending flange 82 on the base of the mast M. The spring 81 acts
to urge the parallelogram linkages 64, 65 to assume the vertical
position and the lower positions are caused by wind impinging on
the vane 74 to deflect the assembly down against the spring. It is
understood that the spring could be adjustable and it is further
understood that other mechanisms such as pneumatic or hydraulic
dampers could replace the spring. The maximum height of the
assembly S is approximately 6 metres.
[0050] As mentioned above, the spray head H incorporates four
adjustable flat nozzles, each associated with a compresses air jet.
The association of each adjustable flat nozzle 10 with the
compressed air is illustrated in FIGS. 9 to 11. The air jet 75 is
in the form of a tapered jet body 76 of triangular cross section
that is inclined downwardly from the horizontal by 21.degree.. The
jet body 75 terminates in a plurality, preferably between three and
fourteen small apertures 77. The underside of each aperture 77 has
a trailing scalloped groove 78 that is cut out of the underside of
the air jet and the arrangement of the water jets 10 is such that,
as shown in FIG. 10, the water first hits the underside of the air
jet 75 as it tangentially passes the ends of the air jets and the
apertures 77. The holes 77 in the end 79 of the tapered nozzle body
are drilled so that they extend to the bottom surface to merge with
the trailing scalloped grooves 78. The thin edge that is defined at
the top of the apertures reduces the surface area for ice to
adhere. Furthermore, the velocity of the water plume P, as it
passes the apertures, clears the ice away.
[0051] FIGS. 6a to 6c illustrates the adjustability of the air
nozzle 75 and water jets 10. The air tube 76 is mounted on a
elongate shaft 101 that is axially displaceable about a sleeve 102
that is held to a support bracket via a screw 103. The jets 75 are
in turn mounted to the shaft to be rotatable about a substantially
horizontally axis as shown in FIGS. 6a and 6c. The jets 75 can also
be inclined relative to the air tube 76 through a flange bracket
assembly 105 shown in FIG. 6c. The position of the water jets and
water supply arm are substantially fixed to the support bracket as
shown in FIGS. 6a, 6b and 6c.
[0052] The adjustment of the nozzle orifice size is carried out by
displacement of the pins 21, 22. As shown in FIGS. 7 and 8. To
displace the pins to vary the cross section of the outlet aperture
20 of each nozzle 10, the pin support sleeves 30 are connected to
slides 32 via webs 39. The slides are positioned co-axial of the
air pipe 76 and, as shown in FIG. 7a, each sleeve 32 is arranged to
be a sliding fit on the air pipe 76. All the left hand sleeves 30
of the adjustable nozzles 10 are connected to a first elongate rod
90 and all the right hand sleeves 30 are connected to a second
elongate rod 91. The rods 90 and 91 are bolted to the respective
sleeves 32 so that displacement of the rods 90, 91 has the effect
of moving the sleeves 32 to in turn move the pins 21 or 22 in and
out of the aperture 20 of each nozzle 10. The rods 90 and 91 are
coupled to threaded bosses 97, 98 that support externally threaded
rods 92, 93 that extend from opposite sides of a bevel gear 94. The
bevel gear 94 meshes with a second bevel gear 95 connected to a
shaft 96 that extends down the mast so that it can be driven from
the base of the mast. Thus, rotation of the shaft 96 imparts
rotation to the two rods 92, 93 extending from the beveled gear 94.
The two shafts 92, 93 have opposite threads so that the left hand
shaft has a left hand thread that has the effect of moving the boss
97 to displace the first rod 90 in one direction and the right hand
shaft 93 has a right hand thread to move the boss 98 to displace
the rod 91 in the opposite direction.
[0053] As shown in FIGS. 8a and 8b, fine tuning of the position of
the pins 21, 22 can be done by adjusting the threaded end 26 of the
pins in their sleeve by use of an Allen key.
[0054] FIGS. 12 to 16 illustrate a second embodiment of a head 110
for use with snow making equipment. It is understood that the head
would be supported by a mast assembly of the kind described
earlier.
[0055] The head 110 comprises four spray head assemblies 111-114
mounted across a main beam 115 that is in the form of a
substantially rectangular aluminium extrusion. The main beam 115
provides a firm base for each spray head assembly 111-114 and also
supports a centrally positioned wind mechanism 120 that facilitates
the adjustment of the flat water jet nozzles 10. A pair of elongate
drive rails 116, 117 that are also extruded in aluminium are
positioned in a parallel array direction behind the main beam 115
to be driven by the wind mechanism 120 to in turn move the
adjustment pins 21, 22 of the nozzles 10.
[0056] As shown in FIG. 12 the wind mechanism 120 is positioned
centrally of the beam 115 and the four nozzle assemblies 111-114
are positioned equally spaced along the beam 115. The winder
mechanism 120 which is shown in greater detail in FIG. 15 comprises
a winding shaft (not shown) that comes up from beneath the head.
The shaft enters a wind block 121 and through bevelled gears (not
shown) drives two co-axially extending shafts 123, 124 that project
from either side of the wind block parallel to the rails. The gears
provide a 7:1 ratio to introduce fine control and a mechanical
advantage. Each shaft is in turn threadedly engaged with a drive
block 125, 126 that is secured to a rectangular bracket 130, 131
that is a sliding fit on the main beam 115. Each block 125, 126 is
reverse threaded so that rotation of the shafts 123, 124 in the
same direction imparts linear movement of the blocks 125, 126 and a
sliding movement of the brackets 130, 131 in opposed directions.
Each bracket 130, 131 is in turn bolted to different drive rails so
that, as shown in FIG. 5, the left hand bracket 130 drives the
outer rail 117 and the right hand bracket 131 drives the inner rail
116. In this way rotation of the shaft that comes into the base of
the mast has the effect of displacing the drive rails 116, 117 in
opposite directions.
[0057] Each nozzle 111 to 114 assembly is the same and one 111 is
shown in greater detail in FIG. 16. The nozzle assembly 111
includes a fixed central bracket 140 that is bolted to the main
beam 115. The central bracket 140 has a rear face 141 that is in
turn welded to a flange 142 and a pair of upstanding columns 143,
144 that engage a nozzle arm support 150. The central bracket 140
also supports a water jet body 145 that is in the form of a
rectangular block. The water jet body 145 includes a water inlet
passage 146 coming from a water inlet pipe 147 and a head passage
148 in the manner of the earlier embodiments. The head passage 148
supports two adjustment pins 21, 22 that are axially displaceable
across an outlet aperture 20 in a similar manner to the earlier
embodiments. The end of each pin 21, 22 is bolted to a flange 152,
153 that is in turn supported by a pin drive 154, 155 that
surrounds the main beam 115 to be slidable thereon. The pin drives
154, 155 are also secured to flanges 156, 157 that are respectively
bolted to the drive rails 116, 117 so that movement of that drive
rails imparts movement to the pin drives.
[0058] The air nozzle 75 is coupled through a nozzle arm 160 into
the nozzle arm support 150 to be coupled to an air supply pipe 161.
The nozzle arm support 150 is adjustable vertically through a nut
163 that engages the column 143, horizontally through a screw
threaded coupling 164 along the length of the arm and rotationally
through two different planes due to a pivotal linkage 165 of the
air nozzle to the arm. This universal adjustability allows fine
tuning between the relationship of the air nozzle 75 and the flat
jet water nozzle 10. The relationship is the same as described
earlier in the specification.
[0059] As described with reference to FIG. 15, operation of the
wind mechanism 20 causes opposed movement of the drive rails 116,
117 to in turn cause opposed movements of the pin drives 154, 155
to effect displacement of the pins 21, 22 to vary the cross section
of the outlet aperture 20 of the flat jet nozzle 10. FIGS. 14a and
14b illustrate the drive to displace the pins towards one another
in FIG. 14A and away from one another in 14b.
[0060] The assembly has the advantage that the use of square tubing
provides positive guidance to the componentry as well as a sturdy
support on which the nozzle assemblies can be mounted. The nozzle
assemblies are also secured to the main support with a degree of
axial adjustability so that in setup, the position of the nozzles
along the length of the main support can be altered. Since the pin
movement is about a maximum of 4 mm the mechanism must have a level
of accuracy to provide the precise incremental changes. This is
achieved by the use of the square tubing and bracket arrangement of
a 2 m head.
[0061] In order to explain the operation of the snowmaking
equipment described above and, in particular, the sophistications
and important characteristics that result in an improved snowmaking
technique, it is first necessary to consider, in general terms, the
science of snowmaking.
Snowmaking
[0062] Snowmaking is a heat exchange process. Heat is removed from
snowmaking water by evaporative and convective cooling and released
into the surrounding environment. This heat creates a micro-climate
inside the snowmaking plume that is very different from ambient
conditions. There are many variables that affect snowmaking. Three
of the most important variables are wet bulb temperature,
nucleation temperature and droplet size. Wet bulb temperature, the
temperature of a water droplet exiting a snow gun is typically
between +1.degree. C. and +6.5.degree. C. Once a water droplet
passes a nozzle and is released into the air, its temperature falls
rapidly due to expansive and convective cooling and evaporative
effects. The droplet's temperature will continue to fall until
equilibrium is reached.
[0063] This is the wet bulb temperature and it is as important as
dry bulb (ambient) temperature in predicting snowmaking success.
For example, snowmaking temperatures at -2.degree. C. and 10%
humidity are equivalent to those at -7.degree. C. and 90%
humidity.
[0064] Once the wet bulb temperature is known, there must be a way
to predict whether water droplets will actually freeze at that
temperature. Ice is the result of a liquid (water) becoming a solid
(ice) by an event called nucleation. In order to freeze, a water
droplet must first reach its nucleation temperature. There are two
types of nucleation, homogeneous nucleation and heterogeneous
nucleation.
[0065] Homogeneous nucleation occurs in pure water in which there
is no contact with any other foreign substance or surface. With
homogeneous nucleation, the conversion of the liquid state to solid
state is done by either lowering temperatures or by changes in
pressure. However, temperature is the primary influence on the
conversion of water to ice or ice to water. In homogeneous
nucleation, the nucleation begins when a very small volume of water
molecules reaches the solid state. This small volume of molecules
is called the embryo and becomes the basis for further growth until
all of the water is converted. The growth process is controlled by
the rate of removal of the latent heat being released. Molecules
are attaching and detaching from the embryo at roughly equal and
very rapid rates. As more molecules attach to the embryo, energy is
released causing the temperature of the attached molecules to be
lower than the temperature of the unattached molecules. The growth
rate continues until all the molecules are attached. At this point,
the solid state (ice) is established. Many people think that pure
water freezes at 0.degree. C. or 32.degree. F. In fact, the
nucleation event (freezing) for pure water will take place as low
as minus 40.degree. C. or minus 40.degree. F. This is most likely
to occur in laboratory experiments or high in the upper atmosphere
(upper troposphere).
[0066] Heterogeneous nucleation occurs when ice forms at
temperatures above minus 40.degree. C. or minus 40.degree. F. due
to the presence of a foreign material in the water. This foreign
material acts as the embryo and grows more rapidly than embryos of
pure water. The location at which an ice embryo is formed is called
the ice-nucleating site. As with homogeneous nucleation,
heterogeneous nucleation is governed by two major factors: the free
energy change involved in forming the embryo and the dynamics of
fluctuating embryo growth. In heterogeneous nucleation, the
configuration of molecules and energy of interaction at the
nucleating site become the dominating influence in the conversion
of water to ice. Snowmaking involves the process of heterogeneous
nucleation. There are many materials and substances which act as
nucleators; each one promotes freezing at a specific temperature or
nucleation temperature. These nucleators are generally categorised
as a high-temperature (i.e. silver iodide, dry ice, ice and
nucleating proteins) or low-temperature (i.e. calcium, magnesium,
dust and silt) nucleators. It is low-temperature nucleators that
are found in large numbers in untreated snowmaking water. The
nucleation temperature of snowmaking water is between -10.degree.
C. and -7.degree. C.
[0067] Research has demonstrated that 95% of natural, untreated
water droplets will freeze at widely different temperatures, the
average temperature being 18.2.degree. F. Introducing a consistent
high temperature nucleator into the water will raise the freezing
point. As a water droplet cools, heat energy is released into the
atmosphere at a rate of one calorie per gram of water. As it
freezes into an ice crystal, the water droplet will release
additional energy at a rate of 80 calories per gram of water. This
quick release of energy raises the water droplet temperature to
32.degree. F., where it will remain while freezing continues. This
is one reason why we are accustomed to thinking that water freezes
at 32.degree. F. or 0.degree. C. The water will continue to freeze
as long as it remains at or below 32.degree. F. or 0.degree. C.,
but only after it has first cooled to its nucleation temperature.
Any excess energy will be dissipated into the atmosphere. Since the
distribution of various nucleators in a given volume of water is
totally random, the size of the water droplet or the number of
high-temperature nucleators has a significant effect on the
temperature at which freezing occurs (nucleation temperature). In
natural water, as the size of the water droplet decreases, the
likelihood that the droplet will contain a high-temperature
nucleator also decreases. Conversely, larger water droplets stand a
better chance of containing high-temperature nucleators. The
optimum situation for snowmakers is one in which every droplet of
water passing through the snow gun nozzle contains at least one
high-temperature nucleators and freezes in the plume.
[0068] The relationship between the variables of nucleation
temperature and droplet size is summarised in two statistically
valid conclusions. First, a 50% increase in the droplet size
results in a one-degree, F increase in nucleation temperature.
Second, a 50% decrease in droplet size results in a three-degree, F
decrease in nucleation temperature. These conclusions are based on
an average droplet size of 300 microns, and indicate that
decreasing the droplet size can be counter-productive to promoting
high-temperature nucleation, unless enough high-temperature
nucleators are present. Looking at the relationship between droplet
size and evaporation, research in cloud seeding shows that: *A 50%
decrease in droplet size produces, a four-fold increase in the
evaporation rate. *A droplet that is 50% smaller will evaporate to
nothing after falling just one-eighth the distance that the average
300 micron droplet falls. These conclusions further point out the
undesirable results from using very small droplets, especially in
areas where water loss is a critical issue. Relating droplets size
to nucleation temperature, it is possible to increase snowmaking
production and efficiency by using high-temperature nucleators with
larger water droplets. This method frequently allows for increased
water flow, reduces evaporation, and yields more snow on the
ground. In fact, studies indicate that a 20% increase in water flow
can increase snow volume up to 40% if droplet size and nucleation
temperature are optimised.
Summary
[0069] The snowmaking process involves spraying water droplets into
the cold ambient air, heat from the water droplets is transferred
into the ambient air and the water droplets begin to freeze. If
there is sufficient temperature differential between the water
droplets and sufficient hang time the water droplet will freeze
before hitting the ground. The volume of water that can be
converted into snow depends on many factors.
[0070] Initial Water Temperature
[0071] a higher temperature of the water means that more heat needs
to be removed before freezing can occur.
[0072] High-Temperature Nucleators
[0073] Once a water droplet achieves a temperature of 0.degree. C.
it needs a high temperature nucleator to be present before the
water droplet will give off its latent heat and convert to
snow.
[0074] Droplet Size
[0075] The size of the water droplet determines its ability to
convert to snow. There are many methods to convert a water stream
into water droplets of varying sizes, use of water nozzles and
compressed air are two of the predominant methods. Small water
droplets offer more surface area to the ambient air but are prone
to evaporation in low humidity and are less likely to have high
temperature nucleators present. Being smaller they have less mass
and are vulnerable to high winds which can carry them away--smaller
particles also have a lower velocity and a greater hang time. Small
water droplets are desirable at marginal snowmaking temperatures
due to the larger surface area and a greater hang time which aids
when there is a low temperature differential with the ambient air.
The larger surface area also assists the evaporative cooling
effect.
[0076] Larger water droplets have less surface area, greater mass,
higher velocity and have a higher chance of having high temperature
nucleators present. When the ambient air is colder the temperature
differential is greater with the particle temperature therefore a
greater heat exchange occurs. The latent heat that is given off by
the water particles is easily dissipated into the surrounding
ambient air. The higher the velocity the greater the heat
exchange.
[0077] A snowmaking gun should therefore produce a small droplet
size in marginal conditions and a larger particle in colder
conditions.
[0078] Hang Time
[0079] The longer the water droplet is in contact with the ambient
air the more chance the particle has to freeze. A snowmaking gun
has a greater production the higher it is in the air. Droplets
projected at a higher velocity will also achieve a greater hang. It
is imperative to get a snowmaking gun as high as possible and
project the particles as fast as possible.
[0080] Water Volume
[0081] Given the above factors there is only a certain volume of
water that can be converted in snow depending on the efficiencies
of the above factors. Control of the water volume needs to be
incorporated into any snowgun design to compensate for the change
in ambient temperatures.
[0082] High Temperature Nucleation
[0083] Most snowmaking guns have a system that produces high
temperature nucleators mostly in the form of ice crystals. This is
usually achieved by combining water and compressed air.
[0084] Compressed Air
[0085] Air is a gas--or more accurately, a mix of gases. Unlike
liquids, gases are compressible; a given volume of air can be
contained in a much smaller space. In order to fill that smaller
space, however, the gas will exist at a higher pressure. A basic
law of physics indicates that the pressure of a gas and its volume
are related to its temperature; when pressure goes up, so does the
temperature. But the temperature doesn't necessarily stay high--it
can be decreased.
[0086] When a compressed gas is released and goes back to its
original pressure, a great deal of mechanical energy is released.
At the same time, a great deal of heat is absorbed. It is these
last two characteristics that make compressed air such important
factor in snowmaking. The mechanical energy released by the air
disrupts the stream of water in tiny droplets, and then propels
them into the atmosphere. As compressed air escapes the gun, it
absorbs heat--in other words, cools.
Current Art of Snowmaking
[0087] Currently there are four different methods of snowmaking:
[0088] 1. Fan Guns [0089] 2. Internal mix Air water guns [0090] 3.
External mix--Air water guns [0091] 4. Water only guns
[0092] Fan Guns consist of a large barrel with an enclosed electric
fan that forces large volumes of ambient air through the barrel. On
the end of the barrel there is a configuration of water nozzles
usually arranged in banks that can be turned on independently of
each other. Each bank can consist of up to 90 small capacity hollow
cone nozzles which produce very fine particles. The water particles
are projected into the ambient air by the large volume of air that
the fan produces. Fan Guns usually have an outer ring that is
called the nucleating ring. This ring has a small number of
miniature air/water nozzles that operate in the same way as an
internal mix air/water gun. An onboard compressor is used to
operate this ring. The nucleating ring's primary role is to produce
ice crystals. The ice crystals are carried along the outside of the
bulk water plume for a distance before becoming ingested into the
plume thus nucleating the bulk water plume. Operation of the fan
gun is achieved by opening one bank of nozzles at a time and
altering the water pressure to the nozzles. Once full pressure is
achieved on a bank another bank is opened and the water pressure is
adjusted.
[0093] Internal Mix Air/Water Guns
[0094] consist of a compressed air line and a water line converging
into a common chamber with an exit orifice. Compressed air enters
the common chamber and expands breaking up the water stream into
smaller particles and projecting them into the ambient air.
Operation of the gun is achieved by regulating the water pressure
entering the common chamber. A common feature of the internal mix
gun is that when water flow is increased air flow is decreased and
visa versa. Water pressure cannot usually exceed the air pressure
which is usually 80-125 psi. There are a multitude of orifice and
mixing chamber shapes that produce a wide variety of plumes and
droplet sizes.
[0095] External Mix Air/Water Guns
[0096] usually consist of a configuration of fixed orifice flat jet
nozzles arranged on a head that spray water into the ambient air.
The head is usually put on a mast in order to give the water
droplets more hang time due to the fact there is no compressed air
to break the water droplets into smaller particles or to propel
them. As with the fan guns the external mix guns have nucleating
nozzles that use small internal mix nozzles to produce ice crystals
which are directed into the bulk water plume. Control of the gun is
by changing the fixed orifice flat jet nozzles for a different size
or opening banks of nozzles as with the fan gun.
[0097] Water Only Guns
[0098] Water only snow guns have no compressed air or nucleating
nozzles. The head comprises a number of flat jet nozzles assembled
on a high mast, usually a minimum of 6 metres in height. Snowguns
of this type can only be used at temperatures starting at
-6.degree. C. and work better with a high temperature nucleation
additive.
THE PREFERRED EMBODIMENTS
[0099] The snowmaking equipment that is the subject of this
application differs from the existing technology by the fact that
it uses the maximum efficiencies of each component involved in the
process. The snowmaking equipment S is an external mix air/water
gun utilising a bank of four variable nozzles 10 that provide a
flat output pattern for the water to configure on a flat horizontal
plan. Compressed air is introduced into the water plume P in a flat
configuration and has the same dimensions as the water plume at the
point of intersection. A significant feature of this snowmaking
equipment is that control of the gun is by adjusting the nozzle
orifice size and thus changing the water flow. This allows the
maximum pressure of the water to be utilised creating a consistent
droplet size with a higher velocity and throw than the conventional
snowmaking guns.
[0100] The compressed air is introduced into the water plume P
directly at the point where the compressed air has the most energy.
The maximum energy from the compressed air greatly increases the
atomization of the water particles, and gives the maximum cooling
and projection of the water droplets. The temperature directly at
the exit of the air orifices can be as low as -40.degree. C. which
drops the bulk water plume to around 0.degree. C. and lower, the
extreme cold air also creates ice crystals, some which are carried
in the bulk water plume while some are blown out of the plume and
are re-ingested at a further distance. This high concentration of
ice crystals ensures that there is an abundance of high temperature
nucleators to seed the majority of the water droplets.
[0101] If ice crystals are injected into the bulk water plume
before the plume temperature is 0.degree. C. the ice crystals will
melt, this is why other external mix guns project the ice crystals
that are produced into the plume at a further distance away from
the water nozzle so that the bulk water has had enough time for the
heat in the water to be carried away by the ambient air before they
are introduced. In windy conditions some of these ice crystals can
be carried away reducing the nucleation of the bulk water.
[0102] Internal mix guns utilise the compressed air in the same way
with the exception that the energy of the water pressure is not
utilised as it is regulated to control the water flow. The maximum
water pressure for most internal mix guns usually does not exceed
the compressed air pressure (that is 7 bar--whereas the variable
flat jet can operate at pressures exceeding 40 bar). The nature of
a fixed chamber dictates that the more water is used the less air
that can be in the chamber by volume and the same in reverse. The
compressed air is the only means for projection and atomisation of
the water; when the amount of compressed air is limited by a
greater water flow efficiencies are decreased. Because the energy
of the water is not utilised there has to be an increase in the
volume of compressed air that is used making the gun more expensive
and noisy to run.
[0103] The snowmaking equipment of the preferred embodiments uses
the same amount of compressed air no matter what the water flow
giving a more linear curve and allowing greater production per gun
and because it has lower consumption of compressed air applied
directly into the plume using smaller air orifice size resulting in
considerably quieter operation. The synergy of these two mediums
gives the most efficiency that can be obtained creating a
consistent plume of homogenous medium sized water particles that
have the highest possible velocity and high temperature nucleators
(ice crystals) possible.
[0104] Because external mix guns do not use compressed air to
atomise the water plume the droplets that are formed are much
larger with a greater range of differing sizes within the plume. At
lower pressures the droplets can be as large as 1000 to 4000
microns where as the preferred embodiment produces droplets in the
300 to 600 micron range.
[0105] The preferred embodiments have a very high plume velocity
and surface area which causes more ambient air to be inducted into
the plum giving added cooling. The shape of the wind vane 74 on the
head H resembles a tilted airplane wing and directs the wind from
behind the head to accelerate over the nozzle outlet increasing the
amount of cold air into the plume and helping to accelerate its
velocity.
[0106] The preferred embodiments utilise a portable mast
arrangement that allows the head to be positioned 1 metre to 6
metres above the ground. The main mast members form a parallelogram
to which the head is attached to the top, when the mast is lowered
and raised the head maintains a constant angle giving a consistency
in the trajectory of the plume. Other snowgun masts have a fixed
mast so that when the mast is lowered the angle of the head points
progressively more into the ground decreasing the snowguns
efficiency. Most external mix guns cannot be lowered as they rely
on the height of the mast to produce sufficient hang time for the
water droplets to freeze. The apparatus of the preferred embodiment
can produce snow efficiently 1 metre above the ground--the
efficiency increases with height.
[0107] Most 6 metre masts for snowguns are in permanently fixed
ground positions. The apparatus of the preferred embodiment can be
towed by a snowmobile and set up at different locations. The legs
of the mast has skids attached so that it can be easily towed; the
legs are also adjustable so that the mast can be levelled on uneven
terrain, see FIG. 4. The flat profile of the legs reduces the
hazard to skiers. The main mast swivels at the base which allows
the head to be turned with the wind. The wind vane 74 on the head H
catches the wind and pushes the head downwind in the same way a
weather vane works. This increases the gun's efficiency as cross
winds affect the efficiency of the plume by blowing the bulk water
together lessening the surface area and velocity. The mast is
counterbalanced by a spring 81 which a quick, easy raising and
lowering of the mast. The wind vane 74 is tilted upward and in the
event of high winds this automatically lowers the height by pushing
the head closer to the ground. This aids in more snow being
deposited on the ski run; if the mast were to remain at its maximum
height in high winds the snow produced would be more likely to be
carried away.
[0108] In the event of heavy ice conditions the head lowers itself
under the weight of the ice so that it can be easily de-iced by
staff.
[0109] The apparatus of the preferred embodiments has the same
efficiency and production as a fan gun but produces larger water
particles. Fan guns are more expensive to purchase and need more
electrical infrastructure on the mountain therefore limiting their
movement. Movement of fan guns require the use of expensive snow
grooming machines because of their size and weight. Expensive
permanent tower designs are necessary to raise a fan gun 6 metres
into the air which introduces additional risks to the staff as the
fan guns require staff to perform duties at height e.g. taking off
covers, de-icing of controls.
[0110] In a more sophisticated version of the equipment, a wet bulb
temperature sensor is incorporated with an ambient temperature
sensor that also sensors the temperature of the water. A water
pressure sensor is also included. A computer constantly monitors
the readings of the sensors and selectors a nozzle aperture size
that it is optimum to produce snow most efficiently in the set
conditions. The use of electrically powered servo motors thus
allows continual adjustment of the nozzle apertures in dependence
on changes in the ambient conditions. Changes in direction and
strength of the wind is accommodated by the vane on the head of the
mast that causes the mast point down wind and the head to assume
the appropriate height as directed by the wind. The parallel
linkage ensures that the nozzles are inclined at the right angle to
the horizontal regardless of the effective height of the mast.
* * * * *