Note: Descriptions are shown in the official language in which they were submitted.
CA 02216341 1997-09-24
PATENT
1 1 14.00002
MET~OD AND SYSTEM FOR CREATING
AND MAINTAINING A FROZEN SURFACE
Field of the Invention
This invention relates to a method of m~nllf~cturing a tube. This invention also
5 relates to a system for creating and m~int~ining a frozen surface, for example, for recreational
exhibitions and athletic competitions at an ice skating rink. In particular? this in~ention relates to
a system for efficiently conveying a coolant through a medium to be frozen. This invention also
relates to a system that lends itself to facilitate i~st~ tion and maintenance.
Ba~k~round of the Invention
The earliest ice skating rinks were frozen ponds or lakes. Such ice sport venues
had the sizeable limitation that their existence was entirely dependent upon the temperature of the
environment. For a long time, tke dependency upon naturally-formed ice restricted the enjoyment
of ice sports in most countries to a limited seasonal period.
In the late nineteenth century, indoor ice skating rinks were designed to provide
15 venues on which ice sports could be enjoyed in most countries year-round. These early indoor
ice skating rinks used a system of steel or iron pipes to carry an artificially-cooled refrigerant, such
as calcium chloride brine, under a tank of water to create a frozen surface capable of being skated
upon. The steel or iron pipes were embedded in concrete or sand beneath the tank, and had an
inner diameter of 1 to 1-l/2 inches with 4 inches between the centers.
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2 PATENT
1 1 14.00002
While capable of providing a frozen surface which could be skated upon indoors
year-round, the steel or iron pipe construction had its drawbacks. Perhaps, one of the greatest
limitations on the steel or iron constructions was the surface area that these systems provided for
heat e~rh~nge with the mP~ m to be frozen, also known as the dynamic surface area. In the steel
5 or iron constructions, as structurally and dimensionally described above, the dynamic surface area
was substantially less than the area of the skating surface available for heat exchange with the
environrnent. The dynamic surface area of the steel or iron constructions is çstim~ted to be at
most 82% of the skating surface area.
More recently, ice skating rink systems have been constructed using smaller
13 diameter plastic tubing, such as those systems described in U.S. Patent Nos. 3,751,935;
3,893,507; and 3,910,059. In operation, a main supply pipe, or header, feeds into a plurality of
supply subheaders, each of which in turn is attached to the proximal ends of a plurality of coolant
tubes. The plurality of coolant tubes can be fastened at their distal ends to one end of a plurality
of U-shaped connectors, which in turn are fastened to a second plurality of coolant tubes. The
second plurality of coolant tubes is attached at their proximal ends to a plurality of return
subheaders, which in turn feed into a main return header. The inner diameter of the coolant tubes
used in these plastic constructions generally varies from 1/4 to 1/2 inches. By using a smaller
center spacing between smaller tubes, these plastic systems may provide a larger dynamic surface
area than the steel or iron constructions.
However, the dynamic surface area is only one factor influencing the overall
efficiency of a system designed to create and .l~ a frozen surface. As important to the
efficiency of the system as the dynamic surface area is the ability of the coolant to flow through
the system without significant pressure loss or flow interruption. As a consequence, even though
the plastic systems may have improved the dynamic surface area over the iron and steel
CA 02216341 1997-09-24
3 PATENT
1114.00002
constructions, the efficiency ofthese plastic systems is often significantly col.lplolllised in practice
by un~ti~f~ctory coolant flow characteristics at various points in the system.
For example, as shown in Figs. 1 and 2 herein, one common area for flow
restriction to occur is at the transfer point between a subheader 30 and a coolant tube 32. In the
conventional construction shown in Figs. 1 and 2, the subheader 30 has an opening 34, through
which is disposed a connection fitting 36. The connection fitting 36 is soldered into place with
the p~lldte end ofthe fitting 36 ocr~ in~ as much as 2S percent ofthe interior cross-sectional
area ofthe subheader 30. This occlusion can cause a layer 38 of coolant to build up against the
fitting 36, and seriously degrade the flow characteristics ofthe coolant in the area adjoining the
transfer point.
Moreover, at the distal end of the tube 32, where the tube 32 attaches to a U-
shaped connector 40, the conventional methods of construction can cause additional flow
restriction problems. One flow restriction problem commonly occurring in conventional
constructions is illustrated in Figs.3 and 4. The U-shaped connector 40 shown is fabricated by
bending a copper tube having an internal tii~meter similar to that of the coolant tube 32. By using
this method of fabrication, the resulting inner diameter at a bight 42 of the U-shaped connector
40 may be reduced to apploxi-lla~ely half the diameter of the original copper tube. The dramatic
decrease in the inner diameter of the U-shaped connector 40 at the bight 42 has a proportionally
dramatic effect on the fluid flow throughout the system.
Additionally, loss of fiow pressure can result from the present methods of system
construction used to join the coolant tubes 32 with the U-shaped connectors 40. The coolant
tubes 32 are fastened directly to the U-shaped connectors 40 by means of glue and a circular
clamp or an eyelet, as shown in Figs. 3 and 4. As a consequence, the tubes 32 have a tendency
to leak or even pop off of the U-shaped connector 40, spilling coolant directly into the medium
CA 02216341 1997-09-24
4 PATFNT
1 1 14.00002
to be frozen and underlying foundational material and decreasing the pressure and flow rate at
which the coolant is being transported throughout the system.
Furthermore, these plastic systems are often constructed using a type of plastic
coolant tube having unfavorable performance characteristics. Commonly, polyethylene or
S polypropylene tubing is used for the coolant tubes in plastic ice skating rink systems. During
m~n~lfactllre, the polyethylene or polypropylene tubing is usually extruded, and then passed
through a ~L~ dard length (10-14 foot) cooling tank before being machine-coiled on to spools for
delivery. As a consequence of this method of fabrication, the polyethylene or polypropylene
tubing thermally sets with a curved, rather than a straight, structure in the memory of the plastic.
10 Therefore, when the tubing is uncoiled to be used in the plastic construction illustrated in the
patents mentioned above, the tubing does not naturally lay straight and flat, but takes on a
serpentine structure in at least one plane.
As a further consequence, when these polyethylene or polypropylene ice rink
systems are installed, the coolant tubing will commonly force its way under pressure to the skating
15 surface, and protrude from the surface of the ice, providing a substantial obstacle and hazard for
persons, for example skaters, using the frozen surface. It is therefore necessary to resubmerge
the tubing under the surface of the ice through a method known as "burning in". The tubing is
"burned" into the surface of the ice by melting the surrounding ice, and then holding the tube in
place under pressure until the ice reforms around the problematic section of tubing. Because of
20 the pressure ofthe coolant running through the tubing, as well as the thermally-set disposition of
the tubing to return to the serpentine structure, it may be necessary to repeat the "burning in"
process a number of times each season to m~int~in a skating surface free from obstructions and
to prevent damage to the tubing.
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S PATENT
1 1 14.00002
However, polyethylene and polypropylene tubing is sensitive to repeated bending.
Repeated bending of the polyethylene or polypropylene tubing has been known to cause
permanent damage to the tubing, and can result in the cracking or rupture of the tubing with a
concomitant loss of coolant pressure in the system.
S Summary of the Invention
According to an aspect ofthe present invention, a method of m~nl~f~ct~lring a tube
includes the steps of p~epa ing a composition using ethylene vinyl acetate, extruding the
composition to form a tube, and cooling the tube with the tube in a subst~nti~lly straight
configuration so that the tube is subst~nti~lly set in a substantially straight configuration.
According to another aspect of the present invention, a system for creating a
frozen surface on a medium includes a mech~ni~m for exc.h~nging thermal energy between a
medium and a coolant, a mech~ni~m for removing thermal energy from a coolant, and a
mechanism for transporting a coolant between the me~.h~nicm for ~Ych~nging thermal energy
between a meAillm and a coolant and the ,n~.h~llicm for removing thermal energy from a coolant.
15 The mesh~ni~m for transporting a coolant includes first and second pipes and a mechanism for
releasable connPsting the first pipe to the second pipe so as to prevent the first pipe from moving
axially relative to the second pipe in a first operational state, and to allow the first pipe to be
moved axially relative to the second pipe in a second operational state.
According to a further aspect of the present invention, a system for creating and
20 ll~ inillg a frozen surface on a medium includes a mechanism for exch~nging thermal energy
between a medium and a coolant, the meçh~ni~m for exch~n.~ing thermal energy between a
medium and a coolant having a substantially uniform cross-sectional area for passing a coolant
therethrough. The system also includes a mP~h~ni~m for removing thermal energy from a coolan~.
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6 PATENT
1 1 14.00002
The system further includes a meçh~ni.em for transporting a coolant between the mech~nism for
exch~ngin~ thermal energy b~lween a medillm and a coolant and the mech~niem for removing
thermal energy from a coolant. The mech~niem for transporting a coolant is connected to the
"~.hAn e~, for ~ h~l~.lg thermal energy between a medi~m and a coolant so that subst~nti~lly
S all of a coolant flowing from the meçh~niem for transporting a coolant to the meçh~ni.em for
P.Ych~nging thermal energy between a medium and a coolant flows directly from the meçh~niem
for ~ sl~olling a coolant into the menh~niem for exch~np~ing thermal energy between a me~ium
and a coolant.
Brief Description of the Dr~. in~s
Figs. 1 is a partial cross-sectional view of a portion of a prior art subheader
showing in detail the transfer point between the subheader and a coolant tube;
Fig. 2 is a partial cross-sectional view of the transfer point between the subheader
and the coolant tube taken about line 2-2 in Fig. 1;
Fig. 3 is a partial cross-sectional view of a prior art U-shaped connector showing
in detail the connection ofthe U-shaped connector and a coolant tube;
Fig. 4 is a partial cross-sectional view ofthe conne~;lion ofthe U-shaped connector
and the coolant tube taken about line 4-4 in Fig. 3;
Fig. 5 is an overall plan view of an ice skating rink including an embodiment of the
present invention for creating and m~int~ining a frozen surface;
Fig. 6 is an enlarged, partial cross-sectional view of an insulation blanket or layer
which is useful for in.eul~ting below the system shown in Fig. S;
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7 PATENT
1 1 14.00002
Fig. 7 is an e.~ ed plan view showing in detail an embodiment of a panel for use
in the embodiment shown in Fig. 5, and the interconnection of the panel with supply and return
headers;
Fig. 8 is an enlarged plan view showing in detail another embodiment of a panel
5 for use in the embodiment shown in Fig. 5 in particular at the curved ends of the ice skating rink,
and the interconnection of the panel with supply and return headers;
Fig. 9 is an overall plan view of an ice skating rink inc~ ing another embodiment
the present invention for clealing and ~ i"t~ining a frozen surface with the spacers and spacing
bars removed;
Fig. 10 is an enlarged plan view of an embodiment of a spline-connector used to
connect two adjoining pipes in the header in the embodiment shown in Fig. 5, the spline-connector
in~hltlinp a releasably aKachable female coupling connected to a flexible hose element;
Fig. 11 is an enl~b~ed plan view of another embodiment of a spline-connector for
use in the embodiment shown in Fig. 5, the spline-connector including a releasably ~tt~ch~ble
coupling connected to a fixed coupling attached directly to the spline-connector;
Fig. 12 is an enlarged plan view of still another embodiment of a spline-connector
for use in the embodiment shown in Fig. 5, the spline-connector including a valve connected
between a releasably ~tt~ch~ble coupling and a fixed coupling attached directly to the spline-
connector;
Fig. 13 is an enlarged, partial cross-sectional view of a flexible hose used to
colmecl a spline-connector with either a supply or a return subheader;
Fig. 14 is an enlarged, partial cross-sectional view of any of the embodiments of
a spline-connector shown in Figs. 10, 11, and 12 showing in detail a first and a second locking
mecl~ sm used to prevent relative movement between the spline-connector and a header pipe;
CA 02216341 1997-09-24
8 PATENT
1114.00002
Fig. 15 is a partial cross-sectional view of an embodiment ofthe present invention
showing in detail a transfer point at the intersection of a subheader with a coolant tube;
Fig. 16 is a partial cross-sectional view of the transfer point at the intersection of
the subheader and the coolant tube taken about the line 16-16 in Fig. 15;
S Fig. 17 is a cross-sectional view of an embodiment of the present invention
showing in detail a U-shaped connector;
Fig. 18 is a cross-sectional view ofthe U-shaped connector taken about line 18-18
inFig. 17;
Fig. 19 is a partial cross-sectional view of the U-shaped connector of Figs. 17 and
18, showing in detail the interconnection of the U-shaped connector and a coolant tube; and
Fig. 20 is a cross-sectional view of the U-shaped connector and the coolant tubetaken about the line 20-20 in Fig. 19.
Dese. ;,~,lion of the Preferred Embodiments
In general terms, the system of the present invention creates and m~int~in.~ a frozen
surface, such as ice, by removing thermal energy from a liquid medium, such as water, and
~xh~llsting the thermal energy at a location remote to the medium to be frozen. Specifically with
reference to Fig. 5, pressurized, chilled coolant passes through a plurality of tubes spaced within
a tank or container 46 holding the medium to be frozen. As the coolant passes through the
plurality oftubes, thermal energy is ~ led from the medium to the coolant through the walls
of the tubes. The coolant then passes from the tubes to a pump 54, and from the pump 54 to a
refrigeration unit 70. The refrigeratior. unit 70 extracts the thermal energy from the coolant and
returns the chilled coolant to the collection tank 68, whereupon the cycle is repeated.
CA 02216341 1997-09-24
9 PATENT
1114.00002
According to an embodirnent of the present invention, a system 44 for creating and
,.,~;"~ . a frozen surface is shown in Fig. 5. The system 44 in Fig. 5 is shown fitted in a tank
or rink 46. The rink system 44 includes a main supply header 48, a main return header 50, and
a plurality of panels 52. Unlike the constructions discussed above, the panels 52 used in the
embodiments of the present invention ~i.ccu~sed herein are placed within the medium to be frozen,
rather than being embedded in or placed underneath inches of sand or concrete beneath the rink
46, although such a configuration is possible using the present invention. As a consequence of
the direct thermal energy .oxch~n~e relationship between the coolant in the panels 52 and the
m~lillm to be frozen, the efficiency of the system 44 is improved as a whole as it is unnecessary
to first cool the floor of the tank 46 prior to cooling the medium to be frozen.To preserve the advantages of this direct thermal energy exchange relationship by
preventing thermal energy from entering the tank from surface below the tank 46, an insulation
layer or blanket 53, as shown in Fig. 6, is placed beneath the panels 52. The insulation layer 53
is fabricated in a sandwich construction in which two layers of bubble pac~ging material 53a are
laid face to face such that the bubbles of one layer fit within the dimples of the other layer. The
two layers 53a are then covered on the ext~ lly facing surfaces 53b, 53c with a layer 53d of foil
on the surface 53b, and a layer 53e of foil, or polyethylene, on the surface 53c. During
in~ tinn, the layer 53d is placed against the surface below the tank 46, while the layer 53e faces
and is covered by the medium to be frozen.
A pump 54 is connected at an outlet 56 to the main supply header 48 via the
refrigeration system 70 and the collection tank 68, and forces a coolant, for example, a mixture
of either ethylene glycol or propylene gylcol and water, into the main supply header 48 under
pressure. Under most conditions, the coolant is, for example, a mixture of either ethylene glycol
or propylene glycol and water in a ratio of 45:55. If the system 44 is intended for use in a
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10 PATENT
1114.00002
environment where the temperature of the surrounding environment is less than -20 degrees F,
the coolant is, for example, a mixture of either ethylene glycol or propylene glycol and water in
a ratio of 55:45. The coolant passes from the main supply header 48 and into the individual
panels 52.
Each panel 52, generally indicated in Fig. 5 and shown in greater detail in Figs. 7
and 8, is four feet wide and 100 feet long, and in~ des a supply subheader 58, a return subheader
60, first and second plurality of tubes 62, 64, and a plurality of U-shaped connectors 66. The
pressurized coolant flows from the main header 48 into the supply subheader 58, which feeds into
the first plurality of tubes 62. As the coolant flows through the medium, thermal energy is
~ srell~d from the medium to the coolant through the walls ofthe tubes 62. The coolant then
passes through the plurality of U-shaped connectors 66 and into the second plurality of tubes 64.
As the coolant flows through the medium for a second time, additional thermal energy is
srell ed from the medium to the coolant.
The coolant feeds from the plurality of tubes 64 to the retum subheaders 60, which
are conne ;~ed to the return header 50. The coolant is transported along the return header 50 to
the pump 54, from which the coolant returns to the refrigeration system 70. The refrigeration
system 70 extracts the thermal energy from the coolant, and exhausts the thermal energy to the
environment. The chilled coolant is then returned to the collection tank 68, for example a 15
gallon tank, to be re-introduced into the main header 48.
Alternatively, the system 44 may be configured to accommodate placement of the
refrigeration system 70 and pump 54 at the center of the rink 46. As shown in Fig. 9, with like
numbers used for like Pl~mPnt~, a central supply header 72 is connected through the refrigeration
system 70 and a collection tank 68 to the pump 54, branching offat a first Tjoint 74 to form two
main supply headers 48, one for each half of the rink 46. The supply headers 48 each feed into
CA 02216341 1997-09-24
11 PATENT
1114.00002
a plurality of subheaders 58, which in turn feed into a plurality of panels 52 in a direct thermal
energy transfer relationship with the medi-lm to be frozen. The coolant returns to the refrigeration
system 70 via a system of return subheaders 60 and return headers 50. The return headers 50
are connected at a second Tjoint 76 to form a main return header 78, which feeds directly into
5 the pump 54.
Because the system 44 can be assembled to accommodate rinks of di~erenl widths
and lengths by adding additional panels 52, the requhe~ ..Ls for the pump size and the pressure
and flow rate of coolant (expressed as gallons per unit of time) will necessarily differ according
to the exact dimensions of the assembled system 44. The coolant has an inlet temperature (as
measured at the inlet of the supply header 48) of 18-20 degrees F, and an outlet temperature (as
measured at the inlet of the pump 54) of 20-24 degrees F. It has been found experimentally that
to pro~ide a uniform thermal energy transfer, or thermal energy extraction, from the medium to
be frozen, the velocity of the coolant in the system 44 should be at least 1 foot/second.
In an embodiment of the present invention, wherein the rink system 44 may be
15 assembled and disassembled, for example at the end of a seasonal period or after an athletic
co..l~tilion or exhibition, the supply header 48 and the return header 50 are made from lengths
of pipe 80, for ~Y~mplç, Pnh~nced PVC pipe (type 1, grade 1, 2000 psi hydrostatic stress material,
in accordance with ASTM D1784) with an inner diameter of between 2 to 6 inches, for example
4 inches, joined together at spaced intervals by connectors 82, 84, also fabricated from enhanced
20 PVC schedule 80 pipe. The lengths of pipe 80 are joined together at four foot intervals to
coincide with the four foot width of the panels 52.
The connector 82, as shown in Figs. 10, 11 and 12, is used in the main supply
header 48 and the first section of the main return header 50 upstream to the U-shaped joint 86 in
the system 44 shown in Fig. 5, and U-shaped joints 88 and 90 in the system 44 shown in Fig. 9.
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12 PATENT
1114.00002
The connector 82 is also designed to connect the main supply header 48 and the main return
header 50 to the supply subheaders 58 and the return subheaders 60.
The connector 82 may include a pipe section 92, a flexible hose 94, a fixed
coupling 96 and either a male or female coupling 98. An opening 100 is machined in the pipe
section 92 at half the di~t~nce from the ends. The opening 100 is then tapped to accept the
threads of the fixed coupling 96. The pipe section 92 and the fixed coupling 96 are screwed
together until the pipe section 92 and the fixed coupling 96 mate securely.
A first, proAi.male end of the flexible hose 94, which has an inner diameter of one
inch and is m~nllf~ctlred as shown in Fig. 13 with a helical steel spring 102 embedded within the
wall of the hose 94, is then placed over a portion of the distal end ofthe fixed coupling 96 and
secured using a circular clamp, for exarnple, a stainless steel clamp. The second, distal end of the
flexible hose 94 is then placed over a portion of the proximate end of the ~tt~çh~ble coupling 98
and secured using a circular clamp, also a stainless steel clamp. The ~tt~rh~ble coupling 98 allows
the connector 82 to be connected to a mating male or female coupling 99 attached at the ends of
the subheaders 58, 60.
Alternatively, the ~tt~h~ble coupling 98 is attached directly to the fixed coupling
96 of the supply header 48, while a mating male or female coupling 99 is attached via a flexible
hose 94 to the supply subheader 58 and return subheader 60 corresponding to the given panel 52,
as shown in Fig. 8. The mating couplings 99 are alternated between the supply and return
subheaders 58, 60 for a given panel 52, i.e., each of the supply subheaders 58 may have a male
coupling 99, while the retum subheaders 60 may have a female coupling 99. In this fashion, when
the system 44 is to be ~ csembled to be transported or stored, the coolant in the panel 52 can
be isolated in the panel 52 by attaching the male coupling 99 of the supply subheader 58 to the
female coupling 99 of the return subheader 60.
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13 PATENT
1114.00002
Moreover, the panels 52 may be isolated in operation as well as in storage by
disposing a valve 104, for e~-~'e, a brass or ~ ess steel ball valve, between the fixed coupling
96 and the ~ c.h~ble coupling 98 on the spline-connector 82, as shown in Figs. 7 and 12. By
c~lu-~ g the valves 104 to the supply and return header connectors 82, the coolant in a panel
552 may be isolated by closing the valves 104.
By way of example only, isolation of the panel 52 could be advantageous should
one of the coolant tubes 62, 64 of a panel 52 rupture. Isolation could prevent loss of the coolant
into the me~ m to be frozen and the underlying foundational material, prevent loss of pressure
throughout the system 44, and otherwise allow the repair of the panel 52 with the ruptured tube
1062 or 64 to be performed while m~ g the frozen surface on the portions of the medium
unaffected by the loss of coolant flow through the isolated panel 52.
Additionally, again by way of example only, isolation of the panels 52 could be
advantageous during the freezing ofthe medium. Specifically, the panels 52 could be isolated so
that the m~li~lm is frozen in stages, panel by panel, until all of the medium in the rink 46 is frozen.
15Such a staged process could be especially advantageous when attempting to freeze a medium
when the temperature of the surrounding en~ilonlllenl is substantially greater than the temperature
at which the medium will freeze.
Fig. 14 shows the locking mech~ni~m.~ used in any of the embodiments of the
connectors 82 shown in Figs. 10, 11 and 12. Particularly, each end of the connector 82 is
20m~.hined to include a shoulder 110, an interior o-ring groove 112 and an interior spline groove
114. Similarly, each end of the pipe 80 is machined to have an exterior spline groove 116, which
corresponds axially with the interior spline groove 114 of the connector 82 when the end 118 of
the pipe 80 abuts the shoulder 110 of the connector 82.
CA 02216341 1997-09-24
14 PATENI
1114.00002
In operation, an O-ring 108 is first placed in the interior O-ring groove 112. The
pipe 80 is then placed into the connector 82 until the end 118 abuts the shoulder 110. The o-ring
108 and the exterior surface of the pipe 80 thus forms a first sealing and locking mech~ni.~m 120
preventing relative movement ofthe pipe 80 and the connector 82 in the axial direction. A second
S locking n~e~ .. 122 is formed when the spline 106 is placed through a hole 124, the hole 124
being connected through the wall of the connector 82 to the interior spline groove 114. The
spline 106 fills the channel formed by the corresponding intenor and exterior spline grooves 114,
116, also preventing the relative movement of the pipe 80 and the connector 82 in the axial
direction.
A further embodiment ofthe spline-connector, design~ted 84 in Figs. 5, 7, 8, and~, is used to couple the pipes 80 used in the second section of the main return header 50. Because
the connectors 84 are not intended to be connected to the return subheaders 60, the connectors
84 are not m~n~lf~ctured with the opening 100 into which the fixed coupling 96 can be screwed.
The connectors 84, like the connectors 82, however, do feature both the first and second locking
mech~ni~m~ 120, 122.
As sho-wn in Figs. 7 and 8, the panel 52 is defined by of the supply subheader 58,
the return subheader 60, the first and second plurality of tubes 62, 64 and the plurality of U-
shaped sections 66. As further illustrated in Figs. 15 and 16, the supply and return subheaders
62, 64, fabricated from copper pipe, are machined with plurality of openings 126. A barbed
saddle fitting 128, for example a copper fitting, is soldered over each opening 126, using a silver
based solder. Use ofthe saddle fitting 128 is advantageous i.n that there is limited obstruction of
the fluid fiowing from the subheader 58, 60 into the tubes 62, 64 and the subheaders 58, 60 have
a substantially uniforrn cross-sectional area. One end of one of the tubes 62, 64 is fitted over the
CA 02216341 1997-09-24
PATl::NT
1114.03002
barbed end 130 of saddle fitting 128 and fastened with a circular clamp. The use of barbed ends
allows a secure ~tt~chment between the tubes 62, 64 and the subheader 58, 60 to be formed.
The tubes 62, 64 are made with a 1/2 inch inner diameter from a composition
prepared using ethylene vinyl acetate (EVA), for example, from a composition prepared using
5 18% by weight of EVA colllbined with 82% by weight of polyethylene. The percentage of EVA
may vary from between 15-25% by weight, while the polyethylene may vary from between 75-
85% by weight. During m~mlf~ct ~re, the composition is extruded to form the tubes and is passed
through a cooling tank at a rate of 1 foot per second. Unlike the conventional methods for
m~mlf~lring the polyethylene or polypropylene tubing described above, the EVA/polyet'nylene
10 tubes a}e passed through a cooling tank or tanks for a distance of between 25 and 36 feet with
the tubes in a substantially straight configuration. The tubes may be cooled by spraying the tubes
with water in the cooling tanlc or tanks, or by passing the tubes through a water bath ...~ ed
in the cooling tank or tanks. It is thought that the time spent by the tubes in the cooling tank or
tanks allows the EVA/polyethylene tubes to therrnally-set in a subst~nti~lly straight configuration.
15 The extruded, cooled product, having a final inner diameter of 1/2 inch, is then hand-coiled with
the effective diameter of the coil being no less than 2.5 ~eet, and placed into a gaylord container
for shipping. The tubes are fabricated in lengths of between 515 to 520 feet.
The tubes 62, 64 are joined in pairs, the proxim~e end of the tube 62 attached to
the supply subheader 58 and the proximate end of the tube 64 to the return subheader 60.
20 Similarly, the distal ends of the pair of tubes 62, 64 are connected to one of the ends of the
plurality of U-shaped connectors 66.
As illustrated in Figs. 17 and 18, each U-shaped connector 66 has a U-shaped
section 132 and a pair of barbed fittings 134. The U-shaped section 132 and the barbed fittings
i34 are made of copper. The distal ends 136 of the barbed fittings 134 are placed inside of ends
CA 02216341 1997-09-24
16 PA~EN~
1114.00~02
138 ofthe U-shaped section 132 and soldered in place using a silver based solder. As shown in
Figs. 19 and 20, one of the distal ends of tubes 62, 64 is then placed over each of the barbed,
pro~"ale ends 140 ofthe barbed fitting 134, and fastened into place using a circular clamp 139.
The U-shaped section 132 is of a constant inner diameter, for example, of nearlyequal ~ m~t~r to the tubes 62, 64 and thus provides a substantially continuous and substantially
uniform cross-sectional area through which the coolant medium can pass. Furtherrnore, the
barbed ends 140 ofthe fitting 134 provide for a secure attachment site to attach the ends ofthe
tubes 62, 64 to the U-shaped connector 66.
A ull;foll-l spacing between the centers of the tubes 62, 64 is achieved in part by
10welding a bar 142, for example, a brass bar of hexagonal or rect~n~ll~r cross-section, to the U-
shaped bend in each of the U-shaped connectors 66 that make up the panel 52. As shown in Figs.
7 and 8, the bar 142 can be straight Qr curved to keep the proper spacing between tubes 62, 64
even in the rounded corners of the ice rink 46. In addition, spacers 144, for example, made of
polyethylene, are placed at intervals along the tubes 62, 64 to m~int~in the spacing between the
15tubes 62, 64 and the spacing between the tubes 62, 64 and the surface over which the system 44
is installed. The spacing between the centers of the tubes 62, 64 is between 1 and 1 - 1/2 inches,
while the spacing between the spacers 144 is approxi--lately 14 inches.
The spacers 144 may either be removable or non-removable. If the spacers 14¢
are non-removable, i.e. enclose the entire circumference of the tubes 62, 64, then it is preferable
2ûto place the tubes 62, 64 through the spacers 144 before attaching the tubes 62, 64 to the barbed
saddle fittings 128 ofthe supply and return subheaders 58, 60. If the spacers are removable, i.e.
m~y be snapped around the tubes 62, 64, the spacers may be attached to the tubes 62, 64 after
the tubes 62, 64 are connected to the respective supply and re~urn subheaders 58, 60.
CA 02216341 1997-09-24
17 PAl'ENT
I 1 14.00002
Still other aspects, objects, and advantages of the present invention can be obtained
from a study of the specification, the drawings, and the appended claims.
