U.S. patent number 3,893,507 [Application Number 05/387,148] was granted by the patent office on 1975-07-08 for apparatus for creating and maintaining an ice slab.
This patent grant is currently assigned to Calmac Manufacturing Corporation. Invention is credited to Calvin D. MacCracken, Helmut J. Schmidt.
United States Patent |
3,893,507 |
MacCracken , et al. |
July 8, 1975 |
Apparatus for creating and maintaining an ice slab
Abstract
Apparatus for creating and maintaining an ice slab for skating
purposes, or an ice chute for a toboggan slide, or for maintaining
a layer of snow for skiing. The apparatus includes pluralities of
small diameter flexible plastic tubes arranged in grids in portable
mats with the tubes placed close to one another and arranged with
each input or supply tube portion closely adjacent to an outlet or
return tube portion providing an advantageous uniform temperature
effect at a small distance above the tubes. A low temperature
anti-freeze liquid is pumped through the tubes to provide the
desired uniform cooling effect, and the portable mats each include
a pair of sub-headers which can conveniently be coupled together
with main headers to form a large grid the size of an ice skating
rink, or a ski slope. For a rink these small flexible tubes may
thereafter be covered with a thin layer of sand, or other
protective material, and water is then introduced into the rink and
is frozen by the low temperature refrigerant passing through the
various tubes. By virtue of the small diameter of the tubes,
ethylene glycol or other similar low temperature anti-freeze liquid
(which would be very expensive with conventional systems) can
economically be used to practice the invention disclosed herein. In
the case of a ski slope, the small flexible tubes are covered with
a thin layer of sand or dirt, and the circulation of the low
temperature refrigerant serves to maintain, i.e. to "hold," a
skiable layer of snow (either natural or manmade snow or a mixture
of them) on the ski slope during thawing periods when the snow
normally would melt away.
Inventors: |
MacCracken; Calvin D. (Fort
Lee, NJ), Schmidt; Helmut J. (Oakland, NJ) |
Assignee: |
Calmac Manufacturing
Corporation (Englewood, NJ)
|
Family
ID: |
26899192 |
Appl.
No.: |
05/387,148 |
Filed: |
August 9, 1973 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
204112 |
Dec 2, 1971 |
3751935 |
Aug 14, 1974 |
|
|
Current U.S.
Class: |
165/46; 165/171;
126/624; 62/235; 126/665; 165/175 |
Current CPC
Class: |
F25C
3/02 (20130101) |
Current International
Class: |
F25C
3/02 (20060101); F25C 3/00 (20060101); F28f
007/00 (); A63c 019/10 () |
Field of
Search: |
;165/46,175,180
;62/235,260 ;264/209 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wayner; William E.
Attorney, Agent or Firm: Parmelee, Johnson &
Bollinger
Parent Case Text
This application is a division of prior copending application Ser.
No. 204,112, filed Dec. 2, 1971, which issued as U.S. Pat. No.
3,751,935 on Aug. 14, 1974.
Claims
We claim:
1. A flexible portable plastic tubing mat adapted to be laid
side-by-side with other similar mats for creating and maintaining
an ice slab for skating and for preventing snow from melting on a
ski slope and adapted to be laid end-to-end with other similar mats
for creating an ice chute or trough for a toboggan slide or similar
sliding purposes,
a. said portable mat having a length many times greater than its
width with a plurality of small diameter flexible plastic tubing
members extending lengthwise of said mat adapted to have cooled
anti-freeze liquid pumped therethrough,
b. said flexible plastic tubing members having an inside diameter
in the range from one-eighth to three-eighth of an inch,
c. securing means connected to said tubing members for securing
them in a grid pattern in said mat,
d. said mat including supply and return sub-headers extending
across one end of said mat with the ends of a plurality of said
tubing members being connected respectively to said supply and
return sub-headers with the direction of flow of the anti-freeze
liquid being opposite in neighboring tubing members in the mat,
e. said flexible portable mat being rollable into a roll for ease
of transportation, and
f. said sub-headers being adapted to be connected to main headers
in an installation for interconnecting the plurality of said tubing
members through the subheaders to the main headers.
2. A flexible portable plastic tubing mat as claimed in claim 1 in
which said small diameter plastic tubing members are co-extruded in
pairs of such members and the ends of the tubing members are
connected to said supply and return sub-headers to produce an
opposite direction of the anti-freeze flow in the respective tubing
members of each pair.
3. A flexible portable plastic tubing mat as claimed in claim 1 in
which the mat is about 4 feet wide and at least 85 feet long.
4. A flexible portable plastic tubing mat as claimed in claim 1 in
which supply and return sub-headers extend across both ends of said
mat with the ends of a plurality of the tubing members connected
respectively to supply and return sub-headers at opposite ends of
the mat.
5. A flexible portable plastic tubing mat as claimed in claim 1 in
which said small diameter plastic tubes are composed of ethylene
vinyl acetate.
6. A flexible portable plastic tubing mat as claimed in claim 5 in
which said securing means include tapes extending transversely
along the mat at spaced positions along the length of said mat.
Description
The present invention relates to an apparatus for creating and
maintaining an ice slab for skating purposes or for maintaining a
layer of snow for skiing and in particular relates to a novel
economic apparatus for providing portable system formed by multiple
interconnected mats of small diameter flexible plastic tubes
arranged in grids with the tubes placed close to one another and
arranged with each input or supply tube portion closely adjacent to
an outlet or return tube portion providing uniform temperature
effect at a small distance above the tubes. The portable mats each
include an individual supply sub-header and return sub-header for
connection to main supply and return headers and the small plastic
tubes are adapted to have a low temperature refrigerant pumped
therethrough to provide the desired cooling effect.
In the prior art, ice skating rinks have commonly been frozen by
the use of large diameter metal pipes having an internal diameter
(I.D.) of approximately 1.25 inches, a wall thickness of one-eighth
of an inch spaced 4.0 to 4.5 inches center-to-center spacing which
have usually been embedded in concrete to provide a floor upon
which the water was placed and thereafter frozen. These large
diameter pipes in the prior art were filled with calcium chloride
(CaCl.sub.2) brine as the cooling medium, and such a system
involved a brine volume of about 3,200 gallons in the piping under
the rink plus additional brine in the tanks and piping of the brine
cooling equipment. In the prior art systems, the brine was passed
through the refrigeration system to bring its temperature down to
approximately 15.degree. to 18.degree. F at the supply point
entering the floor of the rink, and the return brine temperature
was approximately 17.degree. to 20.degree.F leaving the rink floor,
depending upon the ambient temperature and the number of skaters.
The ASHRAE Guide and Data Book on "Applications" (1968 Edition)
published by the American Society of Heating, Refrigerating and
Air-Conditioning Engineers, in Chapter 51, on Skating Rinks at page
616, states that the brine pump should be of sufficient capacity,
so that the temperature difference between incoming and outgoing
brine does not exceed 2.degree.F under design conditions.
For many years, the prior art has assumed that the above type of
under the floor cooling ice skating rink system is the "final
word." And the book mentioned above confirms that such a system has
been long considered by those skilled in the art to be the "final
word." Nevertheless, such a conventional prior art system was very
expensive in that the pipes must be assembled together
piece-by-piece and welded, or otherwise laboriously and accurately
connected and installed at the rink site by trained personnel.
Thereafter, the assembled piping was usually embedded in concrete.
With this prior art system, the ice rink was permanent and could
not be moved from place to place. Additionally, large volumes of
brine (about 3,200 gallons in the rink floor plus additional brine
in the cooling system) had to be refrigerated and pumped through
the pipe network in the floor to freeze the ice. A further problem
which was encountered when a prior art system needed servicing was
that the rusted metal pipes had to be laboriously chipped out from
the concrete floor to be replaced. In addition, a large amount of
pumping power was continuously consumed in a prior art system in
circulating the large volume of brine at a sufficient velocity to
hold a temperature difference between the supply point at entrance
to the pipe network in the floor and the return point at exit from
the floor at no more than about 2.degree.F.
The present invention is a radical departure from the prior art, an
important technological jump which represents a real breakthrough
in the ice skating rink field. Instead of 2.degree.F differential
in the supply and return temperatures, a differential from
15.degree. up to 25.degree.F or more can be employed. Instead of
heavy walled metal pipes having an I.D. of 1.25 inches and an O.D.
of 1.50 inches, thin-walled, flexible, small diameter plastic
tubing is used having an I.D. of between one-eighth and
three-eighth of an inch, such tubing having a wall thickness of
about one-thirty-second of an inch. Instead of using 3,200 gallons
of brine in the rink floor, only 300 gallons of low temperature
anti-freeze liquid, such as ethylene glycol, is used and operating
at a supply temperature of no more than 10.degree. and preferably
no more than 5.degree.F, instead of 15.degree. to 18.degree.F, as
required in the conventional prior art.. Moreover, instead of
utilizing a high level of pumping power to circulate brine, only
one-third or less pump power is utilized, which represents a great
saving in electricity extending into the future; typically $6,000
to $7,000 per year savings or more in a full size rink application.
Instead of using large diameter headers to supply and return the
brine, the present invention enables the use of headers which are
only about one-tenth of the cross-sectional area of the prior art
headers.
The present invention advantageously enables the use of small
diameter flexible plastic tubing which can be pre-assembled into
portable mats in a factory and thereafter conveniently rolled up
and carried to a site to be quickly coupled together with other
mats to form the cooling grid for an ice rink. Manufacturing these
plastic tubing mats in a factory each with a supply and return
sub-header adapted to be easily coupled together with the main
supply and return header enables the initial cost of a system
embodying this invention to be drastically lower than that of the
prior art. Advantageously, once these plastic tubing mats are
formed at the factory, they can be rolled up so as to form a
conveniently portable roll, similar to a roll of carpeting, and
which can be taken by pick-up truck or station wagon from the
factory to the rink site to be unrolled and laid down like strips
of carpet. This, therefore, means that the present invention gives
to the user practicable and economic portability.
Further, by virtue of the fact that the plastic tubing has been
pre-assembled in mats, servicing is much easier to perform and far
less costly because one mat can be quickly and conveniently removed
and exchanged for another. Additionally, the present system enables
much smaller header piping and related equipment to be employed
because of the smaller volume of liquid involved, thus representing
a further savings because all of the valves and fittings are only
about one-tenth as large as in the prior art.
The plastic tubing mats which can be employed in practice of the
present invention are many times greater in length than they are in
width. For example, in a flexible plastic tubing mat adapted to
extend the length of a full-size skating rink, the mat is generally
200 feet in length and four feet wide. In the case where the
flexible plastic tubing mat is to extend transversely of such a
rink, the mat is generally 85 feet long and 4 feet wide. The
circulation in the tubing is arranged to double back on itself such
that both the supply and return sub-headers are at the same end of
the 85 foot mat for all of the tubing therein.
For mats extending the length of the rink, the small diameter,
flexible plastic tubes are arranged to run the length of the mat in
closely spaced parallel relationship with the ends of the tubes
being connected to supply and return sub-headers at opposite ends
of the mat. The direction of liquid flow is in opposite directions
in closely spaced adjacent tubes to provide uniform cooling action
in the ice in spite of the temperature differentials of 15.degree.
to 25.degree., so keeping the temperature of the ice as uniform as
is possible across its face. Fastening means in transverse relation
to the axis of the small plastic tubes are arranged so as to form
the plastic tubing into a grid-like form. Supply sub-headers each
having a length approximately equal to the width of the mat are
arranged so as to supply each tube with cold anti-freeze liquid and
similar return sub-headers are arranged so as to receive the
refrigerant after it has passed through the tubes. Thereafter, the
fluid is transferred from the return sub-header into cooling
apparatus to be again refrigerated and, thereafter, recirculated
through the system.
These flexible plastic tubing mats embodying the present invention
can be constructed and assembled in the factory where mass
production techniques can be used. In the presently preferred
embodiments, these mats are formed from plastic tubes of ethylene
vinyl acetate (EVA). Fastening means running transverse to the
direction of the axis of the tubing forms the tubing into a
grid-like form. After assembly with their sub-headers, the tubing
mats can be rolled into an easily portable form and transported to
the location wherein the skating rink is to be assembled. The ice
rink is formed on a level and approximately rectangular area of
ground with a layer of insulating material preferably separating
the flexible tubing mat from the ground. Several of these mats,
each of which comprises a plurality of plastic tubes arranged in
grid-like form, are arranged on the rectangular area that will form
the ice rink. The sub-headers of the individual mats, thereafter,
are interconnected with appropriate headers and freezing equipment
so as to complete the ice freezing system. The tubing mats are
usually covered with a thin layer of sand or other similar
material, so as to prevent a skater's blade from penetrating the
ice surface and thereby cutting, tearing, or otherwise damaging the
plastic tubing. When these preparations are complete, water is
sprayed onto this surface and allowed to freeze. Because of the low
temperature of the anti-freeze liquid passed through the tubes, the
ice is quickly frozen and the ice rink formed.
The various advantages, features and objects of the present
invention will become more fully understood from a consideration of
the following descriptin of certain preferred embodiments of the
invention in conjunction with the accompanying drawings, in which
corresponding reference numbers are used to indicate parts
performing corresponding functions in the various embodiments:
THE DRAWINGS
FIG. 1 is an overall plan view of a full size ice skating rink
having the freezing system of the present invention in which a
plurality of flexible tubing mats containing small diameter
flexible plastic tubing extend lengthwise of the rink area and are
interconnected in a grid covering the whole area of the rink and
containing a low temperature liquid;
FIG. 2 is an elevational cross-sectional view taken across the line
2--2 in FIG. 1 and shown on enlarged scale to disclose in detail
the main header and sub-header assembly and the interconnection of
the flexible plastic tubing therewith;
FIG. 3 is an enlarged plan view of one of the flexible tubing mats
of the system shown in FIG. 1. This particular flexible tubing mat
as shown in FIG. 3 is adapted to be laid lengthwise of the rink
area shown in FIG. 1;
FIGS. 4 and 5 show in detail means for securing the plastic tubing
in closely spaced parallel relationship to one another to hold the
same in a grid-like assembly. FIG. 4 is an enlarged partial
sectional view taken across the line 4--4 in FIG. 3, and FIG. 5 is
a partial sectional view taken along 5--5 in FIG. 4;
FIG. 6 is a plan view on the same scale as FIG. 3 showing a portion
of a flexible tubing mat wherein an alternate type of securing
means is employed to hold the tubing of the mat in a grid-like
assembly;
FIG. 7 is a plan view similar to FIG. 3 in which the flexible
tubing mat has four sub-headers and wherein pairs of the small
diameter plastic tubes are adjacent to one another with the low
temperature liquid therein flowing in opposite direction;
FIGS. 8, 9, and 10 are cross-sectional and plan views showing means
for securing the pairs of tubes adjacent to one another and for
holding them in a grid assembly as is shown in FIG. 7. FIG. 8 is a
partial sectional view taken along the line 8--8 in FIG. 7; FIG. 9
is a partial plan view as seen from the line 9--9 in FIG. 9; and
FIG. 10 is a sectional view similar to FIG. 8 and showing
alternative securing means;
FIG. 11 is an overall plan view of a full size skating rink having
the ice making system of the present invention, wherein a plurality
of flexible tubing mats run the width of the rink and are
interconnected in a grid covering the whole area of the rink. Only
two main headers are employed in the system of FIG. 11, both
extending along the same side of the rink. The small diameter
flexible tubes are bent back in U-bends at the left in FIG. 12 and
are connected to a pair of sub-headers at the right;
FIGS. 12, 13, 14, and 15 are detailed plan views of embodiments of
flexible tubing mats generally similar to FIG. 11 incorporating the
use of two sub-headers as is shown in FIG. 11 and using different
configurations of the plastic tubing and of the tubing securing
means to achieve the uniform cooling effect in the ice above the
mat;
FIGS. 16 and 17 are cross-sectional views shown in full size of the
present invention disclosing the advantages over the prior art of
the use of small diameter closely spaced plastic tubes; and
FIG. 18 is a cross-sectional view of a conventional prior art ice
making system using large diameter pipes embedded in concrete.
DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS
Referring now to the drawings in greater detail, FIG. 1 illustrates
a tyical installation of the freezing system of the present
invention. Ethylene glycol or other similar low temperature
anti-freeze liquid such as methyl alcohol (or ethylene glycol or
methyl alcohol somewhat diluted with water) which has been cooled
to a temperature of no more than 10.degree.F and preferably of
about 5.degree.F or lower is pumped through headers 11 and 13 into
individual supply sub-headers at opposite ends of the ice slab. The
individual supply sub-headers 15 are arranged to service each of
the individual flexible tubing mats M. Such mats M, as shown, are
approximately 200 feet long and 4 feet wide to extend
longitudinally beneath the ice rink. Typically, there are
approximately twenty-one such mats laid down side by side like long
strips of carpeting to cover the entire area beneath the skating
surface of a full size skating rink. The low temperature
anti-freeze liquid, as stated above, flows from the main supply
header 11 into the supply sub-header 15 of the flexible tubing mat
M indicated at 17. Additionally, such coolant flows through the
main supply header 13 into supply sub-header 16 on the opposite end
of the mat 17.
As is shown in the drawing of FIG. 3, the coolant from the
sub-header 15 flows through the individual small diameter flexible
plastic tubes T towards a return subheader 21 wherein it is
collected to be fed into a main return header 23 (FIG. 1) to be
returned to the refrigeration station 30. Simultaneously, coolant
from sub-header 16 flows downward through individual tubes T to a
return sub-header 25, wherein it is collected and then returned by
a main header 27 to the refrigeration station 30. The temperature
of the anti-freeze liquid in the main return headers 23 and 27 is
approximately 25.degree.F during typical operating conditions. By
having the low temperature coolant run through the closely spaced
tubes T of the mat M in opposite directions through successive
tubes, close temperature averaging in cooling effect is obtained,
i.e., the coldest liquid near the inlet end in each tube T is near
the least cold liquid near the outlet end of the neighboring tubes
T, and liquid at intermediate temperatures in each tube T is near
the liquid at intermediate temperatures in the neighboring tubes T.
The result is to obtain substantially uniform temperature along the
surface of the ice.
The liquid flow in the other flexible tubing mats, 18, 19, 20, and
in the others shown in FIG. 1, operates in substantially the same
way.
At the cooling station 30 shown in FIG. 1, the main return header
23 joins the other main header 27 to form a single outlet
connection pipe 31 whose output is collected in a tank 33. From
tank 33, the anti-freeze liquid is passed through a chiller 35 to
reduce its temperature to no more than 10.degree.F and preferably
to approximately 5.degree.F or lower and again is pumped back into
the supply headers 11 and 13 by pump means 37 feeding an inlet
connection pipe 36 to headers 13 and 11. The chiller 35 is a heat
exchanger wherein a primary refrigerant (such as Freon) from a
refrigerant circuit is expanded, and it, therefore, absorbs the
heat from the anti-freeze coolant liquid as it passes through the
chiller 35. The refrigerant circuit for this system includes a
compressor 38 which passes the compressed Freon through a condenser
39, and wherein the heat is extracted. Then the cooled compressed
Freon passes into the chiller 35, wherein it is expanded as
mentioned above. Condenser 39, tank 41, and cooling tower 40 have
water circulated therethrough which serves to remove heat energy
from the compressed Freon and to discharge the heat energy in the
cooling tower.
In FIG. 2 the relationship of the supply and return headers is
clearly shown. The main supply header 11 is connected by a short
line 12 to each of the supply subheaders 15 which, in turn, are
connected to the individual tubes T in each of the mats M. The
coolant, therefore, flows from the supply header 11 into each of
the supply sub-headers 15 and into the various tubes T. The coolant
passes the length of each tube T and is returned to the cooling
station 30, as was discussed above. As was also noted, coolant
passes through the supply sub-headers 16 and is removed by return
sub-headers 25 to return to the refrigeration station 30. This is
shown above in FIG. 2, wherein a tube T, representative of a
plurality of tubes in each mat M, is joned with a return sub-header
25 and the coolant is thereafter passed through short connecting
lines 26 from subheaders 25 into the main header 27 to return to
the station 30.
FIG. 2 discloses in detail the method of constructing an ice rink
by utilizing the present invention. The flexible tubing mats M are
laid upon a suitably prepared surface. The base 55 upon which the
mats are laid is of a suitable material such as a layer of sand
which had been placed over a layer of insulation material 57, such
as a layer of foamed polyurethane. Once the mats M have been
positioned on the surface 55, the sub-headers on each mat are
connected by the short coupling lines 12 and 26 to the main supply
and return headers, as described. A layer of sand or other suitable
protective material 53 may be applied so as to cover the tubes T.
This sand layer 53 protects the tubes T in that should the ice 59
be penetrated by a skater's blade, it will not cut, tear or
otherwise injure the tubing. As shown in the drawing, dasherboard
60 serves as a splash board to protect the header assemblies from
damage which are conveniently protected beneath a seat bench 51
attached to the dasherboard 60. Thereafter, fresh water is sprayed
upon the sand 53 and the coolant is pumped through the network of
tubes T below the water to freeze it so as to form the ice slab
59.
FIG. 3 shows in greater detail the sub-header assemblies and tubing
T of a mat M such as is used in the system of FIG. 1. In this
embodiment in which the flexible tubing mats extend, the length of
a rink, the mat is approximately 4 feet wide and approximately 200
feet long, and each of the sub-headers 15, 16, 21 and 25 are about
4 feet long. The short connection lines 12, 14, 20 and 26 are
connected to the mid-poits of the respective sub-headers 15, 16, 21
and 25 through T-shaped couplings 61. Connections 12 and 26 extend
to the main headers 11 and 27, as shown in FIG. 2, and connections
14 and 26 extend to the main headers 13 and 23, respectively.
While as is shown in FIG. 3, most of the tubes T throughout the
whole area of the flexible tubing mat M are closely spaced and
parallel to one another, a few of the tubes in the coupling regions
68 and 69 are displaced a small distance from their centerline at
the ends thereof to make room for the respective couplings 61 at
the mid-points of the sub-headers. A preferred spacing is about
three-quarters of an inch center-to-center average for tubing
having an I.D. of about three-sixteenths of an inch.
As is shown in FIGS. 3, 4 and 5, the various tubes T are kept
closely spaced and parallel to one another by securing means S
including the spacer strip assembly 70 which are arranged
transverse to the axis of the tubing T. FIGS. 4 and 5 show in more
detail the construction of the securing means S. The securing means
S includes a stiffener wire 72 which runs perpendicular to the
longidudinal axis of the parallel tubes. The stiffener wire 72 and
the individual tubes T are held in place by means of spacer tape
assembly 70 which, of course, must be unaffected by water. The
spacer strip assembly 70 comprises an upper woven glass fiber
fabric tape 74, which is arranged so as to bend up and over to
surround and embrace the tubing and a lower woven glass fiber
fabric tape 75, which is beneath and encases the stiffener wire 72.
When the upper and lower tapes 74 and 75 are placed together with
the wire 72 they form a grid-securing structure as is shown in FIG.
4. The exact arrangement of the upper and lower tape with respect
to the tubing is best seen in FIG. 4 and the centerline
relationship of the stiffener wire with respect to the tape
assembly is best seen in FIG. 5. The upper and lower tapes may be
secured to each other by waterproof adhesive or by stitching.
The flexible tubing mats M provided by the present invention can be
readily pre-fabricated in a factory, rolled into a roll and
transported to the construction site where they are interconnected
to form the grid system. This is in marked contrast to the large
diameter piping of the prior art which was laboriously assembled on
the job. The method of construction is such that the small diameter
flexible tubes are extended along the length of the mat and closely
spaced from one another. Thereafter, the tubes are cut to the
desired length and connected to the appropriate subheaders. As
shown in FIG. 3, the first tube 51 at the left is connected with
supply sub-header 15 and return sub-header 21; the second tube,
tube 52 is alternately connected with supply sub-header 16 and
return sub-header 25. The successive tubes shown in FIG. 3 are
connected in a similar fashion so that the direction of the coolant
in each tube is opposite to the direction of the coolant in each
immediately neighboring tube. Thereafter, the spacer strip
assemblies 70, running transverse to the axis of the tubes and at
predetermined intervals are installed, so as to secure the tubing
into a grid-like network. When completed, the sub-headers and their
tubes can be conveniently rolled into a roll and transported to the
construction site.
In FIG. 6 is shown an alternative flexible tubing mat embodiment
M-1 to the structure shown in FIG. 3. In FIG. 6 the tubes T are
slightly bent away and toward one another so as to form an
elongated X grid web of the tubes, as shown in FIG. 6. The
arrangement of the tubes T with respect to the sub-headers is
essentially the same as has been described in connection with FIG.
3, and therefore only the sub-headers 15 and 25 at one end of the
mat M-1 are shown. Clips 77 of non-corrosive metal or plastic are
placed at regular intervals along the lengths of the tubes T
surrounding two adjacent portions of the tubes to hold them to one
another to form the elongated X grid structure shown in FIG. 6. The
coolant flows in opposite directions through the successive tubes
T.
FIG. 7 shows a further alternative flexible tubing mat embodiment
M-2 to those which have been discussed above. As noted below,
anti-freeze liquid from the supply sub-headers 15 and 16 flows
through the tubes T and to the appropriate return sub-headers 21
and 25. Because of the configuration of the sub-headers, coolant
will flow through tubes 78 and 79, for example, in a direction
opposite to that of the fluid in the respective adjacent tubes 80
and 81. Correspondingly throughout the mat M-2 coolant in each of
the immediately adjacent pairs of tubes flows in opposite
directions. As discussed above, this flow pattern produces an
advantageous temperature averaging effect at a small distance above
the mat.
It will be noted that at the beginning of its travel, the liquid
within tube 79 has been freshly refrigerated and is commencing to
flow through the mat while near the same point, the fluid in tube
80 has already passed through most of the mat and is at its least
cold temperature. Likewise, where the liquid commences passing
through the tube 80, it is immediately adjacent to the portion of
tube 79 in which the liquid has traversed most of the mat and is
also in its least cold condition.
Also, it can be noted in FIG. 7 that tubes in the regions 68 and 69
have been bent slightly off of their center lines to allow room for
the couplings 61 that are centrally located in the sub-headers 15,
16, 21 and 25, respectively. Further, spacer strip means S are used
in the mat M-2. These spacer strips are placed equidistant apart,
at predetermined intervals along the length of the mat M-2. The
spacer strips S not only hold the tubes T to one another in pairs,
but they also serve to hold the entire formation together and to
keep it in a grid-like form after is has been rolled and
transported to a construction site.
FIGS. 8, 9 and 10 more completely illustrate the configuration of
the spacer strip assemblies. In FIG. 8, it can be seen that the
spacer strips include a woven glass-fiber fabric tape 82 and a
plurality of brass notebook-type fasteners 83 have been used to
penetrate the spacer strip. The two legs 84 of each fastener have
been inserted between the pair of tubes T and wrapped up around
them, so as to hold the tubing in place and to one another to form
pairs. A top view of the securing means S is shown in FIG. 9
wherein it is possible to see the tape 82 which has been penetrated
by the brass fasteners and which is holding the pair of tubes T in
place. The heads of the brass fasteners 83 are visible in FIG.
9.
FIG. 10 shows an alternative mat embodiment M-3 in which different
securing means S are used for holding the tubes in an arrangement
similar to that shown in FIG. 8. In FIG. 10, the upper tape 74 and
lower tape 75 embrace the pairs of tubes T which have been placed
adjacent to one another. To further strengthen the grid structure,
a stiffener wire 72 has been encased between the tapes extending
transverse to the tubes. This wire 72 serves to give transverse
stiffness to the grid-like construction of the mat M-3, to hold the
pairs of tubes spaced apart, as shown while allowing the mat to be
rolled up lengthwise without hindrance from the stiff wires.
It will be understood that any of the alternative flexible tubing
mat embodiments M-1, M-2 or M-3 can be used in the system of FIGS.
1 and 2 in lieu of the mats M, as shown.
FIG. 11 shows a system including a transverse grid configuration
different from those which have been discussed above. In FIG. 11,
while the ice rink is essentially of the same dimensions, the
flexible tubing mats M-4 instead of running the length of the rink,
run transversely across the shorter width of the rink. This
particular construction makes it possible for the coolant to
transverse the width of the rink twice, -- once across and once
back --, and thereby enables the use of only two headers, -- a
supply and return header, instead of the four header arrangement
which has been discussed previously. Moreover, each transverse mat
has only two sub-headers.
FIG. 11 shows a refrigeration station 30 which is similar to that
which was described in connection with FIG. 1. It comprises a means
for cooling the low temperature coolant down to a temperature of
5.degree.F or lower.
As shown in FIG. 11, the ice freezing system includes a pipe 85
which supplies the coolant from the refrigeration section 30 to the
ice rink and a return pipe 86 which removes the coolant after it
has passed through the system and returns it to the section 30 for
recycling. As can be noted therein, pipe 85 is connected with a
main supply header 87 and supplies fluid to the various supply
subheaders in the mats M-4; and the outlet pipe 86 is connected to
a main return header 88.
FIGS. 12, 13, 14 and 15 more clearly describe the particular
constructions of the transversely arranged mats which can be
utilized in the system that is shown in FIG. 11. In FIG. 12, supply
sub-header 90 is coupled to the main supply header 87 through
coupling 61 and connecting line 91. The liquid enters into the
sub-header 90, passes into tubes T, and because of the "U" bend 92
at the center of each tube, the coolant flows (in the tubes) across
the full width of the ice rink and returns, as shown by the arrows.
This flow path thereby enables the system to have liquid flowing,
in neighboring tube portions, in opposite directions so as to
provide uniformity of effective cooling in the ice as discussed
above. The return sub-header 93 is connected through the coupling
61 and short connecting line 94 with the main return header 88.
The tube securing means S shown in FIG. 12 for the tubes T in the
mat M-4 is the same as the securing means S with the tape assembly
70, shown in FIGS. 3, 4 and 5. We have found that the mats can be
handled conveniently and easily when the securing means S includes
tapes of glass-fiber fabric approximately one-half inch wide and
spaced from 6 to 18 inches apart along the length of the mat.
FIG. 13 shows an alternative embodiment of a transverse mat M-5.
This mat M-5 is similar in grid configuration to the mat M-1 which
was discussed with respect to FIG. 6, but the mat M-5 also employs
the same principles as shown in FIG. 12, wherein a "U" bend 92 at
the center of each tube T enables the fluid to pass once across the
ice and then return before it is received by the return sub-header
93 to flow back to the cooling station.
As is noted with respect to FIG. 6, clips 77 have been attached at
various intervals along the length of the tubing so as to join
adjacent tubes into forming an elongated X pattern or quilt-like
grid.
In FIG. 14 an alternative embodiment of a transverse mat M-6 is
shown similar to the mat M-2 which was disclosed in FIG. 7. This
mat M-6 can be utilized with respect to the system shown in FIG.
11.
Both the first and second halves of each tube T are held closely
adjacent to one another by securing means S shown as spacer strips
82 with fasteners 83 similar to those which were described with
respect to FIGS. 8 and 9. The legs of the fasteners 83 are wrapped
around the tubes so as to hold the tubing in place with respect to
the other tubes and to keep the two adjacent halves of each tube
held closely against one another.
FIG. 15 shows a mat embodiment M-7 having a coolant flow
configuration which is particularly adapted for use beneath very
short expanses of ice. Each of the tubes T shown in FIG. 15 cross
beneath the width of the ice, return, recross beneath the width of
the ice, return and recross and return again for several times
thereafter. The uniform cooling effect is enhanced by the fact that
the tubes are arranged so that each pair of tubes is arranged as a
set 96. The two tubes in each set of tubes overlaps and alternates
with the other tube in the set of tubes, and the coolant is flowing
in opposite directions in the two tubes in each set. Running the
flow in the tubes in opposite directions accomplishes, again,
balancing of the cooling effect, as uniformly as possible, across
the surface of the ice.
The details of this mat configuration M-7 are shown in FIG. 15
wherein the coolant is supplied through a short line 91 and a
coupling 61 and through a sub-header 98. On its first pass through
the tubes 99 at the bottom of FIG. 15, coolant traverses the mat
M-7 to point 101 where because of a "U" bend, it is re-routed
across the mat on its pass in a direction opposite to the first and
returns to point 102 where it is again, because of a "U" bend,
re-routed across the ice on its third pass to point 103, and from
this point 103 it is again re-routed across the ice for a fourth
pass to the point 104. It is re-routed across the ice as is shown
in FIG. 15 for an additional four times by going to "U" bend 105,
to "U" bend 106, to "U" bend 107 to point 108 and is thereafter
connected to return sub-header 100. On each pass, the coolant in
this tube 99 is moving in a direction opposite that of the coolant
in a tube 109 immediately neightboring thereto and interlaced with
the tube 99. This tube 109 also has seven "U" bends 111-117 which
are positioned adjacent to and overlapping with the respective
seven "U" bends 107-101 of the tube 99. Thus, the two tubes 99 and
109 comprises one of the tubing sets 96.
It is to be understood that any of the embodiments of the flexible
tubing mats M-4, M-5, or M-6 can be employed in the system shown in
FIG. 11 in which the mats extend transversely across the full size
rink. In this case, the mats M-4, M-5, or M-6 are about 85 feet
long and 4 feet wide. The sub-headers 90 and 93 are about 4 feet
long.
The flexible tubing mat M-7 is adapted for use with smaller ice
rinks as indicated above.
The dimensions of a flexible tubing, as shown in FIG. 1 or FIG. 11
are such that the main headers 11, 13, 23, 27 or 87 or 88 have an
inside diameter of approximately 2 inches, the sub-headers in the
mats M, M-1, M-2, M-3, M-4, M-5, M-6, and M-7 which supply and
return the coolant directly to and from the tubing T in the mats
themselves have an inside diameter of approximately three quarters
of an inch. A convenient way to make these sub-headers 15, 16, 21,
25 and 90 and 93 is to use copper pipes 4 feet long having holes
punched therein and then short copper spuds having an outside
diameter (O.D.) slightly larger than the inside diameter (I.D.) of
the tubes T are soldered into the holes in the pipe or otherwise
fastened to the main body of the sub-header to serve as a
connection spud between the subheader and the end of each plastic
tube T. These coupling spuds, for example, as shown in FIG. 3 at
120, are typically one-quarter inch in outside diameter. The
plastic tubing of the mat has an average inside diameter of
three-sixteenths of an inch. When installed, the ends of the tubing
is expanded from its normal three-sixteenth inch inside diameter to
one-quarter inch to fit onto the coupling spuds on the sub-header.
Thereafter, the tubing is clamped upon the spuds by a small
commercially available spring clamp 122 (sometimes called a "hose
clamp") which encircles the end portion of the tubing T surrounding
the spud 120.
In practicing the present invention, the flexible plastic tubes T
have an inside diameter between one-eighth and three-eighth of an
inch. It is to be understood that tubing having an oval shaped
passage can be used. Thus, the term "inside diameter" or "I.D." is
to be interpreted broadly enough to include such oval tubing having
an average inside dimension of between one-eighth and three-eighth
of an inch.
It is not necessary that the protective layer 53 of sand or other
protective material be used, providing that the operator of the
rink is careful to maintain an unbroken slab of ice over the
otherwise bare tubing T.
For the best results, it has been found that ethylene vinyl acetate
is the preferred material from which the tubes T for the flexible
mats are made. It has been noted that ethylene vinyl acetate (EVA)
is inert to low temperature anti-freeze liquids such as ethylene
glycol or methyl alcohol and has good temperature characteristics,
and its elasticity remains at low temperature (down to
approximately 5.degree.F to zero [0] degree F). Moreover, this
elasticity enables the tubes to be stretched over the spuds 120.
Further, we have found that EVA is preferable to polyethylene
because EVA has better temperature characteristics, i.e., it is not
brittle and that it has a higher degree of stretchability than does
polyethylene. Thus, advantageously, the stretchability of the
tubing accommodates the expansion and contraction due to
temperature changes. For example, the tubing mats may be laid down
in the fall when the temperature is approximately 60.degree.F, and
then the tubing is cooled to 5.degree.F or below by the
coolant.
Generally, it has been found that the optimum results from the
invention are obtained when the spacing of the tubes is such that
the distance between the tubes T is less than the thickness of the
ice. This is shown more clearly in FIGS. 16 and 17. In FIG. 16,
small diameter flexible tubes T are parallel to one another and
equidistant apart. The tubes T may be located within a protective
layer of material 53 which is preferably sand. The ice above the
tubing is preferably of a thickness, for example, 1.25 inches, such
that the thickness (X) of the ice is greater than the
center-to-center distance (D) between neighboring tubes T. The same
distance (D) exists between all other tubes shown in FIG. 16, which
is shown as three-quarters of an inch with the tubes T having an
I.D. of three-sixteenth of an inch. By virtue of the close spacing
of the tubing T, the temperature differential between a point N at
the surface of the ice midway between, e.g. equidistant from, the
two neighboring tubes and a point O directly over each tube will be
substantially less than that which is experienced in the prior art
system. The distance shown by the dashed lines 124 from points N to
the respective tubes T is not much greater than the distance 126
from the points O to the respective tubes T.
It is to be noted that the cooling of the surface points N and O is
accomplished by withdrawing heat down through the ice along the
lines 124 and 126. Since these lines are almost of equal length,
the effective cooling action is substantially uniform over the
entire surface of the ice.
FIG. 17 shows the effective cooling action when the tubes are in
adjacent pairs, as shown in the mats M-2 (FIG. 7) and M-6 (FIG.
14). The pairs of tubes are spaced by an approximate distance 2D,
and thus the average spacing per tube is about D. The ice thickness
X is preferably greater than D, as discussed above in connection
with FIG. 16. Once again, it is seen that the distances 127 from
the points N to the respective pairs of tubes is not much greater
than the distance 128 from points O. Thus, a substantially uniform
cooling action is obtained at the surface of the ice.
A prior art system is shown in FIG. 18 where wide diameter
thick-walled metal pipes 130 are embedded in concrete 132. The
centers of the pipes 130 have been customarily spaced approximately
4 to 41/2 inches apart. A 4 inch center-to-center spacing is shown.
At points N midway between these pipes, there will be found an
8.degree. differential between the temperature of the ice surfce at
that point N, and the temperature of the brine within the pipes.
Because of this wide differential in the temperatures, it is
possible for soft spots or melting to occur at the ice surface at
midpoints N in the prior art system. The distances 133 from the
midpoints N at the ice surface to the widely spaced pipes 130 are
much greater than the distance 134 from points O directly over the
pipes. Thus, a much different effective cooling rate occurs at
points N and O.
The system of the present invention utilizes small diameter
flexible plastic tubing placed much closer together and low
temperature coolant, and thus (a) the points N and O are all at
almost the same temperature, and (b) the differential between the
temperature at the surface of the ice and the temperature of the
concrete at various points is more uniform and the cooling path
lengths 124, 126, 127 and 128 are all fairly short, and this,
therefore, provides a better quality of ice.
Thus, it has been found that even though the present system has
only about one-tenth the volume of a conventional system for a rink
of the same size, better cooling and a better quality of ice are
provided by having a much greater number of very small diameter
tubes very close together with very cold coolant. The inlet and
outlet temperature of the coolant is approximately 5.degree. and
25.degree.F, respectively. However, inlet and outlet temperatures
of - 5.degree. and 25.degree.F can also be used to advantage.
As is noted in FIG. 18, because the temperature of brine being at
15.degree. to 18.degree.F at the inlet and 17.degree. to
20.degree.F at the outlet (an average brine temperature of
approximately 17.5.degree.F), it is sometimes possible with the two
pipes 130 being separated by a distance of 4 to 41/2 inches that
the point N half way between these two pipes could be at a
temperature greater than that of the melting point of fresh water.
Therefore, the regions near N on the ice would be in the form of
troughs or valleys of slush, causing a ripple appearance of ridges
and valleys in the ice surface. In FIGS. 16 and 17, the average
coolant temperature in the tubes T is approximately 15.degree.F and
the heat flow paths 126 and 128 are shorter than the heat flow
paths 133 (FIG. 18); thus, surface melting is less likely to occur
and significant ridges and valleys do not occur in the ice
surface.
With respect to this particular layout of FIGS. 16 and 17, it has
been noted the dimensions which seem best suited for this
application are 11/4 inch for the thickness of the ice, a quarter
inch of sand 53 or other material above the tops of the tubing to
protect them as has been noted above, and an average
center-to-center spacing D of three-quarter inch between tubes.
Again, by virtue of the extremely low temperatures at which the
systems of this invention operate and the extremely close placement
of the tubes, better cooling and better quality ice results.
The prior art systems utilize calcium chloride (CaCl.sub.2) brine
from the coolant solution on the basis of economics, i.e., it has
usually been financially impractical to use any other type of
coolant because of the large volumes under the rink floor of such a
system (3,200 gallons). The present invention can use a coolant
such as an ethylene glycol mixture because of its small capacity
under the rink floor (less than one-tenth that of the prior art
systems), and it can operate at a much, much lower temperature than
the typical prior brine solution system.
The combination of very cold tubing coupled with close spacing of
numerous small diameter tubes gives the invention the desired
characteristics of better quality ice and better cooling
results.
The small diameter plastic tubes have an I.D. in the range from
one-eighth to three-eighth of an inch and are spaced closer
together than the ice thickness, which should be less than 2
inches. The average center-to-center tube spacing is from 1/2 to
11/2 inches, and is shown as being three-quarter inch in FIG. 16. A
large temperature differential of 20.degree. to 30.degree.F is
utilized between the inlet and outlet temperatures of the
circulating coolant. A flow rate of less than one-fiftieth gallon
per minute per square foot of ice surface can be used, as compared
with the prior art systems in which usual flows are many times that
fraction. The coolant inlet temperature is not more than
10.degree.F and preferably not more than 5.degree.F, or lower. The
pairs of tubes T in FIGS. 7, 8, 9, 10, 14 and 17 can be extruded
together as a co-extruded pair, if desired. The loweor flows
allowed by the great temperature differential of 20.degree. to
30.degree.F allow for smaller size fittings and lower pumping
costs. By virtue of the fact that the ice temperature is not nearly
as responsive to the temperature of the low temperature coolant in
view of the large temperature difference, variations produced in
circulation flow rate by changing the circulating pumping pressures
of the pumps 37 provide an easy and reliable means of control of
the overall ice freezing and maintaining system.
It is to be understood that the various flexible tubing mats M,
M-1, M-2, M-3, M-4, M-5, M-6 and M-7 can also be utilized to "hold"
snow on a ski slope under conditions when the snow would otherwise
begin to melt. On a ski slope the mats are laid transverse to the
slope, i.e., are laid with the tubes T extending along horizontal
contour lines of the slope. It is more convenient to utilize the
types of mats M-4, M-5, M-6 and M-7 as employed in the apparatus of
FIG. 11, because this enables main headers to be extended along
only one border of the ski slope. The refrigeration station can be
located off to one side of the slope near the top, middle or bottom
of the slope, whatever may be convenient.
Moreover, the present invention can be employed to advantage in
creating and maintaining an ice trough or chute to be used as a
toboggan slide or for similar sliding purposes. For example, in
such an application, a flexible mat 4 feet wide and 100 feet long
having the two headers at only one end, such as the mats M-4, M-5
and M-6, can be employed. For a slide 2 feet wide, the mat is
folded in half along its length to make it 100 feet long and 2 feet
wide with a double layer of tubing resulting from such folding. The
mat can be bent around curves of the toboggan slide and inclined to
create banked curves. Tyically, the mats are laid end-to-end with
the sub-headers near each other so that one mat extends down the
slide from the sub-header location and the other extends up the
slide from that location. Thus, an icy trough can be created and
maintained with curves and straight stretches, as desired.
From the foregoing, it will be understood that the illustrative
embodiments of the small diameter flexible plastic tubing mats, as
shown above, are well suited to provide the advantages set forth.
And since many possible embodiments may be made of various features
of the invention and as the apparatus here described may be varied
in various parts, all without departing from the scope of the
invention, it is to be understood that all matter here and before
set forth shown in the accompanying drawings is to be interpreted
as illustrative and not in a limiting sense in that certain
features of these embodiments may be used without a corresponding
use of other features without departing from the scope of the
invention.
* * * * *