Note: Descriptions are shown in the official language in which they were submitted.
Method and device for 'the production of an ice sheet, more
particularly for model tests with ships or marine structures
SCOPE OF APPLICATION
The present invention relates to a method for the production
of an ice sheet, more particularly for model tests with ships
or marine structures, on the water sur ca of a water body
and means for performing the method.
STATE OF THE ART
In order to be able in the project stage to make statements
on the icebreaking behaviour of ice breaking ships or regar-
ding ice loads on marine structures, models of these ships
or marine structures are tested in the ice tank. An ice tank
is a coolable model tank for hydraulic model tests in the
presence of ice on the water. The ice in the ice tank, des-
cribed as model ice, acts in this case as the physical model
of the natural ice on the sea or on inland waters. The pro-
perties of the model ice, in particular the mechanical proper-
ties, have to be scaled in accordance with the scale of the
model.
Asa rule, natural ice is not suited for the purpose of model
tests an the ice tank already owing to its strength being too
great. That is why various methods for the production of mo-
del ice have been developed. It is thus known to add chemicals
which lower the thawing point to water from which the model
ice is to be frozen, such as e.g. common salt, urea or glycol.
or to admix other, property-altering additives, such as e.g.
sugar or detergents. Ice sheets frozen on the surface of do-
ped water in the conventiorial manner by means of thermal with-
drawal, are, as soon as they have approximately reached the
~~0~2~3
- 2 -
desired thickness, subjected to a tempering process. The tem-
pering serves to adjust the model scale-wise requisite mecha-
nical properties. It is known, furthermore, to influence the
density of the conventionally frozen model ice by, in the
course of the freezing operation, continuously or periodically,
blowing small gas bubbles into the body of water with the aid
of a finely perforated hose. The gas bubbles ascend, deposit
themselves on the momentary ice underside and, with the conti-
nuing growth of the ice, are entrapped by the ice (Spencer
D.S. and G.W. Timco, Proc. IAHR°ICE Symposium, Espoo, 1990,
Uol. II, 745 - 755).
It is also known to introduce small plastic particles which
almost possess the density of the water to be frozen into the
water body. The plastic particles are entrapped by the ice
being formed. In the ice they form points of disruption or
imperfection and thereby let the model ice saturated with them
appear to be more brittle.
Also known is the production of a model ice sheet by means of
a spraying operation. In the DE-OS 33 45 548, a method for
the production of an ice sheet, more particularly for ship
model tests, on a water surface with the aid of a spraying ope-
ration is described. According to this method, the ice sheet
is produced in that water droplets that freeze in the air
being sprayed onto the water surface or onto an extremely thin
ice sheet produced on the water surface by conventional free-
zing, this operation being continued for so long until the
entire, or at Least the substantially entire, ice sheet thick-
ness is reached. On this occasion the spraying is effected at
cold ambient atmosphere so that the ice sheet is built up in
the upward direction.
The model ice sheets produced by conventional freezing with
the aid of thermal withdrawal on the surface possess substan-
tially a columnar nuclear structure. The freezing process of
210~2~~
_ 3 -
such model ice sheets is normally initiated in that, into the
cold air above the water that is ready to be frozen of the
ice tank freed from all ice, a fine mist is sprayed. The mist
droplets freeze while still in the air and descend in the form
of fine ice crystals onto the water surface where they spon-
taneously form an extremely thin skim of ice. The c-axes of
the ice crystals of this ice skim are randomly orientated.
The c-axis is the main anisotropic axis of the hexagonal
crystal lattice structure of ice. Sice the rate of growth of
ice crystals is maximal vertically to the c-axis, those crys-
tals of the spontaneously formed skim of ice whose c-axis is
approximately horizontal, grow faster than other, more unfa-
vourably oriented crystal, because their direction of maxi-
mal rate of growth is located parallel to the direction of the
thermal flow. As a consequence, the more favourably oriented
crystal nuclei grow more rapidly in a columnar form into the
body of water and, with increasing length, displace adjacent,
less favourably oriented crystal nuclei. Due to this circum-
stance, the number of the crystal nuclei on a horizontal sec-
tion also decreases with increasing depth and increases ac-
cording to the diameters of these crystal nuclei.
In doped water that is to be frozen, underneath the skim of
ice formed from the frozen mist, a thin upper layer of ice is
formed first which consists of relatively small, non-columnar
or hardly columnar ice crystal nuclei CFig.3). The thickness
of this fine-crystalline top layer, depending on added water
and freezing rate, is up to 1 cm, but it may also be entirely
absent. The above-described columnar crystal nuclei begin on
the underside of this top layer - as far as this layer exists
- and extend, provided that they are not displaced by more
favourably oriented adjacent crystal nuclei, up to the under-
side of the entire ice sheet. The mechanical properties of
coLumnarly grown model ice are anisotropic. If columnarly
- 4 -
grown model ice sheets are subjected to bending stress ° a
typical stress form in icebreaking by ships - then cracks are
formed preferably along the nuclear boundaries of the columnar
boundary nuclei (Fig.4), i.e. in vertical sections through 'the
ice sheet transversally to the crack, these cracks proceed
approximately vertically and linearity through the entire ice
sheet. Under compressive stress, when the ice is crushed - a
typical form of behaviour of the ice in interaction with ma-
rine structures - transgranular cracks occur as well. However,
since the individual ice crystal nucleus in the model ice con-
sists of natural ice and, consequently, also possesses the
strength of natural ice, the forces which are necessary for
the production of transgranular cracks in model ice are dis-
proportionally powerful.
The ice crystal nuclei in model ice sheets that are built up
by means of spraying operations (Fig. S) are without exception
fine°grained and randomly oriented. The texture of such ice
is termed "granular". The mechanical properties of granular
ice are approximately isotropic. Cracks formed under stress
follow also here preferably the nuclear boundaries. But since
the crystal nuclei are approximately spherical and lie packed
closely next to each other, such cracks that occur in bending
stress, possess an uneven surface. In vertical sections through
the ice sheet transversely to the crack, they appear in the
form of a substantially vertically oriented zig-zag line. In
orderto~crush fine-granular model ice under compressive stress,
due to the presence of many small crys~val nuclei and, thus_r of
many nuclear boundaries, it is not necessary to produce trans-
granular cracks. That is why it is possible in the case of
model ice which was produced by the spraying method, to appro-
ximately correctly scale the forces necessary for crushing the
ice.
The growth of ice sheets on the sea or on calm inland waters
(Fig.6) does for the most part take place approximately as
2~fl5~~~
described in the foregoing regarding columnar model ice that
was frozen in a conventional fashion. f~lere, too, as a rule,
in accordance with the crystal lattice structure of ice, a
columnar texture is formed. Especially in sea ice, an appro-
ximately 5 to 30 cm thick top layer of granular ice is fre-
quently found. However, the same owes its origin substantially
to either the freezing together of soaked snow on the ice sur-
face or to a disruption of the columnar ice growth at the be
ginning of the ice sheet growth. The causes of this are e.g.
wind, waves or current. However, due to various external dis-
ruptions, also the elongated crystal nuclei in the columnarly
textures lower area of the natural ice sheets do as a rule
not extend from the ice surface (or the underside of the gra-
nular top layer) as far as to the underside of the ice. The
greatest Length of these crystal nuclei is rarely more than
20 to 30 cm. Frequently, especially in ice that is several
years old on polar waters, more or less thick layers of gra-
nular ice are also found which are embdedded in the colum-
nar ice. The anisotropy of the ice which is due to the co-
lumnar texture is lessened by all this. But the preferably
vertical orientation of the nuclear boundaries does bring
about that cracks caused by bending stress in ice in nature
are passing approximately linearity through 'the entire ice
sheet. When subjected to compressive stress, natural ice is
often srushed into a more or less fine granulate. As a rule,
natural ice sheets exhibit an exceedingly brittle failure
behaviour.
Model ice sheets which are produced according to the known
methods only incompletely meet the purpose of supplying a
physical, correctly scaled model of ice sheets as exist in
nature. Depending on the production method, individual sub-
areas are reproduced well, others however inadequately.
Thus the columnarly textured model ice sheets produced by
2~~52~3
conventional freezing reproduce the anisotropy of the natu-
ral ice and the smooth cracks under bending stress fairly
well. Poorly represented is the crushing of the ice under
compressive stress because, in this type of failure, also
transgranular cracks through the columnar crystal nuclei
have to be produced. But the individual crystal nuclei pos-
sess - also after atempering process - the approximate
strength of ice crystals in nature, that ~s to say, their
strength cannot be scaled in a manner which is true to the
model. zn addition, the columnar crystal nuclei of such
model ice are far too large. The failure behaviour of co-
lumnarly textured model ice sheets which were frozen in a
conventional manner and tempered so as to obtain a true-
to-model strength, is too brittle.
Moreover, the density of the model ice which is decisive for
the buoyancy behaviour of broken ice floes is substantially
too high. The entrapment of gas bubbles (Fig.7) in the ice
body brought about by gas having been blown into the water
body with the aid of perforated hoses makes the adjustment
of a density similar to nature possible in conventionally
frozen columnar model ice. Besides that, the gas entrapped
in the ice also reduces the supporting cross-section of the
same, whereby a weakening of the model ice is achieved which
is otherwise achieved by a part of the tempering process.
A reduced tempering results in a more brittle failure beha-
viour of the ice. But the gas-filled pores produced by gas
being blown into the water body by means of perforated
hoses are, with a diameter of 1 mm, too large for serving
as effective stress concentrators.
The texture of the model ice is not greatly influenced the
occlusion of gas bubbles. The same applies to to the free-
zing in of plastic particles into the ice body. The thick-
ness of the fine-granular top Layer of columnar model ice
which was conventionally frozenon the ice surface by means
of 'thermal withdrawal is, as far as the same is present,
established by the selection of the dopant and the condi-
tions in the ice tank in question. To all intents and pur-
poses it cannot be influenced.
On the other hand, the model ice sheets produced by a spray-
ing operation reproduce the crushing of the ice under com-
pressive stress well. They fail due to brittleness similar
to nature. Due to the spraying operation, more or less many
small gas pores become entrapped in the ice body. The buoy°
ancy behaviour of broken 'floes of such model ice sheets is
more similar to nature thereby than that of conventional,
columnar model ice devoid of gas occlusions. But it is im-
possible for the density to be controlled. The crystal nu-
clei in model ice which was produced by a spraying operation
are desirably small. However, since they are randomly orien-
ted, mechanical properties of such model ice are isotropic.
The typical anisotropy of ice sheets in nature is not repre-
sented. Cracks produced by bending stress possess a jagged,
uneven surface similar to the one encountered in nature.
In none of the known methods for the production of model ice
sheets is it possible to produce a sufficiantly fine-granular
texture which, at the same time, appropriately represents
the anisotropy and the texture of the ice in nature. The ad-
justment of the density by means of a controlled introduc-
tion of gas has up to now been possible only in columnarly
textured ice sheets which are produced by conventional free-
zing with the aid of thermal withdrawal on the surface. How-
ever, these do possess disproportionally Large crystal nuclei.
TECHNICAL PROBLEM, SOLUTION, ADVANTAGES
That is why it is the technical problem of the invention
to produce ice sheets, more particularly, for model tests
P C~ ~1
;~~ fuel ~J !j
involving ships and marine structures that possess a texture
which corresponds at least approximately to that of ice sheets
occurring in nature and whose deformational and failure be-
haviour furnish a very largely true-to-scale reproduction
of what is observed in ice sheets in nature. The latter also
applies to the configuration of crack surfaces and forms of
fractures subjected to diffierent stresses.
This technical problem is resolved by the method steps stated
in the Claims 1, 2 and 3.
A first method according to the invention consists in that
an ice sheet is produced on a water surface in that the co-
lumnar growth of the ice is disrupted by the introduction
of 'fine-grain ice growth nuclei into the body of water in
such a way that a fine-granular ice is obtained over the en-
tire ice sheet or in one or several layers. The ice sheet
possesses a to a large extent desired texture, but preferably
a texture which resembles that of ice sheets in nature.
Furthermore, the invention provides for the solution of the
technical problem a second method for the praduction of an
ice sheet on a water surface, according to which the sheet
of ice is producsr~n'~hat the columnar growth of the ice sheet
is disrupted by the separation of fine-grain ice growth nu-
clei from the underside of the ice sheet in such a way that
a fine-granular ice is obtained over the entire ice sheet
or in one or several Layers.
A third method consists in that the ice sheet is produced
by the columnar growth of the ice being disrupted by the
production of fine-grain ice growth nuclei which are scraped
or brushed off by means of a mechanical treatment of the ice
formed on the surface of a refrigerator disposed in the body
of water with the aid of a device in such a way that a fine-
granular ice is obtained over the entire ice sheet or in one
or several layers.
2~0~~~3
- 9 -
According to the methods, a texture-controlled ice is pro-
duced. An ice is obtained, whose texture corresponds to that
of naturally occurring ice sheets or comes close to the same.
According to the method it is also possible to selectively
reproduce in a manner similar to nature, natural ice sheets
possessing varying textures. It is also possible according
to the method to limit the length and diameter of the co-
lumnar ice crystals, provided they are desired at all. On
the whole it is possible to produce any desired texture what-
ever ranging between the one extreme "strictly columnar tex-
ture with long ice crystals extending over approximately
the entire ice sheet" (Figs. 2 and 3) - produced by undis-
rupted conventional growth ° and the other extreme "a granu-
lar texture extending over approximately the entire ice
sheet and having fine, approximately spherical, very largely
randomly oriented ice crystals" Csimilar to Fig. S) - produ-
ced by continuous or brief periodic disruption of the co-
lumnar growth. It is thus possible for layers of granular
ice and columnar ice having in identical or differing thick-
ness to alternate and the size of the columnar crystal nu-
clei within a columnarly textured layer can be Limited by
embedding one or several very thin Layers of ice growth nu-
clei. The ice sheets produced according to the methods pro-
vide a better reproduction of the texture of ice sheets en-
countered in nature.
The disruption of the columnar ice growth is brought about
according to the one method in that fine ice growth nuclei,
e.g. fine ice granulate or the like are conveyed into the
water body below the ice sheet and, in the process, are dis-
tributed in such a way that they are deposited over the en-
tire area of the sheet or subareas thereof in an approxima-
tely uniform manner on the underside of the ice. Preferably
210293
- 10 -
the ice growth nuclei are conveyed with the aid of water
that is laden with 'the same into the water body underneath
the ice sheet. In this case the growth nuclei can be sup-
plied either from without the water body or by means of
suitable means, e.g. refrigeration means with mechanical
comminution of the ice produced there inside the body of
water.
In the other method the disruption of the columnar growth
is brought about in that the underside of the ice is treated
by suitable steps in such a way that, in the process, fine
ice particles are detached or broken off from the material
of the ice sheet which are subsequently deposited in the
form of new ice growth nuclei on the underside of the ice.
The treatment of the ice underside is preferably effected
in the form of a mechanical processing, e.g. with the aid
of machining steps with suitable tools being employed, such
as brushes or scrapers. For the mechanical abrasion of ice
crystals from the underside of the ice sheet, preferably
one or several scrapers are made use of, in particular such
scrapers which have a sawtooth-like contour on the edge
which bears against the ice. Supplementarily or alternati-
vely it is also possible to employ one or several brushes
which are moved parallel to the ice underside and/or are
rotatingly driven. The contact pressure with which the ma-
chining tools are urged against the ice underside is, with
the aid of suitable means, adjusted or limited in such a
way that a damaging of the ice sheet as a whole is avoided.
The machining tools are by preference mounted on a floating
body which, in the submerged state, supplies a uniformly
distributed and constant contact pressure by means of hydro-
static buoyancy. The contact pressure can be adjusted by
ballasting the floating body. In addition, the machining
tools can be hinged onto the floating body in a flexible
manner. The floating body can be moved by suitable means,
~1~~~~3
- 11 -
such as tackles, underneath the ice sheet. It may also be
moved with the aid of an underwater carriage travelling be-
neath the ice sheet and/or be guided by the same. It is
also possible to mount the machining tools by means of a
spring mechanism on an underwater carriage. In lieu of the
spring mechanism or in connection with the same it is also
possible for a power-controlled pressing-on means to be
employed. The generation of the contact pressure can also
be effected with the aid of hydrostatic buoyancy.
In both methods it is possible to influence the density of
the ice and the gas porosity of the ice in that, in a manner
known in principle, fine gas bubbles are introduced into the
water body under the ice which ascend, deposit themselves on
the underside of the ice and, with increasing ice growth,
freeze into the ice body. This can be effected in a known
fashion by the blowing in of air with the aid of finely per-
forated hoses. However, by preference the gas bubbles are,
according to the invention, produced in that water that has
been super-saturated with gas under pressure, is pumped un-
der the ice. When the water surface tension is reduced, the
pressure-supersaturated water degasifies and, in the process,
forms exceedingly fine gas bubbles. The thusly produced gas
bubbles are so small that, when they are entrapped in the
ice body, they are also able to serve as effective stress
concentrators and in this way bring about in a desirable
manner a more brittle failure of the model ice saturated
with them. But it is also possible, for the purpose of char-
ging with gas, to introduce gas-forming chemicals, such as
e.g. ammonium bicarbonate, into the water body.
~~o~z~~
- 12 -
Moreover, it is also possible in the method to flush, in
a known manner, solids particles into the water body that
are almost suspended in the water or are buoyant therein,
which do not act as ice growth nuclei, e.g. fine plastic
granulate, so that said particles become embedded in the
ice in the form of disruptive points and, in this fashion,
influence the mechanical properties of the ice favourably.
Advantages forms of the invention are characterized in the
subclaims.
BRIEF DESCRIPTION OF THE DRAWINGS
The method according to the invention is explained with the
aid of the embodiment examples illustrated in the drawings.
Thus, in schematic representations,
F i g. 1 shows a vertical section through a layer of ice
produced according to the method with entrapped
gas-filled pores and with a substantially smooth,
continuous bending crack;
Figs.Zto7 show representations for explaining ice produced
according to known methods and the ice in nature
to be reproduced;
F i g. 2 shows a vertical section through a columnarly
textured layer of ice produced by conventional
freezing;
F i g. 3 shows a vertical section through a columnarly
textured layer of ice with a fine-granular top
layer produced from doped water by conventional
freezing;
F i g. 4 shows a vertical section through a columnarly
textured layer of ice with a smooth continuous
bending crack;
~.~fl~2~3
- 13 -
F i g. 5 shows a vertical section through a granularly tex-
tured layer of ice with an uneven bending crack
produced by means of a spraying method;
F i g. 6 shows, in a vertical section through a typical
ice sheet in nature with a fine-granular top layer
having a length Limited by columnarly textured
crystal nuclei, with embedded layers of fine-granu-
lar ice and a smooth, continuous bending crack;
F i g. 7 shows a vertical section through a columnarly tex-
tured layer of ice produced by conventional free-
zing with entrapped gas bubbles which were produ-
ced by the direct blowing in of gas into the water
body underneath the ice;
F i g. 8 shows a distributing means for the introduction of
ice growth nuclei into the water body underneath
the ice for the production of an ice sheet which
is obtained from a conventionally grown layer of
ice and a texture-controlled Layer of ice on the
surface of a water body in a tank;
F i g. 9 shows, in a side view, a device for the production
of a layer of ice, in which the underside of the
ice is mechanically treated by means of a scraping
tool, the contact pressure being generated with
the aid of a hydrostatic buoyancy;
F i g. 10 shows the device according to Fig. 9 in a front
view;
F i g. 11 shows, in a side view, a device and a schematic
control diagram of the production of a layer of
ice, in which the underside of the ice Layer is
mechanically treated with the aid of a rotating
brush, while the contact pressure is maintained
constant in a power-controlled manner;
1c, _
F i g. 12 shows, in a side view, a device for the production
of an ice layer, in which the ice growth nuclei
are conduced to the underside of the layer of ice
and produced there, and in which, for the purpose
of producing gas-filled pores in the ice with the
aid of water that has been supersaturated under
pressure, fine gas bubbles are introduced into the
water body underneath the ice, and
F i g. 13 shows, in a side view, a device for the production
of an ice layer, in which the ice growth nuclei are
produced in the water body underneath the ice.
DETAILED DESCRIPTION OF THE INVENTION AND THE BEST WAY OF
REALIZING THE INVENTION
In the Figs. 2 to 7, explanations regarding the state of the
art and the ice in nature to be reproduced are depicted, whi-
le in Fig.2, an extremely thin skim of ice is identified
with 110, orientated crystal nuclei with 130, in Fig.3, a
skim of ice with 210, a thin top layer of ice with 220, colum-
nar crystal nuclei with 230, in Fig.4, columnar crystal nuclei
with 330, cracks in the ice sheet with 340, in Fig.S, ice
crystal nuclei with 410, a crack proceeding in a zig-zag
line with 440, in Fig. b, a top layer of granular ice with
520, a columnar texture with 530, cracks with 5~a0 and a
layer of granular ice with 560. In all the figures, the water
body is identified with W.
For the production of an ice sheet, more particularly for
model tests with ships and marine structures, on the water
surface of the body of water depicted at W in the Figs. 1,
8 to 11, an ice layer 734,834,934,1034,1134,1234 and 1334
is frozen by conventional freezing to begin with. By prefe-
rence, the ice growth is initiated in a known manner in
that a fine mist 733,833,933,1033,1133,1233 and 1333 is
- 15 -
sprayed into the cold air L above the ready-to-be-frozen
water which has been freed of all ice. The fine mist droplets
freeze while still in the air, descend upon the ice-free sur-
face of the water and spontaneously form there an extremely
thin, fine-crystalline skim of ice 1210. Beneath this skim
of ice, a fine-crystalline, hardly columnarly textured top
layer of ice 1220 is formed when doped freezing water is em-
ployed, whose thickness depends on the type of dopant used as
well as on the freezing conditions of the ice tank in question
and mostly ranges between 0 and 5 mm. On the underside 1221
of the fine-crystalline top layer 1220, or, if the latter
does not exist, on the underside 1211 of the skim of ice
1210, the growth of columnar ice crystals 1233 begins while
the cooling of the ice surface is continued.
The growth of these columnar ice crystals 1233 is disturbed
or disrupted by ice growth nuclei 1201, e.g. fine ice granu-
late or suchlike, which is conducted to the underside of the
ice. The introduction of ice growth nuclei does in this case
comprise the production of these nuclei from the material
of the already existing ice Layer. From these ice growth
nuclei 1202, a thin layer of fine-grained ice ice 1250 of
granular texture is formed, from which, in turn, columnar
crystal nuclei 1230 begin to grow. The length of these colum-
nar crystal nuclei 1230 can be limited by a renewed intro-
duction of ice growth nuclei 1202 to the underside of of the
ice which, after all, constitutes the growth front. If the
bringing up of the ice growth nuclei 1202 is continued con-
stantly or for a short time periodically, it is also possible
to obtain a layer of fine-granular ice 12b2 in any desired
thickness whatever. As soon as the bringing up of the ice
growth nuclei 1202 is discontinued together with a continued
cooling of the ice surface, the growth of columnar ice crys-
tals 1231 recommences. The bringing up of the ice growth nuclei
1202 to the momentary ice underside can be continued for any
°
16 -
length of time whatever and be interrupted for any length
of time whatever so that, to all intents and purposes, over
the entire ice sheet, an ice layer of the desired texture,
so-called texture-controlled ice 735,835,935,1035,1135,1235
and 1335 can be obtained. Cracks 1240, as arise due to ben-
ding stresses in a thusly produced ice layer, run approxi-
mately smoothly through the entire ice sheet. However, wi-
thin thicker regions of granular ice 1261, these cracks
1240a may also be uneven.
The density of the texture-controlled ice 1235 including
that of the undisruptedly grown ice on the surface of the
ice layer 1234 can, in a manner known in principle, be ad-
justed by the introduction of gas bubbles 741,841,941,1041,
1141,1241 and 1241 during the growth of the ice in 'the
water body W underneath the ice. The gas bubbles are entrap-
ped in the form of gas-filled pores 1270 on any horizons
whatever of the ice Layer in the ice. When the gaseous pores
1270 are distinctly smaller than approximately 1 mm in dia-
meter, they can, besides the anyhow brought-about weakening
of the supporting cross-section, also serve as effective
stress concentrators which lead to a desirable more brittle
failure of the gas pore-permeated ice)
In the method illustrated in the Fig.8, an ice sheet consis-
ting of a conventially grown ice layer 734 and a texture-
controlled ice Layer 735 on the surface of a water body W
is obtained in a tank 701 in that, in the course of the
growth of the texture-controlled ice 735, ice growth nuclei
702 are introduced into the water body W underneath the ice
with the aid of a suitable distributing means 703. The dis-
tributing means 703 can be moved underneath the ice so
that a uniform or approximately uniform distribution of the
ice growth nuclei 702 is brought about over the entire area
of the ice sheet or parts thereof. The ice growth nuclei
are, in the style of a particle-laden current, suspended
- 1 7 -
in the water and, with the aid of a pump 704, conveyed from
a supply tank 706 to the distributing means 703. It is also
possible for a device for the production of ice growth nu-
clei to be integrated into the supply tank 706. The water
with which the ice growth nuclei are conveyed to the dis-
tributing means 703 is, with the aid of a pump 705, re-
moved from the water body W into the tank 701 and pumped
to the supply tank 706. In this method it is also possible
to dispense with the initial production of a conventional
layer of ice 734 produced by means of frozen mist 733 and
the ice growth can instead be initiated in that, into the
water body W which was freed from ice on the surface, ice
growth nuclei 702 are introduced which rise to the surface
and there form a fine-granular layer of ice in the style
of the ice Layer identified with 1260 and.12b1 in F-ig.1.
In this case the ice sheet produced consists over its entire
thickness of texture-controlled ice 735.
In the method illustrated in the Figs. 9 and 10, an ice
sheet comprising a conventionally grown ice layer 834,934
and a layer of texture-controlled ice 835,935 on the surface
of a water body W is obtained in that, during the growth of
the texture-controlled ice 835,935, with the aid of scraping
tools 811,911, fine ice crystals are detached from the under-
side of the ice sheet which deposit themselves in the form
of ice growth nuclei 802 on the ice underside. In order to
be able to equalize unevennesses in the ice underside during
the machining operation and to thus achieve a to a very large
extent uniform production of the ice growth nuclei 802 over
the treated surface, it is advantageous to subdivide the
scraping tools 811,911 into shorter sections and to flexibly
hinge on the same. In this connection it is of advantage to
mount the sections of the scraping tools 811,911 on rotatably
v~ Fr 'ri ea
- 18 -
supported lever mechanisms 812,912, in which case the flexi-
bility is produced by means of springs 913,913. It is advan-
tageous, furthermore, to construct the edge 811a,911a of
the scraping tool 811,911 which bears against the ice in the
form of a toothed spatula or trowel or the like in a saw-
toothed fashion. It is further advantageous to apply the
contact pressure necessary for machining the ice underside
by means of a buoyant body 814,914. A very largely constant
and uniformly distributed contact pressure is obtained there-
by. By ballasting the buoyant body 814,914 with the aid of
weights 915 or other suitable steps, the contact pressure
can be reduced to zero and thus be adadpted to the require-
ments. By means of a force P that counteracts the buoyancy,
the scraping tools 811,911 can be raised from the ice sheet.
In order to absorb the tilting moment produced by the scra-
ping operation which acts upon the buoyancy body, it is ex-
pedient to hinge the buoyancy body with the aid of a moun-
ting means which does not impede the submersion movement,
e.g. a scissors elevating mechanism 816,91b or the like
to an underwater carriage 817,917, which runs e.g. on late-
rally disposed tracks 818,918. It is then also possible for
the force F to act upon the underwater carriage 817, which
is necessray for moving the device along underneath the ice
sheet in one or the other direction. This force may e.g. be
generated by a cable line mechanism or the like by an own
drive of the underwater carriage.
In the method illustrated in the Fig. 11, an ice sheet con-
sisting of a conventionally grown ice layer 1034 and a layer
of texture-controlled ice 1035 is obtained on the surface
of a water body W in that, during the course of the growth
of the texture-controlled ice 1035, with the aid of brush-
like tools, fine ice crystals are detached from the under-
side of the ice sheet which deposit themselves in the form
Y~~ 1'e/ :,~ :~
- 19 -
of ice growth nuclei 1002 on the underside o-F the ice. It
is advantageous to employ as tools for this purpose rota-
tingly driven brushes 1003 which are disposed on a contact
mechanism 1010 which provides the contact pressure that
is required for the detachment of the ice crystals. As an
alternative to the contact pressure generation depicted in
the Figs. 9 and 10 with the aid of hydrostatic buoyancy, in
Fig.11, a Lever mechanism is shown by way of example, in
which the contact pressure is maintained constant in a
power-controlled manner. A rotating brush 1003 - several
brushes may be used - is mounted at the end of a lever 1005
which is rotatably supported on a bearing 1006. On the free
end 1005a of the lever 1005, a controllable power generator
1007 engages over a spring 1008 which supplies the reaction
force for the desired contact pressure. The contact pressure
with which the brush 1003 presses against th,e ice underside
is measured with the aid of a power metering element 1004
which is shown here as having been integrated into the lever
1005. The bearing 1006 and the power generator 1007 are sup-
ported on an underwater carriage 1017, which e.g. runs on
laterally disposed tracks 1018. It is also possible then
for force F to act upon the underwater carriage which is
necessary for moving the device along underneath the ice
sheet in one or the other direction. This force may e.g. be
generated by means of a cable line or suchlike or by an own
drive of the underwater carriage. The momentary contact
pressure measured on the force metering element 1004 is sup-.
plied in the form of actual force value to a controller 1022
which compares this value with the theoretical value fed
into a nominal value guide 1021 and, depending on the diffe-
rence, sends the control signal to a power circuit 1023. The
power circuit 1023 can e.g. be a servohydraulic system or
the like. The power circuit brings about the actions of the
_ 20 - 2~.~~~a
power generator 1007, i.e. for instance in a servohydraulic
system, the displacements of the hydraulic pistion. In a
simpler model, the power regulating circuit comprising
power metering element 1004, set point guide 1021, control-
ler 1022, power circuit 1023 and power generator 1007 is
dispensed with and the contact pressure is determined solely
by the geometry of the assembly, the spring characteristic
of the spring 1008 and the momentary deflection of the same
In the method illustrated in Fig.13, an ice sheet consisting
of a conventionally grown Layer of ice 1334 and a layer of
texture-controlled ice 133'5 is obtained on the surface of a
body of water W in that, during the growth of the texture-
controlled ice 1335, ice growth nuclei are produced in the
water body W underneath the ice. For that, a refrigerator
1303, e.g. a heat exchanger filled with a coolant or the
like is introduced into the water body W. On the surface of
the refrigerator 1303, ice 1304 is formed, from which, with
the aid of mechanical treatment with a suitable means 1305,
for example, by scraping or brushing off with a rotating
brush or the like, or by vibration, fine ice crystals are
detached which serve as ice growth nuclei 1302. It is ad-
vantageous to mount the refrigerator 1303 and the means
1305 for detaching the ice crystals from the formed ice
1304 on a common underwater carriage 1317, which runs on
tracks 1318 and can be moved to and fro underneath the ice
sheet. In this method, too, it is possible, to dispense with
the initial production of a conventional layer of ice 1334
with the aid of frozen mist 1333 and, instead, to initiate
the ice growth in that, into the water body W which was
freed from ice, ice growth nuclei 1302 are introduced which
rise to the surface and form there a fine-granular layer of.,
ice according to the ice Layer identified with 1260 and 1261
in the Fig.1. In this case the produced ice sheet likewise
consists over its entire thickness of texture°controlled
ice 1335.
21~J~;
- 21 -
In the Figs. 8 to 13, at 741,841,941,1041,1141,1241 or 1341,
gas bubbles rising in the water are indicated which, when
frozen into the body of the ice, serve for adjusting the
ice density and, possibly, for weakening the ice. In the
interest of as small bubbles as possible being produced,
it is advantageous for the same to be generated by way of
the degasification of water that has been supersaturated
with gas under pressure. In this connection it is advanta-
geous to connect the means for introducing the gas bubbles
into the water body with the device that is meant to pro-
duce the texture-controlled ice. Fig. 12 shows such an as-
sembly by way of example. In the body of~water W underneath
the ice sheet, which possibly comprises a conventionally
frozen layer of ice 1134 and a layer of texture-controlled
ice 1135, a device 1103 for the production of ice growth
nuclei according to one of the methods is disposed on an
underwater carriage 1117 which possibly travels on tracks
1118. On the same underwater carriage 1117, a discharge
means for the gas-supersaturated water 1142, e.g. a perfora-
ted pipe or suchlike is mounted. The gas-supersaturated wa-
ter originates from from a means 1143, in which water that
has been removed with the aid of a pump 1145 from the water
body W, is supersaturated with gas under pressure. The pres-
sure gas is removed from a pressure gas generator 1144, e.g.
an air compressor, a compressed air flask or suchlike and
pressed into a supersaturation apparatus 1143. The means for
the production of the gas-supersaturated water can also be
disposed wholly or in part on the underwater carriage 1117.
In this connection it has to be stated that the invention is
not restricted to the embodiments described in the 'Foregoing
and claimed hereinafter. Another form of combination of the
described method steps or devices does come into the scope
- z2
o-f the invention just as much as the employment of, in each
case, equivalent means and steps such as e.g. the use of a
hydrostatic buoyancy for the purpose of generating the con-
tact pressure, the use of processing methods other than ma-
chining ones for detaching ice crystals from the underside
of the ice, such as e.g. by means of water set in motion
or by means of vibrations or by means of thermally produced
stress cracks, or, for the production of gas bubbles in the
water, e.g. the use of gas-forming chemicals or the employ-
ment of vibrations which cause gas dissolved in 'the water
to effervesce.
With the methods described in the foregoing and the means
and devices constructed for the same, a texture-controlled
ice possessing a predetermined crystal structure for model
tests is obtained which corresponds to the structure of na-
tural ice, which also applies to the configuration if crack
surfaces and fracture forms.
