U.S. patent number RE32,673 [Application Number 06/898,796] was granted by the patent office on 1988-05-24 for process for the production of calcium silicate-containing stone blanks useful in constructing building walls.
This patent grant is currently assigned to SICOWA Verfahrenstechnik fur Baustoffe GmbH. Invention is credited to Volker Hermann, Reimund Keller, Hermann Pfeifer, Peter Schubert, Eckhard Schulz.
United States Patent |
RE32,673 |
Schubert , et al. |
May 24, 1988 |
Process for the production of calcium silicate-containing stone
blanks useful in constructing building walls
Abstract
A process and apparatus is provided for the production of
calcium silicate-containing stone blanks which are useful in
constructing building walls. A crude mixture, of a granulated
silicate-containing material, lime, water, a cement and a foaming
agent, is subjected to no more than a minimum application of
external pressure and is subsequently hardened in an autoclave. The
cement produces the necessary strength for the blank, so that the
latter becomes transportable while the final strength is achieved
by reaction of the silicate-containing material during the
autoclave treatment. In order to arrive at acceptable molding times
and in order to achieve a simplified process with slight fragment
bulk density and optimal head damping characteristics, the crude
mixture is rendered pourable, is filled into molds in a quantity
corresponding to the fragment volume of the stone blank, and the
crude mixture in the mold is heated essentially uniformly to a
temperature between 45.degree. C. and 90.degree. C. until achieving
the desired blank-strength. The production of the blanks is carried
out in molds, which are equipped with a heating system for heating
the crude mixture in the molds, whereby the heating takes place by
means of an electric high frequency field and/or indirectly via the
molds and possibly via mold spikes, which are individually heatable
and serve for the development of a pattern of holes in the
stone.
Inventors: |
Schubert; Peter (Aachen,
DE), Pfeifer; Hermann (Aachen, DE), Keller;
Reimund (Hattingen, DE), Hermann; Volker (Bad
Schwalbach, DE), Schulz; Eckhard (Wallenhorst,
DE) |
Assignee: |
SICOWA Verfahrenstechnik fur
Baustoffe GmbH (DE)
|
Family
ID: |
6100647 |
Appl.
No.: |
06/898,796 |
Filed: |
August 19, 1986 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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709311 |
Mar 7, 1985 |
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Reissue of: |
256614 |
Apr 22, 1981 |
04376086 |
Mar 8, 1983 |
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Foreign Application Priority Data
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Apr 22, 1980 [DE] |
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3015432 |
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Current U.S.
Class: |
264/414; 106/678;
264/154; 264/42; 264/82; 264/333 |
Current CPC
Class: |
B28B
7/42 (20130101); B28B 1/44 (20130101); C04B
28/18 (20130101); C04B 28/18 (20130101); C04B
7/00 (20130101); C04B 14/06 (20130101); C04B
38/10 (20130101); C04B 40/024 (20130101); C04B
2103/10 (20130101); C04B 2103/20 (20130101); Y02P
40/60 (20151101) |
Current International
Class: |
B28B
1/44 (20060101); C04B 28/20 (20060101); B28B
7/40 (20060101); B28B 1/00 (20060101); B28B
7/42 (20060101); C04B 28/00 (20060101); B29C
035/00 () |
Field of
Search: |
;264/26,42,82,154,333
;106/120 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lieberman; Paul
Assistant Examiner: Thompson; Willie J.
Parent Case Text
.Iadd.CROSS REFERENCE TO RELATED PATENT
This is a continuation of co-pending application Ser. No. 709,311
filed on Mar. 7, 1985, now abandoned, which is for reissue of U.S.
Pat. No. 4,376,086, issued Mar. 8, 1983, and entitled "Process for
the Production of Calcium Silicate-Containing Stone Blanks Useful
in Constructing Building Walls". .Iaddend.
Claims
What is claimed is:
1. A method for producing stones on calcium silicate-basis, which
are useful in constructing building walls, the method comprising
the following steps:
a. forming a crude mixture .[.of granulated.]. .Iadd.comprising a
.Iaddend.silicate-containing material, .[.lime, water, cement and a
foaming agent, using such an amount of water that the crude mixture
is pourable.]. .Iadd.selected from the group consisting of quartz
sand, pumice, alumina, quartz powder, boiler slag, and fly ash; a
calcium containing material selected from the group consisting of
calcium oxide, partially hydrated lime and calcium hydroxide and in
addition to the silicate containing material and calcium containing
material a cement, said cement acting as a binder, a foaming agent
and water, said water added in an amount sufficient to render the
crude mixture pourable .Iaddend.and by using a cement composition
starting with strength-forming reactions substantially at elevated
temperatures,
b. pouring the crude mixture of step (a) into molds,
c. heating the crude mixture in the molds to a temperature of
between 45.degree. C. and 90.degree. C.--substantially without
compacting the crude mixture to start the strength-forming
reactions of the cement,
d. subjecting the crude mixture in the molds to the elevated
temperature for 10 seconds to 5 minutes until the stone blanks
formed in the molds from the crude mixture by heating to the
elevated temperature achieves the desired blank strength necessary
for removing the blanks from the molds,
e. removing the blanks from the molds and transporting the blanks
to an autoclave, and
f. steam hardening the stone blanks in the autoclave.
2. The process as defined in claim 1, wherein an accelerating agent
and/or a retarding agent are added to the mixture in step (a) for
accelerating or retarding the cement reaction.
3. The process as defined in claim 1, wherein the crude mixture in
the molds is subjected to the elevated temperature of 45.degree. C.
to 90.degree. C. for 30 seconds to 1 minute, the heating of the
crude mixture being carried out by contact heating of the
molds.
4. The process as defined in claim 1, wherein the crude mixture in
the molds is subjected to the elevated temperatures of 45.degree.
C. to 90.degree. C. for 10 to 60 seconds, the heating of the crude
mixture being carried out by applying a high frequency voltage to
the molds.
5. The process as defined in claim 1, including the step of
gravimetrically measuring the volume of crude mixture added to the
molds and thereafter controlling the amount of water and foam added
in step (a).
6. The process as defined in claim 1, including slightly
compressing the crude mixture poured into the molds in step (b) to
achieve its intended volume.
7. The process as defined in claim 1, wherein the foaming agent
added in step (a) has a bulk density of from about 50 to 100
g/l.
8. The process as defined in claim 7, wherein the foaming agent is
a sulfated fatty alcohol.
9. The process is defined in claim 1, wherein the foaming agent
contains CO.sub.2.
10. The process as defined in claim 1, wherein the lime and water
are added in the form in step (a).
11. The process as defined in claim 1, wherein said lime is slaked
lime.
12. The process as defined in claim 1, including forming holes in
the crude mixture while in the molds in step (c) simultaneously
with the heating of the crude mixture.
13. The process as defined in claim 2, wherein the accelerating
agent and/or a retarding agent are added to the mixture in step (a)
at the same elevated temperatures to which the crude mixture is
subjected.
14. The process as defined in claim 13, wherein the temperature of
the accelerating agent and/or retarding agent and the crude mixture
are maintained constant. .Iadd.15. A method for producing stones in
constructing building walls, said method comprising the steps
of:
(a) forming a pourable crude mixture including a foam, said crude
mixture having a temperature wherein the temperature does not
exceed the instability temperature of the foam, and which mixture
is hardenable by chemical reaction of its ingredients to a final
strength state, suitable for a construction stone, by a curing
process, said crude mixture including water and foam and also
including a cement adjusted by at least one agent so that strength
forming reactions of the cement are initiated at an elevated
temperatures of between 45.degree. C. and 90.degree. C.,
(b) pouring the crude mixture of step (a) into mold means,
(c) heating the crude mixture in the mold means to a temperature of
between 45.degree. C. and 90.degree. C.--substantially without
compacting the crude mixture--to start the strength forming
reactions of the cement,
(d) subjecting the crude mixture in the mold means to said
temperature of between 45.degree. C. and 90.degree. C. for 10
seconds to 5 minutes until the mixture in the mold means achieves a
blank strength, due to strength forming reactions of said cement,
substantially less than that of said final strength state but
sufficient for the material to be removed from the mold means as
blanks which retain the shape of the mold means after removal,
(e) removing the blanks from the mold means, and
(f) then curing the blanks to said final strength state. .Iaddend.
.Iadd.16. The method defined in claim 15 wherein said at least one
agent is an accelerating agent and/or a retarding agent for
accelerating and/or
retarding said cement strength forming reactions. .Iaddend.
.Iadd.17. The process defined in claim 15 wherein said crude
mixture after being poured into said mold means is subjected to the
elevated temperature of 45.degree. C. to 90.degree. C. for thirty
seconds to one minute, the heating of the crude mixture being
carried out by contact heating of the mold means. .Iaddend.
.Iadd.18. The method defined in claim 15, wherein said crude
mixture after being poured into said mold means is subjected to the
elevated temperature of 45.degree. C. to 90.degree. C. for ten to
sixty seconds, the heating of the crude mixture being carried out
by applying a high frequency voltage to the molds. .Iaddend.
.Iadd.19. The method defined in claim 15, including the step of
gravimetrically measuring the volume of crude mixture added to the
mold means and thereafter controlling the amount of water and foam
added in step (a). .Iaddend. .Iadd.20. The method defined in claim
15, including slightly compressing said crude mixture after it is
poured into said mold means in step (b) to achieve its intended
volume. .Iaddend. .Iadd.21. The method defined in claim 15, wherein
the foam included in said crude mixture in
step (a) has a bulk density of from 50 to 100 g/l. .Iaddend.
.Iadd.22. The method defined in claim 21, wherein said foam is
produced from a sulfated fatty alcohol. .Iaddend. .Iadd.23. The
method defined in claim 15, wherein said foam contains CO.sub.2.
.Iaddend. .Iadd.24. The method defined in claim 16 wherein the
accelerating agent and/or retarding agent are added to said crude
mixture in step (a) depending upon the temperature of said crude
mixture. .Iaddend. .Iadd.25. The method defined in claim 16 wherein
the temperature of said crude mixture and of said accelerating
agent and/or retarding agent added to said crude mixture is
maintained constant. .Iaddend.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a process for the production of
calcium silicate stones as well as an apparatus for the production
of stone blocks, especially the production of stone blocks useful
in construction building walls.
Calcium silicate stones having densified structures, e.g., sandy
limestones, are customarily produced by preparing a mixture of
quartz sand, lime and water, the lime thereafter becoming slaked
with the water, thereby producing a crude mixture having an
essentially dry, almost dusty to slightly soil-moist consistency.
Such a crude mixture, when subjected to high pressure on the order
of magnitude of more than 15 m.kg/sec.sup.2 /mm.sup.2, can be
compacted in a compacting apparatus to form stone blanks. As a
result of this compacting, physical bonding forces arise in the
stone blanks which, because of the high pressure, are sufficient to
allow the blanks to be removed from the mold without damage and
thereafter to be transported to an autoclave in which steam curing
will take place. The steam curing will result in the development of
chemical bonding forces, i.e., due to the formation of calcium
silicate hydroxide bridges. However, the use of such high pressures
for the production of the stone blanks is disadvantageous, not only
because of the apparatus which is required but because the produced
stone blanks will have a high fragment bulk density and a low heat
damping capacity. In addition, the high fragment bulk density means
that the stone blanks cannot be made too large since they will be
too heavy for the bricklayers to handle during bricklaying.
According to U.S. Pat. No. 4,229,393, the fragment bulk density of
stone blanks can be reduced and the heat damping characteristics
increased if cement in a quantity of at least 1% by weight, as well
as foam or pore formers, are added to the customary crude mixture
of sandy limestone and subsequent compaction pressures of
significantly lower than 15 m.kg/sec.sup.2 /mm.sup.2 are used. The
addition of cement provides chemical binding forces which partially
replaces the physical bonding forces needed to achieve a sufficient
strength in the stone blanks since strength-building reactions of
the cement are allowed to start prior to the molding of the stone
blank. In addition, the fragment bulk density will be considerably
reduced by use of a reduced compacting pressure and it is then
possible to add lightweight aggregates which further improve the
heat damping characteristics of the stone blanks. Stones are
produced which have a pattern of holes, a high number of the holes
being separated from one another by bridges. These bridges provide
a favorable effect on the heat damping characteristics of the stone
blanks and moreover will considerably reduce the total weight of
the blanks. The strengths of the bridges, however, may not be
reduced to the lowest desireable level because to achieve such
desired low bridge strengths the bridges must be developed
perfectly during formation of the blank. Moreover, the process is
difficult to accomplish whenever an intermediate storage of the
crude mixture is required prior to the commencement of the
strength-creating reactions of the cement. Moreover, the processing
of the crude mixture is problematic per se whenever intermediate
storage is necessary, and this is especially so with breakdowns in
the subsequently utilized elements of the apparatus.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a process and
an apparatus of the initially described type which will be simplied
yet will result in optimal heat-damping characteristics in the
produced calcium silicate stones, make possible the production of
calcium silicate stones with especially low fragment density while
displaying an optimum hole pattern.
According to the invention the raw mixture used has a suitable
pouring consistency, i.e., it has no spreading dimension that can
be measured (>K3 according to DIN 1045), and it is essentially
automatically levelling (it will retain no natural embankment angle
when poured). The crude mixture will have cavities which are
essentially formed only by the added foam. Viewed without the added
foam, the cavities between the individual particles of the crude
mixture are practically completely filled with water, so that the
exertion of a pressure, as in the case of conventional sandy
limestone production into stone blanks, would not lead to an
increase of physical bonding forces and to a blank capable of easy
handling. The pouring consistency makes possible an easy and simple
adding and filling of the mold with the required volume of crude
mixture by pouring in, etc., whereby the crude mixture essentially
and without difficulty fills the mold.
In addition, this pourable consistency makes it possible to further
reduce the bridges between the holes in the stones as far as their
width is concerned, so that the number of holes and the total
portion of holes in the case of an optimum hole pattern with regard
to heat damping may be increased, without any mechanical problems
occurring due to the development of holes affecting the strength of
the blank.
Furthermore, the present process is suitable for producing solid
stones with low bulk density as well as stones with holes and solid
stones with integrated heat damping, so that by the latter is made
possible the filling of a hole extending essentially over the width
and length of the stone with a heat damping material, such as for
example a polystyrene block which is inserted into this hole. The
stone blanks obtain sufficient strength to facilitate removal from
the mold and succeeding transportation by the heat treatment that
is to be carried out during molding, which leads not only to short
cycle times during production of the blanks, and in the case of
stones with holes makes possible the development of bridges with
the desired low strength of the wall and nevertheless with the
required strength in the blank, but which generally permits an
economically acceptable processing of a crude mixture with a
pourable consistency without pressure or essentially without
pressure, and especially without the need for an intermediate
storage of the crude mixture prior to molding. The tarry time in
the mold and thus the cycle time will drop with the increase of the
heating temperature for the raw mixture and/or of the portion of
cement. Because of the practically pressureless production of the
blanks, the addition of foam to the crude mixture is particularly
effective since the foam-pores are practically not crushed during
the production of the blank and thus contribute fully to the
lowering of the fragment bulk density of the stone and thus also to
the increase of the heat damping characteristics. It is to be noted
that the pores which have been predetermined by the foam remaining
intact, although the foam per se in the case of the heating
temperatures provided for the crude mixture in the mold, still only
has a low stability in the event the latter is still extant at all
in the case of the temperatures used.
This process has nothing to do with the production of aerated
cements, known per se, where the pores are produced by the
development of gas in a crude mixture already located in the mold,
whereby the aerated cement remains for two hours and more in the
mold, an imprecisely determinable expansion occurs which requires a
succeeding cutting up of the aerated cement into blocks of desired
size which then possibly even have to be ground. In the case of the
production of aerated cement, the shaping is connected with the
bonding process and only sands with a fine grading curve which must
have a very small grain size may be used. As compared to that, in
the case of the process according to the present invention, the
true measurement of the stones produced is assured by the shaping
which is independent of the chemical reactions taking place which
essentially differ from the manner in which such occur during the
production of aerated cement), so that no reprocessing of any kind
is needed and, moreover, even sands with coarse grain parts or
other silicate-containing materials may be used.
As compared to the hitherto known production of sandy limestone,
the present invention permits the use of slaked lime, calcium
hydroxide, etc., as a starting material instead of quick lime. The
temperature problems are thus essentially reduced which may
otherwise occur as a result of the heat developing during the
slaking of the lime. Moreover, the addition of water may be
accomplished more easily, since the moisture in the sand may be
well determined. On the other hand, it may not be easily determined
in the just slaked lime because of the crystal water available
which is also measured during the determination of the water
content. In the case of the conventional production of sandy
limestone, the use of slaked lime, such as hydrated lime, etc., is
not possible on the contrary, because of the normally present and
usually even fluctuating water content of the sand, since as a
result of that so much moisture is fed to the crude mixture that it
would not be possible any longer to unmold blanks.
Instead of the customarily used quartz sand, other
silicate-containing material may be used, for example, pumice,
alumina or fly ash, etc., which may replace the quartz sand wholly
or partially and possibly may also in addition contribute to a
decrease in the weight of the finished stone.
As a cement, a Portland cement may be used, for example, in
combination with a certain quantity of hardening accelerators and
possible delaying agents, but also, for example, a quick-setting
cement with a correspondingly adjusted beginning of the hardening
time may be used. As a setting accelerator, for example, alkaline
aluminates, such as sodium aluminate, sodium carbonate, sodium
silicate; chlorine containing aluminates such as aluminum and
calcium chloride as well as water soluble aluminates and silicates
may be used, and as delaying agents, sulfates and sugar derivatives
may be used.
Lightweight additives in the form of cork or powered wood,
polystyrene pellets, etc., may be added to the crude mixture. It is
also possible to use liquefiers known per se which additionally
liquefy the crude mixture.
The crude mixture may be dosed both volumetrically as well as
gravimetrically into the molds although the former is preferred for
simply and quickly producing stones with essentially constant
weight. Possible fluctuations of the bulk density of the crude
mixture are balanced out by weighing the volumetrically dosed
quantity and subsequently regulating the density of the crude
mixture for the following charge corresponding to the measurement
value obtained thereby. This is accomplished by corresponding
dimensioning of the water or foam quantity in the crude
mixture.
It will be effective to excessively fill the molds with the crude
mixture and to then compress the crude mixture with a slight
pressure to the determined volume, so that even in the case of a
fluctuation of the bulk density, the crude mixture will be measured
at greater values than the mold when completely filled by the dosed
quantity of crude mixture. In this case, a small part of the foam
pores is crushed, but the foam part of the crude mixture may be
adjusted previously at a correspondingly higher value in order to
take this into consideration. Also the excess filling facilitates
the development of sharp-edged stones since a quicker and better
filling of the mold especially in the area of the bridges is
achieved, whenever the crude mixture must rise between the mandrels
in order to fill the mold. The degree of excess filling depends on
the size of the stone and on its proportion of holes and may amount
to up to 20% by volume or more. On the other hand, for solid
stones, a very slight excess filling will suffice.
For forming the holes, molds may be used which have correspondingly
developed spikes, although it is preferred to develop the holes by
moving the spikes into the partly filled mold, especially from
above through the cover plate of the mold, as a result of which the
mold is then filled with the crude mixture. For a mold, which is
closed on all sides and is excessively filled relative to its stone
volume, the shaped blank is assured of having a sharp edge, while
the pourable consistency of the crude mixture makes possible the
rising of same between the spikes and thus the development of the
holes with only a very slight load on the spikes which are to be
moved in. And, the holes are developed preferably as blind
holes.
The heating is accomplished generally during a period of time of
about 15 seconds to 1 minute., preferably 0.5 min. to 1 min., in
heating by contact heat, and 10 to 60 seconds in heating by means
of a high frequency field, and a hardening of the cement (but
essentially not of the calcium hydroxide by the developing of
calcium silicate hydroxide bridges) in such a degree that the
required strength of the blanks of greater than 0.1 m.kg/sec.sup.2
/mm.sup.2 is reached in this period, despite the pouring
consistency of the crude mixture, whereby a surface, as hard as
leather, of the stone blank results without a surface area
completely poor in fluid, so that no crumbling away takes place.
The cycle times achieved in such manner are industrially acceptable
and avoid a complex intermediate storage which is problematic in
regard to the temporal course of the process.
The foam is added either as such to the crude mixture or developed
in it prior to filling it into the mold by addition of a foam
maker, although the former is preferred. Bulk densities of foam of
about 50 to 100 g/l, especially of about 70 to 80 g/l, are
preferred. Rather than air, the foam may also be filled with
CO.sub.2 as a result of which, in case of an excess filling of the
mold, and a successive crushing of the overdosed foam and/or in the
case of crumbling of the foam under the action of heat, CO.sub.2
becomes free, which leads to additional strength forming reactions
as in the case of nonhydraulic lime. By adjusting the foam quantity
and possible the other components of the crude mixture, the latter
is preferably adjusted so as to achieve a fragment bulk density of
the stone which is greater than 1600 kg/m.sup.3 for a porous stone,
whereby fragment bulk densities below 1200 kg/m.sup.3 may be easily
achieved, and densities greater than 900 kg/m.sup.3 result for a
solid stone.
Since foams often are temperature sensitive, it will be effective
to maintain the temperature of the crude mixture so low up to the
time it is filled into the mold, that the stability of the foam
will practically not be affected by the temperature. The use of
slaked lime presents no problem, since the crude mixture has a
temperature which is composed of the temperature of the starting
materials which essentially are only subject to seasonal
fluctuations. If however, the slaking heat of unslaked lime, which
is used as a starting material, is added, then a cooling, such as
by a corresponding reduction of heat, etc., must be accomplished.
Thus synthetic foams have sufficient stability essentially only
below 30.degree. C., while protein foams have a sufficient
stability even above 30.degree. to 40.degree. C. and possibly above
such range. Depending on the foam used and the temperature of the
materials used as well as the type of installation employed, it
will be possible therefore to maintain the temperature of the
mixture of silicate-containing material, lime and water, constant,
and thus the addition of cement, accelerator and delaying agent as
well as of foam, constant or in correspondence with the starting
temperature of the mixture of silicate-containing material, lime
and water, to dose the quantity of foam, and/or the quantity of
delaying agent and/or the accelerator for the cement.
At the same time the cement is to be adjusted such that, depending
on the start of strength-forming reactions by the corresponding
addition of accelerators and delaying agents depending upon the
temperature of the crude mixture, the reaction will be triggered
only by the action of heat in the mold. It may therefore also be
necessary to correspondingly discharge heat originating from the
slaking of the lime. Therefore, it will be effective to add the
type and quantity of foam and a retarder, corresponding to the
temperature of the mixture of silicate-containing material, lime
and water in a regulated manner.
In order to facilitate the removal of the molded blank from the
mold and to avoid a baking-on, it will be preferable to wet the
mold and the spikes, prior to the pouring in of the crude mixture,
with a separator known per se. This may be accomplished by spraying
or immersion, whereby in the latter case it will be effective to
use a separator bath energized by means of ultrasonics, in order to
thereby remove remnants of the crude mixture from the mold and the
spikes.
The heating of the crude mixture by means of an electric field is
suitable for both solid as well as porous stones and may be
supplemented by heating the mold itself, while the use of heatable
molds and heatable spikes (contact heat) is suitable only for
porous stones. For the heating of the crude mixture in the mold by
means of a high frequency field, frequencies greater than 600 kHz
with voltages greater than 5 kV may be used, whereby frequencies up
to 30 MHz may be used.
The filling arrangement may be a device which facilitates a pouring
in of the crude mixture into the mold, since the crude mixture has
a pourable consistency. It may at the same time facilitate a dosing
of the crude mixture.
In such a device, spikes may be disposed in the desired dimensions
in the hole-pattern provided and may be moved in altogether into a
mold filled with crude mixture and preferably from above but only
up to a certain distance above the bottom of the mold for the
development of blind holes. At the same time the mold may have a
cover plate for closing same, which may be moved into a closing
position, which has corresponding holes for insertion of the spikes
and is disposed with the spikes possibly on a support for the
spikes lowered to a predetermined level.
The device however, may also have a bottom that may be moved
upwardly toward a cover plate, which is stationary during the
shaping, whereby the spikes may possibly be fixedly disposed on the
bottom and may be moved up with it. The bottom however, may also
include an endless, revolving conveyor belt, such as a steel belt,
which for example, may be driven intermittently at regular
intervals.
The free ends of the spikes may be tapered, with conical or rounded
tips, to facilitate their removal from the mold. Also, each spike
at its free end may have an aerating aperture, in order to prevent
the development of a vacuum in this area during extraction of the
spikes from the molded blank, since this could lead to a crumbling
of the bridges.
The bridges may be heated preferably with an electric heating
device (heating cartridges), whereby the heating intensity is
variable over the length of the spikes continuously and by sections
(for example, in three steps), so that a temperature gradient is
developed, adapted to the heat requirement of the crude mixture,
developing during insertion of the spikes into the filled-in crude
mixture, so as to achieve a uniform as possible heating of the mass
of the blank. Since the heat requirement, viewed over the cross
section of the molded blank is likewise not uniform, because of the
walls of the mold, heated by contact heating plates, the heating
intensity of the spikes, distributed over the base surface, should
be designed of variable intensity, in order to take into
consideration the mass of one spike to be heated as well as the
heat supply of other units, such as that of the mold.
The bottom plate, which is developed as a pallet or as a conveyor
belt, etc, may be preheated, such as inductively or by infrared
radiation.
If a separating bath is used for the spikes, the mutual distance
between the mold disposed essentially on the same level, and the
bath may be equal to the mutual distance between a filling
arrangement for the mold and the spikes disposed as a perforation
arrangement, so that the bath, disposed on a joint moveable support
with the mold, is moved beneath the spikes of the perforating
device, whenever the mold moves toward the filling arrangement.
The cover plate is first held in its position during removal from
the mold, until the lateral walls of the mold and the spikes are
lifted at least partly from the blank, in order to make possible in
this way a removal free of problems from the mold.
Whenever a conveyor belt is used as the bottom plate of the mold,
it will be possible to remove the blanks even if they have not yet
reached the strength desired for gripping and stacking them, after
which they are guided by means of a conveyor belt through a
reheating arrangement, for example, a heating tunnel or an infrared
heater, where an additional strengthening to the desired strength
of the blank for gripping and stacking takes place as a result of
the heat acting there. Such is possible, since the blanks need only
be ready for handling at the end of the conveyor belt, since they
will be seized there in order to be conveyed to an autoclave in
stacked form.
The invention will be described subsequently in more detail when
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 schematically illustrates the process steps carried out in
accordance with two embodiments of the invention.
FIG. 2 schematically illustrates a step-by-step production of a
blank by shaping and heating.
FIG. 3 is a sectional detail view of the molding-in of holes into
the blank.
FIG. 4 is a top plan view of an embodiment of a cover plate for a
mold for the production of a blank.
FIG. 5 is a perspective view of an arrangement of spikes for
molding a predetermined pattern of holes into a blank.
FIG. 6 is a front elevational view, partly in section, of an
embodiment of an apparatus for the production of a blank.
FIG. 7 is a partial top view taken substantially along line
VII--VII of FIG. 6.
FIG. 8 is a side elevational view, partly in section, of the
apparatus of FIG. 6.
FIG. 9 is a front elevational view, partly in section, of a filling
apparatus for the device of FIG. 6.
FIG. 10 is a side elevational view, partly in section, of the FIG.
9 filling apparatus.
FIG. 11 is a schematic illustration of another embodiment of an
apparatus for the production of blands.
FIG. 12 illustrates a closing device for the apparatus of FIG.
11.
DETAILED DESCRIPTION OF THE INVENTION
According to a first embodiment of the process as shown in FIG. 1,
quartz sand contained in a silo 1', and ground quick lime contained
in a silo 1", are fed to a pre-mixer 2, to which water is added to
the same time in sufficient quantity. The mixture is allowed to
react in a reactor 2' for a sufficient length of time in order to
slake the lime. The slaked lime and sand mixture is then fed to a
mixer 3, into which water is also fed, in order to achieve a
sufficiently fluid consistency of the final crude mixture. Thus the
temperature of the mixture of slaked lime and sand, still possibly
relatively warm from slaking, is reduced at the same time by
(according to the season) values fluctuating, for example, by about
20.degree. C. Furthermore, a foam-producing device 4, such as a
foam gun, is provided, from which produced foam is added likewise
to the mixer 3, via a regulating means 5 in a controlled manner.
Cement is fed from a supply container 6 directly to the mixer 3 and
into a secondary mixer 7, to which moreover a hardening accelerator
is added from a container 8' and a hardening retarder from a
container 8". This cement component together with the accelerator
and the retarder are at first premixed in the secondary mixer 7
prior to a better, later thorough mixing in the mixer 3. The
addition of accelerator and retarder takes place via regulating
means 9' and 9".
The mixture produced in the secondary mixer 7 is then fed to mixer
3 via a regulating means 9. The regulation of the regulating means
9, 9' and 9" takes place corresponding to a temperature T, which
has the mixture reaching the mixer 3, in order to adjust the recipe
of cement, accelerator and retarder to the pertinent conditions.
For example, after a mixing time of 1 minute., the finished crude
mixture reaches an apparatus 10 from mixer 3, for the production of
the blanks by molding and heating. In this case, the adding may be
accomplished volumetrically, after which the weight of the
volumetrically determined volume of crude mixture is determined and
is used for regulating the water and foam volume for the following
charge via the regulators 5 and 5', in order to produce a crude
mixture with the most constant possible bulk density. After removal
from the mold, the blanks are stacked on hardening trucks and are
moved to an autoclave 11, where they are subjected to a steam
hardening, and they leave the autoclave as finished lime-silicate
stones.
Whenever slaked lime is used instead of unslaked lime, the former
is fed to the mixer 3 from silo 1" just like the sand, as shown in
a broken outline in FIG. 1.
FIG. 2 shows the course of shaping a porous stone blank. First, a
heated mold 20 (FIG. 2a) is filled by a filling device 21 with
crude mixture of a certain volume, which is proportioned
volumetrically. Then the mold 20 is disposed beneath downwardly
moveable spikes 23 attached to a carrier plate 22 and disposed for
the desired pattern of holes (FIG. 2b), whereby the free ends of
the spikes 23 are located at about the level of openings in a cover
plate 24 for mold 20. After that the spikes 23 are first moved
downwardly with the cover plate 24, until the cover plate 24
reaches the intended final position corresponding to the height of
the stone to be produced, after which the spikes are moved further
downwardly through the openings in the cover plate 24 into the mold
20, until they are above the bottom plate 25 of mold 20 (FIG. 2C).
The mold 20 is now closed and as a result of the displacement of
the crude mixture, brought about by spikes 23, the entire mold 20
is now filled while developing sharp edges on the blank. In this
moved-in condition of spikes 23 with a closed mold 20, heating of
the crude mixture in mold 20 is carried out for example, for 0.5 to
1 min. at for example, about 80.degree. C., whereby the
temperatures of the individual spikes 23 and of the walls of mold
20 are controlled such that an as uniform as possible a temperature
distribution over the blank results, which rises slowly during the
initial period of the cycle to the final temperature. Such heating
may be effected by a control heater 12 (FIG. 3) in contact with
mold 20 and cover plate 24. A preheater 16 in contact with bottom
plate 25 may be provided for preheating this plate in a preceding
heating arrangement. And, the heating may be accomplished by
applying a high frequency voltage to cover plate 24 and to bottom
plate 25 (forming condenser plates) via leads 13 and 14 for a
period of 10 to 20 seconds.
Obviously, with this type of shaping, the mold or a series of
succeeding molds may be disposed on a track revolving cyclically or
immovably and with filling devices and spikes positioned above the
molds, or reciprocally movable in regard to the filling devices and
the spikes. The time needed all together for one cycle is somewhat
above the tarry time of the blank in mold 20.
FIG. 3 shows in detail, and in steps, the insertion of a typical
spike 23 which at first is located with its free end section 23'
(developed tapering conically) at about the level of the cover
plate 24 by means, for example, of flexible strands 15 extending
between carrier plate 22 and cover plate 24. Of course, other
suitable means may be provided. First the cover plate 24 with
spikes 23 is moved downwardly until the intended height of the
stone is reached, at which level its downward movement is stopped,
while the spikes 23 tapering conically toward the free end 23' are
moved farther into the mold 20, until they are at a short distance
above the bottom plate 25. As a result of the slight conical
development of spike 23 and of the lower end section 23' with a
greater conical development, both the insertion and removal from
the mold is facilitated. And, each of the spikes may have an
aerating passage 17 formed therein and terminating in an aerating
opening in the free end thereof. Such will serve to prevent the
development of a vacuum at the tip ends of the spikes during
removal from the molded blank.
The cover plate 24 is shown in FIG. 4 for a predetermined pattern
of holes and has a series of substantially parallel elongated
apertures 27 separated by narrow bridges, into which corresponding
spikes 23 may be moved, the spikes being developed correspondingly
plate-shaped (nevertheless conically in an axial direction), and
which in the moved-in condition close the apertures 27. The mold of
the cover plates 24 corresponds to the view of the top sides of the
blanks 26 molded therewith.
FIG. 5 shows an arrangement of spikes 23 in perspective, which are
attached to a carrier plate 22 for a different hole-pattern than
that shown in FIG. 4. The conical development of the spikes 23 and
of the end section 23' thereof have not been shown for reasons of
simplification.
The embodiment of the apparatus for the production of stone blanks,
shown in FIGS. 6 to 8, has a basic frame 30 which is supported on
the ground 32 via elastomeric buffers 31 such as rubber. A carriage
35 is disposed horizontally and is reciprocally movable along
guides 34, in the embodiment shown, by means of a piston-cylinder
unit 33. The carriage supports the bottom plate 25 of mold 20 as
well as a mold box 20' forming the lateral walls of the mold 20.
The mold box 20' is attached to a frame 36 (FIG. 7) is guided along
vertical columns 37 disposed on the sides of the carriage 35,
adjacent guides 34, and are movable up and down by means of
piston-cylinder units 38.
Furthermore columns 39 extend vertically upwardly from the base
frame 30 on which a crosshead 40 is guided and movable up and down
by means of a suitable drive. The carrier plate 22, from which
spikes 23 extends, is fastened to cross head 40. The spikes 23 may
therefore be moved by means of the cross head phantom outline and
solid outline positions of FIG. 3 respectively above and into the
mold 20.
The cover plate 24 for the mold 20, which in FIG. 6 in its lower
position is shown pulled through and inserted into the mold box
20', is attached to two bars 41 which are fastened to another cross
head 42 which is disposed above cross head 40 and is likewise
guided along the columns 39. At the upper ends of columns 39 there
is a traverse element 43, from which two piston-cylinder units 44
extend downwardly to the cross head 42, so that the latter may be
moved up and down. The cross head 40 is connected with cross head
40 with spikes 23 and cover plate 24 may be moved jointly
downwardly by operation of the piston-cylinder units 44, whereby
the cover plate 24 reaches its terminal position at the end of the
movement after which the piston-cylinder unit 45 is operated in
order to move the spikes 23 into the mold 20. Corresponding stops
(not shown) for the movement of cross heads 40 and 42 may be
provided.
FIG. 8 moreover illustrates the manner of shifting the carriage 35,
which first is in the filling position (the filling arrangement,
however, has been omitted here), then moves into the shaping and
heating position and from there moves the finished blank 26 into
the removal position.
The heating system, such as heating cartridges for the spikes 23
and contact heating plates for mold 20, just like an arrangement
for wetting of mold 20 and of the spikes 23 with a separating
agent, have not been shown here in detail.
FIGS. 9 and 10 show the filling station including a filler
arrangement 50 comprising a pot-shaped container 51 which may be
filled with crude mixture 52 from a mixer (not shown). While the
dosing of the crude mixture into the container 51 is accomplished
volumetrically, the container 51 with the pertinent parts suspended
from ropes 51a is weighed, whereby a measuring cylinder for tensile
force 51b delivers the corresponding measuring signal, so that the
addition of water and/or foam to the crude mixture may be
controlled via a control circuit in order to achieve a practically
constant bulk density.
Above container 51 a piston 54, guided along two guide rods 53 is
disposed which may be lowered from above into the container 51. The
container 51 is closed on its underside by means of a slide 55,
which may be opened for emptying the container 51 into the mold box
20', while the piston 54 for complete emptying and thus for
cleaning of container 51 may be moved into the latter during or
after the emptying process. A single or bipartite flap (not shown)
could also be used instead of slide 55.
The container 51 is movable in a frame 56 between a filling station
for the container 51 through a volumetrically operated dosing
apparatus (not shown) which is connected to the mixer (not shown),
and a filling station for the mold 20 via guides 57 disposed in
frame 56, by which the container 51 is supported with running
wheels 58, by a drive (not shown), while the piston 54 in the
filling station for the mold 20, is suspended locally fixed in the
frame 56, and may be moved up or down via a piston cylinder unit
59.
The molding of the blank in the mold 20 is accomplished essentially
without pressure, for the slight force exerted perforce by the
cover plate 24, limiting the tolerance of the blank, which also
serves for the development of the sharp edge of the blank merely
leads to a practically negligible pressure, which even in case of a
possible excess filling of the mold is not followed by any kind of
noticeable compacting of the blank, except of a corresponding
crushing of pores in the form, as is also desired by the
invention.
It should be noted that, upon removal of the spikes 23 from the
blank 26 after heating, no collapse of the bridges are found to
occur because of the development of a hardened surface, although
the holes molded by the spikes 23 are dead-end holes, so that no
air can enter from the opposite sides of these holes, and it could
be expected that the bridges of the blank would collapse or at
least could suffer considerable damage as the result of a
developing vacuum. Nevertheless, the pore structure of the crude
mixture in the blank is also preserved, although the foam is
destroyed by the heating.
The spikes 23 can be developed mutually variably heatable by
sections (for example, in three steps) or else continuously over
their length, in order not only to achieve as uniform a heating as
possible of the crude mixture 52 in mold 20, but ultimately to
obtain stones or blanks with the greatest possible homogeneity,
whereby otherwise by a control or regulation of the heating of the
spikes 23 and of the mold 20 for the purpose of heating of the
crude mixture 52 as opposed to a uniform heating of mold 20 and
spikes 23 and thus of a generally uneven heating of the crude
mixture 52, energy might still be saved. For this purpose, the
spikes 23 are preferably generally not heated with the heat
intensity, but spikes 23, located further out in the area of the
mold box 20' may be heated with a different, as a rule lesser
intensity in order to achieve a uniform heating of the crude
mixture 52, then spikes 23 located farther inside.
FIG. 11 shows a volumetric dosing device 60, which is disposed
below the mixer 3, and which is equipped with a stirring mechanism
3' and a funnel-shaped mouth. The dosing device 60 comprises two
semi-cylindrical parts 61, 62, whereby parts 62--disposed coaxially
with part 61--is rotatable about an axle relative to the locally
fixed part 61 and glides with its outer surface along the inner
surface of part 61. The part 61 has an inlet opening 63 in the area
of the funnel-shaped mouth of the mixer 3 and a discharge opening
64, which is directed obliquely downwardly. The part 62 has a
chamber 65, open to the outside, in which an intake piston 66 is
disposed for movement by means of a piston cylinder unit 67. For
filling the chamber 65, its opening is aligned with the inlet
opening 63 of part 61, while the intake piston 66 is in its
outwardly moved position (FIG. 11) in which its outer surface is
aligned with the outer surface of part 62. Then the intake piston
66 is moved inwardly a predetermined distance which is determined
by a path guide 68. In such manner, the crude mixture is absorbed
volumetrically into the chamber 65. Displaced air may exit via air
discharge apertures 69, adjacent the inner end of the chamber. The
path guide 68 serves for adjusting the volume, corresponding to the
size of the stone to be produced.
The part 62 is then rotated (counter-clockwise in FIG. 11) with a
filled chamber 65 in relation to part 61, until the aperture of
chamber 65 is aligned with the discharge opening 64 of part 61. The
piston 66 is again moved outwardly and thus the chamber 65 is
emptied. After that part 62 is rotated back for renewed filling of
chamber 65, the edge 64' of the discharge opening 64 serves as a
wiper blade for remnants of the crude mixture. The rotating of part
62 relative to part 61 may be carried out by means of a rotating
cylinder (not shown).
The part 62 with filled chamber 65 may be weighed and the
measurement value obtained thereby may be used for adjustment of
the bulk density of the crude mixture.
Whenever there are several molds 20, a corresponding number of
chambers 65 with pistons 66 and openings 63, 64 may be
provided.
FIG. 12 schematically illustrates another embodiment of an
apparatus for the production of blanks, and includes a conveyor
belt 80, which may be in the form of a steel belt, guided aroung
two reversing rolls 81, of which at least one is driven. The upper
strand of the conveyor belt 80 may run over a steel plate (not
shown) for support. The mold box 20' lies initially beneath the
dosing mechanism 60, which is connected with the mixer 3. The mold
box 20', filled with the desired volume of crude mixture, is then
moved into the shaping station, where the spikes 23 and the cover
plate 24 are moved into the mold box 20', such as in the previously
described manner, for finishing-molding the blank.
In lieu of, or in addition to, the previously described indirect
heating of the crude mixture in the mold 20, the latter may be
heated by a high frequency field, whereby the conveyor belt 80 and
the cover plate 24 serve as condenser plates.
The molding box 20' is connected with a carriage 82, by which the
molding box 20' may be moved back and forth between the filling
station and the shaping station, by means of a piston-cylinder unit
83 which engages the carriage 82.
Whenever the molded blank 26 has reached a sufficient strength, the
molding box 20' is lifted (say by means of a piston-cylinder unit
and guided on vertical bars, not shown) after which the spikes 23
and the cover plate 24 are removed. The blank 26 removed from the
mold in such manner is conveyed further by the conveying belt 80 in
order to be taken over at the end of the conveyor belt 80 by a
stacking device 84, which is for example, equipped with grippers
85.
Effectively, the conveyor belt is sprayed with a separate agent by
way of a nozzle 86 before the filling station. A corresponding
spraying device 87 is provided for the mold box 20'. Instead of
that however, it may also be possible to immerse the molding box
20' and the spikes 23 in a bath of a separating agent energized
preferably ultrasonically, so that adhering remnants may be removed
from the crude mixture.
For this a cleaning apparatus (not shown) in the form of a
stripping roller, of a scraper, etc., may be provided at the
delivery end of the conveyor belt 80.
The method of operation of the apparatus shown in FIG. 12 is suited
particularly for shortening the heating process in order to achieve
the desired stability of the blank 26 in such a way, that the
latter will be removed from the mold, whenever it has such
strength, that it might be transported without trouble by means of
the conveyor belt 80, but may not yet be grasped by the stacking
mechanism 84, since its strength is not yet sufficient for
handling. The further strengthening of the blank 26 up to the
required strength of the blank takes place then by reheating,
possible conduction of the conveyor belt 80, transporting the
blanks 26 underneath a reheating arrangement 88 with for example,
infrared radiators or through a heating tunnel, etc.
The process and the apparatus of the invention make it possible to
produce light-weight stones with almost optimal characteristics in
an extraordinarily quick and therefore economical manner.
Light-weight stones which because of their low bulk density and
their perforations have outstanding heat damping characteristics,
and may be handled relatively easily and simply despite their large
size so that a correspondingly increased building performance may
be achieved.
The production of stones according to the invention will now be
explained on the basis of the following examples. According to
these examples, 10-DF-stones, i.e., stones having dimensions of 428
mm.times.300 mm (basic surface).times.238 mm (height) were produced
which had a proportion of holes of about 41%. The individual
components in this case were made available by weight and the
adding of foam was adjusted by preselection of the foaming time of
a foam gun. The dry components were put in a mixer and the
adding-in of water began after its start. After 35 seconds of
mixing time, foam was added. At the end of a foaming time of 8
seconds, an additional re- and intermixing of the foam took place
for 25 seconds. At the end of the total mixing time of 60 seconds,
the adding of the crude mixture into a mold took place, which
together with its spikes was heated. After a certain molding time
in the mold, the blank was removed from the mold and transported to
an autoclave, where it was subjected to steam-hardening (in case of
saturated steam for 5 hours at 15 bar; 1 hour heating at an
increasing pressure of from 0 to 15 bar, 5 hours at a constant 15
bar and 198.degree. C., then 1 hour cooling at 0 bar).
EXAMPLE 1
A crude mixture of the following components was produced:
10 kg quartz sand (washed natural sand) having a grand size between
0 and 4 mm, mean grain size 0.6 to 1 mm;
5 kg of quartz powder, grain size<0.16 mm;
2.2 kg of water;
1.5 kg of calcium hydroxide (according to DIN 1060);
2.5 kg cement. (Heidelberg quick-cement-made at Heidelberg Portland
cement plant AG Leimen, Federal Republic of Germany);
600 g foam (sulfated fatty alcohol made by Chemische Fabrik Gruenau
GmbH, Illertissen, Federal Republic of Germany) corresponding to a
foam running time of 8.5 seconds and a foam bulk density of about
80 .[.g/cm.sup.3 .]. .Iadd.g/liter.Iaddend..
The resulting crude mixture had a temperature of 15.degree. C. and
was filled into a mold, the box of which was heated to a
temperature of 75.degree. C. and the spikes of which were heated to
a temperature of top of 76.degree. C. and on the bottom of
82.degree. C. Prior to shaping, the mold and the spikes were
treated with a release agent. After a molding time of 80 seconds,
the stove blank was removed from the mold. The degree of excess
filling of the mold amounted to 12%.
The crude mixture had a bulk density of 1150 kg/m.sup.3, the blank
had a fragment bulk density of 1285 kg/m.sup.3 and a blank strength
of more than 0.12 m.kg/sec.sup.2 /mm.sup.2.
EXAMPLE 2
A crude mixture was produced from the following components;
10 kg sand, as in Example 1;
5 kg boiler slag, crushed to a grain size of 0 to 4 mm;
2.3 kg of water;
1.5 kg calcium hydroxide;
2.25 kg cement, as in Example 1;
500 g foam, as in Example 1.
The resulting crude mixture had a temperature of 20.degree. C. and
was filled into a mold, the box of which had a temperature of
78.degree. C. and the spikes of which have a temperature on top of
77.degree. C. and on the bottom of 83.degree. C. After a molding
time of 70 seconds, it was removed from the mold. The degree of
excess filling of the mold amounted to 15%.
The crude mixture had a bulk density of 1250 kg/m.sup.3, the blank
had a fragment bulk density of 1375 kg/m.sup.3 and a blank strength
of more than 0.12 m.kg/sec.sup.2 /mm.sup.2 and the finished stone
had a fragment density of 1240 kg/m.sup.3, a total density of 735
kg/m.sup.3 and a stength of 5 m.kg/sec.sup.2 /mm.sup.2.
EXAMPLE 3
A crude mixture was produced from the following components:
12 kg sand, as in Example 1;
3 kg fly ash with a grain size of 0 to 4 mm;
2.8 kg water;
1.5 kg calcium hydroxide;
2.25 kg cement, as in Example 1;
420 g foam, as in Example 1,
The resulting crude mixture had a temperature of 20.degree. C. and
was filled into a mold, which was heated as in Example 2. After a
molding time of 60 seconds, it was removed from the mold. The
degree of excess filling amounted to 7%.
The crude mixture had a bulk density of 1490 kg/m.sup.3, the blank
had a fragment bulk density of 1595 kg/m.sup.3 and a blank strength
of more than 0.12 m.kg/sec.sup.2 /mm.sup.2 and the finished stone
had a fragment bulk density of 1435 kg/m.sup.3, a total density of
855 kg/m.sup.3 and a strength of 5 m.kg/sec.sup.2 /mm.sup.2.
* * * * *