U.S. patent number 3,708,148 [Application Number 05/160,282] was granted by the patent office on 1973-01-02 for mold for casting cellular concrete bodies.
This patent grant is currently assigned to Internationella Siporex Aktiebolaget. Invention is credited to Rolf Erik Goransson.
United States Patent |
3,708,148 |
Goransson |
January 2, 1973 |
MOLD FOR CASTING CELLULAR CONCRETE BODIES
Abstract
A heat, insulated mold for casting cellular concrete bodies and
having a non-warping bottom member comprising a number of
table-like structures, each including a sheet metal top welded to a
stiffening metal framework having a few, widely spaced legs of low
heat-conductivity, a common support for said table-like structures
permitting certain horizontal movements of their legs to compensate
for expansive variations in the planar size of said structures and
a heat-insulating covering on the lower side of all said table-like
structures for maintaining their stiffening frameworks at
substantially the same temperature as the concrete mass received in
the mold. The legs of said table-like structures contacting the
support in a manner to prevent distortion of the latter by heat
transferred through said legs, and the longitudinal side wall
members of the mold being also of a non-warping design.
Inventors: |
Goransson; Rolf Erik (Alvsjo,
SW) |
Assignee: |
Internationella Siporex
Aktiebolaget (Stockholm, SW)
|
Family
ID: |
20292470 |
Appl.
No.: |
05/160,282 |
Filed: |
July 7, 1971 |
Foreign Application Priority Data
|
|
|
|
|
Jul 31, 1970 [SW] |
|
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10531/70 |
|
Current U.S.
Class: |
249/111;
249/172 |
Current CPC
Class: |
B28B
1/503 (20130101) |
Current International
Class: |
B28B
1/50 (20060101); B28b 007/34 () |
Field of
Search: |
;249/79,80,82,111
;25/DIG.10 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Overholser; J. Spencer
Assistant Examiner: Tabor; Ben D.
Claims
I claim:
1. A mold for casting cellular concrete bodies and comprising a
main supporting structure, a bottom member and a number of wall
members, each of said bottom and wall members including a heat
insulating layer for reducing heat losses from the concrete mass
cast in the mold, at least said bottom member comprising a
stiffening open framework of metal and a sheet metal covering
secured to the top side thereof to form the mold bottom proper,
said framework being supported above and vertically spaced from
said supporting structure by means of a limited number of widely
spaced apart leg-like members being formed in a manner to carry
away only negligible amounts of heat from said framework, and said
heat insulating filling of the bottom member covering both the
lower side of said open framework and of those portions of said
sheet metal covering exposed through the openings of said
framework, with the exception only of the areas occupied by said
leg-like members, all in such a manner that said framework will as
a whole assume and be maintained at approximately the same
temperature as its sheet metal covering and the cast mass contained
in the mold.
2. A mold as claimed in claim 1, wherein said framework of the
bottom member comprises a number of separate sections, each of
which is supported by four leg-like members and has its own sheet
metal covering, said sections being supported in line, the one
behind the other, by said supporting frame structure to form
together an elongate rectangular mold bottom member in which each
of said sections has an extension in the longitudinal direction
which is at most equal to the width of said mold bottom member,
movable joints permitting separate expansion and contraction of
said sections being provided between the sheet metal coverings
thereof.
3. A mold as claimed in claim 2, wherein the lower ends of said
leg-like supporting members are connected to said supporting
structure at points thereon, from which heat transmitted through
said legs can spread in the supporting structure without causing
distortion and bending of the latter.
4. A mold as claimed in claim 1, wherein said leg-like members have
their upper ends rigidly connected to said framework and their
lower ends movably connected to brackets on said supporting
structure.
5. A mold for casting cellular concrete bodies as claimed in claim
1, wherein at least two opposed wall members each comprises a
stiffening beam element, a covering plate secured to the inwardly
facing side of said beam element, and a heat insulating layer
extending practically uninterrupted over the outwardly facing side
of said beam element and of said covering plate for preventing heat
losses therefrom.
Description
In the manufacture of slabs and blocks from cellular concrete it is
common practice to first produce a large, porous body of expanded
concrete mass in a casting mold and to then divide this large body
into the desired slabs or blocks, usually when the expanded, porous
mass is still in a semi-plastic condition, i.e. before
steam-hardening of the cellular lightweight concrete has been
carried out. The casting molds used in this connection are commonly
of a considerable size, e.g. having a length of 5-7 meters, a width
of 1.5-2.5 meters and a depth of 0.5-1.5 meter.
As is well known, the temperature of the lightweight concrete mass
expanding and binding in the casting mold is considerably increased
as a result of internal exothermic reactions. The temperature of
the mass frequently reaches the magnitude of 80.degree.-90.degree.
C. This temperature increase is desirable from a productional point
of view, because it accelerates the binding of the mass. On the
other hand, the temperature differences occuring between the
contents of the mold and the surrounding cause problems as far as
the construction of the casting mold is concerned, because they
easily give rise to strains causing distortion of at least the
bottom member and the longitudinal side wall members of the mold.
This in turn may easily damage the set, but still semi-plastic,
cellular concrete bodies produced in the mold, e.g. by forming
cracks therein, and also cause difficulties during the subsequent
handling of the bodies, especially when the latter are moved from
one support to another in connection with the cutting
operation.
The problems caused by the fact that the bottom member of a mold
used in casting cellular concrete shows a tendency to crook as a
result of the temperature variations of the mold contents have been
previously noted but hitherto rather unsuccessfully attacked. So,
for instance, the U.S. Pat. No. 3,298,076 suggests that the said
problems should be eliminated by composing the mold bottom
structure from a supporting frame and a metal plate thereabove,
said plate forming the mold bottom proper and being mounted in a
manner to freely expand and contract longitudinally relatively to
the frame. In order to prevent as far as possible temperature
variations in the frame, the plate is supported a certain distance
above the same by means of a plurality of spacer elements, in which
the plate is slidable with its lower side practically entirely
accessible to the surrounding air. However, such an arrangement is
objectionable from many points of view. The plate must either be
made extremely thick in order to remain flat between a relatively
few number of widely distributed supporting spacer elements under
the heavy load of the cast mass, in which case considerable
temperature strains with accompanying harmful bending tendencies
will unavoidably occur in the plate itself, or else the number of
supporting spacer elements must be very large, in which case the
conduction of heat to the frame with accompanying risk of
distortion of the latter will still be considerable. Also, the
known mold bottom design is based on an almost entirely free
equalization of temperature between the cast mass and the air on
the lower side of the plate, which means that the contents of the
mold will be cooled in an undesirable manner, even if the heat
conduction to the frame can be kept low.
As has been mentioned already the temperature increase of the cast
mass at the expansion and binding of the same is solely beneficial
for the mass itself and, accordingly, it is desirable to prevent
cooling of the contents of the mold as far as possible. The less
the mold contents is cooled, the faster the binding of the mass
will take place and the quicker the porous, but still semi-plastic,
cast body can be taken out of the mold for further treatment, so
that the mold can be used again for casting another body.
Therefore, the manufacturers of cellular concrete products have now
and then tried using molds in which the bottom and wall members had
certain heat insulating qualities. The bottom and wall members of
these molds were each composed of a stiffening open framework of
metal, on the upper or inner side of which a covering sheet metal
plate had been secured, such as by welding, and of fillings of heat
insulating material, such as mineral wool, which were inserted in
the openings of the framework so as to cover the exposed portions
of the plate but not the framework. However, molds of this kind
were found very objectionable because their tendency of crooking or
warping was very obvious and their heat insulating capacity rather
poor.
The manufacturers of cellular concrete products nowadays usually
prefer using entirely uninsulated, simplier molds, which during the
expansion and bindning of the cast mass are moved into stationary,
well insulated so called conditioning tunnels or chambers, which
frequently are provided also with special heating equipment for
maintaining a substantially uniform, increased temperature therein,
although such conditioning tunnels or chambers are expensive and
require much space.
The object of the present invention is to provide a mold for
casting cellular concrete, in which the drawbacks of the previously
known types of molds as referred to herein before are eliminated
and in which the heat generated during the expansion and binding of
the cast mass can be effectively retained and successfully utilized
to accelerate the solidification of the cast mass without it being
necessary to use expensive conditioning tunnels or the like. More
particularly it is the object of the invention to provide a mold
having a high heat insulating capacity and in which the bottom and
wall members do not show any inconvenient tendencies to crook or
warp in spite of the fact that mold structure is sturdy and simple
and does not depend on a delicate interaction of movable parts.
A mold according to this invention for casting cellular concrete
bodies comprises a bottom member and a number of wall members, each
of said members including a heat insulating filling for reducting
heat losses from the concrete mass cast in the mold, and for thus
preserving the increased temperature attained by the cast mass at
the expansion and binding thereof, at least said bottom member of
the mold comprising a stiffening open framework of metal and a
sheet metal covering secured to the top side thereof in order to
form the mold bottom proper. The invention is primarily
characterized by the facts that said framework is supported above
and vertically spaced from a supporting structure by means of a
limited number of widely spaced apart leg-like members being formed
in a manner to carry away only negligible amounts of heat from said
framework, and that the heat insulating filling of the bottom
member covers both the lower side of said open framework and those
portions of said sheet metal covering thereon, which are exposed
through the openings of said framework, with the exception only of
the areas occupied by said leg-like members, all in such a manner
that said framework will as a whole assume and be maintained at
approximately the same temperature as its sheet metal covering and
the cast mass contained in the mold.
As will be readily understood, a mold bottom member of this kind
will not only assist in preventing an undesirable cooling of the
concrete mass but will also show substantially no tendency to crook
or warp because of temperature variations in the cast mass.
In a preferred form of the mold embodying the invention the
framework of the bottom member comprises a number of separate
sections, each of which is supported by four leg-like members and
has its own sheet metal covering, said sections being supported in
line, the one behind the other, by a common supporting frame
structure to form together a rectangular mold bottom in which each
of said sections has an extension in the longitudinal direc-tion of
said mold bottom which is at most equal to the width of said mold
bottom, movable joints permitting separate expansion and
contraction of said sections being provided between the sheet metal
coverings. By such a design of the mold bottom member, the
construction of the mold will be highly simplified, the
possibilities of adjusting the level and the evenness of the mold
bottom proper are improved, and possible repairs of damaged parts
are facilitated.
For further elucidation of the invention an embodiment thereof will
be described in the following, reference being had therein to the
accompanying drawing, in which:
FIg. 1 is a side view of the one half of a mold for casting large
bodies of cellular concrete,
FIG. 2 is a longitudinal sectional elevation of the remaining half
of the mold,
FIG. 3 is an end view, partly in section, of the same mold, and
FIG. 4 is a fragmentary sectional elevation illustrating on an
enlarged scale the attachment of one of the legs of each mold
bottom section to a related bracket on the supporting frame
structure.
The casting mold illustrated in the drawing comprises a bottom
member, generally designated by 1, two longitudinal side wall
members, generally designated by 2, and two end wall members,
generally designated by 3. In addition, the mold comprises a
supporting frame structure 4, to which the wall members 2 and 3 are
connected by means of hinges 5 and 6, respectively, in a manner to
be folded outwardly and downwardly, when dismantling of the
cellular concrete body cast in the mold is to be effected. The
structure 4 also serves as a carrier for the mold bottom member 1,
and has, in the form illustrated, wheels 7 permitting movement of
the entire mold unit. However, these wheels 7 may obviously be
omitted, if the mold is to be stationary.
The mold bottom member 1 is composed of a suitable number of
table-like units, four in the drawing, which each comprise a
stiffening framework section 8 consisting of a plurality of
transverse U-beam elements 9 and a pair of longitudinally extending
U-beam elements 10 forming together a sort of grate. The beam
elements 9 and 10 are suitably made of iron or steel. On top of
each framework section 8 there is rigidly secured, e.g. by welding,
a comparatively thin sheet iron or sheet steel covering 11 forming
the mold bottom proper. Each framework section 8 has four
supporting legs 12 made of relatively thin-walled steel tubes
having their upper ends welded to the beams 9 and their lower ends
resting on brackets 13 mounted on the outside of the supporting
frame structure 4, which is narrower than the mold bottom
proper.
Thereby, four separate and identical table-like units are formed,
each comprising a framework section 8 and a covering plate 11 and
each having an extension in the transverse direction of the mold
which is equal to the full width of the mold bottom and an
extension in the longitudinal direction of the mold which is at
most equal to said width. Between the sheet metal coverings 11 of
the various table-like units there are provided movable joints 14
of a design permitting a certain independent expansion and
contraction of each separate table-like unit. These joints 14 may
be lap joints with or without elastic filling strips.
The table-like units are supported in line, the one behind the
other, on the supporting frame structure 4, which means that the
joints 14 extend transversally. Under the complete mold bottom thus
formed there is arranged a thick layer of filling 15 of any
suitable heat insulating material, such as mineral wool, said
filling extending not only under the covering plates 11 but also
under the entire mold bottom framework formed by the framework
sections 8. The insulating filling 15 is kept in position by means
of a cup-shaped thin-walled sheet metal casting 16 resting on top
of the supporting frame structure 4. Through the insulating filling
15 only the supporting legs 12 of the table-like units extend
downwardly to the supporting frame 4, and these legs have by their
tubular configuration a very limited heat conducting capacity.
When the concrete mass to be cast is filled into the mold and
expands and binds therein, only a negligible portion of the heat
formed will be able to escape through the mold bottom. Accordingly,
not only the covering formed by plates 11 but also the entire
framework formed by sections 8 will rapidly assume and maintain
approximately the same temperature throughout as the contents of
the mold. This fact will effectively prevent the mold bottom from
crooking and warping despite the rigid connection between each
covering plate 11 and its related, stiffening framework section 8
which is very valuable from a structural point of view.
The supporting legs 12 of each table-like unit are at their lower
ends provided with shoes 17 resting slidably on their related
brackets 13 and being attached to the latter by means of bolts 18.
These bolts extend with a certain radial play through holes 19 in
the brackets 13 and are provided with cup springs 20 and lock nuts
21 under the same. In this manner, each table-like unit is to a
certain extent free to expand and contract separately in all
directions, but nevertheless the relative positions of the units
are sufficiently fixed to always maintain the required sealing
effect of the movable joints 14.
The brackets 13 are mounted on the supporting frame structure 4 in
such positions, viz. close to a horizontal plane through the latter
which is substantially neutral from the viewpoint of heat
distribution in the vertical direction through the structure, that
the heat supplied to the brackets through the legs 12 can spread in
the supporting frame without causing distortion or bending of the
same. Although the amount of heat transmitted through the legs 12
is small, the last-mentioned arrangement will warrant that also the
supporting frame structure 4 remains undistorted, so that the mold
bottom will always maintain its flatness within very narrow
tolerances entirely independent of any temperature variations in
the mold contents.
It should be noted that the covering plates 11 forming the mold
bottom proper may be thin because they are effectively supported
and stiffened by their related framework section 8, and these
framework sections may in turn be light and yet strong enough,
because the covering plates add strenght to them and because they
are relatively small in size. Accordingly, the heat transfer from
the cast mass to the mold bottom member required to keep the latter
at the same temperature as the mold contents will cause only a
negligible decrease of the temperature of the cast mass.
The longitudinal side wall members 2 of the casting mold are
generally built up in the same manner as the bottom member 1 in
order to prevent, as far as possible, heat losses form the mold
contents and distortion. Each side wall member 2 comprises an inner
sheet metal covering 25 which by welding is secured to the internal
side of a stiffening U-beam element 26 extending in practically the
full length of the mold. To the beam element 26 there are attached
a few hinge halves 5' approximately resembling the supporting legs
12 of the mold bottom member as far as heat dissipation is
concerned. These hinge halves 5' thus carry away only negligible
amounts of heat. To the beam element 26 there are also attached a
number of widely distributed bolts 27 serving to retain an outer
thin-walled sheet metal casing 28 for a heat insulating filling 29
which entirely covers the outside of the beam element 26 as well as
the portion of the covering plate 25 which projects above the same.
As appears from FIG. 3, the insulating filling is, in addition,
extended downwardly below the upper side of the mold bottom, at
29', in order to reduce the possible heat losses from the
longitudinal edges of the covering plates 11 of the mold bottom
member.
The end wall members 3 of the casting mold consist in their turn
each of an inner sheet metal plate 30 and an external heat
insulating filling 31, which is protected by a sheet metal casing
32. In view of the moderate size of the end wall members, no
stiffening framework or beam element is required in them, but the
plate 30 is provided with a framing of bars 33 in order not to
become damaged when the casting mold is used.
In their folded up positions, the side wall members 2 and the end
wall members 3 are kept together by means of bolts 34 mounted on
the end wall members and co-operating with ears 35 at the ends of
the side wall members. The folded up wall members 2 and 3 seal
against the upper side of the bottom member 1 by means of elastic
strips 36. When the wall members of the mold are folded down into
horizontal position, their formerly inner sides, now facing
upwards, will be on a level with or somewhat below the upper side
of the bottom member 1, so that the cast body can easily be
removed. If desired the inner faces of the mold, i.e. the upper
face of the bottom member 1 and the inner face of the wall members,
may be coated with rubber, plastic or similar material preventing
the cast mass from adhering and hence facilitating dismantling or
stripping of the cast body.
* * * * *