Note: Descriptions are shown in the official language in which they were submitted.
~X~L8~5
This invention relates to a method and apparatus for apply-
in a screwed coat to a roof surface.
The method according to the invention is particularly import
lent for use in the renovation of existing flat roofs that have become
5 deficient, and in the following description special attention will be
paid -to this use of the method, but as will be realized by the man
skilled in the art, the method may also be used in connection with the
construction of new roofs, where this may be Found -to be a practical
and economic proposition.
Though it is an elementary rule that a roof should always
be built in such a manner as to allow the rainwater to run of-f complex
tell when the rain stops, this rule has nevertheless been neglected to
a large extent in modern building, especially in the case of houses
erected from prefabricated elements. In the interest of rationalization
15 by using elements of uniform height, it became a temptation to make
roofs not only flat, but level, with no gradient towards drains and
gutters. The confidence in the water resistance and durability of
modern roofing materials, such as high grade bitumen felt, was so
great that it was found responsible to disregard the requirement of a
20 gradient sufficient to permit rainwater to run off completely without
fail. This practice was even accepted by the building authorities.
However, experience has shown that such gradient-less
roofs are extremely apt to deteriorate, often after a relatively short
period of time, and that this may have disastrous consequences for
25 -the whole of the building. After some time the roof supporting strikeout-
no is apt to subside, whereby cavities are formed in the surface of
the roof. The water cannot run off from these cavities, and in certain
climates these roofs are more or less under water all the year round.
The roof covering will tend to crack in these cavities, whereby the
30 water will leak into the roof supporting structure, which then begins
to decompose. Wooden structures are attacked by rot and dry rot,
steel structures by rust, and insulating materials loose their insulating
power .
There exists -therefore an imminent need For methods and
35 means for renovating such roofs, before deterioration has started, or
at least before it has proceeded so far that complete rebuilding is
wreck red .
1~8~
It is an object of the invention to provide a method that
may be used for applying to deficient roofs of the type described a
screwed coat which at the same time fills the cavities and, when correct-
lye applied, forms a layer which has a gradient from all areas of the
roof surface towards drains and gutters. Such a layer may serve as a
base for the superposition of insulation hoards and a new waterproof
roof covering.
The material used for building up the screwed coat in carry-
in out the method according to the invention consists of a mixture of
an expanded inorganic material of low specific gravity and an adhesive
consisting of water glass and a hardener there-for. Important examples
of expanded inorganic materials are those referred to as vermiculite,
which is an "exfoliated" mica product, and puerility, which is a product
of volcanic origin.
Materials of the type described are known per so.
It has been found, however, that special conditions have to
be observed both in the production and in the further handling of
such materials in order to make them useful for building up a screwed
coat on a roof surface.
Based on these premises, the method according to the in-
mention comprises the steps of subjecting a granular expanded
inorganic material to an atomized spray of an adhesive consisting of a
solution of water glass and a hardener therefore in such a manner as to
form a film coating of said adhesive on the surface of each grain
without affecting the granular nature of the material, causing the
spray coated granular material immediately after it has been thus
produced and without any intervening mechanical working or compress
soon, to be poured out on the roof surface, spreading it over that
surface and compressing and smoothing it to form a coherent layer of
a geometrical surface configuration showing a gradient From all points
of the surface towards rainwater outlets.
By proceeding in this manner the advantage is obtained
that the material remains in its -free granular state until it is poured
out on the roof and is only thereafter compressed to make the spray
coated grains stick together to form a coherent layer. In this manner
the grains are efficiently protected against collapsing so that the
screwed coat will have a very low density e.g. of the order of 150
kg/m3 after compression and hardening. This is particularly important
12~8825
in the case of renovating deficient roofs of the type previously describe
Ed because such roofs are frequently constructed with a very light
supporting structure, because this structure was not originally design-
Ed for carrying any substantial load beyond possibly a snow load and
the load arising from foot -tragic in connection with cleaning and
maintenance of the roof. The screwed coat is incombustible because it
does not contain any organic materials, and for the same reason it is
unassailable to rot and dry rot. It has a high degree of water resistant
go so that it will not suffer damage if some water gets access to it by
accident. It is also to be mentioned that the components, of which the
screwed coat is made, art not harmful to the environment.
The components of the material can be so selected that her-
dining proceeds very fast so that subsequent steps of the full reproof-
in process can be commenced very soon after the screwed coat has
been applied. The compression Al strength is fully satisfactory when
the screwed has been covered with insulating boards or the like, which
distribute the pressure created e . g . by foot tragic on the roof .
The invention will now be described in further detail with no-
furriness to the accompanying drawings, in which
Fig. 1 is an overall diagrammatic view of a complete mobile
plant for carrying out the method according to the invention.
Fig. 2 is a diagrammatical perspective view of the main
components of the plant and associated piping.
Fig. 3 is a vertical section through a spray coating appear-
tusk of the plant and parts directly associated therewith.
Raw materials suitable for carrying out the method according
to the invention are:
1 ) An expanded mineral granulate having a grain size of
.5-6 mm and a bulk specific gravity of 50-100 kg/m3 e.g. puerility or
vermiculite.
2) A saturated aqueous solution o-f sodium silicate (sodium
water glass) having an Sweeney ratio 3.0, a density of approximate-
lye 1400 kg/m and a dry substance content of 30-40%.
3) The organic ester Tristan, which is a liquid having a
density of 1170 kg/m3.
Raw material 1 ) may advantageously be used in the form of
a hydrophobized product. Hydrophobization is a process by which an
expanded mineral granulate, while still hot from the expansion process,
is sprayed with a hydrophobizing agent to make the granulate hydra-
I ~1~3ZS
phobic, i.e. water repellent. Hydrophobizing agents are available on
the market. Examples are the products marketed by Hoechst Aktienge-
sellschaft under the product names Hoe 3187 and Hoe 2745. Expanded
mineral granular material treated by such hydrophobizing agents are
also available on the market from the producers of expanded puerility,
vermiculite and similar materials. it has been Found that the use of a
hydrophobized mineral raw material does not give rise to any problems
in carrying out the spray coating or other steps of the method accord-
in to the invention, nor does it detract from the adhesive power of
the adhesive, and that the water repellence created by the hydropho-
bization of the mineral raw material remains in the finished screwed
coat, so that this is protected against absorption of water that may
unintentionally get access to it. While such absorbed water would not
destroy the screwed coat as such, it is clearly an advantage to avoid
it.
The proportion of granulate/waterglass/hardener may be
approximately 16/10/1 by weight, corresponding to approximately
250/8/1 by volume. Good results have been obtained with a composition
containing 55-65% by weight of exfoliated mica, 30-42% by weight of
water glass solution and 3~5% by weight of hardener.
When the water glass and the ester are mixed in the propriety-
ion 10.1, they constitute a light-fluid adhesive, the ester undergoes a
hydrolysis by taking up part o-f the water chemically bound in the
water glass, thereby liberating a volatile alcohol and a weak acid. The
hydrolysis is completed in ~z-1 h whereby the adhesive has become
solidified .
The alcohol evaporates and diffuses out of the screwed coat
in thy course of the setting time . The weak acid is neutralized by the
mineral granulate.
The machine components of -the mobile plant illustrated in
the drawings are mounted in a housing 1 constructed as a trailer
which can be transported from one working site to another by means
of a motor car, e.g. a passenger car, to be left standing on the
ground in the close vicinity of a building on the roof of which a
screwed coat is to be built up. Placed on the ground are also a silo 2
for the supply of granulate and drums 3 and 4 for the supply of
water glass solution and hardener respectively. An operator on the
ground has the job of controlling and surveying the machinery and of
replenishing the supplies of raw material. For the latter purpose he
Lowe
should dispose of a small tractor with a fork elevator for the transport
station of pallets with granulate, which is normally delivered in bags,
and drums with water glass and hardener.
The personnel on the roof comprises two or three men, or,
5 depending on the size and nature of the roofing job, even more, e.g.
four or five. These should be skilled workers having routine in the
setting up of guide bars and the laying and smoothing of plaster and
concrete layers to form wry surfaces so as to provide a gradient
towards an outlet (such as floors in wet premises, e.g. slitter-
10 Swiss.
The machinery mounted in the trailer comprises a spray coating apparatus 5 housed in a container which has an upper cylinder-
eel portion 6 closed by a top wall 7, and a lower conical portion 8. A
central opening 9 in the top wall 7 is connected through a cell feeder
15 10 to a bottom opening 11 of a cylindrical buffer silo 12 mounted
above the spray coating container. The cell feeder 10 is similar to the
cell sluices normally used in suction blower conveying systems, and
thus consists of a cylindrical housing in which there is mounted a
rotor carrying a number of radial vanes sliding along the cylindrical
20 wall of the housing to form cells serving to sluice material from one
environment to another. The cell feeder 10 may be constructed as an
ordinary cell sluice, but since there is no difference of air pressure
between its inlet and outlet, the requirement of sealing effect is
lower. The cell feeder 10 is driven by an electric motor, not shown,
25 which is fed through a conductor 13.
At its top the buffer silo is connected through an ordinary
cell sluice 14 to the bottom of a cyclone separator 15, forming part of
a suction blower conveying system. To the tangential inlet of the
cyclone separator 15 is connected piping 16 extending to and below
30 the bottom of the silo 2 and thereafter opening into the atmosphere.
A bottom opening of the silo 2 is connected to the interior of the
piping 16 through a sliding gate that can be opened and closed by
means of an electric or pneumatic actuator 17 controlled by a conductor
18. The top outlet of the cyclone separator 15 is connected through
35 piping 19 to the suction inlet of the suction blower 20 o-f the conveying
system. The pipings 16 and 19 and further piping to be mentioned
below are built up from pipe elements, bends, etc. assembled by
means of quick release clamps in the manner usual in suction blower
systems so that they can easily be adapted to the circumstances in
38;~5
each individual case.
It will be realized that when the bottom gate of the silo 2 is
opened by means of the actuator 17 granular material will be conveyed
by the suction blower system to -the cyclone separator 15 and will be
5 sluiced -from the bottom of the latter through the cell sluice lo into
the buffer silo 12. To control this supply the buffer silo is provided
with two capacitive sensors 21 and 22 connected through conductors
23 and 24 to a preferably computerized control box mounted in a
convenient position on the trailer and diagrammatically represented at
10 25 in jig. 1. This is a central unit to which all control conductors,
thus also the previously mentioned conductors 13 and 18, are connect-
Ed The arrangement is such that the actuator 17 is caused to close
the bottom gate of the silo 2 when the level of granular material rises
to the level of the upper sensor 21, and to open said gate when the
15 level of granular material falls to -the level of the lower sensor 22.
The time of fall from the upper to the lower level provides an indication,
from which the control box can determine the rate at which granular
material is consumed by the spray coating apparatus 5.
In the cylindrical portion 6 of the housing of the spray
20 coating apparatus there is mounted a stationary spreader 26 shaped
as an inverted cone. The tip of the spreader is located directly below
a spout 27 connected to the central opening 9 of the top wall 7. The
spout 27 has an upper wider portion 27 a and a lower narrower
portion 27 b connected through a Funnel portion 27 c. When the colt
25 feeder 10 is running fast enough to keep the spout 27 constantly
filled with granular material, the rate at which the material drops
from the spout onto the tip of the spreader 26 will be determined
mainly by the dimensions of the narrow portion 27 b of the spout.
Therefore, the spray coating apparatus can be calibrated for a
30 certain job by selecting a suitable spout.
The granular material dropping onto the spreader 26 slides
and/or rolls down its conical surface and leaves its lower edge in the
form of a cylindrical curtain 28 o-f -freely falling grains.
Below the spreader there is mounted a rotational atomizer 29
35 of a type well known per so. The atomizer consists mainly of an in-
vented cup, which is rotated at high speed, e.g. 5,000-6,000
rum by means of an electrical motor 31 having a hollow shaft.
Water glass and hardener are supplied from the drums 3 and 4 to the
atomizer through hoses 32 and 33 with built-in mono-pumps 34 and 35
I 8~25
and flow meters 36 and 37. Conductors 38 and 39 for controlling the
mono-pumps and signal conductors 40 and 41 From the flow meters 36
and 37 are connected to the control box 25 . I n the atomizer the two
liquids are conducted through stationary concentric tubes 42 and 43,
5 extending through the hollow shaft of the motor 31, to separate spray
heads 44 and 45 from which they are sprayed towards the inner wall
of the inverted cup 30 to form films of liquid flowing down the inner
wall and beginning to mix where the hardener liquid sprayed -from the
upper spray head 44 reaches the film of water glass solution sprayed
10 from the lower spray head 45. At the lower edge of the cup 30 the
mixture of the two liquids is atomized to form a mist 46 which impinges
and penetrates into the curtain 28 of freely falling grains, whereby
each grain is spray coated with a thin film consisting of a mixture of
the two liquids. In this phase the liquid film is very little sticky so
15 that the spray coated material will remain in granular form. The
spray coated grains now roll down the inner face of the conical wall
8, and at the same time liquid remains, that may not have been
caught by the particles, trickle down the same inner face, which is
coated with Teflon in order efficiently to prevent particles and liquid
from sticking to it. During this travel the liquid will be even more
uniformly distributed over the surfaces of all grains by the gentle
rubbing of the grains against each other and against any remains old
liquid trickling down the wall. Surface tension effect will also assist
in uniformly distributing -the liquid over the surfaces of the grains.
At a bottom opening 47 of the conical wall 8 the spray coated
granular material is caught by a cell sluice 48 and sluiced in-to piping
49 extending from the pressure side of the suction blower 20 and ox-
tending Further to the tangential inlet of a cyclone separator 50 on
the roof on which a screwed coat is to be laid. The cell sluice 48, the
30 piping 49 therefrom to the cyclone separator 50, and the cyclone
separator itself are interiorly coated with Teflon. Part o-f the piping
49 leading to the cyclone separator 50 is in the form of one or more
hoses so that the cyclone separator 50 will be freely movable from
spot to spot on the roof. It may be carried by a man in a sling, or i-t
may be supported on the roof on a barrow frame or the like. The
cyclone separator 50 is provided at its bottom with a laterally directed
opening 51 for pouring out the spray coated granular material. The
team on the roof immediately spreads the poured out material, lightly
compresses it, such as by beating or stroking it with a shovel or a
&~: j
float, and smoothes it with a straight-edge or screwed board following
guide bars that have beforehand been laid with -the correct gradient
towards the roof outlet. When an area of the screwed has been -finished,
the guide bars may be removed and remounted for use in the
finishing of the next successive area to be covered.
In the condition in which the material is poured out on the
roof, fresh from the spray coating process, it is excellently workable
for laying and shaping. Any compression before laying would detract
from the workability and tend to make the material lumpy. By contrast,
the pneumatic transportation of the freshly spray coated material
rather has the effect of maintaining or improving the free granular
nature of the material.
Another important consideration is that only a rather limited
time is available for spreading, compressing and smoothing the Metro-
at on the roof. After the spray coating has been performed the her-
dining of the adhesive at first progresses very slowly, but after a
certain time interval the degree of hardening suddenly rises very
steeply to a high percentage, and then again flats out asymptotically
towards full hardening. After the said time interval the material is no
longer workable, and compression will not make the grains stick
together. When the above mentioned raw materials 1)-3) are used, the
Sweeney ratio being = 3. 0, the said time interval is about 20-25
minutes, and a few minutes after the layer will be stiff enough to
support the load of a cover board and of foot tragic on that board.
From the above explanation it will be understood that it is
important that the production and delivery of spray coated granular
material should be adapted to the progress of the laying procedure on
the roof, so that the material will never heap up, but will always be
available in a sufficient quantity, allowance to be made for periods of
slow progress and for intermissions. I-t will now be explained how this
is achieved in the disclosed embodiment of the invention.
During working hours, the suction blower system is con-
scantly running, and this also includes the cell sluices 14 and 48 and
the atomizer 29. When spray coated material is being produced and
delivered on the roof, the cell feeder 10 runs at a predetermined
speed sufficient to keep the spout 27 filled with fresh granular Metro-
at. The rate at which this material is fed to the atomizing device is
calculated by the computer of the control box from the signals o-f -the
capacitive sensors 21 and 22, as previously explained, and from -the
value of this rate the computer calculates the correct rates of supply
of water glass and hardener -to obtain the predetermined proportions of
all three components in the screwed material. By means of the signals
received from the flow meters 36 and 37, the computer controls the
speeds of the mono-pumps 34 and 35 to obtain -the calculated rates of
supply .
When -the production and delivery of spray coated granular
material is to be stopped for an interval of time, the cell feeder 10 is
stopped by a signal from the control box. This signal is preferably
released by an operator on the roof . E . g . the man handling the
cyclone separator 50 may be equipped with a signal transmitter 52 by
means of which he can transmit stop and start signals to the control
box 25 by pressing corresponding buttons. When the cell feeder 10 is
stopped, the granular material pry event in the spout 27 and the cell or
cells in position immediately above same will drop out of the spout and
onto -the spreader 26 at the same speed as before, and during the
short time when there is still granular material present in the spout
above the level of a capacitive sensor 53 provided at the conical
portion 27 c of the spout the mono-pumps 34 and 35 will continue to
run, but at the moment the last grains pass the level of the capacitive
sensor 53 a signal is transmitted through a conductor 54 to the
control box 25 which again transmits stop signals to the mono-pumps
34 and 35. Thereby the supply of all three components to the spray
coating apparatus 5 is stopped in such a manner that at least practical-
Z5 Ivy all grains will be regularly spray coated and there will be no
surplus water glass and hardener present in the atomizer or impinging
the inner wall of the spray coating apparatus. This apparatus will
soon be completely emptied by the cell sluice I and all the material
fed into the piping 49 will be blown to the cyclone separator 50 and
poured out on the roof so that the machinery in its entirety is clean
and ready for resuming production and delivery when a start signal
is again released. When this occurs, -the cell feeder 10 is firs-t started
and the mono-pumps 34 and 35 are started after the first grains have
passed the level of the capacitive sensor 53.
After the screwed coat has been laid it is covered by insulate
in boards or other cover boards, where no additional insulation is
required. These may be placed on the screwed coat a few minutes after
this has been laid and compressed.
The optimum ratio of compression has been found to be
approximately 3:2, and the skilled workers very quickly learn to feel,
in their handling of the material, when the proper degree of come
press ion has been reached. With this degree of compression, the
density o-f -the layer upon completion of the hardening will be about
5 150 kg/m3, and its compressive strength for distributed pressure will
be above 800 kg/m .
After the insulating boards have been placed on the screwed
coat, they are attached to the roof supporting structure by means of
screws having an insulating shaft in order not to form cold bridges
10 from the surface of the roof to the roof supporting structure. The
placing and fixing of the insulating boards may be performed concur-
gently with the further progress of the laying of the screwed so that
the team on the roof may take care of both jobs in a continuous
p rowed u no .
As a final step in the roofing procedure the insulating
boards are covered with waterproof sheet material in well known
manner .
