Note: Descriptions are shown in the official language in which they were submitted.
llZ5143
Technical Field
This invention is in the field of flow control.
Background of Prior Art
The present invention is concerned with regulation
of evolutive pulps. Evolutive pulps are liquids in which a
certain reaction resulting in a physical or chemical transfor-
mation takes place such as producing a solid phase or modi-
fying the characteristics of the solid phase initially carried
by said liquid. One example of evolutive pulp would be
plaster powder mixed with water. This invention can be
applied to the hydraulic binders industry, plaster industry
and generally to any industry in which there is a need to
control the flow rate of evolutive pulps carried through
piping.
In order to cutoff, introduce variations, or regu-
late a liquid flow rate to a given value, the use of elastic
shape-changing valves is widespread. Such valves consist of a
rigid tubular housing and a cylindrical inner cell, such as a
sleeve, with enough elastic property to change shape. Valve
closing is achieved through compression of the elastic sleeve
by either the mechanical effect of a screw-nut-flywheel
mechanism or by the effect of a pressurized fluid, such as
water or air, sent between the housing and sleeve. When no
mechanical or pneumatic action is exerted upon the sleeve, the
valve allows direct passage of the product at full rate of
flow; when the sleeve is subjected to a shape-changing action,
the aperture of the sleeve opening is reduced and the valve
allows only a reduced flow rate of the product. With a suf-
ficiently strong mechanical or pneumatic action, the elastic
walls of the sleeve eventually become joined, thus completely
closing the valve.
112S143
Such manually controlled valves are recommended for
viscous, pasty or abrasive liquids. But in the case of evolu-
tive pulps, deposits form in the narrow channel created by the
compressed sleeve, deposits which change the size of the
sleeve aperture alter the valve setting and eventually create
an obstruction.
It is also known to pulsate elastic shape-changing
valves to keep material in a liquid state and to use large
elastic sleeves to break up solids.
Brief Summary of the Invention
The invention is aimed at preventing the deposit of
evolutive pulps in a narrow channel created by a valve and is
characterized by the fact that it comprises superimposing a
pulsating signal on a regulation signal which is advantageous
in maintaining a constant amount of ingredients in a mixing
container continuously supplied with evolutive pulp ingredi-
ents.
The invention offers as well a regulating mechanism
for the rate of flow of evolutive pulps characterized by the
fact that it includes a flow rate regulating valve, valve
opening control means and modulating means causing a variation
of the valve opening either way from an opening setting fixed
by the control means which is advantageous in maintaining a
constant amount of ingredients in a mixing container continu-
ously supplied with evolutive pulp ingredients.
According to another characteristic, the invention'smechanism is characterized by the fact that the flow rate
regulating valve is an elastic shape-changing pneumatic valve,
consisting of a rigid housing, of a inner elastic sleeve, and
of a valve opening control fluid intake between rigid housing
and sleeve.
~12S~43
In accordance with the process and apparatus of the
invention, the amount of material is maintained constant in a
mixing tank, and the time of the material in the mixing tank
is maintained constant, by supplying a regulating or sensing
signal to a discharge control valve and superimposing a
pulsating or vibrating or modulating signal on the sensing
signal. This vibrating signal prevents deposit of material in
the valve. Advantageously, the sensing signal is responsive
to the weight of the mixing tank which preferably is free from
upstream and downstream equipment. In accordance with the
invention, the vibrating or pulsating signal may be caused by
vibration of the mixing tank which is advantageous because it
keeps the valve sleeve vibrating to prevent deposit of
material on the interior surface of the sleeve. If necessary,
a modulating piston may be used instead of, or to supplement,
the pulsating signal supplied by the motor vibrations. The
motor shaft is seldom exactly vertical, and therefore creates
vibrations. Also, the irregular delivery of the gypsum powder
to the mixing tank creates vibrations.
The pneumatic valve of the invention employs an
inner elastic sleeve that is star-shaped in cross-section when
subjected to pressure, which is advantageous because the star-
shape makes deposit of the material more difficult.
Brief Description of the Drawings
Figure 1 is a schematic view of a shape-changing
elastic pneumatic valve;
Figure 2 is a schematic view of a setting mechanism
for the rate of flow of evolutive pulps;
Figure 3 is a schematic section of the valve in
Figure 1 illustrating its operation;
Figure 4 is a schematic view of a regulating
~lZ~i~43
mechanism for the rate of flow of evolutive pulps;
Figure 5 is a schematic view of apparatus in
accordance with the invention for making a plasterboard
building component;
Figure 6 is a perspective view of a receiving
container in accordance with the invention;
Figure 7 is an enlarged view of the nozzle 18 and
its associated parts; and
Figure 8 is an enlarged view in section of the
valve V.
Detailed Description of the Invention
Figure 1 shows an elastic shape-changing valve V of
the type used in our invention. It comprises a housing or
rigid casing 1 of cylindrical shape with a lateral control
fluid intake pipe 2, and an inner elastic sleeve 3, of for
example rubber, also cylindrical and whose section is equal to
that of the internal diameter of the rigid casing, or slightly
stretched to contact the inner surface of the rigid casing.
The sleeve 3 assumes the star-shape cross-section of Figure 2
when a very low air pressure is applied to the outer surface
of the sleeve 3. The ends of said sleeve 3 may be secured to
casing 1 by being turned over the edge of casing 1 and
tightened by securing rings. As shown in Figure 1, each end
of sleeve 3 is held to casing 1 by a piece of tube 4 with the
same shape as casing 1 but with slightly smaller dimension
which is pushed in at each end of valve V. The tube 4
elements are connected by a threaded rod-nuts assembly 5
which is also used when securing rings are employed.
Advantageously, the sleeve 3 has a star configur-
ation in cross-section as shown in Figure 2 when under
pressure. This configuration keeps the sleeve 3 vibrating to
llZS143
prevent deposit of mix on that surface. For example, the
inscribed diameter of the sleeve varies from 21 mm to 15 mm
when the air pressure varies from 100 to 300 mm of mercury.
~y way of example, in a typical sleeve of 0.8 mm thickness,
its inscribed diameter varies from 21 mm to 15 mm when the
controlling air pressure goes from 100 to 300 mm Hg where the
initial at rest diameter is 32 mm and length is 82 mm. By
inscribed diameter is meant the diameter of the inscribed
circle 3a in the star-shaped sleeve 3b in Figure 3.
Figure 2 shows a mechanism for the setting of evolu-
tive pulp flow rates which is in accordance with the invention.
A mixer 6 is provided in its lower part with a drainage open-
ing on which is fitted a pipe 7 equipped with the flow rate
regulating valve V of Figure 1.
Mixer 6 is continuously filled with an evolutive
pulp product 8 whose flow rate regulation through pipe 7 is
sought. This filling may be carried out using the apparatus
disclosed in our copending Canadian patent applications Serial
Nos. 321,011 and 321,012, respectively, entitled "Continuous
Process Mixing of Pulverized Solids and Liquids and Mixing
Apparatus" and "Plaster Board and Process and Device for Making
Plaster Board" filed concurrently herewith. Lateral control
fluid intake pipe 2 of control valve V is supplied witn com-
pressed air, the pressure of this air being controlled by a
pressure regulating assembly 9 set to a value corresponding to
a set rate of flow of product 8 through valve V, therefore to
a set change of shape of inner sleeve 3.
In accordance with the invention, a piston 10 actu-
ated with a reciprocating motion and modulating the pressure
of compressed air sent between housing 1 and elastic sleeve 3
of valve V is installed on control fluid intake pipe 2.
~lZ5143
Piston 10 may be reciprocated, for example, by a crank on a
motor driven shaft (not shown) to create a modulation of the
pressure in the valve V. The modulation frequency preferably
may be about 2.4 Hz and may be in a width range on both sides
of 2.4 Hz.
In other types of construction, piston 10 may be
replaced by any other mechanism able to induce a modulation of
valve V control fluid pressure.
The Figure 2 mechanism operates as follows : com-
pressed air, whose pressure is set by pressure regulatingassembly 9 to a preset value Po, is sent through valve V to
control pipe 2. This air pressurizes sleeve 3, which assumes
a star-shape as represented in Figure 3, and the aperture of
the channel in valve V for product 8 contained in container 6
becomes thus restricted. The selected flow rate to maintain
the desired level of product 8 is obtained by the setting of
pressure regulating assembly 9.
Alternating motion actuated piston 10 creates a
modulation of the pressure in valve V above and below the
value Po, which causes a periodic compression and release of
sleeve 3. In this way, the sleeve is continuously in motion
and this prevents any accumulation of product 8 when valve V
forms a narrow channel.
Figure 4 shows an evolutive pulp flow rate regu-
lating mechanism in accordance with the invention.
Product 8 (or its separate constituents) is continu-
ously introduced into mixer 6 at a constant rate by con-
ventional mechanism (not shown). Mixer 6 is provided in its
lower part with a drainage opening connected to pipe 7
equipped with valve V. The mixer 6 is supported by an arm llb
of a force balance beam 11 in equilibrium on fulcrum 12, the
llZ5143
equilibrium of beam 11 being achieved through a spring 14 and
a counterweight 13 acting upon the other balance 11 beam arm.
The counterweight's position on beam arm 11 may be
adjusted so that equilibrium is attained for any level of
product 8 in the mixer 6. A damping piston 15 is connected to
beam arm lla. The setting control of valve V is obtained
through a pneumatic escape mechanism F. Such a mechanism F
has a fluid, generally air, under a pressure Po, and supplies
the air to pipe 16, that is, connected to control fluid intake
pipe 2. A pipe 17 also is connected with pipe 16 and vents
the air through a nozzle 18 and directs the air against the
bottom of beam arm lla. Two safety stops 19 and 20 are placed
above and below the beam end lla, thus limiting movement of
beam arm lla and the mixer's weight variations in relation
with the selected weight adjusted with counterweight 13.
Pressure P is regulated through pressure regulator 9 and
measured by a pressure gauge 21 represented as a mercury con-
taining U-shaped tube.
Product 8 is stirred inside mixer 6 by a mixing
impeller or agitator 22.
This evolutive pulp flow rate regulating mechanism
operates as follows : the mixer 6 receives a supply of product
8 in continuous process. Said product 8 is stirred by
agitator 22 and flows through discharge pipe 7 in a continuous
process, the flow rate being regulated by valve V.
The pressure of air in pipe 16 is set using pressure
regulating 9 at value Po in order to obtain, when escape flow
through valve 18 is shut off (by moving manually the tip of
beam arm lla onto nozzle 18), a position of valve V providing
a product flow rate below the selected flow rate, and when
escape flow through nozzle 18 is increased to its maximum (by
-- 7
~S.Z~;143
having the beam tip of arm lla touching top safety stop 19), a
position of valve V such that the product flow rate is higher
than the one selected. Then the position of counterweight 13
on beam arm llb is adjusted so that beam 11 assumes a position
intermediate its position completely blocking flow through
nozzle 18 and its position against stop 19, in which position
the selected flow rate of product 8 is achieved which is equal
to the flow rate at which product 8 is introduced into mixer
6 in order to keep constantly a set amount of product 8 in
mixer 6.
Any weight variation of product 8 in mixer 6 causes
a deflection of balance beam ll. Thus, an overweight results
in increasing the distance between beam arm lla and nozzle 18,
therefore increasing the flow of air escaping from nozzle 18
and reducing the pressure of the air between sleeve 3 and
housing 1 of valve V. Thus sleeve 3 expands to increase the
size of the valve opening, to increase the flow of product
through the valve V increases, so that mixer 6 empties more
rapidly until the weight of product 8 is again at the desired
point at which time beam 11 has returned to its original
position, thus regaining equilibrium. In the opposite case,
too small a weight of mixture in mixer 6 results in con-
tracting sleeve 3 of valve V and therefore in greater holding
back of product 8 in mixer 6, which results in regaining equi-
librium at a predetermined weight of product 8 in mixer 6.
In the mechanism illustrated in Figure 2, a piston10 induces a modulation of the pressure of control air sent to
valve V. In the case of the Figure 4 mechanism, which is
preferred, vibrations in the pressure of control air are
induced by vibrations from the mixer 6 including vibrations
from agitator 22. These vibrations result in oscillations of
112~3
beam 11 and, consequently variations in the amount of air
escaping through nozzle 18, causing pulsations in pressure of
the air sent to valve V. Thus, sleeve 3 vibrates and
contracts and expands rapidly. Under the effect of pressure
it assumes a star-shape, and the vibrations from mixer 6
vibrates the valve sleeve 3 rapidly, thus preventing formation
of deposits of product 8 on the interior surface of sleeve 3.
Sleeve 3 can be made with any leakproof elastic substance but
it is necessary, before any setting of the mechanism, to
determine the elastic characteristics of material used by
establishing a diagram giving valve aperture size against
pressure.
The elastic sleeve can be made with a very pliable
inner tube material. This gives a light valve, reacting to a
15 low pressure of the order of .25 bar (7.38 in.Hg), total
pressure in the escape pneumatic system being of the order of
- 1 bar (29.52 in.Hg).
Damping device 15 is selected so that it allows
preferred vibrations to be felt. A valve 23 is in the pneu-
matic circuit downstream from the`pressure gauge before saidcircuit divides into pipes 16 and 17. Thus, once operating
conditions of the installation are determined, it is easier to
restart the installation after stoppage without any need to
proceed with new settings. Valve 23 is closed and pressure is
set at value Po already known. Safety stop may be connected
with a valve that shuts off product 8 supply to mixer 6 when
beam tip 11 makes contact with it.
A constant flow needle valve 24 is downstream of
pressure regulating assembly 9 and acts to give constant flow
and prevent back up from downstream.
Figure 5 shows apparatus in accordance with the
l~ZS1~3
invention for making reinforced plasterboard building com-
ponents. Pulverized plaster powder 200 contained in a hopper
202 is distributed on a constant weight weight-sensitive
conveyor belt 204 set beforehand for a predetermined constant
flow rate of plaster powder. Conveyor belt 204 discharges the
plaster powder onto a vibrating pouring screened spout 206
which delivers it into mixer 6 having an agitator 22. A water
reservoir 210 discharges into a line 212 having a valve 214
with line 212 being connected to a flow meter 216 discharging
into a line 218 which in turn discharges into overflow trough
220 secured about the periphery of mixer 6 and adapted to
overflow to supply mixer 6 with water adjacent the inner wall
of mixer 6 to wash the inner wall. A line 217 branches off
from line 218 and washes the upper portion of impeller shaft
222, and a line 219 branches off from line 218 and washes the
lower portion of impeller shaft 222. In this manner plaster
powder and water are supplied to mixer 6 at a constant rate to
mix together.
The plaster powder-water mixture 8 (the evolutive
pulp) discharges through the open lower end 224 of mixer 6
into pipe 226 controlled by valve V. Pipe 226 discharges into
a receiving container 228 to permit the weighing of mixer 6
separately from the apparatus downstream of pipe 226. Con-
tainer 228 is connected by a pipe 230 to a pump 232 that dis-
charges into a pipe 234 supplying a distributing container 238.
Distributing container 238 discharges into a line 240 that
supplies lines 242, 244 and 246 which discharge horizontally
into a pouring head C having an upstream plate 248 and a
downstream plate 250 connected to a guide plate 254. Pouring
head C is mounted above a moving conveyor 256. A reinforce-
ment sheet 258 of, for example, woven fiberglass is fed in
- 10 -
llZ5143
between pouring head C and conveyor 256 to reinforce plaster
poured onto conveyor 256 for the formation of a plasterboard
building element.
With given rates of introduction of plaster powder
and water, the mixing container filling level determines the
mean time during which the plaster remains in the mixing
container (at least 3 seconds and preferably for 15 to 30
seconds for plaster as well as other evolutive pulps). Here-
tofore the filling level was attempted to be maintained by
varying the rate of introduction of the ingredients while not
changing their ratio which is very difficult. In the appa-
ratus of Figure 5, it is accomplished by the invention by
controlling flow through valve V that is made practical by the
modulation of the control or sensing signal to valve V to keep
the valve clear of any deposits, so that the relationship
between the controlling signal and the flow rate of valve V is
not changed by deposits in the valve that would partially
block the flow through valve V.
As shown in Figure 6, receiving container 228 is fed
by a pipe 226 that discharges into receiving container 228
having an open top 302 and a bottom 304. Discharge pipe 230
is tightly secured to bottom 304 and has a funnel 306 con-
nected to its upper end for reception of material discharged
from pipe 226, funnel 306 and pipe 226 being coaxial. A spray
nozzle 310 is connected to a water line 312 to flush the
bottom 304 in order to wash out any material not collected by
funnel 306. A drain 314 in bottom 304 is connected to a dis-
charge line 316. In addition to serving the function of dis-
connecting mixer 6 from the apparatus downstream of pipe 226
for purposes of weighing mixer 6, receiving container 228
performs the function of preventing the hydrostatic pressure
~1;Z;5143
upstream of container 228 from affecting downstream pump 232.
Figure 7 is a partial view on an enlarged scale of
the apparatus around nozzle 18 of Figure 4. Pipe 17 extends
upwardly to feed the compressed air to nozzle 18 which is
protected from being damaged from contact with plate 316 of
beam arm lla by a sturdy nozzle head 318. Pipe 17 is sup-
ported by a plate 320. The distance between beam plate 316
and nozzle 18 controls the amount of air vented from pipe 17,
and controls the pressure of the air delivered in valve sleeve
3 through control pipe 2.
Figure 8 is an enlarged view in longitudinal section
of valve V, which is diagrammatically shown in Figure 1, with
control pipe 2, tubes 4 extending into both ends of pipe 1 and
clamping the ends of sleeve 3 to the inner surface of pipe 1
except for middle portion 322 which is free to expand inwardly
in a star-shape when actuated by the compressed air from
control pipe 2, and clamps 324, 325 that clamp sleeve ends 326
and 328 to tubes 4. Pipe 1 may be 82 mm long and 33.5 mm in
diameter, with the outside diameter of tubes 4 being 32 mm to
fasten sleeve 3 between them. The initial length of sleeve 3
may be 140 mm, and 0.8 mm thick. In assembly, the bottom 328
of sleeve 3 may be rolled back and clamped to pipe 1 by clamp
325. Sleeve 3 is then stretched upwardly about 15 mm to keep
sleeve 3 in tension, with half the perimeter of the sleeve 3
being about 46 mm and the average diameter of sleeve 3 being
about 29 mm. Then upper sleeve end 326 is rolled back onto
the upper end of tube 1 and clamped thereto by clamp 324.
The characteristics of the sleeve 3 material is such
that a piece 10 cm long and 2 cm wide is stretched by 5 cm
when held at the top and a weight of 1.2 kg is applied to its
bottom. A very small variation in pressure varies the star-
~Z5~3
shape of sleeve 3.
The invention deals with setting the flow rate ofevolutive pulp, but it also deals with the setting of evolu-
tive pulps containing finely broken up inert loads, for
instance, chopped fiberglass, also, the invention deals with
setting the flow rate of non-evolutive liquids, whether loaded
or non-loaded with finely divided inert loads such as chopped
glass fibers.
Therefore, under the term of evolutive pulps,
properly speaking, can be included evolutive pulps containing
in addition inert loads, and loaded or non-loaded liquids.
Referring again to Figure 5, it is to be noted that
the impeller 22 is driven by a motor 400 that drives a gear
box 402 that in turn drives gear box 404 which drives shaft
222. Structural member 406 connects tank 6 and motor 400 so
that they are mounted together and are carried by beam arm
410b. Spring 14 and modulating piston 15 are mounted on
structural member 412 and are mounted on beam arm 41Oa. Knife
edge 414 is positioned between motor 400 and mixing tank 6 so
as to be in a position to maintain the motor and tank in equi-
librium with a minimum amount of mixture in the tank.
- 13 -
