IE47824B1 - Process and apparatus for controlling the discharge of evolutive pulps at the outlet of a container - Google Patents

Abstract

The present invention is concerned with regulation of evolutive pulp. It offers a regulation process and mechanism, said mechanism including an elastic shape-changing pneumatic valve, valve opening control means, and modulating means causing a variation of said valve opening either way from an opening setting achieved through control means. The present invention can be applied to a continuous process for mixing plaster.

Description

The present invention relates to a process and to apparatus for controlling the discharge of evolutive pulps at the outlet of a container.

The invention provides a process for controlling 5 the discharge of evolutive pulps, especially a mixture of plaster and water at the outlet of a container, so as to maintain constant the quantity of pulp in the interior of the said container, in which the output of the outlet of the container is continuously controlled with the aid of a direct passage valve having an elastic sleeve controlled by a pneumatic control system associated with an apparatus which takes account of the quantity of the said pulp in the container and in which, in order to prevent the formation of deposits on the internal walls of the elastic sleeve, a system of pulsed signals is superimposed on the control signal proper which determines the cross-section of the passage through this sleeve in the direct passage valve; in which the pneumatic control system is a leakage system /0 . with-which·is associated a balance of forces which simultaneously takes into account the weight of the container containing the evolutive pulp and vibrations generated in the said container to produce the control signal proper which is thus directly and permanently nodulated by the said system of pulsed signals corresponding to the vibrations generated in the container, and in which the pulsed signals thus permanently superimposed on the control signal proper cause, permanently, periodic deformation of the elastic sleeve of the direct passage valve practically without changing the value of the passage cross-section defined by the said sleeve, this latter being a function of the control signal proper.

The invention also provides apparatus for controlling the discharge of evolutive pulps, especially a mixture of plaster and water, from the outlet of a container so as to maintain constant the quantity of pulp inside the container, in which a direct passage valve having an elastic sleeve arranged at the outlet of the said container continuously controls the said discharge as a function of a control signal produced by a pneumatic control system associated with a device which takes account of the quantity of the said pulp within the container and in which to prevent the formation of deposits on the internal wall of the elastic sleeve means are provided to superimpose a 824 system of pulsed signals on the control signal proper which determines the passage cross-section through the sleeve in the direct passage valve: in which the pneumatic control system is a leakage system with which is associated a balance of forces which takes account simultaneously of the weight of the container containing the evolutive pulp and the vibrations generated in the said container, to produce the control signal proper, which is thus directly and permanently modulated by the said system of pulsed signals which correspond to the vibrations caused in the container by the modulating means, and in which the pulsed signals thus permanently superimposed on the control signal proper permanently cause periodic deformations of the elastic sleeve of the direct passage valve practically without changing the value of the passage cross-section defined by the said sleeve, this latter being a function of the control signal proper.

The invention will now be described more particularly, by way of example, with reference to the drawings, in which: 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 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.

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 3 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 - 5 47 824 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 rods-nuts assembly 5 which is also used when securing rings are employed.

Advantageously, the sleeve 3 has a star configuration in cross-section as shown in Figure 3 when under pressure. This configuration keeps the sleeve 3 vibrating to prevent deposit of mix on that surface.

For example, the inscribed diameter of the sleeve varies from 21mm to 15mm when the air pressure varies from 100 to 300mm of mercury. By way of example, in a typical sleeve of 0.8 mm thickness, its inscribed diameter varies from 21mm to 15mm when the controlling air pressure goes from 100 to 300mm Hg where the initial at rest diameter is 32mm and length is 82mm. 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 evolutive pulp flow rates which is in accordance with the invention. A mixer 6 is provided in its lower part with a drainage opening 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 patent Applications Nos. 225/79 (Patent No ) entitled Process and Apparatus for continuously mixing pulverulent solids and liquids and 226/79 (Patent No ) entitled Process and Apparatus for the manufacture of a band or boards of plaster. Lateral control fluid intake pipe 2 of control valve V is supplied with compressed 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 actuated 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. 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: compressed air, whose pressure is set by pressure regulating assembly 9 to a preset value Po, is sent through to valve V / 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 regulating mechanism in accordance with the invention.

Product 8 (or its separate constituents) is continuously introduced into mixer 6 at a constant rate by conventional means (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 11b of a force balance beam 11 in· equilibrium on fulcrum 12, the equilibrium of beam 11 being achieved through a spring 14 and a counterweight 13 acting upon the other balance beam arm Ila.

The counterweight1s 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 11a. 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 11a. Two safety stops 19 and 20 are placed above and below the beam end 11a, thus limiting movement of beam arm 11a 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 containing ϋ-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 assembly 9 at value Po in order to obtain, when escape flow through nozzle 18 is shut off (by moving manually the tip of beam arm 11a onto nozfle 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 having the beam tip of arm 11a 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 11b 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 11. Thus, an overweight results in increasing the distance between beam ~ .4-7 8 24 arm 11a 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. 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 contracting sleeve 3 of valve V and therefore in greater holding back of product 8 in mixer 6, which results in regaining equilibrium at a predetermined weight of product 8 in mixer 6.

In the mechanism illustrated in Figure 2, a piston 10 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 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 vibrate 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 low pressure of the order of .25 bar (7.38in.Hg,, total pressure in the escape pneumatic system being of the order of 1 bar (29.52 in.Kg).

Damping device 15 is selected so that it allows preferred vibrations to be felt. A valve 23 is in the pneumatic circuit downstream from the pressure gauge before said circuit 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 19 may be connected with a valve that shuts off product 8 supply to mixer 6 when beam tip 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 invention for making reinforced plasterboard building components. 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. Container 228 is connected by a pipe 230 to a pump 232 that discharges 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 reinforcement sheet 258 of, for example, woven fiberglass is fed in 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) . Heretofore 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 apparatus 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 225 is fee 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 connected 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 discharge line 316. In addition to serving the function of disconnecting 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 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 frora being damaged from contact with plate 316 of beam arm 11a by a sturdy nozzle head 318.

Pipe 17 is supported 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 lone 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 shape of sleeve 3.

The invention deals with setting the flow rate of evolutive pulp, but it also deals with the setting of evolutive pulps containing finely broken up inert loads, for instance, chopped fibreglass, 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 fibres.

Therefore, under the term of evolutive pulps, properly speaking, can be included evolutive pulps containing in addition inert loads, and loaded or nonloaded liquids.

Referring again to Figure 5, it is to be noted that the impeller 22 is driven by a motor 400 which 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 410a. 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 equilibrium with a minimum amount of mixture in the tank.

Claims (10)

1. A process for controlling the discharge of evolutive pulps, especially a mixture of plaster and water at the outlet of a container, so as to maintain constant the quantity of pulp in the interior of the said container, in which the output of the outlet of the container is continuously controlled with the aid of a direct passage valve having an elastic sleeve controlled by a pneumatic control system associated with an apparatus which takes account of the quantity of the said pulp in the container and in which, in order to prevent the formation of deposits on the internal walls of the elastic sleeve, a system of pulsed signals is superimposed on the control signal proper which determines the cross-section of the passage through this sleeve in the direct passage valve; in which the pneumatic control system is a leakage system with which is associated a balance of forces which simultaneously takes into account the weight of the container containing the evolutive pulp and vibrations generated in the said container to produce the control signal proper which is thus directly and permanently modulated by the said system of pulsed signals corresponding to the vibrations generated in the container, and in which the pulsed signals thus permanently superimposed on the control signal proper cause, permanently, periodic deformation of the elastic sleeve of the direct passage valve practically without changing the value of the passage crosssection defined by the said sleeve, this latter being a function of the control signal proper.

2. A process according to claim 1, in which the frequency of the deformation of the elastic sleeve due to the pulsed signals is of the order of 2.4 Hz.

3. A process according to either of claims 1 or 2, in which the vibrations which give rise to the pulsed signals are caused by a mixing turbine operating within the container.

4. A process according to any of claims 1 to 3, in which under operative conditions the elastic sleeve becomes star-shaped.

5. Apparatus for controlling the discharge of evolutive pulps, especially a mixture of plaster and water, from the outlet of a container so as to maintain constant the quantity of pulp inside the container, in which a direct passage valve having an elastic sleeve arranged at the outlet of the said container continuously controls the said discharge as a function of a control signal produced by a pneumatic control system associated with a device which takes account of the quantity of the said pulp within the container and in which to prevent the formation of deposits on the internal wall of the elastic sleeve means are provided to superimpose a system of pulsed signals on the control signal proper which determines the passage cross-section through the sleeve in the direct passage valve; in which the pneumatic control system is a leakage system with which is associated a balance of forces which takes account simultaneously of the weight of the container containing the evolutive pulp and the vibrations generated in the said container, to produce the control signal proper, which is thus directly and permanently modulated by the said system of pulsed signals which correspond to the vibrations caused in the container by the modulating means, and in which the pulsed signals thus permanently superimposed on the control signal proper permanently cause periodic deformations of the elastic sleeve of the direct passage valve practically without changing the value of the passage cross-section defined by the said sleeve, this latter being a function of the control signal proper.

6. Apparatus according to claim 5, in which the modulating means comprises a mixing turbine rotating inside the container.

7. Apparatus according to either of claims 5 or 6, in which the cross section of the passage defined by the sleeve of the valve is folded into a star-shape when the said sleeve is submitted to a control signal.

8. Apparatus according to claim 7, in which the sleeve which adopts a star-shaped folded form when submitted to a control signal is a sleeve of flexible rubber of the rubber air-chamber type, cylindrical and 5 substantially of the same cross-section when at rest as the interior of the rigid casing of the valve which contains it, mounted inside the said valve with little or no longitudinal tension.

9. A process for controlling the discharge of 10. Evolutive pulps, substantially as herein described with reference to the accompanying drawings.

10. Apparatus for controlling the discharge of evolutive pulps, substantially as herein described with reference to and as shown in the accompanying drawings.