Patent Application
20090194716
This invention relates to a device for regulating the flow of a liquid, in particular an abrasive liquid which may be supplied to/drained from moulds for the manufacture of ceramic products.
The use is well known of a liquid called “slip”, in trade jargon, in the field of manufacture of the above-mentioned ceramic products (such as, for example, washbasins, toilets, bidets, shower trays, etc.).
This fluid mixture, comprising a watery part and a ceramic part in suspension, is cast into “shell” moulds which have a known structure of a porous type, in particular obtained with resin.
The above-mentioned mould is part of a plant, of a known type, having, amongst other things, flexible and elastically deformable pipes enabling, on the one hand, supply of the slip to the mould, and, on the other hand, draining off of the spent slip.
This plant is designed to perform a type of casting which, in its simplest and most basic form, comprises the following steps:
flushing the supply circuits with fresh slip;
filling the mould at an initial pressure;
forming the thickness with pressure profiles greater than the filling pressure;
emptying the mould with return, normally, to atmospheric pressure;
consolidating the product with air;
decompressing the product.
The casting cycle starts with the mould closed and product cavities perfectly clean and empty and ends with the mould closed, but with product cavities containing the product just produced, the mechanical strength of which must be sufficient to support its weight when it is extracted from the mould.
In order to complete the production cycle it will be necessary, as known, to provide a mould closing step before the casting cycle and a step of demoulding the product after its manufacture.
Usually, the above-mentioned supply pipes and, in turn, the pipes for draining off the spent slip, are fitted with devices to regulate the flow of the fluid, in order to control the flow, based on the requirements of the ceramic product during the casting steps in the plant: in this respect, the mould filling and emptying steps are particularly critical.
The slip, due to its intrinsic nature, is an abrasive liquid and, therefore, the regulators currently used are exposed to relatively fast wear, in particular the moving parts used to reduce the cross-section of the fluid passage: the presence of known mechanical metal valves, such as, for example, butterfly valves, tend to wear quite quickly.
Solutions have therefore been sought for regulators which could have good reliability characteristics, precision in regulating the fluid flow and a good resistance to wear.
One of these solutions is known from patent IT—1.257.661 which illustrates a flow regulating valve comprising a connection body between two segments of a pipe and in which there is a connection chamber between the same pipe segments.
The chamber houses an intermediate fluid passage mouth fitted with a mechanical valve protected, from contact with the passing fluid, by an elastic membrane fixed peripherally to the connection body.
In another solution known from patent GB 2.042.128, the valve comprises a section of deformable pipe placed between/associated with relative fluid pipe segments.
This section of pipe is acted on, in contraposition, by a fixed striker block and a half-ring element or mobile pressure cradle on a point of the pipe.
This pressure cradle is acted upon, on one side, by a thrust spring designed to maintain the section of pipe squashed towards the block in a closed passage configuration, and, on the other side, by a cursor controlled by an actuator to enable movement of the cradle, in both directions, by a force greater than the force generated by the spring: in this way, the cross-section of the pipe section may be opened at this point.
On the one hand, both these solutions limit the risk of wear of the structure due to the presence of rubber or deformable plastic elements (membrane and pipe section), but, on the other hand, they are inadequate in terms of speed, flow control variability, reliability and working life of the regulator.
In particular, the dynamic nature and the precision in fluid flow the control are important variables, since, in the specific case of slip, for example, the flow must have a kind of initial increasing ramp and a final decreasing ramp, in order to avoid the formation of air bubbles and spray inside the mould during the casting and product forming cycle.
These limitations are caused, in particular, by the reduced control zone and by the presence of an intermediate element between the two sections of the pipe.
Basically, the narrowings generated in these solutions are limited to a short length of the pipe resulting in high head losses in a limited section of the pipe; this situation leads to a transformation of the energy of the fluid into heat, which is dissipated in this section of the pipe and tends to critically accelerate the wear of the material in contact with the fluid itself.
Another consequence of reducing the cross-section of the pipe is the increase of the speed of the fluid, the generated kinetic energy of which, striking the walls of the pipe, could cause a stress on the surfaces in question which the material (rubber or plastic) is unable to support, over time, and wears prematurely.
The presence of an intermediate element which forms part of the valve unit structure for connection with the pipe sections, combined with the presence of mobile regulation elements with complex movement mechanisms, makes these solutions costly and results in poor reliability over time.
An aim of this invention is therefore to overcome these shortcomings by providing a device for regulating the flow of a fluid, in particular an abrasive fluid, with an extremely simple and inexpensive structure with a long life and precise functional characteristics correlated to the operational needs of the ceramic product forming cycle.
In accordance with this invention, the above-mentioned aim is achieved by a flow regulation device, in particular a device for regulating the flow of abrasive fluids, comprising the technical characteristics described in one or more of the appended claims.
The technical characteristics of the invention, with reference to the above aims, are clearly described in the appended claims and its advantages are apparent from the detailed description which follows, with reference to the accompanying drawings which illustrate a preferred embodiment of the invention provided merely by way of example without restricting the scope of the inventive concept, and in which:
With reference to the accompanying drawings, and with particular reference to
In particular, this device 1 is applicable in plants 2 with at least one elastically deformable pipe 3, for supplying and/or draining the liquid to/from the mould, which is not illustrated here since it is prior art and does not strictly form part of this invention, for the formation of the ceramic product.
Obviously, a plant 2 of this type usually comprises a tank for storing the slip arriving from pipe 3 and which enables, using additional pipes, supply of the slip to the mould according to specific pressures determined by the casting cycle during formation of the solid.
It also comprises pipes which drain off the spent slip which is normally carried to a second storage tank.
These elements are not described and illustrated as they do not strictly form part of this invention.
It should be noted, however, that the device according to this invention may be applied to any elastically deformable pipe forming part of the plant, without limiting the inventive concept.
With reference to
More precisely, the actuator element 5 is placed in contact with an outer surface 3a of the pipe 3; this actuator 5 may generate a controlled pressure, indicated generically with arrows P5, unilaterally on the outer surface 3a of the portion of the pipe 3 with which it is in contact.
The fixed contrast elements 6 are fitted to and acting on at least the outer surface 3b of the pipe 3 opposite to the surface 3a in contact with the actuator and for a length L6 comparable to the length L5 in contact with the actuator 5: in this way, when the actuator 5 is activated, the portion of the pipe 3 can be deformed in a controlled and uniform manner, thereby reducing the cross-section of the pipe 3.
Preferably, this contrast length L6 may be substantially equal to the length L5, without restricting the scope of the inventive concept, since small increases or decreases to the contrast surface may be permitted depending on the operational requirements.
In other words, the length L6 of the contrast elements 6 may be less than the length L5 of contact of the actuator 5.
On the other hand, the length L6 of the contrast elements 6 may be greater than the contact length L5 of the actuator 5
As may be clearly seen in
In the case illustrated, the characteristic dimension is given by the diameter D of the pipe 3 used which has a circular shape, but the dimension D represents, more generically, a characteristic dimension of the cross-section of the pipe 3 used, if it is not circular in shape.
Preferably, in order to minimize the damage which may be caused by the wear on the pipe 3, this length L5 of contact may be between two and twenty-five times the diameter D of the pipe 3, even though these dimensions are not mandatory and may vary on the basis of various parameters, such as, the shapes and sizes of the pipes used and their construction material.
As may be seen in
In a preferred embodiment illustrated in
This sleeve 9 is opportunely closed at the respective ends by a pair of sealing clamps 12 and 13.
With regard to the above-mentioned contrast elements 6, these may comprise a cylindrical tubular element 14 through which the pipe 3 passes and which houses the sleeve 9: in this way, a contrast wall 6 is defined for the pipe 3 on its surface 3b and a striker wall 8 also for the sleeve 9 on its free surface.
Obviously this cylindrical tubular element 14 must have a very precise size in order to obtain the desired result, that is, it must have:
a length L6 comparable to the length L5 of the surface 3a of the pipe 3 in contact with the sleeve 9, and
a diameter D14 comparable to the dimension of the sleeve 9 in the above-mentioned fully extended configuration.
Basically, the diameter D14, indicated as the internal diameter for contact between the cylindrical element 14 and pipe 3—sleeve 9 may be practically identical to the sleeve 9 in the fully extended configuration or slightly greater than the sleeve 9 in this configuration.
Looking more closely at the details, the sleeve 9 may be supplied, by the above-mentioned supply/drainage pipe 11, with a fluid which may be, for example, without restricting the scope of the inventive concept, air coming from a main supply.
This fluid supply/drainage pipe 11 may be fitted with operation and measurement elements 15 (for example, a proportional valve 15a and a transducer/pressure measurement device 15b) to enable the controlled supply and drainage of the fluid upon the command of a main control unit 16. In order to optimize the operation of this flow regulating device 1, the pipe 3 may be fitted with several units for observation and measurement of parameters useful for its operation.
As may be observed in
In the specific case of
In addition, the pipe 3 may be fitted with an additional unit 19 for measuring the pressure P3 (for example, a pressure transducer) present in the pipe 3 connected to the main control unit 16.
This unit 19 for measuring the pressure P3 may also be fitted upstream of the device 1 relative to the direction VF of supply of the liquid to the mould.
In addition to these elements, the pipe 3 may also be fitted with a liquid flow on-off valve 18, connected to the main control unit 16, to enable supply of the pipe 3 at a pressure P3 preferably constant (at least in the liquid inlet section) and, respectively, a complete closure of the pipe 3.
In
The actuator 5 is also connected to the main control unit 16, which has memory banks BM for setting the controlled activation/deactivation of the actuator 5 on the basis of parameters PF for operation of the plant 2 which may be pre-set and/or stored, even in real time.
These parameters PF may comprise the relation between the pressure P9 present in the sleeve 9 and the flow PT of the fluid through the pipe 3 based on the temperature data T3 for the liquid, the size of the supply pipe 3, that is, the diameter D of the pipe 3, the inlet pressure P3 in the pipe 3, the direction VF of the liquid flow, based on the steps of the operational cycle of the plant 2.
With these parameters PF known and thanks to the overall control of the unit 16 it is possible to obtain the desired flow rate in the pipes in a precise, constant and fast manner thanks to a variation of the passage cross-section in the portion of pipe 3 in which the sleeve 9 acts.
These considerations are confirmed by the graph shown in
The two curves generated (the dashed line is the curve for the flow obtained for increasing values of P9 and, therefore, of P5, too, and the continuous line is the curve for the flow obtained for decreasing values of P9 and, therefore, of P5, too, which may be different due to an erratic behavior of the chain of command of P5) confirm that, even though the reduction of the pipe cross-section is controlled by means of a compressible fluid, the correlation with the desired flows occurs with a high precision, and it is therefore possible to carry out a particularly sophisticated setting of the values of the system depending on the requirements of the plant and the cycle which must be carried out to process the ceramic product in an appropriate manner.
A device manufactured in this way therefore fully achieves the above mentioned aims thanks to a flow regulator having the following characteristics:
inexpensive and simple to manufacture (reduced cost of its components and simple materials);
may be fitted to any type of pipe in the plant, if it is elastically deformable, without diversifying its structure, that of the pipe and its precision and operational reliability;
long operational life thanks to the possibility of varying the cross-section of the pipe from the outside of the pipe and over a large contact surface given by an adaptable surface, in order to reduce wear of both the pipe component and the actuator.
This device, therefore, enables a reduction of the cross-section of the pipe generating variable and controlled head losses, in a fast manner, enabling the mass quantity of the fluid to be controlled through a section of the pipe in the unit of time: this, as mentioned above, is very important in the processes for manufacturing ceramic products with slip in order to avoid alterations of the liquid during its supply to/drainage from the mould.
The invention described above is susceptible of industrial application and can be modified and adapted in several ways without thereby departing from the scope of the inventive concept. Moreover, all details of the invention may be substituted by technically equivalent elements.
| Number | Date | Country | Kind |
|---|---|---|---|
| BO2008A000073 | Feb 2008 | IT | national |
