VALVE INTENDED TO BE USED IN ALUMINA PRODUCTION PLANTS

Abstract: The valve is provided at its stopper (3) with a pin (4) combined to a spindle (5) which are coaxial and prevented to move in this direction but capable of rotating freely one with respect to the other so that, by means of the spindle (5), the nut (6) and the corresponding motor (9), the longitudinal movement of the stopper (3) is obtained in the valve opening and closing operations whereas, by applying directly a rotary motion by means of a second motor (23) to the pin (4) which does not affect the spindle (5), the stopper (3) rotates on the valve seat (2), to the closing position, causing a friction and consequent closer self-cleaning action.

Description: OBJECT OF THE INVENTION The present invention relates to a valve of those employed in alumina producing plants, valve which as well as meeting its function as an opening/shutting element, is equipped with self-cleaning means which assures a perfect fit and consequently a perfect seal, between the valve gate and its corresponding seat, according to the preamble of claim 1. A valve disclosing these features is known from US 3 220 431. BACKGROUND OF THE INVENTION It is well known that aluminium is obtained by electrolysis, from bauxite, it being necessary for the bauxite to pass through different stages or steps in processing prior to obtaining alumina and subsequently aluminium. In the plants where these processes are carried out, ducts exist which are equipped with valves, which must be periodically subjected to a cleaning phase because the bauxite adheres in an irregular manner both to the valve seat and to the gate itself, forming sediment which with time impairs the sealing of the closure. Generally speaking these valves have an elbow-shaped construction, in such a manner that the valve gate is extended on a shaft which traverses the valve body and is terminated in a spindle having a complementary nut, so that said nut, through whatever means of conventional operation, provides the spindle with the necessary axial motion for carrying out valve opening/shutting, to which end said spindle must be conveniently immobilised in the angular sense. Conventionally the periodical cleaning of the valve is carried out by hand, after it has been dismantled, which clearly involves an interruption in the process of producing alumina, with the consequent repercussion that this implies. In an endeavour to overcome this problem the applicant himself is holder of the PCT with application number ES 98/00146, in which the use was foreseen of a blocking collar capable of being manually coupled to and decoupled from the valve assembly, in such a manner that through said collar and with the valve in a shut position, the nut and the spindle could be blocked, with an accompanying release of the spindle in the angular sense, in such a manner that the rotary movement applied to the nut, instead of being converted into an axial displacement of the spindle, was directly transmitted to said spindle, whereby the gate, instead of being retracted with respect to the valve seat, turned with respect to the latter producing a friction effect and the consequent elimination of bauxite deposits or scale, that is, a valve self-cleaning effect was obtained, with no need to proceed to the dismantling of the valve body. This solution in addition to requiring a manual intervention for the coupling/decoupling of the blocking collar, meant that in a situation of keying of the nut to the spindle, that is, in the cleaning phase, the spindle could not be advanced, so that the duration of the cleaning operation became longer as the depth of the scale became deeper, since after a first friction application, in which the surface layer of the scale was removed, the friction effect between gate and seat likewise disappeared, it being necessary to dismantle the blocking collar, re-adjust the gate to the seat and re-couple the blocking collar, it even being necessary for the operation to be repeated several times, depending on, as already stated, the depth of the scaling. DESCRIPTION OF THE INVENTION The valve for alumina production plants in accordance with the invention is defined in claim 1. Accordingly, the valve is based on the same principle of self-cleaning through friction, by rotation of the gate against the valve seat, and overcomes the aforementioned problem in a fully satisfactory manner, permitting complete automation of the cleaning process, with optimum results. To this end, in a more specific way and based on a conventional valve body with its pertinent valve seat and gate. the latter in association with a shaft capable of undergoing a movement of axial displacement by means of a spindle-nut mechanism, the valve of the invention centres its characteristics on the fact that in said spindle two coaxial sectors are established, one constituting the spindle itself, axially displaceable with the collaboration of the corresponding and aforesaid nut, and another constituting the gate supporting shaft, with the particularity that these two elements, shaft and spindle, are inter-coupled with the assistance of a sleeve which, immobilising one with respect to the other in the axial sense, permits however the free rotation of the shaft with respect to the spindle. Complementing the structure described the sleeve mentioned is conveniently keyed to another external sleeve, through which the internal sleeve and consequently the shaft to which the gate is joined and the gate itself, can undergo a rotation, at the cost of second driving element, without the latter in any way affecting the spindle, whereby the latter can turn freely with respect to the shaft, as has already been stated. However, the key that connects the two sleeves mentioned has to lie in a groove in one of them, preferentially the internal sleeve, of sufficient length to permit the relative axial movement between the two sleeves corresponding to the change from one of the limiting positions to the other of the gate with respect to the valve seat. In accordance with another of the characteristics of the invention, both the nut corresponding to the spindle, and the external sleeve that transmits the rotary movement to the gate, shall each have a toothed crown wheel, said wheels being operable by means of bevel pinions, through respective reduction gear motors, electrical or hydraulic, in such a manner that the operating of one of them shall produce the valve opening-shutting action, and the operating of the other shall produce the rotary movement of the gate with respect to its seat, it being clear that both motors can work simultaneously, in such a manner that in the cleaning phase and as the scale is progressively removed by friction from the gate and from the valve seat, said gate shall gradually progress towards the seat, in order that this self-cleaning phase does not lose its efficacy. With the convenient programming of the operation of the aforementioned motors, the valve self-cleaning can be done in a fully automatic form, as has been stated beforehand. DESCRIPTION OF THE DRAWINGS To complement this description and in order to assist in a better understanding of the characteristics of the invention, in accordance with a practical embodiment thereof, a single drawing sheet is attached forming an integral part of said description, the single figure on said drawing sheet being by way of illustration and not restrictive in nature, showing, according to a side elevation and in diametric cross section, a valve for alumina producing plants implemented in accordance with the purpose of the present invention, said valve appearing in the shut position. PREFERRED EMBODIMENT OF THE INVENTION From the figure mentioned it may be seen how the valve which is being proposed is constituted of a valve body (1) in which is formed a valve seat (2) on which a gate (3) acts, said gate being conveniently in association with a shaft (4), axially displaceable by the action of a spindle (5) on which acts a nut (6), conveniently joined to a toothed crown wheel (7) which, via a bevel pinion (8), receives the movement of a reduction gear motor (9), all of this in such a way that the rotation of said reduction gear motor (9) in a determined direction produces the separation of the gate (3) with respect to the valve seat and its turning in the opposite direction produces similarly in the opposite direction the operation corresponding to shutting. The spindle (5), equipped at its free end and opposite to the valve itself with a diametric pin (10), the ends of which run in grooves (11) operationally formed in a hood (12) extension of the casing (13) which houses the crown wheel (7) and the transmission pinion (8), grooves (11) which permit the amplitude of axial movement necessary to achieve the also necessary amplitude of displacement in the gate (3), is finished at its lower extremity with a small enlargement (14) by means of which it is held axially with respect to an intermediate sleeve (15), which, in an axial direction, immobilises the spindle (5) with respect to the shaft (4), but which nonetheless permits the free rotational movement of said shaft (4) with respect to the spindle (5). In more specific terms. the sleeve (15) acts also as driving element for the shaft (4) for which it is not only attached to the latter by screw thread (16), but also with the collaboration of a diametric pin (17). The sleeve (15) has a groove (18) in correspondence with one of its generators, in which sleeve runs a key (19) which, by permitting the free axial displacement of the sleeve ( 15), and consequently die free axial displacement of the assembly formed by the shaft (4) and the spindle (5), immobilises in an angular direction said sleeve (15) with respect to an external sleeve (20) to which is joined a toothed crown wheel (21), similar to the aforementioned crown wheel (7) which, through another bevel pinion (22), receives the movement of a second reduction gear motor (23), also similar to the reduction gear motor (9) already mentioned. This second transmission (21 - 22) is housed likewise in a casing (24) similar to the casing (13), the assembly of these elements being facilitated through the collaboration of brackets (25) and (26), fastened to each other and fastened to the valve body (1) itself, as can be seen in full detail in the figure. A dust guard cover (27) protects the transmission (21 - 22) mentioned, while permitting the necessary axial displacement of the sleeve (15). In accordance with this construction and through the reduction gear motor (9), the axial displacement operations for opening and shutting the valve are performed on the gate (3), to which end said reduction gear motor (9) can be made to work by whatever appropriate means. When it is periodically necessary to carry out a valve self-cleaning operation, the reduction gear motor (23) is brought into operation, preferably also in an automatic way, said reduction gear motor (23) being clearly in a position supporting the gate (3) on the valve seat (2), said position determined in turn by the reduction gear motor (9), the reduction gear motor (23) driving the lower shaft (4) in its rotary movement exclusively, whilst the upper spindle (5) is held immobile, and producing the intended friction effect of the gate (3) against the valve seat (2), operation in which the reduction gear motor (9) can also participate, in such a manner that in parallel with the rotary movement of the gate (3) a slight forward movement thereof is produced, complementing the progressive rubbing away of the deposits or scale present in the contact zones between the gate (3) and valve seat (2).

Claims: Valve for alumina producing plants, which incorporates a valve body in which a seat is established on which acts a gate in association with a shaft which traverses the valve body and which by means of a spindle-nut type transmission, receives an axial displacement produced by whatever driving element that determines the approximation and separation operations of the valve seat with respect to the gate, gate which in turn is capable of receiving, in its shut position, a rotary movement determining a friction effect against the valve seat, for self-cleaning of the assembly, characterised in that the gate (3) is joined to a shaft (4) which is connected by its extremity opposite to said gate (3) with a spindle (5), said shaft (4) being immobilised axially with respect to the spindle (5), but capable of turning freely with respect to the latter, all this so that the displacement of the gate (3) for valve opening and shutting is performed by means of an axial displacement applied to the spindle-shaft assembly (5 - 4) via the spindle itself, whilst the rotary movement of the gate (3), in the self-cleaning operation, is received directly by the shaft (4), from a driving element (23) separate from the driving element (9) acting on the spindle (5). Valve for alumina producing plants, in accordance with claim 1, characterised in that the shaft (4) and the spindle (5) are connected to each other through a common sleeve (15), which receives inside a slight enlargement (14) of the corresponding extremity of the spindle (5), permitting the free rotation of the latter with respect to said sleeve, while said sleeve (15) is rigidly fastened to the shaft (4), preferably by a screw thread (16) accompanied by a diametric pin (17). Valve for alumina producing plants, in accordance with previous claims, characterised in that the sleeve (15) which connects the shaft (4) with the spindle (5) has a groove (18) along one of its generators, in which rests a key (19) in association with a second sleeve (20), enclosing the former and joined to a plate or crown wheel (21) through which, with the collaboration of a pinion (22), the shaft (4) and consequently the gate (3) receives the rotary movement of the driving element (23), all this so that the key (19), as well as transmitting the rotary movement to the gate, permits the necessary axial displacement of the assembly formed by the shaft (4), the spindle (5) and the sleeve ( 15) which connects them, in the valve opening and shutting operation. Valve for alumina producing plants, in accordance with previous claims, characterised in that the nut (6) for the axial displacement of the spindle (5) is fastened to a plate or crown wheel (7) which, with the collaboration of a bevel pinion (8), is driven by the motor (9), with a transmission similar to that which applies the rotary movement to the gate (3), the spindle (5) being held immobile in the angular direction with the collaboration of a transversal pin (10), conveniently joined to the free end thereof, which runs in grooves (11) of a cover (12) duly joined to the casing (13) housing the pertinent transmission mechanisms. Valve for alumina producing plants, in accordance with previous claims, characterised in that driving elements (9) and (23) are capable of acting together and automatically during the self-cleaning phase, in such a manner that whilst the motor (23) is applying a continuous rotary movement to the gate (3), the motor (9) is in turn applying to said gate a slow forward movement towards the valve seat (2), in the measure that the residual bauxite scale or deposits are being removed from these parts.

Inventors: GONI USABIAGA JUAN JOSE, GONI USABIAGA, JUAN JOSE, GONI USABIAGA, Juan José
Applicants: AMPO S COOP, AMPO, S. COOP.
Application year: 1999
Main classification: F16K29
IPC codes: F16K31, F16K1, F16K39, F16K29