Abstract:
The invention relates to the field of fruit and vegetable juice and puree extractors in general. More precisely, it relates to a rotary-type extractor having at least two refinement stages arranged vertically and coaxially and being activated by a single, common motorization.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a rotary pulping machine for the extraction of fruit and vegetable juices and purees. 
     The prior art for the extraction of juices and puree envisages the use of single-or multi-stage extractors of the rotary type. 
     Such extractors generally comprise a rotor with radial blades which impresses centrifugal forces on the product sufficient to cause the product to pass through a sieve of the cylindrical or conical type, made in perforated sheet steel and surrounding the rotor, and thereafter to be collected externally, while the bits or waste stay inside the sieve and can be removed separately through a special waste discharge outlet. 
     Where a rather high degree of product refinement is required, eliminating solid impurities larger than a prefixed qualititive standard permits, a first known regulating modality is that of placing two or three extracting machines in series in order to create several extracting stages, with a consequent increase in costs and constructional complexity since in effect the single extractor is doubled or tripled in number, together with its relative motorization. 
     A second realisation, more often adopted since more economical, envisages the use of one single-stage extractor which performance is increased by increasing the rotation velocity of the rotor, increasing in turn the rotor rotation speed and proportionally the centrifugal forces bearing on the product, or reducing the distance between the rotor blades and the internal surface of the sieve. 
     With higher rotation velocities, however, the risk of sieve breakage is also increased, since the latter is subject to constant stress, the final result being that the entire machine is less reliable. The sieves used usually have a breadth which is equal to the diameter of the holes, so it is obvious that if a single sieve with very small perforations is used, to allow through only the most refined product, the breadth of that sieve will have to be rather small and thus subject to possible breakage. 
     This problem is resolved in various-stage extractors by the use of several sieves having breadth and perforation diameters which decrease in cascade, in such a way that the final sieves with fine perforations undergo stress which is inferior to that of the above since the said sieves are in contact with a product that has already been partially refined. 
     In single-stage machines, the necessary increase in the rotation speed of the rotor and the consequently greater centrifugal forces impressed lead to the fragmentation of the bits (seed fragments, peel), with their subsequent possible passage through the sieve perforations and an ensuing drop in the quality of the final product. 
     SUMMARY OF THE INVENTION 
     An aim of the present invention is that of eliminating the above-mentioned drawbacks by providing a machine having the characteristics and technical advantages of multi-stage machines at a cost which is comparable to that of a simple single-stage machine. 
     In particular, one of the aims of the invention is to provide a particularly reliable machine which is able to produce juices and purees of the highest quality with lower production costs than those of a conventional multi-stage machine. 
     The said aims are fully attained by our rotary pulping machine for the extraction of fruit and vegetable juices and purees. The pulping machine is of the type that has a first extraction stage. The pulping machine has 
     a rotor which central rotation shaft equipped with blades aimed at moving the introduced product and impressing a centrifugal effect on it; 
     a first stage sieve of cylindrical or conical shape, through which liquid extracted from the centrifuged product passes; 
     separate outlets for the waste materials remaining inside the sieve and for the juice or refined part of the product which has passed throught the sieve; 
     motorization means to rotate the rotor central rotation shaft at least a second refinement stage, coaxial to the first extraction stage activated by the same motorization means, each of which the second refinement stages comprising a second bladed rotor applied to the common central rotation shaft, and a refinement sieve. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other characteristics and advantages of the present invention will better emerge from the detailed description that follows, of an embodiment of the invention, herein illustrated purely in the form of a non-limiting example in the accompanying figures, in which: 
     FIG. 1 shows the machine schematically in vertical median section; 
     FIG. 2 shows, in vertical section, a detail of the second refinement stage of the machine, in two different operative configurations; 
     FIG. 3 shows in plan view a detail of a possible blade arragement about a rotor. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the figures, 1 denotes in its entirety a motorization which rotates a single, vertically-arranged central shaft 2. The central shaft 2 has at least two series of blades 3 attached thereto. 
     The central shaft 2 is part of a rotary pulping machine for the extraction of vegetable juices and purees housing a first series of blades 3a relative to a first stage of the machine, and a second series of blades 3b of a second stage, arranged in a cascade below the preceding stage. The blades 3a and 3b, rotating solidly to the central shaft 2, constitute two bladed rotors, in which the rotor of the first stage has preferably a greater number of blades (for example, eight), than those of the second stage (for example, four). 
     The machine has a superiorly or upper inlet 4 for the product which is fed to the machine. The product descends by force of gravity into the zone of the blades 3a from which the said product receives centrifugal movement and is forced against the internal wall of a sieve 5. The sieve 5 is made of perforated sheet steel. 
     The sieve 5, as is shown in FIG. 1, has a superior or upper cylindrical shape, connected to an underlying downwards-opening conical part 5a. 
     The liquid part of the product passes externally through a plurality of perforations 6 in the sieve 5, and can be collected separately with respect to the bits or waste product, which remain inside the sieve 5. 
     A waste discharge outlet 7 is provided for the removal of the waste product left on the bottom of the sieve 5. Two juice or puree outlets 8 and 9 are provided for the juice which has passed through the sieve 5. 
     The first extraction stage is actually separated into two distinct sections, by means of an extractable or removable crown 12 arranged externally to the sieve 5, in the hollow space between the sieve 5 and an outside protection cover 10 of the machine, in the connection zone between the cylindrical part and the conical part of the sieve 5. 
     The outlet 8 is for the purest, while denser juice exits through the outlet 9 which has undergone greater centrifugal and mechanical forces due both to the larger diameter of the conical part of the sieve 5 with repsect to the cylindrical part, and to the greater time the product spends inside the machine. 
     The crown 12, is made for example with two half-rings, and is provided with fixing means to permit its easy extraction or removal from the machine where a first stage with only a single extraction section is desired. 
     The blades 3a can be of conventional radial type or may be as illustrated in FIG. 3, where the blades 3a form among themselves angles of about 45 degrees, if arranged tangentially to the sides of a regular octagon (seen in plan view) solid to the central shaft 2, but may also form among themselves different angles according to the number of side of the reference polygon. 
     The shape of the rotor and the angular arrangement of the blades of the first stage may however vary according to the lightening degree desired for the centrifugal effect, depending on whether quality or production is given precedence, while the rotor of the second stage generally has radial blades. The outlet 9, as illustrated in FIG. 1, brings the juice into the second refinement stage where it is subjected to the forces of the further bladed rotor which forces it against a sieve 15 before sending it, through an outlet pipe 13, to a further stage, or to a collection tank of the finished juice. 
     Also in this last case an outlet 14 is provided for the separate collection of the waste products from the second refinement stage. This waste is obviously finer than that produced by the first stage. 
     As regards the arrangement of the blades 3b, they are preferably radial and substantially rectangular in shape, and are mounted on the central shaft 2. 
     According to an alternative embodiment of the invention which is not illustrated, the first-produced, finest juice, can be sent on to the second stage while the denser juice can be used for other purposes. 
     Concerning the regulation of the degree of pulping obtainable with the first stage of the machine of the invention, it is obtained through the use of a frequency converter, not illustrated, which permits of varying the rotation velocity of the rotor. 
     Where it is necessary to effect an autonomous regulation of the second refinement stage, the second stage rotor is made in the way illustrated in FIG. 2, where it is equipped with blades whose position along the rotor shaft can be varied in height from the outside, hands-off, even while the machine is functioning. 
     The rotor is provided with a series of fixed lower blades 3b and a second series of blades 3c, displaced with regard to the preceding ones and solid or fixed to a radial pivot 16 of a slidable spindle 17 internal to the said central shaft 2. 
     The vertical translation of the spindle 17 is effected by means of a ratiomotor with wormscrew or by means of a pneumatic cylinder, both not illustrated. 
     The spindle 17 with pivots 16 constitute means to regulate the position of the blades 3c along the central shaft 2. 
     On the left is the lower position, the position of minimum use of the sieve, while on the right the blades 3c are represented in their upper position, that of maximum use of the sieve 15. 
     The vertical movement of the blades 3c is limited by the presence of an upper endrun 18 and a lower endrun 19 against which a head 20 of the spindle 17 interferes.