An inner scroll for an olive oil centrifugal separator

Abstract: A rotating inner scroll (10) for a centrifugal separator with a horizontal axis for separating the liquid and solid phases from a past of crushed olives, comprises an elongated central hub (14) of substantially tubular shape and an outer drum of substantially truncated cone shape. The inner scroll comprises one or more baffles (20) oriented in an axial planes. The baffles are radially extending between the tubular hub (14) and the drum so as to form a barrier encompassing at least the boundary zone (A) between the oil and the water being separated by centrifugation.

Description: Field of the invention The present invention falls within the field of machines for separating olive oil. More particularly, the invention relates to an inner rotating scroll for a centrifugal separator with a horizontal axis of rotation. Background of the invention In the food industry it is well known to use centrifugal separators for extracting olive oil. These separators exploit the centrifugal separation principle to separate a composite mixture consisting of a paste of crushed olives into its components (oil, water, solid fraction). The separated components are then collected at distinct zones of the separator. Conventional centrifugal separators comprise a central supply tube in which a crushed olive paste is let in. Around the central supply tube there is mounted a rotating drum of substantially truncated cone shape, formed by the union of adjacent cylindrical and truncated cone drum portions. Rotation of the scroll and the drum fast thereto causes the components to separate from each other in accordance with their specific gravity. The solid phase, being the heaviest, forms a radially outer layer on the peripheral wall of the drum. The liquids, oil and water, stratify radially in cylindrical coaxial layers in the radially innermost zone near the scroll. Specifically, beginning from the outside, the olive husk layer forms in the radially outer part of the drum, followed by an intermediate water layer and a radially inner oil layer. The various separated phases are expelled from zones of the separator drum at axially different locations. The solid olive husk phase is expelled by the rotating inner scroll from one end of the separator, the liquid phases at distinct ports at the axially opposite side. In scrolls of conventional design, the centrifugation creates a rotational speed gradient between the layers of different phases. Owing to friction, a rotational speed gradient is also present within a same layer, as the particles near a layer of another adjacent phase tend to be driven by this and therefore rotate at a different rotational speed with respect to the average angular speed of the particles belonging to a same layer. Owing to such a difference of speed there is no sharp distinction between two radially adjacent layers. Instead, at the boundary zone between two layers of different phases heterogeneous layers are formed wherein the different phases remain mixed. As apparent, this phenomenon adversely affects production efficiency and results in an increase of costs. In order to overcome the above-mentioned drawbacks, well-known types of inner scrolls, such as, for example, the one illustrated in the diagrams entitled "Fig. 1 - Prior Art", and "Fig. 2 - Prior Art", present an elongated central hub 14 of substantially tubular shape and an outer drum of substantially truncated cone shape, and a plurality of axial baffles 20, which are oriented according to axial planes angularly equally spaced around the tubular hub, and radially extend between the tubular hub 14 and the drum so as to form relevant barriers encompassing two boundary zones A and B separated by centrifugation, the zone A between the oil and the water, and a boundary zone B, the zone B between the liquid and solid phases, and so as to define corresponding plurality of compartments 21 open in radially outer directions. These well-known types of inner scrolls which have just been described although they have been demonstrated to be quite suitable for performing their function and also quite efficient in that performance, do present some drawbacks which are essentially determined by the separation of the compartments 21 nearby the cylindrical outer surface of the tubular hub. In fact the presence of these compartments can lead to some imbalances of the load of the aforementioned phases separated by centrifugation and, as a direct consequence, of the scroll. Summary of the invention Accordingly, it is a primary object of the present invention to provide an improved inner scroll capable of overcoming the above mentioned disadvantages and limitations of the prior art. Toward the attainment of this and additional objects and advantages, the present invention, briefly summarised, provides a rotating inner scroll for a centrifugal separator with a horizontal axis for separating the liquid and solid phases from a paste of crushed olives, the scroll comprising an elongated central hub of substantially tubular shape and an outer drum of substantially truncated cone shape, and a plurality of axial baffles, which are oriented according to axial planes angularly equally spaced around the tubular hub, and radially extend between the tubular hub and the drum so as to form relevant barriers encompassing two boundary zones A and B separated by centrifugation and so as to define corresponding plurality of compartments open in radially outer directions, the inner scroll being characterised by the fact that said baffles are provided, in their radially inner zone, with at least one slit which extends for at least 2/3 of the axial length of the baffle to set the liquid present in adjacent compartments in direct fluid communication. Brief description of the drawings In order that the present invention may be well understood there will now be described a preferred embodiment thereof, given by way of example, reference being made to the accompanying drawings, in which: Fig. 1 is an axial sectional view of a first embodiment of an inner scroll for a centrifugal separator in accordance with the present invention; Fig. 2 is a radial cross sectional views, to a line II-II of Fig. 1; and FIG. 3 is an axial sectional view of a first embodiment of an inner scroll for a centrifugal separator in accordance with the present invention; Description of preferred embodiments With reference to FIG. 1 FIGG. 1 and 2 which illustrate a well-known types of inner scroll, numeral 10 designates overall an inner rotating scroll for a centrifugal separator. A conventional outer rotating drum of substantially truncated cone shape (not shown) is fitted around the scroll, said drum being formed by the union of adjacent cylindrical and truncated cone drum portions. The scroll comprises an elongated central hub 14 of substantially tubular shape. A paste of crushed olives is pumped into the drum through an opening 11 formed at one end of tubular hub 14, for separating by centrifugation the liquid phases (oil and water) and the solid phase (olive husk) composing said paste. The olive paste is distributed radially by centrifugation from an inlet zone 12 located proximate to the opening 11 and closed by a radial wall 13. The remainder of tubular hub 14, to the right of radial wall 13, is empty. Formed at the peripheral part of the scroll is a dual spiral 15a, 15b of conventional design for conveying the olive husk accumulated in this peripheral part towards an outlet 16 proximate to the tapered axial end portion of the scroll (to the right in FIG. 1). The two liquid phases, oil and water, are expelled through respective outlets (not shown) located at radially distinct levels near the left end portion of the scroll. Fixed along the outer wall of tubular hub 14, preferably by welding, is a plurality of baffles or axial walls 20, oriented according to axial planes angularly equally spaced around the tubular hub 14. Referring also to FIG. 2, the baffles 20 define a corresponding plurality of compartments 21 open in radially outer directions. More particularly, each compartment 21 is limited laterally by two consecutive baffles 20, and at the radially inner part by the cylindrical outer surface of tubular hub 14. The baffles 20 provides that the three phases being separated (oil, water, olive husk) each maintain a uniform angular speed, equal to the rotational speed of the scroll. Owing to such an arrangement, the different layers are not allowed to gain relative rotational speed with respect to each other. As a result, a clear separation is obtained between the various phases, as schematically depicted by circles A and B shown in phantom line in FIG. 2. An improved and clearer distinction of the phases allows for an increased rate of oil being expelled, this implying an advantage from the production and economic point of view. During rotation of the scroll, in each compartment there can be clearly distinguished a radially inner oil zone 21a, an intermediate water zone 21b, and a radially outer zone 21c containing the solid phase. The baffles 20 have a radial extension sufficient to form a barrier comprising the boundary zone A between the radially inner oil layer and the intermediate water layer adjacent to the oil layer. The baffles 20 have a radial extension such as to form a barrier encompassing both the boundary zones A and B between the different liquid and solid phases separated by centrifugation. Accordingly, there is overcome the inconvenience discussed in the introductory part of the present description, where prior art devices formed rather thick boundary zones comprising a mixture of two radially adjacent phases due to friction in the contact of layers rotating at different angular speeds. The number of baffles 20 may vary according to requirements. Obviously, better results are attained if more than one axial baffle is provided, as shown in the illustrated examples. The clear separation of the phases allows the liquid phases also to be extracted with grater accuracy at different levels in the centrifugal separator. The radial length of the baffles 20 varies following the shape of the scroll and the surrounding drum. Preferably, the radially outer edges 22 of the baffles 20 are at a substantially constant distance from the inner surface of the drum. This determines a dual helical channel 17 of constant cross section between the scroll and the drum, where the olive husk is driven in helical manner by the dual spiral 15a, 15b towards outlet 16. A constant cross section of the dual peripheral channel 17 is beneficial in that it is helpful in rendering the speed of the olive husk uniform and prevents the formation of constipated or empty zones which could adversely affect the separator efficiency. The dual spiral 15a, 15b is welded to the outer edges 22 of baffles 20. Still with reference to FIG. 1, the axial length of the baffles 20 is preferably limited to the zone of the scroll where the liquid phases are present, i.e. the inlet portion (to the left) and the median portion. Where the scroll narrows, to the right end, only the solid phase is present and the baffles are no longer indispensable to achieve the desired scope. In the embodiment illustrated in Fig. 3, in order to render the level of the liquid phase, particularly the oil, uniform in all the compartments 21, the baffles 20 have one or more passages at their radially inner parts, near the attachment to the tubular hub 14. The radially inner edges 24 of the baffles 20 are so shaped as to define with the tubular hub 14 one or more slits 23a setting adjacent compartments in direct fluid communication. While specific embodiments of the invention have been disclosed, it is to be understood that such disclosure has been merely for the purpose of illustration and that the centrifugal separator is not to be limited in any manner thereby. Various other modifications will be apparent to those skilled in the art in view of the foregoing examples.

Claims: A rotating inner scroll (10) for a centrifugal separator with a horizontal axis for separating the liquid and solid phases from a paste of crushed olives, the scroll comprising an elongated central hub (14) of substantially tubular shape to fit an outer drum of substantially truncated cone shape, and a plurality of axial baffles (20), which are oriented according to axial planes angularly equally spaced around the tubular hub, and radially extend between the tubular hub (14) and the drum so as to form relevant barriers encompassing two boundary zones A and B separated by centrifugation and so as to define corresponding plurality of compartments (21) open in radially outer directions, the inner scroll (10) being characterised by the fact that said baffles (20) are provided, in their radially inner zone, with at least one slit (23a) which extends for a substantial part of the axial length of the baffle to set the liquid present in adjacent compartments (21) in direct fluid communication. A scroll as claimed in claim 1, characterised in that the radially outer edges (22) of said baffles (20) are fixed to at least one spiral (15) disposed around the peripheral part of the scroll (10). A scroll as claimed in claim 2, characterised in that the radially outer edges (22) of said baffles (20) are spaced apart from said drum so as to define with said spiral and said drum at least one peripheral helical channel (17) of substantially constant cross section. A scroll as claimed in claim 1, characterised in that the axial length of said at least one baffle (20) is limited to the length of the scroll (10) where the liquid phases are present. A scroll as claimed in claim 1, characterised in that each compartment (21) is limited laterally by two consecutive baffles (20), and at the radially inner side by the cylindrical outer surface of said tubular hub.

Inventors: CORNELLO ALESSANDRO, CORNELLO, ALESSANDRO
Applicants: CORNELLO CENTRIFUGHE S R L, CORNELLO CENTRIFUGHE S.R.L.
Application year: 1997
Main classification: B04B1
IPC codes: B04B1