ROTOR BLADES FOR FOOD PROCESSING MACHINES AND RELATED PROCESS

Abstract: A rotor for food pulping or straining machines is equipped with a plurality of blades (2) designed to act on the food product to force at least part of it out through a sieve (3) that surrounds the rotor (1) and is characterised in that the blades (2) are shaped in such a way as to cause sudden changes of direction in the moving product particles, thus producing a rapid succession of impulses that act on substantially stationary product particles adhering to the sieve (3), these impulses causing the propulsion of the substantially stationary product particles.

Description: ROTOR BLADES FOR FOOD PROCESSING MACHINES AND RELATED PROCESS TECHNICAL FIELD AND BACKGROUND ART. The present invention relates to a rotor for pulping and straining machines for food products and a related process for propelling the product particles. Machines for extracting juices and purees from plant or even animal products essentially consist of a filter or sieve, usually a perforated metal plate, which is cylindrical or conical in shape, and a rotary element (rotor) which turns within the sieve in such a way as to separate the particles that pass through the holes in the sieve from those that do not, the latter being discharged from the sieve as waste. The rotor is a very important part of the system because the part of the product that has to be extracted usually adheres very strongly to the waste (for example, the flesh and peel of a fruit) and the main function of the rotor is to separate them. The rotor usually comprises a central hub attached to a power driven shaft and is equipped with a certain number of blades that act on the product in the machine, causing it to rotate within the sieve. Rotor components vary greatly in shape and size but all rotors known in prior art, whatever their shape, are designed to transmit to the product particles a combined circular and axial motion that causes them to follow a cylindrical or conical spiral path. The useful part of the product is propelled through the holes in the sieve mainly by centrifugal force. All operating conditions being equal, a low viscosity product will be separated out more easily than one with a high viscosity. Indeed, highly viscous products tend to form a layer that adheres to the walls of the sieve and makes it more difficult for the useful part of the product to pass through the holes. This behaviour means that machines of this kind cannot be used on high-viscosity products (for example, banana puree) and, even in the case of medium- viscosity products, reduces machine efficiency. DISCLOSURE OF INVENTION. The aim of the present invention is to overcome the above mentioned disadvantages and to provide a machine and process which, even for products that are difficult to process, allow the particles that adhere to the sieve to be detached and put back into circulation together with the other product particles moving within the machine. These aims are fully accomplished by the rotor and process disclosed by the present invention, whose characteristic features are described in the claims below and which are characterised in particular in that the parts of the rotor blades facing the sieve are shaped in such a way as to cause sudden changes of direction in the moving product particles, thus producing a rapid succession of impulses that act on the product particles adhering to the sieve, which are substantially stationary, these impulses causing the substantially stationary adhering particles to be detached from the sieve and to start moving again. In the process disclosed by the present invention, the moving particles of product are subjected to sudden changes of direction in such a way that they describe a broken spiral path consisting of relatively short, angled lines and thus producing a rapid succession of impulses acting on the product particles which adhere to the walls of the sieve and which are therefore substantially stationary in such a way as to detach them from the sieve and to put them back into circulation together with the other moving product particles. BEST MODE FOR CARRYING OUT THE INVENTION. The invention will now be described in more detail with reference to a preferred embodiment of it illustrated purely by way of example, without restricting the scope of the inventive concept, in the accompanying drawing, in which: - Figure 1 is a schematic representation of the rotor, showing the sieve drawn with a dashed line; - Figure 2 illustrates a detail of a blade viewed in direction A; - Figure 3 illustrates a detail of a blade viewed in direction B. With reference to the illustrations, the numeral 1 denotes in its entirety a rotor for a pulping or straining machine used to make food products and not illustrated since it is substantially of known type. The rotor is equipped with a plurality of blades 2, eight in the embodiment illustrated, which, during the rotation of the rotor 1, are almost in contact with a cylindrical or conical sieve 3 that encloses the rotor and is drawn with a dashed line since it is of a substantially known type. The rotor 1 has a central hub 4 attached to a power-driven shaft which is not illustrated since it is of customary type. One or more of the blades 2 have one or more notches 5 made in the blade edge that faces the sieve 3. The notches 5 on each blade may vary in number from one to ten in (but preferably from two to six) and they make an angle with the surface of the blade, so that the motion transmitted to the moving product particles has an axial component whose direction is concordant with or opposite to the direction of the axial component of the spiral. The angle may vary between 10° and 80° or between 100° and 170°. The width and depth of the notches normally range from one half to double the thickness of the blade. Different rotor blades may have a different number of notches located at different positions. For example, one blade may have three notches in it and another, five notches. Further, the notches on one blade may be in the central zone of the blade, those on another, near the edges of the blade. Notch spacing may also vary. Whatever their angle, size and location, the notches 5 are positioned in such a way as to produce sudden changes of direction in the moving product particles so that the path followed by the particles is not a spiral consisting of a continuous line but a broken spiral made up of a series of relatively short, angled lines. These sudden changes of direction produce a rapid succession of impulses that act on the substantially stationary product particles adhering to the sieve with sufficient force to detach the particles from the sieve, and to put them back in circulation together with the other product particles moving within the machine. In other words, the product particles that strike the angled surfaces of the notches undergo a sudden change of direction and transmit to the layer of particles adhering to the sieve an impulse that cancels their adhesive force and propels them into circulation again, thus neutralising the negative effects due to the viscosity of the product. The number and distribution of the notches and the angle are therefore a function of the physical properties of the product to be processed and, thanks to rotor rotation, may act on the entire surface of the sieve. The amplitude of the angle is such that the motion transmitted to the deflected product particles has an axial component, following the axis of the rotor, whose direction is concordant with or opposite to the direction of the axial component of the spiral. When the direction is concordant, there is acceleration of the axial component. Motion in the opposite direction, on the other hand, causes deceleration. By varying the combination of the two types of notches (those that produce acceleration and those that produce deceleration), it is possible to calculate and fix the average axial speed of the product and hence the duration of the process, which is particularly important in the case of highly viscous products which are difficult to process. The process according to the present invention is original and innovative in that the moving product particles are subjected to sudden changes of direction, in such a way that they describe a broken spiral path consisting of relatively short, angled lines and producing a rapid succession of impulses that act on the substantially stationary product particles adhering to the sieve with sufficient force to detach them from the walls of the sieve and propelled into circulation together with the other moving product particles.

Claims: CLAIMS 1. A rotor for food pulping and straining machines of the type equipped with a plurality of blades (2) designed to act on the food product to force at least part of it out through a sieve (3) that surrounds the rotor (1), characterised in that the parts of the rotor blades (2) facing the sieve (3) are shaped in such a way as to cause sudden changes of direction in the moving product particles, thus producing a rapid succession of impulses that act on the substantially stationary product particles adhering to the sieve (3), these impulses causing the substantially stationary particles to be detached from the sieve. 2. The rotor according to claim 1 , wherein the sudden changes of direction are such that the path followed by the moving product particles is a broken spiral consisting of relatively short, angled lines. 3. The rotor according to claim 1, wherein at least one blade (2) has at least one notch (5) made in the edge of it facing the sieve (3). 4. The rotor according to claim 3, wherein the longitudinal axis of the notch (5) makes an angle with the surface of the blade (2) such that that the motion transmitted to the moving product particles has an axial component according to the rotor (1) whose direction is concordant with the direction of the axial component of the spiral. 5. The rotor according to claim 3, wherein the longitudinal axis of the notch (5) makes an angle α with the surface of the blade (2) such that the motion transmitted to the moving product particles has an axial component according to the rotor (1) whose direction is opposite to the direction of the axial component of the spiral. 6. The rotor according to claim 4 or 5, wherein the angle varies between 10° and 80° or between 100° and 170°. 7. The rotor according to claim 3, wherein at least one blade (2) has one to ten notches (5) made in it. 8. The rotor according to claim 3, wherein the width and depth of the notch (5) range from one half to double the thickness of the blade (2) in which it is made. 9. A process for propelling food product particles in a food pulping and straining machine equipped with at least one rotor surrounded by a sieve, characterised in that the moving product particles are subjected to sudden changes of direction in such a way that they describe a broken spiral path consisting of relatively short, angled lines; these sudden changes of direction producing a rapid succession of impulses acting on the product particles which adhere to the walls of the sieve and which are therefore substantially stationary in such a way as to detach them from the sieve and to put them back into circulation together with the other moving product particles. 10. A pulping or straining machine for food products, characterised in that it comprises at least one rotor (1) according to any of the foregoing claims from 1 to 8 or in that it operates according to a process according to claim 9.

Inventors: BERTOCCHI PRIMO, BERTOCCHI, PRIMO
Applicants: BERTOCCHI PRIMO, BERTOCCHI, PRIMO
Application year: 2001
Main classification: A23L2
IPC codes: A23N1