Method for removing oil from metal chips and plant for removing oil from metal chips

Abstract

An oil-removal plant for removing oil from metal chips of non-ferrous materials comprises a container of such chips and a container for the recovered oil; the chips container cooperates with a magnetic field generator member, one of such container and said generator member being rotary so as to enable the generation of a rotary magnetic field which impacts and passes through the chips heating them, the oil evaporating from the chips and being subsequently condensed and recovered in then oil container. A method for removing oil from chips is also described and claimed herein.

Description

[0001] METHOD FOR REMOVING OIL FROM METAL CHIPS AND PLANT FOR REMOVING OIL FROM METAL CHIPS

[0002] The present invention relates to a method and a plant for removing oil from metal chips according to the introductory parts of the corresponding independent claims .

[0003] As known, chips are generated from the mechanical machining for the removal of chips of metal products , such as their turning, cutting, milling, drilling or the like . Such machining operations are carried out with a simultaneous conveying, at an operating area, a cutting fluid which can be water or oilbased and it may comprise light oils , heavy oils , water-based emulsions , etc . In the present document , such cutting fluid will simply be indicated with the term "oil" . Such oil is used as a lubricant as well as for reducing the heat and friction developed by the tools in such work area; due to this , the chips which are produced retain a percentage of oil which prevents the direct reuse thereof , for example in the foundry .

[0004] Such residual oil present on the chips must therefore be removed so as to enable the reuse, that is the recycling, of the metal material . To this end, currently there are known various methods and corresponding plants adapted to remove, although partially, the oil from the chips .

[0005] A first operating mode is the one that applies a washing of chips using water, heated to a temperature of about 80 ° , in which there are present detergents and / or solvents . Such method requires the use of large amount s of water which therefore need to be disposed periodically . The plant which carries out such washing is significantly large and it usually comprises at least one large cylindrical container driven in rotation around the longitudinal axis thereof . Alternatively, there are provided for one or more augers inside the container to move the chips .

[0006] The prior art method mentioned above reveal various drawbacks : first and foremost , it reveals the problem lying in the fact that the oil is always recovered only partially (while still requiring the use of specific sophisticated plants ) and the chips still retain at least a few percentage points of oil and water . Furthermore, there is the oil-water separation problem as well as the problem related to disposal of the washing water . As mentioned, the water contains significant amounts of oil (even with different density) , water-oil emulsions , solvents and / or detergents which cannot be disposed of in the environment because they are highly pollutant . The disposal must therefore be carried out very carefully and with significant cost .

[0007] Besides the above, there is high consumption of heated water with the entailed problems .

[0008] Furthermore, usually the companies which provide the washing plant do not provide the water treatment and disposal, same case applying to the oily waste disposal plants . Therefore, this waste must be stored, and this entails occupying further ( large ) spaces .

[0009] Lastly, the washed chips must be dried to eliminate moisture .

[0010] Another prior art method for cleaning the metal chips of oil residues provides for the use of ultrasounds : the metal material is immersed in a tank which contains a liquid, mainly water containing additives . Special piezoelectric transducers (or similar high frequency resonant generators ) emit ultrasounds which impact the chips and partially clear them of oil .

[0011] This prior art method also requires the use of dryers for drying the washed chips . Therefore, it reveals the same problems outlined above for the method for washing chips with regard to the disposal of water containing oil, additives and detergents . Another prior art method for removing oil from the chips relates to the use of centrifugation . This method uses a centrifuge which can also operate with a continuous cycle and it allows to obtain a centrifuged material with a moist residue (oil ) around 2% in the best case scenario . However, also with this method the residual oil content in the chips is such to entail problems when the chips are introduced into a melting furnace : as a matter of fact , the presence of oil may result in chemical alterations in the metal material and generate gas in the furnace, this gas should be suitably filtered before it is introduced into the atmosphere .

[0012] Furthermore, the centrifugation plants occupy vast areas given that the centrifuges are significantly large .

[0013] A further method used for removing oil from metal chips deriving from mechanical machining operations is the one that exploits pyrolysis which is implemented in a pyrolysis reactor with an advancement system comprising an auger which can be made of ceramic or stainless steel material . The problem relating to the use of this method relates to the large dimensions of the plant which also provides for, besides the pyrolysis reactor that is per se significantly large in size, other components for loading and unloading chips into and from the reactor which are also significantly large in size .

[0014] In the reactor there are generated gases which can be used in a burner and liquids , partly formed by hydrocarbons which can also be used in the burner . Furthermore, the latter must have a fumes treatment and abatement system which acts on such fumes before being released into the atmosphere .

[0015] However, the system is very expensive, it requires large amounts of energy for the operation thereof , it can treat small amounts of chips and it generates residues that are expensive and difficult to dispose of .

[0016] Other methods comprise the use of infrared rays to evaporate oil from the chips or the use of hot gases emitted by the melting furnace . In this case, the chips are impacted by such gases after they have been placed into a chamber (with funnel ) arranged above the furnace . After the oil has been at least partially evaporated (or after a pre-established dwelling time ) , the chips are mechanically pushed into the furnace and drop thereinto by gravity . This method does not guarantee a correct management of the temperature of the chips . Therefore, this temperature can cause alterations in the chemical composition of chips to an extent of jeopardising the metallurgic characteristics thereof .

[0017] In both cases , the prior art solutions do not consider the gases (oily fumes ) which are generated during the treatment . These fumes cannot be directly released into the atmosphere without a special treatment and filtering .

[0018] EP2862948A1 discloses a method for removing petroleum substances from materials contaminated by them; the method provides for refining the contaminated material by indirectly heating in a closed furnace to temperatures comprised between 250 and 750 ° C, the closed space of the furnace being washed by a protective gas atmosphere with a maximum oxygen content of 15% by volume . Subsequently, the mixture of gases and water vapour generated by the evaporation and by the decomposition of the petroleum substances present and of the liquids coming from contaminated material is removed from the closed space of the furnace and it is cooled and condensed .

[0019] During refining, the material contaminated with petroleum substances is mixed and after reaching the final heating temperature and after completing the refining process it is cooled through water atomisation .

[0020] During condensation, the non-condensed part of the gas and water vapour mixture is discharged for further processing and / or it is at least partially returned to the refining process as process gas .

[0021] There is also described an equipment consisting of a refining furnace provided with a heat source for indirectly heating the chamber of the furnace, with an inlet for loading the material contaminated by petroleum substances as well as a mouth for discharging material cleared of petroleum substances ; the furnace is provided with device for mixing the load, arranged in the chamber of the furnace as well as an inlet for supplying inert gas from a pressurised source .

[0022] There is provided for a pipe for discharging the gas and water vapour mixture, produced by the decomposition and evaporation of the charging fluids , directed to the condenser with branched outflow of the single condensate products .

[0023] GB635436A discloses a method for vacuum distillation comprising the rotation of an electrically conductive material vaporisation surface and on which there is placed the element to be distilled in a magnetic field generated by appropriate magnets and the use of Eddy currents generated in the vaporisation surface to increase temperature up to the distillation point . The magnets may be U-shaped and they may be adjustably approached to the rotary surface so as to control the heating effect or alternatively the magnets may be electromagnets and the current that passes through them may be varied to control the degree of heating .

[0024] The heating of said surface results in the evaporation of an element to be distilled which is collected by condensation on a surface overlying such surface and from which it drops into an annular collection channel from which it is extracted by a special discharge channel .

[0025] An object of the present invention is to provide a method and a plant for removing oil ("oil removal" ) from metal chips of non-ferrous materials coming from mechanical machining operations which are improved with respect to the prior art treatment methods and treatment plants aimed at such removal of oil from such chips .

[0026] In particular, an object of the invention is to provide a method for removing oil from metal chips which allows to remove at least almost all the oil present in and on such chips obtaining oily residues equal to or smaller than 0 . 4% of the initial oil content .

[0027] Another object is to provide a method of the type mentioned above whose implementation is environmental friendly and it does not produce elements to be dispose of or special waste, so as to define a closed system ( circular economy) . In particular, this method has the object of defining a part of a circular economy system which comprises the steps of producing by machining mechanical parts carried out using cutting oil, and the subsequent recovery of chips and therefore through the present method .

[0028] A further object is to provide a method for removing oil from metal chips which allows , at the end of the process , to reutilise such chips in a melting furnace without further prior treatments , such as for example drying and without the chips being subjected to metallurgic alterations such as for example oxidation .

[0029] Another object is to provide a plant for implementing the method mentioned above that is small and with reduced overall dimensions , but which is high-performing and which enables the recovery of the oil present on and in the chips ( light oils , heavy oils , water-based emulsions , etc . ) with purity such that said oil can be reutilised in a mechanical machining process .

[0030] Another object is to provide a plant of the type mentioned above that is cost-effective with respect to similar known plants .

[0031] A further object is to provide a plant of the type mentioned above which has high energy efficiency and whose operation can be fully automated in all its steps .

[0032] These and other objects which shall be more apparent to the person skilled in the art are attained by a method and a plant according to the corresponding attached independent claims .

[0033] For a better understanding of the present invention, the following drawings are attached hereto, purely by way of nonlimiting example, wherein : figure 1 shows a schematic view of a first embodiment of a plant according to the invention; figure 2 shows a perspective view of a part of the plant of figure 1 ; figure 3 shows a top view of the part of figure 2 ; figure 4 shows a cross-sectional view according to line 4-

[0034] 4 of figure 3 ; figure 5 shows a cross-sectional view according to line 5-

[0035] 5 of figure 4 ; figure 6 shows a cross-sectional view according to line 6-

[0036] 6 of figure 5 ; figure 7 shows a cross-sectional view according to line 7-

[0037] 7 of figure 3 ; figure 8 shows an enlarged view of the detail indicated with A in figure 7 ; figure 9 shows a portion of the part of plant of figure 2 ; figure 10 shows an enlarged view of a component of the portion of figure 9 ; figure 11 shows a sectional view according to line 11-11 of figure 10 ; figure 12 shows a top perspective view of a second embodiment of the part of plant according to the invention; figure 13 shows a cross-sectional view according to line 13-13 of figure 12 ; figure 14 shows a cross-sectional view according to line 14-14 of figure 13 ; figure 15 shows a cross-sectional view according to line

[0038] 15-15 of figure 14 ; figure 16 shows an enlarged view of a component of the plant of figure 12 ; figures 17 and 18 show in perspective view another component of the plant of figure 12 in various implementation steps of a method according to the invention; figure 19 shows a lateral schematic view of a third embodiment of a plant according to the invention; and figure 20 shows a perspective view of the part of plant of figure 19 .

[0039] With reference to the figures mentioned above, a first embodiment of an oil-removal plant for removing residual oil from and on metal chips is shown in the figures 1-11 . Such plant comprises a cylindrical container 1 adapted to contain metal chips coming from a mechanical machining of metal products . Such container 1 has a cylindrical body 12 ( for example see figure 4 ) , hollow in 13 , closed at the lower part by a movable and openable lower closing element 14 and at the upper part by a removable or openable lid 15 . The lid 15 is associated with a beam 16 ( see figure 2 ) to cooperate with a lifting member (not shown) whose actuation allows the opening or the closing of the cylindrical body 12 . Such cylindrical body is adapted to contain, in its cavity 13 , metal chips to be subjected to oil removal which are introduced into such cavity through the end of the cylindrical body 12 where the lid 15 is arranged .

[0040] The lower closing element 14 preferably and advantageously comprises an element 17 for connecting to a pipe 18 in turn connected to a reservoir 19 of inert gas , preferably nitrogen . Between the reservoir 19 and the cylindrical body 12 there is present a usual pressure reducer 20 and a usual solenoid valve with a check valve 9 .

[0041] In the advantageous embodiment of the described invention, the connection element 17 opens ( see figure 8 ) in a chamber 21 for the diffusion of inert gas (which will be solely indicated as nitrogen hereinafter) delimited by the closing element 14 and a bottom plate 22 ( shown, in particular, in figure 5 ) shaped like a concave plate and placed on the closing element 14 and fixed thereon . Between the bottom plate 22 and the closing element 14 there are present channels 24 for the diffusion of nitrogen in the chamber 21 which terminate in the proximity of the edges 25 of the bottom plate . Between these edges 25 and the closure 14 there is present a space through which the nitrogen may penetrate into the cavity 13 of the body 12 .

[0042] Such solution allows the inert gas to be evenly distributed in the mass of chips present in the cavity 13 .

[0043] Obviously, the invention may also not provide for the introduction of inert gas into the chamber 21 . The use of such gas is not compulsory : it only serves to decrease the possible oxidation of then chips so as to improve the yield and a subsequent melting operation in a foundry .

[0044] As particularly observable in figure 6, the cavity 13 (containing the metal chips ) is divided into a plurality of sections (at least two) 13A, 13B, 13C by partitions or fins 26 integrally joined with the (outer) wall 27 of the body 12 and with a longitudinal rod 30 present at the median longitudinal axis W of the body 12 . Such rod is made of ferrous or ferromagnetic material . It should be observed that each fin or partition 26 comprises a first part 26A made of non-ferrous materials ( for example stainless steel, copper or aluminium) , like the one that forms the body 12 , fixed using bolts 31 to a second part 26B of partition integrally joined ( for example by welded) with the longitudinal rod 30 ; like the latter, the second part of partition 26B is made of ferrous or ferromagnetic material .

[0045] The partitions or fins 26 terminate at a short distance from the lid 15 so as to define in proximity of the latter a chamber 34 ( in particular see figure 7 ) in which there opens a channel 35 provided for in the lid 15 . The chamber 34 is connected through the channel 35 with an outlet 35A of the gas present in the body 12 to which there is in turn connected a duct 36 on which there is arranged a check valve 37 and a bypass solenoid valve 38 . From this solenoid valve 38 there depart two conduits or ducts 39 e 40 : on the first duct 39 there is arranged a unidirectional solenoid valve 41 while on the second duct there is arranged a solenoid valve 40A and a vacuum pump 42 . The ducts 39 and 40 are reconnected in a T- connector 43 : therefore, the duct 39 defines a bypass conduit with respect to the duct 40 .

[0046] From the T-connector 43 there exit s a last duct or conduit 44 which terminates in an member for the condensation of oil and for the outflow of air 45 . Said member 45 comprises a body 46 which contains a ventilator 47 adapted to suction air and oil which, as will be described, is present in the duct or conduit 44 and direct it towards a f ilter / purif ier 48 inside the body 46 . The air is discharged outside the condensation member 45 , possibly after it has been further filtered by a filter 50 , from an outlet opening 51 of the body 46 .

[0047] The f ilter / purif ier 48 , per se known ( for example a filter membrane or, for example, a conical-shaped metal filter) , instead collects the oil present in the air suctioned by the conduit or duct 44 . The retained oil drops by gravity into a collection tray 52 arranged under the f ilter / purif ier 48 ; such tray is then connected using a duct 53 , schematically shown in figure 1 , to a tank 54 for recovering condensed oil .

[0048] Around the container 1 ( stationary) there is present a member 60 adapted to generate a rotary magnetic field which moves into the cavity 13 of the cylindrical body 12 and it closes on the rod 30 and on the second part 26B, made of ferromagnetic material, of the partitions or fins 26 .

[0049] Such magnetic field generator member 60 is defined, in the embodiment of figures 1-11 , by elements and means adapted to generate, by magnetic induction, a radial rotating magnetic field in the container 1 and into chips present in its cavity 13 , so as to generate in the latter Eddy or Foucault currents which cause the heating thereof up to a desired temperature, for example comprised between 200 ° C and 300 ° C . Such temperature is however sufficient to evaporate the oil present on and in the mass of metal chips arranged in the section 13A, B and C of such cavity . It should be observed that the presence of partitions or fins 26 prevents the chips from rotating in the cavity (driven in motion by the rotary magnetic field) . In this manner, due to the currents mentioned above, such chips only heat , without moving . Furthermore, the partitions are also useful to better propagate heat inside the container 1 and increase the thermal exchange surfaces . Lastly, the partitions also allow to excellently distribute the nitrogen introduced into the lower part of the container and which tends to rise upwards with respect thereto ( suctioned by the ventilator 47 ) .

[0050] The generated radial magnetic field allows to have an even heating of the chips present in the container 1 around which there are arranged the means or elements adapted to generate the rotary magnetic field .

[0051] More particularly, ( for example see figures 7 and 9 ) the magnetic field generator member 60 is adapted to removably contain the container 1 for the heating of chips without such container being subjected to any movement when such member 60 is active for heating, by magnetic induction, the chips mentioned above . Therefore, after a settling step, also the latter are in a substantially fixed and stationary position in the member 60 during the heating thereof .

[0052] The magnetic field generator member 60 which we may also define as "heating member 60" , comprises one or more ( like in the example ) hearing sections 65 , defining the means or elements generating the rotary magnetic field, having coaxial (or annular) electric brushless motors 250 ( see figures 10 and 11 ) , per se known (and which will be described subsequently) . Therefore, each section 65 has a coaxial annular conformation and it is superimposed and / or connected ( see figures 2 , 4 , 5 , 7 and 9 ) with other sections and it therefore delimits a central hole 66 adapted to act as a seat or compartment for the container 1 . Such seat may have vertical ( like in the figures ) or horizontal axis with respect to a plane P on which the member 60-container 1 assembly rests when the chips are subject to heating by magnetic induction . As will be described below, in each of such sections 65 and in the corresponding motor 250 there is provided for an annular rotor carrying permanent magnets in the proximity of which there is inserted the container 1 .

[0053] In the example of the figures ( see figure 9, particularly) , various heating sections 65 are superimposed axially to each other, each section having an annular motor 250 thereof ; the entirety forms the member 60 in which the container 1 is arranged . In said member, the various heating sections are maintained connected by connection plates (not shown) arranged on the sides of each section 65 . Therefore, the member 60 takes a solid form (parallelepiped, cube or cylinder shaped as a function of the number of present sections 65 and the outer shape thereof ) whose upper face is open and delimited by the section arranged at the top part of the stack of sections 65 defining such member 60 . With reference to the figures 9-11 , each heating section 65 comprises an outer containment body 68 that is annularshaped and having a central hole 69 . The corresponding electric motor 250 is positioned in such hole . The motor 250 comprises a stator 70 and an inner rotor with permanent magnets 71 . The stator 70 is electrically powered through connectors 72 projecting from the containment body 30 . In the latter, around the stator 70 there is present a cooling circuit (of then type with water, glycol or any other fluid) supplied through pipes connected to connections 73 present in the body 68 .

[0054] In the motor 250 there is positioned an annular rotor 74 (which is cylindrical in the embodiment of the figures ) defined, in the embodiment of the figures , by at least one annular body 75 containing an annular cylindrical member 75A with an axial hole and carrying a plurality of permanent magnets 76 whose arrangement defines seats 77 that can be conveniently used as channels for cooling the magnets applied to the annular body 75 . Obviously, the body 75 and the member 75A may be a single element .

[0055] The body or annular magnetic rotor 74 rests on bearing members 79 interposed between the permanent magnet rotor 71 and hollow portions 80 provided for in the annular body 75 near its opposite ends ( see figure 11 ) .

[0056] Lastly, each section 65 comprises end lids for closing the bearings 81 and corresponding end magnetic flanges 82 adapted to close the magnetic field of the magnets (and maintain it in the group of the magnets 76 ) .

[0057] However, it should be observed that the motors 250 used are of the ring-like coaxial type disclosed, and advantageously they are of the three-phase synchronised type provided with a number of poles and windings necessary for optimising torque and having the required power . Such motors have a high performance at above 95% . They are " sensorless" i . e . they are not provided with transducers for positioning the rotor and for the motor revolutions . Thanks to a calculation algorithm, a control unit of the plant which controls the operation of the member 60 provides the synchronisation of all motors 250 present in such member and their correct variation in the number of revolutions as a function of the temperature distribution requirement desired in the chips arranged in the container 1 .

[0058] Preferably, the motors 250 of the adjacent and consecutive heating sections are power-supplied so that the relevant annular rotors 74 rotates in a counterclockwise direction so as to reduce the torsional torque acting on the container 1 .

[0059] The temperature of the chips is detected by pin temperature sensors 87 inserted into the sections ( 13A, B, C) of the cavity 13 of the container 1 and they allow to detect the temperature achieved by the chips so as to be able to control and maintain it at optimal values so as to have the evaporation of the oil present on and in the ships , without the chips changing their metallurgic properties or melting, allowing the full evaporation of the oil .

[0060] The temperature sensors are arranged at different heights and depths in the mass pf chips . This allows a widespread and better control of the temperature in each area of such mass of the chips . Such sensors may be arranged parallel to the axis W or perpendicularly to such axis .

[0061] Obviously, such temperature depends on the type of oil that is present in the or on the chips and on the type of chips introduced container 1 . However, an optimal temperature is generally comprised between 200 ° C and 340 ° C .

[0062] The magnetic induction heating member 60 has a high performance . As a matter of fact , the magnets used (Neodymium, Iron, Boron, NdFeB) by their nature do not require magnetisation currents . According to a variant , the rotary magnetic field generating member 60 may comprise electrical coils wound with iron cores , which generate such field by electromagnetic induction, instead of permanent magnets .

[0063] The use of the plant 1 and therefore the implementation of the method according to the invention begins with the insertion of the chips within sections 13A, 13B, 13C of cavity 13 of the container 1 after opening the lid 15 thereof . After closing the latter, the vacuum pump 42 is activated to create a vacuum within the container 1 . The sealing is provided by gaskets located on the lid 15 . The air is removed from the container 1 , passes through conduit 40 and it is e jected from the condensation member 45 .

[0064] After stopping the pump mentioned above, according to the embodiment described and shown in the figures , the solenoid valve 9 is opened and nitrogen can be introduced into the container through the connection element 17 . The nitrogen substantially evenly spreads in sections 13A-C of the cavity 13 due to the shape of the gas diffusion chamber 21 present between closure 14 of the container 1 and bottom plate 22 and the shape of the latter .

[0065] Therefore, the nitrogen spreads evenly between the chips ; such gas advantageously has the function of avoiding the presence of oxygen in the container 1 and the possible oxidation of the chips which would alter their metallurgical characteristics .

[0066] When introducing nitrogen into container 1 , the rotary magnetic field generator member 60 is activated : in the case of the embodiment shown in figures and described above, each motor 250 of the heating sections 65 is activated . This results in the rotation of the annular rotor 74 carrying the permanent magnets 76 ( in a fixed position on the rotor) in a known manner . Such magnets generate a rotary field in the container 1 through the chips , said rotary field, thus creating Eddy or Foucault currents in the chips which, blocked in the cavity 13 , heat up . This leads to the evaporation of the oil associated with the chips , which is collected in chamber 34 of container 1 in vaporised form ( see figure 7 ) .

[0067] Nitrogen is therefore still introduced into container 1 during the heating of the chips described above . This advantageously still in order to avoid the oxidation of the chips . The flow of nitrogen is interrupted after the cycle has been completed and only after the cooling of the chips (that is when they substantially reach a temperature below which the possibility of oxidation ends ) .

[0068] The plant control unit continuously evaluates the temperature within the sections 13A-C inside the container 1 (through the pin sensors 87 ) ; when it has reached a pre- established value ( for example 250 ° C) , such control unit acts on the member 60 , which enters an operating mode to maintain the temperature at a pre-established value for a predefined period of time (determined experimentally) , required at least for the acceptable evaporation of the oil .

[0069] During the entire heating cycle, the by-pass valve 38 opens the connection between container 1 and by-pass conduit 39, and the valve 37 (which opens automatically with the nitrogen pressure and the vacuum created in duct 39 and in the duct 36 directed to the oil condensation member and air outlet ) being open, the oil vapour along with the nitrogen is removed from such container .

[0070] These vapours (and nitrogen) are suctioned by the ventilator 47 into the condensation member 45 into the body 46 of the latter . While the nitrogen is e jected from outlet opening 51 , the oil is trapped by f ilter / purif ier 48 , it condenses thereon and drops by gravity into collecting tray 52 and therefore into tank 54 where it is recovered . Thanks to the oil-removal plant 1 , the oil present in and on the chips can be recovered up to obtaining a residue of less than 0 . 4% of the initial value . In addition, laboratorytests have shown that the recovered oil has purity characteristics that allow it to be reused mixed with first- use oil in mechanical machining operations .

[0071] The chips from which the oil has been removed, instead, are discharged from the container 1 following the opening of the closing element 14 and / or the tipping of the container .

[0072] Substantially, such chips are completely free of oil and they can be directly introduced into a melting furnace without risking the generation of harmful gases from the metal bath or altering the composition of the metal in liquid phase .

[0073] Lastly, the plant 1 is small in size, while having significantly high hourly output . By way of example, the container measures 1000 mm in diameter, 1500 mm in height , has a volume of about 1 m3which is equivalent to a mass of bronze chips weighing about 1500 Kg, and the entire plant occupies an area of about 20-25 m2.

[0074] Lastly, the entire operating cycle is fully automated in all its operating sequences .

[0075] The solution of figures 1-11 shows a plant comprising a chips container 1 around which there is arranged a rotary magnetic field generator member 60 . In other words , such magnetic field is generated outside the container .

[0076] Figures 12-18 show different embodiments of the implant construction according to the invention in which the magnetic field generator member 60 is inside the container 1 , and it is arranged along the median longitudinal axis K of the latter . As a matter of fact , in said figures 12-18 , where parts corresponding to those of figures 1-11 are indicated using the same reference numerals , the container 1 has a toroidal shape and it comprises a hollow central area 100 in which the rotary magnetic field generator member 60 is inserted .

[0077] More particularly, the container 1 comprises a central, preferably circular, wall 101 which delimits the hollow central area 100 ; between the outer wall 27 of the container 1 and its central circular wall there are present the partitions / fins 26 ( four in the example ) . Such partitions / f ins 26 define four sections , indicated with 13A, 13B, 13C, and 13D in the drawings , in which the cavity 13 is partitioned .

[0078] In order to have the penetration of the magnetic field in such cavity 13 and an optimal " closure" of such field, the central wall 101 and a first portion of each partition 26 (obtained like the partitions or fins 26 of the figures relating to the first embodiment of the invention) are made of non-f erromagnetic material ( for example stainless steel ) ; in contrast , the outer wall 27 and a second portion of each partition 26 connected to such outer wall 27 are made of ferromagnetic material .

[0079] With reference to figures 12-18 , it should be observed that the member 60 comprises a cylindrical body 105 on whose outer wall 106 there is arranged a plurality of permanent magnets 76 . Such cylindrical body 105 is integrally joined in any known manner with a rotary shaft 107 on bearings 108 within a base 109 which removably supports the container 1 . The latter is arranged in a cage 110 which contains such container and which guides it when the container is inserted above the cylindrical body 105 , or when removed therefrom, as will be described .

[0080] In the embodiment in question, each section 13A-D autonomously receives nitrogen from the corresponding reservoir (not shown) and from each section air and nitrogen are removed through pipes connected in 112 to the container 1 and connections to the duct 36 ( see figure 12 ) . Furthermore, the container 1 has lateral arms 113 orthogonal to the wall 27 that allow to move the container 1 ( for example by means of a lifting member) with respect to cage 110 so as to load it with and unload it from the chips .

[0081] The loading-unloading operation is carried out using a support 115 ( figures 17-18 ) with which the container 1 is associated so as to rotate around an axis X connecting the lateral arms 113 when they are supported by uprights 116 of such support .

[0082] Thanks to the support 115 , the container 1 can be loaded with chips through a hopper body 15 (which is removed during such loading step) ; this is shown in figure 17 . Through the hopper body 117 , the body 1 can be discharged from the oil- free chips by rotating it on the uprights 116 ( see figure 18 ) .

[0083] Returning to the magnetic field generator member, the shaft 107 is associated with a gear train 120 driven by a transmission member ( for example a belt or chain, not shown) in turn cooperating with a gear train 121 splined to an output shaft 122 of an electric motor 123 arranged on the base 108 next to the cage 110 for container 1 . In this manner, the actuation of electric motor 123 leads to the rotation, around the axis K, of the cylindrical body 105 in the (toroidal ) container 1 and to the generation of the rotary magnetic field inside said container 1 .

[0084] In an alternative embodiment , on the shaft 107 there may be splined the rotor 71 of a coaxial electric motor 250 similar to the one described in relation to figures 9-11 . Such variant is schematically shown in figure 15 .

[0085] According to a further embodiment , the cylindrical support 105 is fixed and the toroidal container 1 rotates around the axis K .

[0086] In figures 19 and 20 , where parts equal to those in the figures described above are indicated using the same reference numerals , the ( fixed) container 1 is supported in any known manner by the base 109 and it is arranged above a rotary table 200 , driven by an electric motor 201 through a transmission element 202 . Obviously, the table 200 can be driven in rotation in other per se known ways .

[0087] The table 200 carrying a plurality of permanent magnets 76 arranged between said table and the container 1 . The assembly forms the magnetic field generator or heating member 60 .

[0088] In this manner, the rotary magnetic field (generated by the rotation of the magnets carried by the rotary table 200 ) is relatively present between said rotary member 60 and the chips in the fixed container; this allows to create Eddy currents that heat the chips to evaporate the oil .

[0089] Also in this case, in a known manner, there is provided for the introduction of nitrogen into the container 1 before and during the heating of the chips (through a pipe 18 ) and the removal of oil vapours for the subsequent condensation (through a conduit or duct 36 ) .

[0090] In a variant of the present embodiment , the rotary magnetic field is generated above the container 1 by a rotary table arranged above the container and carrying magnets arranged between the table and the container .

[0091] The solutions described herein in relation to figures 19 and 20 therefore regard the generation of a rotary magnetic field at an upper or lower end ( as in figures 19 and 20 ) of the container 1 .

[0092] Therefore, the invention comprises magnetic field generator means (permanent magnets , rotating around an axis , fixed electromagnetic coils or windings in which current circulates ) which impacts the metal chips (nickel, cupronickel, magnesium, bronze, aluminium, etc . that is nonferrous materials and / or alloys ) . In general, between the heating member 60 and the container 1 there is generated a relative movement so that the chips present in the container 1 are immersed in a rotary magnetic field ( relatively to the chips ) . As described , this can be achieved through a movement of the permanent magnets of the magnetic field generator or heating member and holding the container 1 stationary (which we will refer to as "movable heating member and fixed container" , preferred solution) , or by rotating the enclosure 1 with respect to the permanent magnets of the magnetic field generator or heating member 60 (which we will refer to as " fixed heating member and rotary container" ) .

[0093] The rotary magnetic field thus generated between the movable heating member and the fixed content passes through the chips and allows in a short time to heat the chips by means of the induced currents circulating in the latter . Such heating is controlled by means of temperature sensors 87 .

[0094] At the end of the operation according to the method described, the oil associated with the chips is removed and recovered through the oil condensation member and air outlet described above .

[0095] This with a small plant with an equally low energy consumption but with a high output . The plant enables treatment of chips with high hourly output .

[0096] Various embodiments of the invention have been described . However, even other variants may be provided within the scope of protection of the invention having the characteristics defined by the claims that follow .

Claims

CLAIMS1. Method for removing oil from metal chips coming from mechanical machining operations, said chips being arranged in a container (1) , characterised in that it is provided for to generate a magnetic field which impacts and passes through said chips, generate a relative movement between the magnetic field and the chips so as to heat the latter, said heating leading to the evaporation of the oil in the container (1) , and the subsequent removal of the oil from the container, said oil being condensed and collected in a recovery tank (54) , the oil-free chips being therefore removed from the container (1) .

2. Method according to claim 1, characterised in that it is provided for that the magnetic field be generated in a rotary manner and the chips be arranged in the container (1) which is kept fixed.

3. Method according to claim 1, characterised in that the magnetic field is static, the container (1) being driven in rotation in the magnetic field.

4. Method according to claim 2 or 3, characterised in that the magnetic field is generated outside the container (1) .

5. Method according to claim 4 characterised in that the magnetic field is alternatively generated around the container (1) or at an end part thereof, such as the lower or upper end part of such container (1) .

6. Method according to claim 2 or 3, characterised in that the magnetic field is generated by a position inside the container .

7. Method according to claim 1, characterised in that it is provided for to create a negative pressure or vacuum in the container (1) and subsequently introduce an inert gas, such as nitrogen, inside the container (1) prior to generating the magnetic field.

8. Method according to claim 7, characterised in that thenitrogen is introduced into the container ( 1 ) even during the period for heating the chips and until the end of the cooling of the chips .9 . Method according to claim 1 , characterised in that there is provided for controlling the temperature inside the container ( 1 ) during the generation of the magnetic field, the latter being interrupted or modulated when the temperature reaches a pre-established value so as not to exceed such value and keep the temperature constant for a predefined period of time .10 . Method according to claim 1 , characterised in that there is provided for preventing the movement of the chips subjected to the magnetic field around a longitudinal axis (W) of the container ( 1 ) .11 . Plant for removing oil from metal chips coming from mechanical machining operations , said chips being arranged in a container ( 1 ) , the plant comprising a magnetic field generator member ( 60 ) arranged at said chips container, between said container ( 1 ) and the generated magnetic field there being provided for a relative movement , the chips in the container being passed through by the magnetic field and heating when such magnetic field is generated so that the oil associated with said chips evaporates , characterised in that there is provided for a device ( 47 ) for removing the oil vapour created in the container ( 1 ) and for sending it into a condensation member ( 45 ) adapted to condense such oil vapour, a tank for recovering the condensed oil ( 54 ) being connected to such condensation member ( 45 ) and receiving and retaining the condensed oil, the container ( 1 ) comprising an internal cavity ( 13 ) wherein there are present at least two partitions ( 26 ) adapted to partition such internal cavity into at least two sections ( 13A, 13B, 13C, 13D) adapted to stably contain the metal chips introduced into the magnetic field, the partitions(26) preventing a movement of the chips placed in said container around a longitudinal axis (W) of the container, a movement generated by the rotary magnetic field.

12. Plant according to claim 11, characterised in that each partition (26) comprises a first and a second part (26A, 26B) connected to each other and made of different materials having different behaviour if immersed in a magnetic field, such first and second part (26A, 26B) being respectively connected to an outer wall (27) of the cylindrical body (12) of the container and to a part (30, 100) arranged along the longitudinal axis (W) of such cylindrical body and therein.

13. Plant according to claim 11, characterised in that the magnetic field generator member (60) comprises permanent magnets or alternatively electrical windings for generating such magnetic field by electromagnetic induction.

14. Plant according to claim 11, characterised in that the magnetic field generator member (60) is alternatively arranged outside the container (1) in which there are arranged the chips or inside such container (1) .

15. Plant according to claim 14, characterised in that the container (1) comprises a cylindrical body (12) , the magnetic field generator member (60) comprising at least one annular section (65) having an annular coaxial electric motor (250) arranged around the cylindrical body (12) of the container, in said annular coaxial electric motor (250) there being arranged an annular rotor (74) having an annular body (75) carrying a plurality of permanent magnets (76) , said annular rotor (74) being driven in rotation around the container (1) by the actuation of the annular coaxial electric motor (250) and generating, through the permanent magnets (76) , a rotary magnetic field in which there are immersed the cylinder (1) , which is kept fixed, and the chips inserted thereinto.

16. Plant according to claim 14, characterised in that thecontainer (1) comprises a toroidal-shaped body having a central wall (101) delimiting a hollow central area (100) within which there is present the magnetic field generator member (60) , such member (60) comprising a cylindrical body (105) , on whose an outer wall (106) there is arranged a plurality of permanent magnets (76) , said cylindrical body (105) alternatively being driven in rotation within the hollow central area (100) of the container or said container being driven in rotation around said central support (105) carrying the permanent magnets (76) .

17. Plant according to claim 14, characterised in that the container (1) is alternatively arranged above or below the magnetic field generator member (60) , between the container and said member there being provided for a relative movement.18 Plant according to claims 12 and 15, characterised in that the outer wall (27) of the cylindrical body (12) arranged within the magnetic field generator member (60) and the first part (26A) of each partition (26) are made of non-f erromagnetic material, the part (30) arranged along the longitudinal axis (W) and the second part (26B) of each partition (26) being made of ferromagnetic material, such part (30) arranged along the longitudinal axis (W) being a rod-like body.

19. Plant according to claim 12, characterised in that the part (100) arranged along the longitudinal axis (W) of the cylindrical body (12) of the container (1) is the hollow central area (100) of the toroidal-shaped container (1) , the second part (26B) or each partition (26) being integrally joined with the central part (101) of said container delimiting said hollow central area (100) in which there is arranged the magnetic field generator member, such second part (26B) of the partition and said central part (101) being made of nonferromagnetic material while the first part (26A) of each portion (26) and the outer part (27) of the container being made of ferromagnetic material.

20. Plant according to claim 11, characterised in that it comprises a reservoir (19) of inert gas, such as nitrogen, connected to the container (1) in which there are arranged the metal chips, a vacuum pump (42) adapted to create a negative pressure in the container prior to generating the magnetic field being connected to said container, said inert gas being evenly distributed in the metal chips.

21. Plant according to the preceding claims, characterised in that it comprises at least one of the following characteristics :- temperature sensors (87) are provided for in the container (1) of the metal chips, said temperature sensors being arranged at different heights and depths in the metal chips;- the device (47) for removing oil vapour comprises an aspirator connected to the container (1) through a duct, said duct being connected to a conduit (40) on which there is present the vacuum pump (42) and with a bypass conduit (39) of such conduit (40) on which the pump is arranged;- the magnetic field generator member (60) comprises permanent magnets, coils or electrical windings for generating such field by electromagnetic induction.

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