Device and process for separating impurities from textile fibres in pneumatic transport lines

Abstract: Device and process for separating impurities from textile fibres in horizontal pneumatic transport conditions which comprises a hollow parallelpiped separator (3) of rectangular cross-section for the passage of the fluids (4) which pass through it, such passage section being sub-divided into an upper part (Y) for the cleaned fluid and a lower part (X) for the separation of the heavy foreign materials in a hopper (30) intercepted by an extractor with seal (31), this sub-division is regulated by a deflector knife (21) which induces an S-shaped motion of the transport fluid and separates the heavy foreign materials by centrifugal effect.

Description: The invention relates to processing in the blow room machines the raw fibres to be prepared for supply to carding, in which the fibrous material in flake form is opened in the form of a single fibre by preparing a sliver of substantially parallelized fibres, from which the majority of the impurities and contamination has been removed, for sending to the subsequent processing stages. On the basis of the baled fibrous material these processings are connected together by pneumatic transport lines in which a stream of transport air lifts the fibrous material in more or less coarse flakes together with its content of impurities, contamination, short fibres, metallic and non-metallic materials and so on and moves them between the various bins which supply the individual machines. In the prior art (see GB-A-2 260 145) the reduction and separation of the content of such impurities from the fibres substantially takes place in the course of the processing in the so-called blow room machines, such as collectors, blenders, openers. In these items of equipment, by centrifugal effect, suction openings, separator knives and separation grilles, these foreign materials are gradually removed from the fibres in flake form. More specifically the present invention relates to a device for separating impurities from textile fibres in pneumatic transport conditions, and preferably to be inserted into the horizontal pneumatic transport lines which connect the processing machines. In its most general aspects the present invention makes use of the fact that such impurities to be removed exhibit the property of a lower lifting effect on the part of the transport fluid, both because of their density which is greater than that of the fibres and because of their shape: they thus tend to undergo a grading action by settling towards the bottom, particularly in the absence of significant turbulence. The phenomenon is known, for example, that in the horizontal sections of the pipes of circular cross-section which are normally used in the pneumatic transport units for the fibres being processed, because of the lower lifting effect the heavy foreign material moves onto the bottom of such pipes and concentrates predominantly in a lower zone of much reduced cross-section, generally delimited by a chord of the transverse cross-section of length of 40-50% of the diameter of the circular duct. The present invention relates more particularly to a system for separating such heavy foreign material constituted by metallic and non-metallic parts and contamination to be inserted into the pipes of pneumatic transport ducts which connect the various stages of the processing of the fibres in flake form. The system according to the invention is directed towards the overall improvement of such processing; it consists of a device which is defined, in respect of its essential characteristics, in the first claim and, in respect of its preferred embodiments, in the claims which depend thereon, and of a process which is defined, in respect of its essential characteristics, in the seventh claim and, in respect of its preferred embodiments, in the claims which depend thereon. To illustrate the characteristics and advantages of the present invention more clearly it will be described with reference to a typical embodiment shown in Figs. 1 to 3, by way of non-exhaustive example. Figure 1 shows a general side view of the separation device. Figure 2 shows the detail of the interception rack and a sectional view of the separator body according to II-II. Figure 3 shows the enlarged zone of the movable knife 21 where the deflection of the flow takes place with separation of the particles of foreign material by fluid dynamics. In the embodiments of the said illustrations the separator according to the invention comprises a connection 1 which connects the pipe of circular cross-section to a duct 2 of equivalent rectangular cross-section: this shape in fact aids the said phenomenon of grading the particles of lower lift with respect to the fibres in flake form. The duct 2 is connected to the body of the separator 3 which in its turn discharges the stream of transport air 4 from the opening 5 towards the rectangular duct 6 which continues transport towards the machine downstream. The body of the separator 3 comprises a hollow containment parallelepiped 10 of rectangular cross-section consistent with the ducts 2 and 6, in which the lower wall 11 is fulcrum-mounted at a pin 12 and is movable so as to be able to regulate the passage area available for the flows of the fluids which pass through the separator 3 with horizontal direction. The angular position of the wall 11 is fixed as a function of the desired adjustment with per se known means, for example with one or more slots 13 and fixing screws 14, moving it according to arrow a), and nonetheless ensuring the tightness of the adjacent lateral walls of the separator. The flow of the transport fluid 4 is directed from left to right and encounters a rack 15 fulcrum-mounted at a fulcrum 16 at the upper wall 17. The details of the rack are shown in Fig. 2 and it consists, for example, of a transverse bar 18 which contains the pin on which the rack is fulcrum-mounted and has a set of parallel and rounded bars 19 which extend towards the bottom so as partially to intercept the passage of the fluid 4 in the body of the separator, for the entire opening of the passage section and particularly in its upper section. The angular position of the rack 15 is fixed as a function of the desired adjustment with per se known means, moving it according to arrow b). In its right hand part the passage section of the hollow parallelepiped 10 of the separator 3 is sub-divided into two parts. The upper part is intended for the transport fluid which continues towards the right, while the lower part is intended for the separation of the foreign materials. The sub-division of the section of the separator is effected with the wall 20 substantially parallel to the upper wall 17 of the parallelepiped 10 and located slightly higher with respect to the lower movable wall 11. At its left hand end is located a movable deflector knife 21 fulcrum-mounted at a pin 22 and which extends for the entire opening of the passage of the fibres inside the parallelpiped 10. The angular position of the knife 21 is fixed as a function of the desired adjustment with per se known means, for example with slot 23 and fixing screws 24, moving it according to arrow c). The movable knife 21 thus sub-divides the height available for the passage of the fluid into two parts: an upper part of height y and a lower part of height x. The values of the heights x and y are adjusted, both in terms of value and in relation to each other, by the adjustments of the positions of the movable wall 11 and of the movable knife 21. The lower section of the passage of height x emerges into a hopper 30 to collect the separated material. The bottom of this hopper is intercepted by an extractor with seal 31, such as a rotary extractor constituted by a rotary body 32. Such rotary body comprises a plurality of vanes 33 equipped with flexible seal membranes 34 which slide against a containment surface 35, which discharge to the outside the solid separated material from the spaces formed between the said vanes 33 but do not allow the flow of the transport air to escape. The extractor rotates at low speed, of the order of magnitude of one revolution per minute. The upper section of the passage of height y is not intercepted and faces instead towards the outlet opening 5 and is intended for the transport flow of the fibres in flake form from which the foreign material has been removed. The process for separating foreign material proceeds as follows, particularly with reference to the enlarged detail of Fig. 3. The transport flow in the duct 2 and in the parallelepiped body 10 concentrates and contains the heavier impurities in its lower part, together with a significant quantity of fibres in flake form which should not, however, be discharged. This grading, or settling, effect of the solids in pneumatic transport phase is intensified by the flattened rectangular cross-section of the duct 2 and of the body 10. The mechanism of the separation between fibres in flake form and foreign material takes place chiefly by effect of the knife 21. This creates an obstacle to the advance of the mixed phase of fibres and impurities which tends to enter into the lower passage and thence into the hopper 30. This advance is obstructed by the fact that the opening 5 is free and permits the outflow of the transport air, while the hopper 30 is blocked by the rotary shutter 31; a pressure differential thus establishes between the two spaces. Through the effect of this obstruction the flow of the transport air which lifts the fibres in flake form and the foreign material finds no outlet and is returned towards the upper passage and the opening 5 which is free instead. The S-shaped course of the flow 35 shown in Fig. 3, which compels the air to make two changes of direction substantially of 180°, with a circular motion according to a diameter of the order of the distance x, is obtained in this way. This sudden deflection generates a significant centrifugal force on the material transported, producing a separation effect as a function of the weight and shape of the particles transported, and of the velocity of the said fluid. The particles of separated foreign material are denoted by the dots 36 which separate from the main flow 35 according to trajectories 37, as shown. This separation takes place by effect of the fact that at the changes of direction the heavier part, or that which requires a greater lifting effect, detaches from the transport flow and enters the hopper 30. In contrast, the lighter part, or the fibres in flake form which require less lift, succeeds in following the flow deflected according to the S-shaped course and follows the stream of transport air towards the opening 5 and the duct 6. This cleaning effect also extends to the contamination entangled in the flakes of fibres which is significantly detached from the flakes in the course of the sudden deflection of the motion and thrust towards the opening of height x. To extend the separation effect to the entire mass of fibres transported in the separator 3, a preferred embodiment of the invention provides the use of the rack 15 hinged at 16. This rack constitutes an element of preferential deflection towards the knife 21 of the fibres in flake form transported pneumatically by the flow 4. In the course of this deflection the detachment of the foreign particles from the flakes of fibre is also promoted. This rack is lowered to intercept with the bars 19 the passage of the fibres towards the upper part of the parallelpiped body 10 according to the passage of height y. This deflects the majority of the fibrous material towards the knife 21 but, to insert it between the bars 19, it does not interrupt the flow of the air and does not significantly interfere with the flow regime and the effect of grading the impurities towards the bottom. Generally speaking the rack 15 is adjusted with the rotation according to arrow b) so that its bars 19 affect a part variable between 25 and 70% of the height x+y of the section available for the passage of the transport fluid. The foreign material separation effect is also regulated on the basis of the requirement to transport the fibrous material efficiently in line and not to lose significant quantities of valuable fibres, by choosing an effective compromise which takes account of these requirements. To this end the distances x and y, and their ratio x/y, are determined with the angular positions of the wall 11 and the knife 21. With the adjustment of the angular position of the lower wall 11, the height x+y which is available overall for the transit of the flow of transport fluid is also regulated and the fluid dynamics conditions in the separator 3 are also influenced. Both the height x and the residual height y, and the ratio x/y, are regulated with the adjustment of the angular position of the knife 21. The adjustment of the rack 15 enables the flakes of fibres which are travelling in the highest part of the station to be carried towards the bottom: still in general terms, this adjustment is made on the basis of the impurities and contamination content of these fibres. If the spontaneous grading of the foreign material in the duct 2 upstream proves already to be sufficient, the requirement to lower the rack to deflect the fibres is less. In general terms, for the separators to be inserted into the transport lines between the blow room machines of normal capacity, the value of the height x is adjusted between 10 and 70 mm, and preferably between 20 and 50 mm. The values of the ratio x/y are kept in the range 0.25-0.70, and preferably between 0.3 and 0.5. Still in general terms, a higher value of x enables a larger quantity of impurities to be caught in the hopper 30 but less selectivity: this would also involve losing a larger quantity of fibres in flake form. If valuable fibres are being processed, the material discharged with the shutter 31 should then be handled to recover the lost fibres. With high values of x the flow 35 thus has less abrupt deflections and a gentler course, the separation is greater but less selective. Substantial advantages are obtained with the device according to the present invention, at least the following of which are worthy of mention. The device is capable of performing a significant cleaning of the flakes of fibre during the pneumatic transport thereof such as to safeguard and mitigate the task of the blow room machines and the lickers-in of the carders and affords them a greater service factor, because of the lower maintenance required to clean and repair the clothings, knives, openings and filters. The device and the process for cleaning in line are easily adjustable and adaptable to the different batches of fibre which are brought for processing.

Claims: Device for separating impurities from textile fibres in conditions of pneumatic transport, to be inserted into the horizontal transport lines (2, 6) which connect the machines for processing fibres in flake form, which comprises a separator body (3), which comprises a hollow containment parallelepiped (10) of rectangular cross-section consistent with the ducts (2, 6), characterized in that the lower wall (11) is movable to regulate the area of the section available for the passage of the fluids which pass through the separator (3) with horizontal direction and in that this passage section of the hollow parallelepiped (10) of the separator (3) is sub-divided into an upper part of height (y) for the cleaned transport fluid which continues towards the right and into a lower part of height (x) intended for the separation of the foreign materials in a hopper (30) to collect the separated material, which hopper is intercepted by an extractor with seal (31), this sub-division being regulated by means of a movable deflector knife (21) which extends for the entire opening of the passage of the fibres inside the parallelepiped (10) mounted on a wall (20) of the separator (3). Device for separating impurities from textile fibres in conditions of pneumatic transport according to Claim 1, characterized in that the angular position of the wall (11) is adjusted by moving it according to arrow a), ensuring the tightness of the adjacent lateral walls of the separator (3). Device for separating impurities from textile fibres in conditions of pneumatic transport according to Claim 1, characterized in that the movable knife (21) is fulcrum-mounted at a pin (22) and its angular position is adjusted according to arrow c). Device for separating impurities from textile fibres in conditions of pneumatic transport according to Claim 1, characterized in that the extractor with seal (31) is a rotary extractor constituted by a rotary body (32) comprising a plurality of vanes (33) equipped with flexible seal membranes (34) which slide against a containment surface (35), which discharge to the outside the solid separated material from the spaces formed between the said vanes (33). Device for separating impurities from textile fibres in conditions of pneumatic transport according to Claim 1, characterized in that the separator (3) comprises a rack (15) fulcrum-mounted at a fulcrum (16) at the upper wall (17) and consisting of a series of bars (19) which extend partially to intercept the passage of the fluid (4) in the separator body (3), particularly in the upper section thereof. Device for separating impurities from textile fibres in conditions of pneumatic transport according to Claim 5, characterized in that the angular position of the rack (15) is adjustable according to arrow b). Device for separating impurities from textile fibres in conditions of pneumatic transport according to one or more of the preceding Claims, characterized in that the value of the height (x) is adjusted between 10 and 70 mm, and preferably between 20 and 50 mm. Device for separating impurities from textile fibres in conditions of pneumatic transport according to Claim 7, characterized in that the values of the ratio (x/y) are kept in the range 0.25-0.70, and preferably between 0.3 and 0.5. Device for separating impurities from textile fibres in conditions of pneumatic transport according to Claim 7, characterized in that the rack (15) is adjusted to affect with its bars (19) a part variable between 25 and 70% of the height (x+y) of the passage section of the transport fluid of the separator (3).

Inventors: MASCHERETTI MARIO, PASINI GIOVANNI BATTISTA, MASCHERETTI, MARIO, PASINI, GIOVANNI BATTISTA
Applicants: MARZOLI SPA, MARZOLI S.P.A.
Application year: 1999
Main classification: D01G23
IPC codes: D01G23, D01G31