Abstract:
An apparatus for separating foreign bodies from a stream of fiber material includes a vertical chute having an upper inlet and a lower outlet; a mechanism for introducing the fiber material into the chute inlet; and a detector positioned in the chute for emitting a sensor signal upon passage of a foreign body. The fiber material is propelled from the detector towards the chute outlet substantially solely by gravity. The apparatus further has a waste discharge opening provided in the chute between the detector and the chute outlet; a deflecting mechanism arranged in the chute and having first and second positions. In the first position the deflecting mechanism causes the stream of fiber material to proceed in the chute to and through the chute outlet and in the second position the deflecting mechanism causes the stream of fiber material to proceed through the waste discharge opening. The deflecting mechanism is moved from the first position into the second position in response to a sensor signal emitted by the detector.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the priority of German Application No. P 40 29 412.9 filed Sep. 17, 1990, which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     This invention relates to an apparatus for separating foreign bodies, particularly metal foreign bodies, from a textile fiber stream advanced in a fiber processing line. In a conventional separating apparatus, the fiber material (fiber tufts) is pneumatically conveyed in a duct which has a branch-off location provided with a deflecting mechanism for the foreign bodies. A metal detector is situated upstream of the branch-off location as viewed in the travelling direction of the fiber tufts. The deflecting mechanism and the metal detector are operatively coupled with a control device in such a manner that the deflecting mechanism is, as a result of a response signal from the metal detector upon passage of a metal foreign body, switched to a position in which the fiber stream is guided to a waste collector. 
     2. Background Art 
     In a known apparatus, as disclosed in European Patent Application 033 a long, closed pneumatic fiber tuft conveying duct includes a metal detector and a branch-off location which is connected to a waste removing conduit in which a complex vacuum generating device--which requires its own compressor--is arranged for generating the suction stream that transports the fiber tufts. Apart from the expensive arrangement, the system is disadvantageous in that a complex collecting device for the separated material is needed in the region of the closed pneumatic transport system which further requires additional gates for material removal. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an improved apparatus of the above-outlined type from which the discussed disadvantages are eliminated and which, in particular, is of simple construction and in which the distance between the metal detector and the deflecting mechanism is shortened as compared to prior art constructions. 
     This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the apparatus for separating foreign bodies from a stream of fiber material includes a vertical chute having an upper inlet and a lower outlet; a mechanism for introducing the fiber material into the chute inlet; and a detector positioned in the chute for emitting a sensor signal upon passage of a foreign body. The fiber material is propelled from the detector towards the chute outlet substantially solely by gravity. The apparatus further has a waste discharge opening provided in the chute between the detector and the chute outlet; a deflecting mechanism arranged in the chute and having first and second positions. In the first position the deflecting mechanism causes the stream of fiber material to proceed in the chute to and through the chute outlet and in the second position the deflecting mechanism causes the stream of fiber material to proceed through the waste discharge opening. The deflecting mechanism is moved from the first position into the second position in response to a sensor signal emitted by the detector. 
     Thus, according to the invention, downstream of a separator assembly (such as a condenser) for the tuft/air mixture and below the exit location for the fiber material a foreign body detector is arranged which is followed in the vertical direction by a separating gate. If in the operative position, the separating gate deflects the free-falling material, together with the foreign body contained therein, from its normal path of conveyance. 
     It is an advantage of the invention that the sensing and the separating operations are performed externally of pneumatic ducts or channels. 
     It is an important feature of the invention to provide for a free fall of the material and to arrange the detector at or close to the location where the free fall starts. The separating gate is arranged spaced from the detector in the direction of free fall. In this manner, the reaction time for the gate is changed by several orders of magnitude which is realized with simple gates without the need of long distances between the detector and the location of separation. For example, the separating gate may be pivoted within 0.5 seconds after receipt of an electric actuating pulse. During such period the foreign body has moved in a free fall only approximately 1.2 m and has a velocity of approximately 4.4 m/sec s that the separating process may be controlled in a simple manner with the apparatus structured according to the invention. It is a further advantage of the construction according to the invention that in contrast to prior art arrangements, a complex and expensive collecting device for the separated material in the region of the closed pneumatic transport system is no longer necessary. Further, an expensive vacuum-generating device may also be dispensed with. It is of particular advantage that a long conveying track of, for example, 8-10 m between the detector and the deflecting device is also no longer necessary. The apparatus according to the invention is operationally reliable because it is based on a fail-safe free fall of the fiber material and the foreign bodies. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic side elevational view of a fiber processing line--including cleaning and carding machines incorporating the invention. 
     FIGS. 2-6, 7a, 7b and 8a are schematic side elevational views of seven preferred embodiments of the invention. 
     FIG. 8b is a diagram illustrating an impact force/time function. 
     FIG. 8c is a diagram illustrating the frequency of fiber tuft size occurrences. 
     FIG. 9 is a schematic side elevational view of yet another preferred embodiment of the invention. 
     FIG. 10 is a schematic side elevational view of a modified detail of the structure illustrated in FIG. 9. 
     FIG. 11 is a schematic side elevational view of the construction of the apparatus in the zone of a metal detector. 
     FIG. 12 is a schematic side elevational view of still another preferred embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning to FIG. 1, there is illustrated therein a fiber processing (cleaning) line which receives fiber tuft material detached from fiber bales 1a by a bale opener 1 which may be, for example, a BLENDOMAT BDT model, manufactured by Trutzschler GmbH &amp; Co. KG, Monchengladbach, Germany. Between the bale opener 1 and a multiple fiber tuft blender 4 there is situated the apparatus 2 according to the invention, followed by a heavy particle separator 3. The multiple blender 4 is followed in the downstream direction by a fine opener 5, and a plurality of card feeders 6 each associated with a carding machine 7 (only a single feeder-and-card assembly is shown). The fiber tufts detached by the bale opener 1 from the fiber bales ia are conveyed pneumatically in a duct 9 to a condenser 8 which is provided with a screening drum. From the condenser 8 there extends a vertical chute 10, the bottom of which opens into a pneumatic duct for advancing material to consecutive processing machines. The chute 10 and the other, downstream-arranged machines are connected to one another with respective pneumatic ducts. No pneumatic conveying duct is provided between the condenser 8 and the chute 10. 
     In the chute 10, vertically underneath the condenser 8 a metal detector coil 11 is arranged. The fiber material A drops from the condenser 8 through the detector coil 11 and a guide element 12 of the chute 10 in a free fall as indicated by the arrow C. Between the guide element 12 and the chute 10 a discharge opening 13 is provided, adjacent which, on the opposite wall of the chute 10, a pivotal gate 14 is mounted which serves as a deflecting member. An upwardly open waste container 15 is arranged laterally of the chute 10 and underneath the discharge opening 13. As soon as the gate 14 pivots into its operative position (shown in FIG. 1) in response to a sensor signal from the detector coil 11, the fiber material, together with the sensed foreign body, is deflected into the waste container 15, as indicated by the arrow B. 
     Downstream of the apparatus 2 a heavy particle separator 3 is arranged which may be a SEPAROMAT model, manufactured by Trutzschler GmbH &amp; Co. KG, Monchengladbach, Germany. The separator 3 has an intake channel 3a to which there is coupled an end of an air branch-off conduit 3b so that air quantities indicated by the arrow E in the air branch conduit 3b may be set by a throttle gate 3c as a function of the air quantities (arrow D) flowing through the intake channel 3a. The intake channel 3a is a rising pneumatic conduit between the apparatuses 2 and 3. 
     In FIG. 2, the detector coil 11 is mounted on a non-illustrated holder underneath the condenser 8. The fiber material A drops in a free fall in the chute 10 and is pneumatically carried away through a suction pipe 16 at the bottom of the chute 10. The deflector gate 14 lies flush against the wall 10a of the chute 10 during normal passage of the fiber material and upon generation of a signal by the detector coil 11, responding to the passage of a metallic foreign body, the deflector gate 14 is pivoted away from its flush position with the chute wall 10a into the phantom-line position 14&#39;. The gate 14 is secured to the wall 10a by a pivot 14a to which there is connected one end of a crank lever 14b, whose other end is operatively connected with a pneumatic cylinder 14c which, in turn, is coupled with the detector coil 11 with the intermediary of a control device as will be discussed in connection with FIG. 4. 
     In FIG. 3, underneath the condenser 8 a detector plate 17, containing a plurality of inductive detector coils, is arranged at an angle α to the horizontal. The chute 10 has at its lower end two slowly rotating, cooperating delivery rolls 18a, 18b which remove the fiber material from the chute 10 and cause the fiber material to fall on a removal conveyor 18c. 
     Turning to FIG. 4, underneath the condenser 8 an obliquely oriented detector plate 17 and an obliquely oriented wall 19a of a guide element 19 are provided. The guide element opens into the chute 10. The wall 19a supports the pivotal deflector gate 14. Upon rotation of the gate 14 into its phantom-line position 14&#39;, a branch-off aperture in the wall 19a is opened, through which the material passes, together with the metal foreign bodies, and falls into the waste container 15. In their travel from the condenser 8 downwardly, the fiber material and the foreign body are exposed exclusively to gravitational forces. The detector plate 17 is electrically connected with a control device 20 which, in turn, is coupled to the pressure cylinder 14c with the intermediary of a transducer 21. 
     In FIG. 5, underneath the branch-off aperture 13 and adjacent the chute 10 a fiber tuft accumulator 22 is arranged. At the bottom of the fiber tuft accumulator 22 two slowly rotating delivery rolls 23a, 23b are mounted. Underneath the delivery rolls 23a, 23b a further detector coil 21 and a pivotal gate 25 as well as a chute 26 are provided. The chute 26 and the chute 10 open into a common suction duct 27. Between the tuft accumulator 22 and the chute 26 an opening 28 is provided under which a waste container is arranged. In this embodiment two separating devices are serially connected to ensure that the useful fiber quantities 31 which are separated out with the metal foreign body 30 are maintained small. Thus, in operation, the coil 11 generates a signal as a metal foreign body passes therethrough, together with useful fiber material. In response, the cylinder 14c places the pivotal gate 14 into its phantom-line position 14&#39; whereupon the fiber material, together with the metal foreign body, falls into the fiber tuft accumulator 22. Thereafter, the gate 14 is returned into its solid-line position whereupon the fiber material dropping from the condenser 8 may fall through the chute 10 into the pneumatic duct 27 to combine with the air stream P into an air/fiber stream R. Parallel to this operation, the slowly rotating delivery rolls 23a, 23b at the bottom of the accumulator 22 advance the material through the sensor coil 24 and as the earlier collected metal foreign body passes through the coil 24 the latter causes energization of the pressure piston 14c&#39; whereupon the gate 25 is pivoted counterclockwise, thus closing the channel 26 and deflecting the fiber material, together with the metal foreign body, through the opening 28 into the waste collector 29. 
     The embodiment illustrated in FIG. 6 is similar to that of FIG. 5 except that in the normal position of the gate 25 the fiber material advanced by the delivery rolls 23a, 23b is deflected into the chute 10 at a location below the gate 14, whereas in the non-illustrated operative position, that is, when the gate 25 is pivoted counterclockwise in response to a sensor signal from the coil 24, the gate 25 allows the fiber material, together with the metal foreign body 30 to fall, as indicated at B, vertically into the waste container 29 situated vertically below the sensor coil 24. 
     Turning to FIG. 7a, underneath the condenser 8 which includes a screening drum 8a and a vaned dispenser wheel 8b, there is mounted an obliquely oriented weighing plate 32 connected with a weighing cell 32a. The fiber stream A 1  impinges on the weighing plate 32 and is deflected thereby as a fiber stream A 2 . FIG. 7b shows that the weighing cell 32a is connected to the control device 20 which, in turn, is coupled to the pneumatic cylinder 14c that operates the gate 14 to guide the fiber material, together with the sensed metal foreign body, into the waste conveyor 15 when a predetermined excess weight is sensed by the weighing plate 32. 
     In FIG. 8a, between the weighing cell 32a which may, for example, comprise expansion measuring strips, and the control device 20 an electric amplifier 33 and an evaluating device 34 are connected. The evaluating device 34 sums in an analog manner the electric signals emitted by the weighing cell 32a for the purpose of determining the weight of the fiber tufts and/or heavy foreign bodies impinging on the weighing plate 32. When a predetermined limit pulse amplitude or energy is reached, the heavy body separating device is triggered as described in connection with FIG. 7b. 
     The evaluating device 34 may be so structured that not only the total weight is evaluated but also the under-the-curve areas of the individual coherent pulse signals are statistically evaluated as shown in FIGS. 8b and 8c. This additionally permits a determination of the fiber tuft sizes and the degree of the opening of the fiber tufts. 
     In the diagram illustrated in FIG. 8b the force P applied to the weighing plate 32 is shown over time t. P1 designates a threshold value for the heavy particle separation. The force signal corresponding to F4 triggers the foreign body separation. 
     The sum of the areas F 1  -F 5  under the curve corresponds to the fiber tuft weight. The magnitude of each area under the curve, for example, F 1  is proportional to the tuft size, that is, to the degree of opening of the fiber tuft. FIG. 8c shows a diagram which illustrates the occurrence frequency as a function of the tuft size F. F m  designates the mean fiber tuft size corresponding to the mean fiber tuft weight. 
     Turning to FIG. 9, there is shown therein an embodiment similar to that illustrated in FIG. 4, except that the surface 17a of the detector plate 17 oriented towards the fiber tufts A is situated at a distance a of a horizontally supported plastic roller 35 which is rapidly rotating in the direction of the arrow H. The fiber material A passes through the gap a and is pressed by the surface of the roller 35 against the face 17a of the detector plate 17. Instead of a plastic roller 35 an endless belt 36 may be provided which is supported by end rollers 35&#39;. 
     The detector plate 17 in FIGS. 9 and 10 is a surface sensor which contains a plurality of inductive sensor elements 17b which generate on their active surfaces a high-frequency electromagnetic field that changes as any metal part passes by. For generating such a field there is provided a coil of a high-frequency oscillator, embedded in a ferrite core. If a metal part enters into the field generated by the coil, in the metal part eddy currents appear which cause an energy loss in the field. The energy loss dampens the amplitude of the oscillation of the field, and this phenomenon is converted into a definite electric switching signal. 
     In FIG. 11, there are provided two cooperating conveyor belts 37, 38 trained about support rollers 39a, 39b, 39c and 40a, 40b, 40c, respectively. The belt portions between the support rollers 39b, 39c and 40b, 40c define a narrow channel 41 through which the fiber material A passes after the free fall. At the inside of the belt portion an area pressure sensor 42 and 43 is arranged. By virtue of the narrow channel 41, the fiber material A, together with any foreign body, is brought into the sensitive operational range of the sensors 42, 43. 
     Turning to FIG. 12, there is illustrated a further embodiment of the invention. In this embodiment, between the condenser 8 and the chute 10 a curved fiber tuft guiding channel 44 is provided. In the zone where the channel 44 merges with the inlet of the chute 10 a roll 35 is arranged which is provided with a plurality of webs 35&#39;. The channel 44 is formed in part by a wall portion 44a which is made of plastic and which is spaced at a distance a from the roll 35. Underneath the chute 10 there is positioned a conveyor 37 which receives fiber material, together with the metal foreign body sensed by the detector plate 17. Between the upper reach and the lower reach of the conveyor 37 a metal detector 42 is disposed. Normally, the endless conveyor belt 37 is driven such that its upper reach travels from the left towards the right as viewed in FIG. 12. Above the upper reach of the conveyor belt 37, generally in alignment with the metal detector 42, a roll 45 is positioned. When the metal detector 42 senses the presence of a metal body on the upper reach of the conveyor belt 37, the driving mechanism of the belt 37 is reversed so that the metal body and some fiber material is moved to a waste collecting location towards the left. It is seen that in the normal, rightward travel of the upper reach of the conveyor belt 37 the material which is deposited onto the conveyor belt by the waste branch extending from the chute 10, rejoins the normal material flow beyond the right-hand end of the conveyor belt 37. 
     It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.