Abstract:
A suction-air system of a textile machine, especially a rotor spinning machine, has at least one suction-air conduit, at least one spark sensor for detecting flying sparks within a measuring extent of the suction-air, the sensor including a measuring device with a sensing range at least partially overlapping the measuring extent, at least one electromagnetic wave receiver for generating an output signal when a spark enters the sensing range, and a driver and evaluation circuit for the measuring device. At least one source for generating electromagnetic waves is associated with the receiver and actuates a purposeful initiation of the spark sensor.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a suction-air system of a textile machine, especially a rotor spinning machine. More particularly, the present invention relates to such a suction-air system having at least one suction-air conduit, at least one spark sensor for detecting flying sparks within a measuring extent of the suction-air system wherein the sensor comprises a measuring device whose sensing range overlaps the measuring extent at least partially, at least one electromagnetic wave receiver which generates an output signal when a spark enters into the sensing range, and a driver and evaluation circuit for the measuring device. 
     BACKGROUND OF THE INVENTION 
     Suction-air systems of the basic type described above are known. Thus, for example, German Patent Publication DE 24 26 961 B2 describes a fire detector which is arranged in a suction-air system of a rotor spinning machine. The task of such a fire detector is to monitor fiber fly of the rotor spinning machine transported within a suction-air conduit for any spark formation. Such a spark formation can arise, e.g., because a rotor of the rotor spinning machine overheats, which can cause an ignition of fibers. Such ignited fibers can be transported via the suction-air conduit over relatively large distances, e.g. into air-conditioning equipment, so that considerable fire damage can occur. 
     It is known that such fire detectors (referred to herein as spark sensors) can be provided with an optical receiver for electromagnetic waves which receiver senses, in particular, infrared signals emitted by a spark. Such electromagnetic waves can be converted into an electrical signal by a photoelement, e.g., a photodiode. This electrical signal can be evaluated with a driver and evaluation circuit. Normally, the photoelements are loaded with a resting current, or zero-signal current, which changes into a switching current after the incidence of an electromagnetic wave to initiate an event-dependent action. This action can be, e.g., an alarm signal to operating personnel of the rotor spinning machine, an automatic deactuation of the rotor spinning machine, the activation of an extinguishing device or the like. 
     While they are being used according to regulation, spark sensors are exposed to significant stress, so that a checking of the operation of the spark sensors is necessary for reliable operation. As a result of the defined switching states of the spark sensors between the resting current, on the one hand, and the switching current, on the other hand, an electrical check can be performed by means of a testing algorithm via the driver and evaluation circuit. In the case of any short circuit of the leads to the measuring device, a current flows which is greater than the resting current, whereas in the case of an interruption of the lead of the measuring device no current flows. In the case of both error states, an alarm signal can be generated which indicates a failure of the spark sensor. 
     However, it is a disadvantage that checking of the optical structural elements of the spark sensor is not possible, so that an operational safety of 100% can not be assured by the electrical test. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the present invention to provide a suction-air system of the basic type described above which offers increased operating safety in a simple manner. 
     The invention solves this problem by providing a suction-air in a textile machine which basically comprises at least one suction-air conduit, at least one spark sensor for detecting flying sparks within a measuring extent of the suction-air system, the sensor comprising a measuring device having a sensing range overlapping at least partially the measuring extent, at least one receiver of electromagnetic waves adapted for generating an output signal when a spark enters the sensing range of the measuring device, and a driver and evaluation circuit for the measuring device. According to the present invention, at least one source for generating electromagnetic waves is provided in association with the at least one electromagnetic wave receiver and is operable for purposefully initiating the spark sensor. As a result, the optical components of the spark sensor can be checked in an advantageous manner in addition to the checking of the electrical and electronic components of the spark sensor, so that a recognition of sparks by the spark sensor becomes significantly more reliable. 
     A preferred development of the invention provides that that the at least one electromagnetic wave generating source can be actuated periodically and the alarm function of the driver and evaluation circuit can be faded out or otherwise deactuated, preferably during the periodically repeating actuation of the electromagnetic wave generating source for self-testing of the optical components of the spark sensor. Thus, the optical components of the spark sensor can be checked in a simple manner and at determinable intervals, during which the initiation of the alarm current of the spark sensor does not result in an initiation of a false alarm signal as a consequence of the testing of the measuring device. 
     A further, preferred development of the invention provides that the electromagnetic wave source is a light-emitting diode which can preferably be driven via the driver and evaluation circuit of the measuring device. As a result thereof, the periodic activation of the electromagnetic wave source can be combined in a simple manner with the deactuation of the alarm function without any great expense for circuit technology being necessary. 
     Furthermore, another preferred development of the invention provides that the source for generating electromagnetic waves and the spark sensor are arranged in a common housing. This makes it possible to create a compact structural form of the spark sensor. A common electrical interface with the driver and evaluation circuit of the spark sensor can preferably be used. This results in a simplified assembly expense since the arrangement and the electrical connection of additional components is not necessary. 
     The invention will be further explained and understood from the description of an exemplary embodiment set forth in the following specification with reference to the associated drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic perspective view of an arrangement of a spark sensor on a suction-air system of a rotor spinning machine, in accordance with a preferred embodiment of the present invention. 
     FIG. 2 is a schematic diagram of an operating circuit of the spark sensor in the system of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the accompanying drawings and initially to FIG. 1, a suction-air system  10  for at least one rotor spinning machine is shown in a fragmentary perspective view. As will be understood, several rotor spinning machines, each with a plurality of spinning units, can be connected to suction-air system  10 . The design and method of operation of the suction-air system and of such rotor spinning machines are known, so that they do not have to be discussed in detail in the framework of the present specification. A vacuum is applied to the rotor spinning machines by means of suction-air system  10 , by which fiber waste, impurities and the like are removed by suction from the rotor spinning machines. 
     To this end, suction-air system  10  comprises a so-called end unit  12  into which communicates suction-air conduit  14  connected to a source of suction air (not shown). Furthermore, suction-air conduits  16  leading to the individual rotor spinning machines empty into end unit  12 . Section  18  of suction-air conduit  14  forms a measuring extent  20  for spark sensor  22 , whose design and method of operation will be explained in more detail with reference to FIG.  2 . Spark sensor  22  is connected via electrical connecting lead  24  to control device  26  which comprises a driver and evaluation circuit for spark sensor  22 . 
     During the regular operation of suction-air system  10 , the fiber waste accumulating on the rotor spinning machines is conducted via the flow of suction air to a filter or separating device. A feeding of sliver on the part of the rotor spinning machine is not turned off as a consequence of an operating disturbance in the rotor spinning machines, e.g., in the case of a yarn break, and the rotor of the rotor spinning machine can be fed too much sliver, causing the rotor to overheat. The frictional heat thereby created can be sufficient to ignite the fiber waste transported off by the flow of suction air. This waste would then be conducted as flowing fiber waste via suction conduits  16 ,  14  to the filter or separating device, where it could result in ignition of the collected fiber waste. 
     The fiber fly is monitored by spark sensor  22  in the area of measuring extent  20 , during which electromagnetic waves in the infrared range emitted by glowing fibers are detected by an optical receiver. This makes it possible to recognize flying sparks within suction-air system  10  and to initiate appropriate countermeasures via control device  26 . These measures can consist, e.g., in generating an optical and/or acoustic alarm so that operating personnel of the rotor spinning machines can initiate appropriate countermeasures. Furthermore, the rotor spinning machines can be automatically turned off. In addition, the direction of the conveyance of air in suction-air system  10  can be reversed or otherwise switched such that, when glowing fiber fly occurs, it is not transported in the direction of the filter and separating device but rather can be directed into a separate storage area optionally equipped with extinguishing means. 
     FIG. 2 shows spark sensor  22  in a block diagram. This sensor comprises optical receiver  28 , whose sensing range is directed into measuring extent  20 . The sensing range encompasses, e.g., an angle of detection of 110°, within which glowing fiber waste transported in measuring extent  20  is recognized. The entire cross section of measuring extent  20  can be detected through the detection angle of 110° by arranging spark sensor  22  at a corner of suction-air conduit  14 , which is preferably designed in an angular configuration. Spark sensor  22  is connected via electrical connecting lead  24  to driver and evaluation circuit  30 , shown here only representatively. Connecting lead  24  is designed as a four-wire lead in which a first wire  32  serves to make available a supply voltage U v  of, e.g., 24 Volts. A second wire  34  and a third wire  36  serve to tap off an electrical signal of optical receiver  28 . Optical receiver  28  is, for example, a photodiode which drives a resting current of, for example, 20 mA via a current interface. If a spark appears in measuring extent  20 , infrared electromagnetic waves emitted by the spark are received by optical receiver  28  and converted into an electrical signal. This electrical signal effects a switching of the resting current into an alarm current of, for example, 4 mA which can be evaluated by control device  26 . Amplifier circuit  38  can be provided to amplify the electrical signals generated by optical receiver  28 . 
     Moreover, spark sensor  22  comprises source  40  for generating electromagnetic waves in a wavelength range which corresponds to the receivable wavelengths of optical receiver  28 , thus, in the infrared range in the present embodiment. Source  40  is preferably designed as a light-emitting diode. Source  40  can be driven with a control pulse via a fourth wire  42  of connecting lead  24 . In order to amplify the control pulse, amplifier circuit  44  can be provided. Corresponding to the function of source  40 , the control pulse produces infrared flash  46  within measuring extent  20 , which flash is recognized by optical receiver  28 . Driver and evaluation circuit  30  comprises timing element  48  by which a defined pulse length, on the one hand, and a pulse interval, on the other hand, can be adjusted. The pulse length determines the period of actuation time of source  40  and is at least 1.1 times, preferably at least 1.5 times, a reaction time of optical receiver  28 . This assures that generated infrared flash  46  is actually recognized by optical receiver  28 . The interval between successive pulses can be selected as appropriate or otherwise desired, e.g., in the range of seconds, minutes, hours or the like. Control signal  50  is generated synchronously with the pulse signal by timing element  48 . Control signal  50  informs control device  26  that an infrared signal detected by spark sensor  22  was not produced by flying sparks inside the suction-air system but rather that this signal was generated by a purposeful and defined actuation of source  40 . In this manner an initiation of an alarm can be suppressed by control device  26  for the duration of the pulse. 
     A self-test of spark sensor  22 , especially of its optical receiver  28 , can thereby be performed by means of a purposeful activation of source  40 . A periodic checking of the operation of spark sensor  22  is thus possible corresponding to the repetition frequency of the test pulses, without the sensor having to be removed from suction-air system  10 , for example. In addition to this checking of the optical operation of spark sensor  22 , a checking of the electrical operation can take place in a known manner by monitoring the resting current. If the resting current exceeds a set value, e.g., 20 mA, a short circuit inside connecting lead  24  or inside spark sensor  22  is indicated. If the resting current is interrupted, for example, an interruption of an electrical lead is indicated. 
     Control device  26  comprises, for example, an optical display which displays a failure of spark sensor  22 . An appropriate replacement of the defective spark sensor  22  can then be performed by the operating personnel. Furthermore, an automatic error signal can be transmitted to a central data processor serving to control the rotor spinning machines so that, in addition to a documentation of the error signal, a defective spark sensor  22  can be identified at the same time. 
     Instead of or in addition to actuating the test pulses via timing element  48 , source  40  can also be actuated manually via a separate switching means by an operating person. This makes a manual check possible at any time, in addition to or independently of the set repetition frequency of the test pulses. Thus, the operation of spark sensor  22  can be tested, e.g., during a check round by operating personnel by actuating the switching means. Control device  26  can make appropriate acknowledging signals available, e.g., optically, for the operating person so that he recognizes whether spark sensor  22  is in working order or defective. 
     Optical receiver  28 , source  40  and amplifier circuits  38 ,  44  are arranged in common housing  52  formed, e.g., by a cylindrical plastic tube. This makes a very compact method of construction possible. Spark sensor  22  is connected to control device  26  by only one connecting lead  24 , here a four-wire lead as described above, so that spark sensor  22  can be connected in a simple manner via an interface. 
     It is of course possible, according to further exemplary embodiments which are not shown to arrange source  40  independently of spark sensor  22 , e.g., in measuring extent  20  diametrically opposite spark sensor  22 . A self-test of spark sensor  22  is also possible in this manner, during which the mode of operation remains the same. 
     It will therefore be readily understood by those persons skilled in the art that the present invention is susceptible of broad utility and application. Many embodiments and adaptations of the present invention other than those herein described, as well as many variations, modifications and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the foregoing description thereof, without departing from the substance or scope of the present invention. Accordingly, while the present invention has been described herein in detail in relation to its preferred embodiment, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for purposes of providing a full and enabling disclosure of the invention. The foregoing disclosure is not intended or to be construed to limit the present invention or otherwise to exclude any such other embodiments, adaptations, variations, modifications and equivalent arrangements, the present invention being limited only by the claims appended hereto and the equivalents thereof.