Abstract:
A device for determining the diameter of a yarn balloon (B) formed by a running yarn at a workstation ( 1 ) of a textile machine utilizes a mechanical, contact scanning sensor ( 22 ), which is designed and arranged so that during the operation of the workstation ( 1 ) it is positioned by a yarn forming the yarn balloon (B) in an operating position dependent on the diameter of a yarn balloon (B), and a sensor device ( 24 ) which detects the operating position (BS) of the scanning sensor ( 22 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from German National Patent Application No. DE 102015005328.0, filed Apr. 27, 2015, entitled “Vorrichtung and Verfahren zum Ermitteln des Durchmessers eines durch einen laufenden Faden gebildeten Fadenballons an einer Arbeitsstelle einer Textilmaschine”, the entire contents of which are incorporated herein by reference. 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates to a device and an associated method for determining the diameter of a yarn balloon formed by a running yarn at a workstation of a textile machine. 
       BACKGROUND OF THE INVENTION 
       [0003]    In the textile machine industry different embodiments of production machines have been known for a long time in which yarn balloons are formed during operation in the region of their often numerous workstations or associated operating devices. 
         [0004]    Such production machines therefore have monitoring devices for determining and limiting the size of said yarn balloon, which can operate in very different ways. The known monitoring devices often have optical sensor devices for example, by means of which the rotating yarn that forms the yarn balloon is observed. 
         [0005]    In German Patent Publication DE 101 03 892 A1 for example a method and a device are described by means of which the yarn take-off speed of feed bobbins arranged in the creel of a beaming machine is optimised. 
         [0006]    It is known that when a yarn is drawn off a feed bobbin, which is positioned in an associated creel during the operating process overhead and at a relatively high take-off speed, a yarn balloon is formed, the diameter of which is dependent on the yarn take-off speed. The size of the yarn balloon thus increases with increasing yarn take-off speed. 
         [0007]    In the method known from German Patent Publication DE 101 03 892 A1 by means of measuring means arranged on the creel the size of at least some of the yarn balloons created during the yarn take off is determined and transmitted to a control device, which when reaching limit values of the yarn balloon ensures that the yarn take-off speed is controlled by intervention. 
         [0008]    As measuring means for determining the yarn balloon size various different optically operating measuring units are used, for example a camera, one or more light barriers or similar devices. 
         [0009]    Optically operating measuring devices for detecting a yarn balloon form and/or a yarn balloon size are known from German Patent Publication DE 22 55 663 A1 and European Patent Publication EP 0 282 745 A1 also in connection with ring spinning machines. 
         [0010]    In German Patent Publication DE 22 55 663 A1 for example a workstation of a ring spinning machine is described which is equipped with an air or magnet-mounted spinning ring, on which a spinning rotor runs driven by the running yarn. 
         [0011]    As during the operation of such workstations, in order to ensure a perfect spinning process, it is known that it is necessary to have a specific difference between the speed of the spinning ring and the speed of the spinning rotor, during the spinning operation both the speed of the air or magnet mounted spinning ring and also the speed of the spinning rotor is controlled. 
         [0012]    Furthermore, in this method there is continuous monitoring of whether a predefined maximum yarn tension is being maintained and the yarn balloon forming during the spinning in the region of the spinning cop is controlled and also stabilised. This means that by measuring the deviation of the yarn curve of the yarn balloon from its meridian plane and adjusting the yarn tension accordingly by means of variably braking the spinning ring, the course of the yarn curve of the yarn balloon is stabilised. The device for detecting the deviation in the yarn curve of the yarn balloon consists essentially of a measuring sensor which comprises a series of small photoelements as well as a trigger device which ensures that the yarn balloon is periodically flashed. 
         [0013]    The known devices are either (German Patent Publication DE 22 55 663 A1) relatively complicated and often very inaccurate or because of their large measurement range (German Patent Publication DE 101 03 892 A1) are often very sensitive to air pollution. 
         [0014]    Therefore in practice these known devices have not won general acceptance. 
         [0015]    European Patent Publication EP 0 282 745 A1 describes a method and a device for monitoring the production and quality of the workstations of a multi-spindle textile machine. 
         [0016]    This means that a ring spinning machine is equipped with an optical monitoring element, which simultaneously checks a plurality of workstations of the textile machine arranged next to one another in series in that the yarn balloons rotating in the region of the workstation are illuminated. 
         [0017]    The monitoring element comprises for this purpose a transmitter and a receiver, which are designed and arranged so that a beam bundle sent by a transmitter on route to a receiver passes through the numerous, rotating yarn balloons and is interrupted or weakened intermittently by the yarn balloons. 
         [0018]    The shadow is converted in the receiver into an electric signal which is used in an associated control device as the basis for further evaluation. 
         [0019]    Also the method described in European Patent Publication EP 0 282 745 A1 is occasionally very inaccurate as the beam bundle is often influenced negatively on route from the transmitter to the receiver by dust and fibre particles which are almost impossible to avoid in the atmosphere of a spinning room. 
         [0020]    Furthermore, by means of European Patent Publication EP 2 419 554 B1 a workstation of a two-for-one twisting and cabling machine is known, the spooling and winding device of which is arranged so that during operation it lies inside a yarn balloon. 
         [0021]    In order to check the size of the yarn balloon the workstation has a monitoring device which can have various different embodiments. 
         [0022]    The size of the yarn balloon can be determined for example by a yarn tension sensor, which is arranged either between a yarn drive device and the inlet of the yarn into a spindle, which ensures the formation of the yarn balloon or by means of a yarn tension sensor, which is positioned between the outlet of the yarn from the spindle and an additional yarn drive device. 
         [0023]    In a further embodiment it is possible to detect the size of the yarn balloon and also measure the output or torque of the drive device of the spindle. This means that by means of a measuring device the power is determined which is received by the spindle drive and from this the size of the yarn balloon can be determined in an evaluation device. 
         [0024]    From European Patent Publication EP 2 419 554 B1 also the use of different optical measuring devices is known which monitor the yarn balloon rotating around the spooling and winding device. 
         [0025]    In a first embodiment for example the use of a light barrier is proposed which has a light source for emitting a light beam and a light-sensitive detector for picking up the light beam. 
         [0026]    In a comparable, second embodiment a type CCD light sensor is used in connection with a beam-like, stroboscope light source, for example LED or laser. 
         [0027]    In the device which operates with a light barrier, during operation the interruption of the light beam is identified by the yarn of the yarn balloon running past. 
         [0028]    In the device which acts with a light sensor and a stroboscopic light source, which is synchronised with the rotation of the spindle, the image and thereby the form of the yarn forming the yarn balloon is localised when it is lit up by a flash. 
         [0029]    The various different monitoring devices described in European Patent Publication EP 2 419 554 B1 in connection with a workstation of a two-for-one twisting and cabling machine can also be improved upon, as they either do not take accurate enough measurements or are also relatively sensitive to dirt. 
       SUMMARY OF THE INVENTION 
       [0030]    On the basis of the aforementioned prior art the invention proposes to develop a device and a method, by means of which the diameter of a yarn balloon formed by a running yarn can be reliably determined even in difficult environmental conditions. 
         [0031]    The relevant device should also be as simple as possible in its construction and also not be sensitive to dirt. 
         [0032]    According to the invention, a device for reliably determining the diameter of a yarn balloon formed by a running yarn at a workstation of a textile machine utilizes a mechanical, contact scanning sensor, which is designed and arranged so that during the operation of the workstation it is positioned by the yarn balloon in an operating position dependent on the diameter of a yarn balloon and a sensor device is provided which detects the operating position of the scanning sensor. 
         [0033]    According to an associated method for operating the device, the operating position of the scanning sensor, which is predefined by the diameter of the yarn balloon (B), is detected by the sensor device. 
         [0034]    Further advantageous embodiments of the device and the associated method according to the invention are also provided. 
         [0035]    The device according to the invention has in particular the advantage that by using a mechanical scanning sensor, which with contact bears on the yarn forming the yarn balloon, regardless of the environmental conditions, for example the dust levels in the region of the workstation, the correct yarn balloon size is always determined directly and in that said yarn balloon size indicated by the operating position of the scanning sensor is identified reliably and exactly by a sensor device and can be transmitted for evaluation to devices connected downstream, which if necessary in connection with the yarn tension of the outer yarn introduce control measures. 
         [0036]    The use of a mechanical scanning sensor also enables a compact structure of the workstation with the result that the space required for setting up a two-for-one twisting or cabling machine is reduced. 
         [0037]    The sensor device, by means of which the operating position of the mechanical scanning sensor is detected can be designed to be very different. As a sensor device an optically operating device is possible for example, e.g. a so-called measuring position sensor. 
         [0038]    A measuring position sensor of this kind optically detects the respective distance between the sensor device and the scanning sensor positioned in the operating position and then sends a corresponding electrical signal to a control circuit connected downstream. 
         [0039]    However, in principle to detect the operating position of a mechanical scanning sensor it is also possible to use other types of sensor devices. 
         [0040]    For example a sensor device can also be used which establishes what angle of rotation the scanning sensor has in relation to a zero position when the scanning sensor is positioned in a specific operating position. 
         [0041]    The mechanical scanning sensor, which bears with contact on the running yarn which forms the yarn balloon and which is thereby positioned in an operating position which corresponds to the respective diameter of the yarn balloon can have different advantageous embodiments. 
         [0042]    In an advantageous embodiment the scanning sensor bears on the spindle pot when the spindle of a workstation is in a position of rest. By means of such a design it is ensured in a simple manner that the scanning sensor is always positioned in a defined position even with a switched off workstation, with the result that the scanning sensor can be immediately activated when the workstation is restarted. 
         [0043]    In a first advantageous embodiment the scanning sensor is designed for example as a clip which is convex relative to the yarn balloon, and mounted pivotably at the ends, which bears on the yarn balloon from the outside. The pivot axis of the clip is thus spaced apart from the yarn balloon and at right angles to the axis of rotation of the yarn balloon so that the clip is lifted by the running yarn which forms the yarn balloon and is positioned in an operating position which is dependent on the diameter of the yarn balloon and which can be identified reliably by an associated sensor device. 
         [0044]    In a further, second embodiment the scanning sensor is designed as a clip which is concave relative to the yarn balloon and pivotable at the ends which also bears on the yarn balloon from the outside. 
         [0045]    Here too the pivot axis of the clip is at right angles to the axis of rotation of the yarn balloon and is arranged so that the clip is lifted by the running yarn and is positioned in an operating position dependent on the diameter of the yarn balloon. As in the first embodiment the operating position of the clip can then be easily detected by an associated sensor device. 
         [0046]    In a third embodiment the scanning sensor, similar to the second embodiment described above is designed as a clip, which is concave relative to the yarn balloon and mounted pivotably at the ends. 
         [0047]    However, the clip in this embodiment bears on the yarn balloon from the inside. 
         [0048]    The operating position of the clip can also be detected here by an associated sensor device. 
         [0049]    Preferably, the scanning sensor in the two embodiments described above in the area in which the clip of the scanning sensor is tangential to the yarn balloon has a curvature pointing respectively in the direction of the yarn balloon. By means of such a curvature the area of contact of the clip with the running yarn which is known to form a yarn balloon is minimised, which has a positive effect on the yarn quality. This means that by means of such a curvature the surface contact of the yarn material which can cause yarn-damage is minimised. 
         [0050]    In a further advantageous embodiment the scanning sensor can also be designed as a spring-loaded scanning feeler bearing on the yarn balloon from the outside. 
         [0051]    The scanning feeler can either be designed to be linear or to have a concave curve relative to the yarn balloon. In both embodiments the operating position, similar to the aforementioned scanning sensors with clip, can be detected reliably by a sensor device. 
         [0052]    In a linear design of the scanning feeler it is advantageous to make the scanning feeler from an elastic, wear-resistant material, for example spring steel, and to position the scanning feeler on one of its end sides in a bearing position so that it bears against the yarn balloon formed by the running yarn. 
         [0053]    If the scanning feeler has a concave curvature relative to the yarn balloon it is advantageous to mount the scanning feeler on one of its ends side in a pivot bearing and load its opposite end sides with a spring element so that the scanning feeler with its concave curvature is tangential to the yarn balloon formed by the running yarn. 
         [0054]    In an advantageous embodiment it is also the case that for influencing the form and the diameter of the yarn balloon a device is provided, by means of which the yarn tension of an outer yarn on a two-for-one twisting or cabling machine can be adjusted and the device is connected to a control circuit which processes the signals of the sensor device. 
         [0055]    The device for influencing the yarn tension of the outer yarns can thus either be designed as a brake or as an active delivery device. The connected control circuit thereby ensures that there is automatically always an optimum yarn balloon size. 
         [0056]    In a further advantageous embodiment the scanning sensor can be positioned optionally in a position of rest, in which there is no contact with the yarn balloon. This means that a scanning sensor according to the invention is preferably used during the start/stop phases of the workstations and can be positioned in a position of rest during normal operation in a way that protects the material in which it is pivoted away from the rotating yarn balloon. 
         [0057]    As already indicated above in connection with the device according to the invention in the method according to the invention the diameter of a yarn balloon formed by a running yarn is determined at a workstation of a textile machine in that the operating position of a scanning sensor, which corresponds to a specific diameter of the yarn balloon, is detected by the sensor device. The operating position of the scanning sensor detected by the sensor device is processed in a control circuit and used in the connected device for influencing the yarn tension of the outer yarn such that the yarn balloon has an optimal diameter. 
         [0058]    By means of the method according to the invention it is ensured in particular that the scanning sensor is immediately active when the workstation is started up. This means that it is ensured that the scanning sensor is operating perfectly particularly in the start/stop phase of a workstation. 
         [0059]    In a further advantageous embodiment the operation position of the scanning sensor detected by the sensor device is processed in a control circuit and used in a connected device for advantageously influencing the yarn tension of an outer yarn and/or an inner yarn on a two-for-one twisting or cabling machine. 
         [0060]    Preferably, the control circuit always ensures that the yarn balloon size is automatically optimal, i.e. it has a minimal yarn balloon size as far as possible according to the existing operating and material parameters. 
         [0061]    The scanning sensor is preferably used during the start/stop phases of the workstation, whereas during normal operation it is positioned in a position of rest in which it is pivoted away from the rotating yarn balloon. 
         [0062]    In this way on the one hand, in particular in the critical phases of the workstation, correct operation can be ensured and on the other hand it can also be ensured that the material stress of the scanning sensor is minimised and thus the lifetime of the scanning sensor is extended. 
         [0063]    The scanning sensor according to the invention can however be used not only for determining the form and the diameter of a yarn balloon but also for monitoring yarn breaks. This means a specific operating position of the scanning sensor can be used as an indication of the presence of a yarn break. Additional yarn break sensors are thus no longer needed at the workstations. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0064]    The invention is explained in more detail in the following with reference to various example embodiments shown in the drawings wherein: 
           [0065]      FIG. 1  shows schematically, in side view a workstation of a two-for-one twisting or cabling machine, which comprises a mechanical scanning sensor for determining the diameter of a yarn balloon, 
           [0066]      FIG. 2  shows a mechanical scanning sensor, which is designed as a convex clip which is mounted pivotably at the ends, which bears on the yarn balloon from the outside, 
           [0067]      FIG. 3  shows a mechanical scanning sensor, which is designed as a concave clip mounted pivotably at the ends which bears on the yarn balloon from the outside and has a curvature pointing in the direction of the yarn balloon, 
           [0068]      FIG. 4  shows a mechanical scanning sensor, which is designed as a concave clip mounted pivotably at the ends, which bears on the yarn balloon from the inside and has a curvature pointing in the direction of the yarn balloon, 
           [0069]      FIG. 5  shows a mechanical scanning sensor which is designed as a linear scanning feeler, 
           [0070]      FIG. 6  shows a mechanical scanning sensor which is designed as a concave scanning feeler. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0071]      FIG. 1  shows schematically, in side view a workstation  1  of a two-for-one twisting or cabling machine, which as usual comprises a creel  4  positioned generally above or behind the workstation  1 , which is used for receiving at least one first feed bobbin  7 , from which the so-called outer yarn  5  is drawn off. 
         [0072]    The workstation  1  also has a spindle  2 , in the present example embodiment a cabling spindle, which is equipped with a spindle pot  19 , in which a second feed bobbin  15  is mounted from which a so-called inner yarn  16  is drawn off overhead. The inner yarn  16  is supplied to balloon eyelet arranged above the spindle  2  or a so-called balancing system  9 . 
         [0073]    The spindle pot  19  is mounted on the rotatable yarn guiding device  20 , which is designed in the example embodiment as a twisting plate  8 . The spindle pot  19  supported on the rotatable yarn guiding device  20  is preferably secured against rotation by a (not shown) magnet device. 
         [0074]    The yarn guiding device  20  of the spindle  2  is loaded by a spindle drive  3  which is either a direct drive or an indirect drive. In the latter case the yarn guiding device  20  is connected for example by a belt drive to a corresponding drive. 
         [0075]    The outer yarn  5  drawn from the first feed bobbin  7  is supplied to a device  6  for influencing the yarn tension arranged in the yarn run between the creel  4  and the spindle  2 , by means of which the yarn tension of the outer yarn  5  can be varied if necessary. 
         [0076]    The device  6  is connected by control lines  27  to a control circuit  18 , which controls the yarn tension supplied by the device  6  to the outer yarn  5 . This means the outer yarn  5  following the device  6  runs through the spindle drive  3  in the region of the rotary axis  28  of the spindle drive and exits underneath the twisting plate  8  through a so-called yarn exit bore in radial direction out of the hollow axis of rotation  28  of the spindle drive  3 . The outer yarn  5  then runs to the outer part of the twisting plate  8 , where a fixed throw-off point  21  is installed for the outer yarn  5 . This fixed throw-off point  21  is designed according to the present example embodiment as an eyelet  23 . 
         [0077]    However, in connection with a yarn guiding device  20 , which has a fixed throw-off point  21 , also other embodiments are possible and can be used in practice. 
         [0078]    In the present example embodiment the outer yarn  5  is diverted upwards in the region of the eyelet  23  of the twisting plate  8  and rotates around the spindle pot  19  of the spindle  2  forming a free yarn balloon B, in which spindle a second feed bobbin  15  is positioned. A mechanical scanning sensor  22  bears with contact on the yarn balloon B, the operating position BS of which is monitored by a sensor device  24  which is connected via a signal line  25  to the control circuit  18 . 
         [0079]    The outer yarn  5  drawn from the first feed bobbin  7  and the inner yarn  16  drawn from the second feed bobbin  15  are brought together in the region of the balloon eyelet or the balancing system  9 . 
         [0080]    As shown in  FIG. 1 , by means of the position of the balloon eyelet or the balancing system  9  the height of the forming free yarn balloon B is determined. In the balloon eyelet or in the balancing system  9  is the so-called cabling or also cording point in which the two yarns, the outer yarn  5  and the inner yarn  16 , run together and form a cord yarn  17  for example. 
         [0081]    Above the cabling point a yarn take-off device  10  is arranged, by means of which the cord yarn  17  is taken off and supplied via a balancing element, such as for example a compensator device  11 , to a spooling and winding device  12 . 
         [0082]    The spooling and winding device  12  comprises, as usual, a drive roller  13  which frictionally drives a bobbin  14 . 
         [0083]    The device  6  for influencing the yarn tension is designed either as an electronically controlled brake or as an active delivery device, wherein also a combination of the two aforementioned components can be used. 
         [0084]    As embodiment variants of a delivery device for example a godet, a lamellar disc or a drive roller with corresponding pressure roller is possible. 
         [0085]    The device  6  is connected via control lines  27  to a control circuit  18  which is also connected via the signal line  25  to the sensor device  24  of the scanning sensor  22 . This means the device  6  controls the yarn tension of the outer yarn  5  as a function of the diameter of the free yarn balloon B, which is determined by contact by means of the scanning sensor  22 , and by means of the sensor device  24 , which converts the operating position BS of the scanning sensor  22  into an electric signal, is conveyed to the control circuit. 
         [0086]    The controllable yarn tension applied by the device  6  to the outer yarn  5  preferably has a size which, depending on the geometry of the spindle  2 , optimises the free yarn balloon B. 
         [0087]      FIGS. 2-6  show various different embodiments of a mechanical scanning sensor. 
         [0088]      FIG. 2  shows for example a mechanical scanning sensor  22 , which is designed as a clip  26  which is convex relative to the yarn balloon B and mounted pivotably at the ends which bears on the yarn balloon B from the outside. The pivot axis  29  of the clip  26  is spaced apart from the yarn balloon B and arranged at right angles to the axis of rotation  30  of the yarn balloon B so that the clip  26  is lifted by the running yarn, in the present example embodiment by the outer yarn  5 , which forms the yarn balloon B and is thus positioned in an operating position BS. 
         [0089]    The operating position BS of the scanning sensor  22  is recognised reliably by the associated sensor device  24  and sent via the signal line  25 , as an electric signal i, for further processing to the control circuit  18 . 
         [0090]      FIG. 3  shows a mechanical scanning sensor  22 , which comprises a clip  26 A which is concave relative to the yarn balloon B and mounted pivotably at the ends, which bears on the yarn balloon B from the outside. The clip  26 A has a curvature  31  in the direction of the yarn balloon B, by means of which the contact of the running outer yarn  5  with the clip  26 A is minimised and thus the yarn is protected. 
         [0091]    The pivot axis  29 A of the clip  26 A is at right angles to the axis of rotation  30  of the yarn balloon B and is arranged so that the clip  26   a  is lifted by the yarn balloon B and thereby positioned in an operating position BS, which as in the example embodiment of  FIG. 2 , is recognised by the associated sensor device  24  and is sent via the signal line  25 , as an electric signal i, for further processing to the control circuit  18 . 
         [0092]    The embodiment of a scanning sensor  22  shown in  FIG. 4  corresponds essentially to the embodiment of a scanning sensor already known from  FIG. 3 . This means that the scanning sensor  22  has a clip  26   b  which is concave relative to the yarn balloon B and mounted pivotably at the ends. 
         [0093]    The clip  26 B bears against the yarn balloon B from the inside and therefore has a curvature  31 B outwards in the direction of the yarn balloon B, by means which, as already explained above, the contact of the running outer yarn  5  with the clip  26 B is minimised and the yarn is thus protected which has a positive effect on the yarn quality. 
         [0094]    The pivot axis  29 B of the clip  26 B is at right angles to the axis of rotation  30  of the yarn balloon B and is arranged so that the clip  26 A is lifted by the yarn balloon B and thereby positioned in an operating position BS, which as in the example embodiment of  FIGS. 2 and 3  is recognised by the associated sensor device  24  and sent via the signal line  25  as an electric signal i for further processing to the control circuit  18 . 
         [0095]    In a further advantageous embodiment the scanning sensor  22  can also be designed however as a spring-loaded scanning feeler  32  bearing on the yarn balloon B from the outside. 
         [0096]    The scanning feeler  32  can be designed to be linear, as shown in  FIG. 5 , or as shown in  FIG. 6  can have a concave curvature  33  relative to the yarn balloon B. 
         [0097]    In the linear design of the scanning feeler  32  shown in  FIG. 5  it is advantageous, to make the scanning feeler  32  from an elastic, wear-resistant material, for example spring steel, and to mount the scanning feeler  32  at one of its ends sides in a bearing position  34  so that it is positioned in the yarn balloon B of the running outer yarn  5  by the yarn in an operating position BS, which as explained above is identified by a sensor device  24  and reported to the control circuit  18 . 
         [0098]    If the scanning feeler  32 A, as shown in  FIG. 6 , has a concave curvature  33  relative to the yarn balloon B, it is advantageous to mount the scanning feeler  32 A at one of its end sides in a pivot bearing  35  and to load the latter on its opposite end side with a spring element  36  so that the scanning feeler  32 A bearing on the yarn balloon B of the running outer yarn  5  is positioned by the yarn in an operating position BS which is identified by the sensor device  24  and reported to the control circuit  18 . 
         [0099]    It will therefore be readily understood by those persons skilled in the art that the present invention is susceptible of a 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 embodiment, adaptations, variations, modifications and equivalent arrangements, the present invention being limited only by the claims appended hereto and the equivalents thereof.