Patent Publication Number: US-7716791-B2

Title: Apparatus at a spinning preparation machine, especially a flat card, roller card or the like, for ascertaining carding process variables

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   The present application claims priority from German Patent Application No. 10 2006 024 132.0 dated May 22, 2006, and German Patent of Application No. 10 2007 005 601.1 dated Jan. 31, 2007, the entire disclosure of which are incorporated herein by reference. 
   BACKGROUND TO THE INVENTION 
   The invention relates to an apparatus at a spinning preparation machine, especially a flat card, roller card or the like, for ascertaining carding process variables, wherein a clothed, rapidly rotating roller is located opposite at least one clothed component. 
   It is known to associate with the clothed component, in contact therewith, a piezoelectric sensor which is connected to an electrical evaluation device in communication with a display device and/or switching device. More particularly, from EP 1 215 312 A1 it is known, in the case of a revolving card top and a stationary carding segment, to measure the carding forces (shear forces) at both carding elements using a piezoelectric layer in each case. These piezoelectric layers are connected to a measurement apparatus. The measurement apparatus passes a corresponding signal to a control and regulation device. The carding forces are measured by means of piezoelectric layers and the associated measurement apparatuses and are passed to the control and regulation device by means of signals. In that arrangement, the carding force at the fixed carding element or at the revolving card top is determined by means of force measurement. It is disadvantageous that the carding forces, which are caused by the fibres between the tips, are minimal and the carding force sensors have a high weight owing to their freely movable carding elements. A further disadvantage lies in the fact that the mass inertia of such a system is very high. Accordingly, the resultant difference between the baseline signal and the useful signal is vanishingly small. If the weight of such a sensor is reduced, the rigidity of the system is reduced and sagging of the carding element is increased, whilst the measurement result is falsified because the spacing between the sensor and the roller changes. In the case of the known apparatus, the force sensor cuts through the lines of force, so that forces and shear forces can be detected. In the process, it is immaterial whether the piezo sensor detects the shear forces between the clothing and carding component holder or, for example, with respect to the side screen, because the lines of force pass through the entire structural unit. Because a force sensor cuts through lines of force, it must always rest against a component. For example, the clothing rests against the carding component, or the carding component rests against the side screen (corresponding force sensors between those components). Therefore it is not possible, in operation, to move a force sensor from one component to another component without changing settings, that is to say without undoing and re-fixing components, and interrupting lines of force. A constant force at the clothing produces a constant force at the piezo sensor and therefore a carding force produces no change in the piezo signal. Electrical filtering of the signal is not necessary because the forces from other machine regions do not influence the carding force measurement. Finally, the outlay for the measurement is, in terms of apparatus, high because the carding component has to be modified for the purpose of integrating the sensor. 
   The problem underlying the invention is accordingly to provide an apparatus of the kind described at the beginning that avoids the mentioned disadvantages and that especially makes it possible, by means that are simple in terms of construction, to ascertain the intensity of contact between fibres and the fibre-guiding clothing of the component (the carding intensity). 
   As a result of the fact that the piezoceramic sensor is a structure-borne sound sensor of high sensitivity, which is associated with a component and in contact therewith, it is possible to ascertain the carding intensity by means that are simple in terms of construction. The structure-borne sound sensor is merely coupled up to a component in which structure-borne sound vibrations occur, as a result of which those structure-borne sound vibrations also pass into and flow through the structure-borne sound sensor, and the vibrations can be detected by means of a measurement arrangement. If the structure-borne sound sensor and the fixed carding element are so constructed that, for example, their connection is, advantageously, magnetic in nature, the structure-borne sound sensor can, in the course of continuing production, be moved from carding element to carding element, being placed thereon, and the carding intensity can be measured. It is accordingly possible, within the shortest time, to investigate all the carding locations of a flat card, including the card top, with regard to the carding intensity thereof, in the course of continuing production. As a result of the fact that the structure-borne sound sensor, which is, for example, a small cuboid, is fixed in, for example, an existing fixed carding element or revolving card top, functions of the fixed carding element or revolving card top are in no way curtailed by a change in geometry etc. 
   In the course of carding, the fibres produce a transverse vibration in the clothing, which propagates through the entire carding component. If the piezo sensor is attached to a carding component through which vibrations pass, the vibration also runs through this mounted sensor. Consequently, the vibration also causes deformation of that component, that is to say the vibration can be described by means of the piezo sensor. Even in the case of a constant force at the clothing, a change in the piezo signal occurs. Electrical filtering of the signal is necessary because the vibrations from other machine regions influence the structure-borne sound measurement. Low-frequency vibrations of all moving components are filtered out. The apparatus is simple in terms of construction, as the piezo sensor merely has to be placed on the component. 
   The structure-borne sound sensor is advantageously of high sensitivity. Preferably, the sensitivity of the structure-borne sound sensor is about 10 V/N to 50 V/N, especially about 25 V/N to 35 V/N. The structure-borne sound sensor may be capable of detecting vibrations in the range from about 2.5 kHz to 12.5 kHz. In certain preferred embodiments, the evaluation device is capable of filtering out low-frequency vibrations, for example, is capable of filtering out frequencies outside the range of about 2.5 kHz to 12 kHz. One illustrative evaluation device has a frequency analysis function (Fourier analysis). A high-pass filter may be used. In certain preferred arrangements, carding is carried out between a clothing-carrying roller and a carding element, a piezoceramic structure-borne sound sensor being associated with one of the clothing-carrying components. The structure-borne sound sensor may, for example, be arranged directly on the rear side of the clothing. The structure-borne sound sensor may, for example, be fixed in the middle of the machine width. In some embodiments, the structure-borne sound sensor is fixed in a fixed carding segment. In other embodiments, the structure-borne sound sensor is fixed in a revolving card top. The structure-borne sound sensor may be fixed to the component by means of adhesion. Other suitable fixing methods include fixing by means of magnetic force, by means of a screw connection, or by means of a shape-based connection. In some embodiments, the structure-borne sound sensor is externally fixed on a component carrying a clothing strip. There may in some arrangements be a direct structure-borne sound line between clothing support and adapter plate, for example, by means of a screw connection. In certain embodiments, the structure-borne sound sensor is fixed on a plate which is flexibly associated with different clothing-strip-carrying components by means of a rapid closure. The rapid closure may be provided, for example, by means of a shape-based or force-based connection. It is advantageous for the structure-borne sound sensor signals to be so filtered that the signal contains no components of structure-borne sound vibrations of the spinning preparation machine that are caused by moving parts of the machine. For example, all structure-borne sound vibrations less than 2.5 kHz are filtered out from the structure-borne sound sensor signals. It is preferred that there are used solely those components of the structure-borne sound sensor signal that are caused by the fibre movement between the carding parts of the machine. The structure-borne sound sensor signals may be evaluated, for example, by means of statistical evaluation methods (mean, standard deviation, CV value). The structure-borne sound sensor signals may, for example, be integrated. The structure-borne sound sensor signals in their course over time and in the frequency range may, for example, be evaluated by means of statistical evaluation methods. The structure-borne sound sensor signals may, for example, be logarithmised to avoid over-valuation of signal peaks. In one embodiment, in the frequency range the structure-borne sound sensor signal curves “with fibre material” are deduced from those “without fibre material” and the course of the difference in the frequency range is evaluated. 
   The carding intensity “with fibre material” may be subtracted from “without fibre material”. Instead, the carding intensity “with fibre material” may be divided by “without fibre material”. Signal peaks in the course over time may be evaluated as thick places. The variables standard deviation and CV value represent a measure of the fibre unraveling. From the determined data, carding intensity classes (amplitude; frequency) are formed in order to be able to evaluate the pulses in detail. With fixed carding between two carding components there will be clearly associated at least one carding coefficient which reflects the carding intensity. On the basis of the carding intensity information at each carding component, the clothing wear can, for example, be assessed and the setting checked. The carding intensity of the machine as a whole can be determined by accumulation of individual measurements and can be set against a quality statement for the machine, for example, flat card. Illustrative of a quality statement for a flat card would be: 95 neps/g; 9.8% short fibres. 
   In certain embodiments there may be a multiplicity of carding elements and each carding element may have its own structure-borne sound sensor associated with it. In other embodiments, the structure-borne sound sensor is in the form of a portable unit which can be used on any machine. In yet further embodiments, the apparatus is so arranged that the operator can associate one and the same structure-borne sound sensor with each carding element in succession, in accordance with a fixed program sequence. The structure-borne sound sensor signals of more than two carding elements may be evaluated relative to one another. In some embodiments, the grading of the carding elements for example with respect to the number of ties, spacing, clothing condition, clothing type, can be assessed by means of the structure-borne sound sensor signal, by comparing the carding coefficients of all the carding elements with specifications relating to desirable grading of the carding intensity. Preferably, in the comparison of the carding coefficients of different carding elements the carding coefficients are normalisable. If desired, the structure-borne sound sensor can be used for analysis at fibre-guiding components, for example web guide, pressure bar, holding-down device, webspeed, funnel, cover plates at the transfers from rollers (drum-doffer). 
   In certain preferred arrangements, the machine is a flat card and the structure-borne sound sensor is associated with the revolving card top, is fixed in or on it and revolves with it. The structure-borne sound sensor may be fixed in a stationary position on the track of the revolving card top flats. Instead, there may be attached to the structure-borne sound sensor a structure-borne sound guide plate, for example, a spring steel plate, by means of which the structure-borne sound of the revolving card top flats is detected and conveyed to the structure-borne sound sensor. The structure-borne sound sensor may in some embodiments be directly or indirectly associated with a blade in order to quantify the waste separation, that is to say composition and amount. It is preferred that the apparatus includes a control system, the clothing condition, that is to say new or worn clothing, for example of a clothing strip, being determined using the structure-borne sound sensor, by means of the fact that the carding coefficient is determined and monitored by the control system and a warning being issued by the control system in the event of a limit value being exceeded. A portable structure-borne sound sensor unit with evaluation device may, in preferred embodiments, consist of, for example, a display for output of the carding coefficient, a start button for activation of the measurement and an LED for display of the operating situation. 
   In the case of revolving card flats, in one embodiment a first flat, having a clothing, carries the structure-borne sound sensor and a second flat, not having a clothing, having on-board electronics units, runs behind the first flat. The first flat is advantageously connected to the second flat by a sensor cable. Between the first flat (having a clothing) and the second flat (having electronics units) there may be arranged no flat or at least one flat having a clothing. The sensor may be associated with a holding element, for example, a clasp or the like, in contact with and touching at least two different wall surfaces of the carrier member. The clasp may be associated with the card flat by means of a shape-based or force-based connection. The clasp may be so associated with the card flat that the sensor is arranged inside the card flat or outside the card flat. The signals of the structure-borne sound sensor are advantageously recordable throughout its travel over the flexible bend. Instead, the signals of the structure-borne sound sensor can be recorded at particular places over the flexible bend, over a period of time. The signals can advantageously be recorded at each change of setting of the card flat. In preferred embodiments, a plurality of structure-borne sound sensors are attached by clasps to a card flat, preferably on both sides, that is, on the left and right sides of the machine. In one embodiment, a clasp and sensor are associated with a carding flat, and an electronics unit can also be arranged, for example, can be insertable, in the same flat in the form of an insert variant. 
   The invention also provides an apparatus at a spinning preparation machine, especially a flat card, roller card or the like, wherein a clothed, rapidly rotating roller is located opposite at least one clothed component, there being associated with the component, in contact therewith, a piezoelectric sensor which is connected to an electrical evaluation device in communication with a display device and/or switching device, wherein the piezoelectric sensor is a structure-borne sound sensor of high sensitivity and the electrical evaluation device is capable of determining from the structure-borne sound the intensity of contact between fibres and the fibre-guiding clothing of the component (the carding intensity). 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagrammatic side view of a flat card with which the apparatus according to the invention may be used; 
       FIG. 2  shows flats of a revolving card top unit and part of the cylinder with a carding nip between the clothings of the revolving card top flats and the clothing of the cylinder; 
       FIG. 3  shows, partly in section, a stationary carding segment and part of a side screen, with a spacing between the carding segment clothing and the cylinder clothing; 
     FIG.  3 ′ shows a detail of  FIG. 3  to an enlarged scale 
       FIG. 3   a  is a section of a carding segment according to  FIG. 3 , with a first embodiment of the structure-borne sound sensor; 
       FIG. 3   b  is a section of a carding segment according to  FIG. 3 , with a further embodiment of the structure-borne sound sensor; 
       FIG. 4  is a schematic side view of a flat for a revolving card top unit according to  FIG. 2 , in the internal space of which a structure-borne sound sensor is provided; 
       FIG. 5  is a plan view of a revolving card top with a stationary structure-borne sound sensor having a structure-borne sound guide plate, by means of which the structure-borne sound of the revolving card top is detected; 
       FIG. 6  is a diagrammatic side view of a carding cylinder with stationary carding elements and a revolving card top, and showing a generalised circuit diagram with an electrical control and regulation apparatus, to which there are connected a structure-borne sound sensor, a filter device, an evaluation device, an actuator for a drive motor and a display device; 
       FIGS. 7   a ,  7   b  are a side view ( FIG. 7   a ) and a front view ( FIG. 7   b ) of a flat including an embodiment having a clasp and a structure-borne sound sensor internally arranged; 
       FIG. 8  is a side view of a card flat including an embodiment having a clasp and a structure-borne sound sensor externally arranged; 
       FIG. 9  is a side view of a plurality of flats, wherein a clasp with a structure-borne sound sensor is associated with a carding flat, and an associated electronics unit is associated with a non-carding flat; and 
       FIG. 10  is a top sectional view of a card flat, wherein both a clasp with a sensor and also the associated electronics unit are associated with the same card flat. 
   

   DETAILED DESCRIPTION OF CERTAIN PREFERRED EMBODIMENTS 
   With reference to  FIG. 1 , a flat card, for example a TC 03 flat card made by Trützschler GmbH &amp; Co. KG of Mönchengladbach, Germany, has a feed roller  1 , feed table  2 , lickers-in  3   a ,  3   b ,  3   c , cylinder  4 , doffer  5 , stripper roller  6 , nip rollers  7 ,  8 , web-guiding element  9 , web funnel  10 , delivery rollers  11 ,  12 , revolving card top  13  having card top guide rollers  13   a ,  13   b  and flats  14 , can  15  and can coiler  16 . The directions of rotation of the rollers are indicated by curved arrows. Reference letter M denotes the centre (axis) of the cylinder  4  and reference letter A denotes the working direction. Reference  4   a  denotes the clothing and reference  4   b  denotes the direction of rotation of the high-speed cylinder  4 . Reference letter C denotes the direction in which the revolving card top  13  revolves at the carding location and reference letter D denotes the return transport direction of the flats  14 . In the pre-carding region—between the licker-in  3   c  and the back card top guide roller  13   a —there are arranged a plurality of fixed carding elements  25 ′ (see  FIG. 3 ), and in the post-carding region—between the front card top guide roller  13   b  and the doffer  5 —there are arranged a plurality of fixed carding elements  25 ″ (see  FIG. 3 ). A structure-borne sound sensor  30   1  is arranged at one of the fixed carding elements  25 ′ in the pre-carding region. 
     FIG. 2  shows a portion of a revolving card top of a flat card of the kind shown in  FIG. 1 . A flexible bend  17  having several adjustment screws is fixed laterally to the frame of the machine on each side, using screws (not shown). The flexible bend  17  has a convex outer surface  17   a  and an underside  17   b . On top of the flexible bend  17  there is a slideway  20 , for example made of low-friction plastics material, which has a convex outer surface  20   a  and a concave inner surface  20   b . The concave inner surface  20   b  rests on top of the convex outer surface  17   a . The card flats  14 , which are extruded from aluminium, have a carrier member  14   c  in the form of a hollow profiled member and, at each of their two ends, a card flat foot  14   a , in which there are mounted in an axial direction two steel pins  18 , which slide on the convex outer surface  20   a  of the slideway  20  in the direction of arrow C. The card flat clothing  24  (small wire hooks) is mounted on the underside of the card flat foot  14   a . Reference numeral  23  denotes the circle of tips of the card flat clothings  24 . On the outside of the carrier member  14   c  of one of the card flats  14  there is arranged a structure-borne sound sensor  30   2 . 
   The cylinder  4  has on its circumference a cylinder clothing  4   a , for example a sawtooth clothing. Reference numeral  22  denotes the circle of the tips of the cylinder clothing  4   a . The spacing (carding nip) between the circle of tips  23  and the circle of tips  22  is denoted by reference letter a and is, for example, 2/1000″. The carding spacing of the flat card, that is to say of the cylinder  4  having the cylinder clothing  4   a  and of the card flats  14  having the card flat clothings  24 , is set in practice. In order to reduce or avoid the risk of collisions, the carding nip between clothings located opposite one another is in practice set to be slightly greater, that is to say a certain safety margin is provided. However, a large carding nip results in undesirable nep formation in the carded sliver. Rather, an optimum, especially a narrow, size is desirable, as a result of which the proportion of neps in the carded sliver is substantially reduced. The spacing between the convex outer surface  20   a  and the circle of tips  22  is denoted by reference letter b. The radius of the convex outer surface  20   a  is denoted by reference letter r 1  and the constant radius of the circle of tips  22  is denoted by reference letter r 2 . The radius r 2  intersects the centre point M (see  FIG. 1 ) of the cylinder  4 . Reference numeral  19  denotes a clamping element, which engages around the card flat pins  18  and which is connected to the drive belt (not shown) for the card flats  14 . 
   In  FIG. 3 , there is shown a stationary carding element, which may be used with a further embodiment of the invention. An approximately semi-circular, rigid side panel  38  is fixed laterally to the machine frame (not shown) on each side of the flat card, on the outside of which panel in the region of the periphery there is integrally cast in a concentric position a rigid arcuate supporting element  39 , which has, as supporting surface, a convex outer surface  39   a  and an underside  39   b . Stationary carding elements  25  have, at both their ends, mounting surfaces, which are mounted on the convex outer surface  39   a  of the mounting element. Fixed to the underneath surface of the carding element  25  are carding segments  26   a ,  26   b  having carding clothings  26   a ′,  26   b . Reference numeral  21  denotes the circle of tips of the clothings  26   a ′,  26   b . The cylinder  4  has, around its circumference, a cylinder clothing  4   a , for example a saw-tooth clothing. Reference numeral  22  denotes the circle of tips of the cylinder clothing  4   a . The spacing between the circle of tips  21  and the circle of tips  22  is indicated by the reference letter c and is, for example, 0.20 mm. Reference letter d denotes the spacing between the convex outer surface  39   a  and the circle of tips  22 . Reference r 1  denotes the radius of the convex outer surface  39   a  and reference r 2  denotes the radius of the circle of tips  22 . The radii r 1  and r 2  intersect in the centre M (see  FIG. 1 ) of the cylinder  4 . The carding element  25  according to  FIG. 3  consists of a carrier  25   a  and two carding segments  26   a ,  26   b , which are arranged one after the other in the direction of rotation (arrow  4   b ) of the cylinder  4 , the clothings ( 26   a ′,  26   b ′) of the carding segments  26   a ,  26   b  and the clothing  4   a  of the cylinder  4  lying opposite one another. The spacing c between the clothings  26   a ′,  26   b ′ of the carding segments  26   a ,  26   b  and the cylinder clothing  4   a  is of great importance to the carding process and to the result of carding. 
   In the embodiment of  FIG. 3   a , a structure-borne sound sensor  30   3  is attached to an inside wall surface of a hollow space  25   b  in the carrier member  25   a . In another embodiment shown in  FIG. 3   b , the carding segments  26   a  and  26   b  are attached to the carrier  25   a  by means of bolts  27   a  and  27   b , respectively. One end region of a bracket  28  is also attached to the carrier  25   a  by means of the bolt  27   b , there being attached to the other end region of the bracket  28  a structure-borne sound sensor  30   4 . 
   In a further embodiment shown in  FIG. 4 , a structure-borne sound sensor is associated with a card flat of a revolving card top.  FIG. 4  shows a section through a card flat  14 , a structure-borne sound sensor  30   5  being attached in the internal space  14   b  of the hollow profiled member, on the card flat foot  14   a.    
   In another embodiment, in  FIG. 5 , a stationary structure-borne sound sensor  30   6  is attached at one end of a structure-borne sound guide plate  29 , the other end of which is in successive contact with the ends of the card flats  14 ′,  14 ″,  14 ″′ slowly moved in direction c, in the course of which the structure-borne sound of the card flats  14 ′,  14 ″,  14 ″′ is detected. 
     FIG. 6  shows schematically the flat card according to  FIG. 1 . The structure-borne sound sensor  30   1  is attached to the fixed carding element  25 ′ and is connected to an electrical control and regulation device  31 , for example a microcomputer with a microprocessor. The electrical control and regulation device  31  comprises a filter device (not shown) and an evaluation device (not shown). The filter device, for example a high-pass filter, filters out low-frequency vibrations. The evaluation device, which comprises, for example, a frequency analysis function, evaluates the signals of the structure-borne sound sensor  30   1 . From the evaluated signals there are produced, in the control and regulation device  31 , actuation signals for the electric drive motor  32 , for example a speed-of-rotation-controlled motor, for driving the cylinder  4 . Also connected to the control and regulation device  31  is a display device  33 , which shows the frequency response, for example, in graphical form. 
   The measurement values of the carding intensity determination are evaluated with respect to:
         Mean   standard deviation   coefficient of variation, CV value   number of peaks with respect to a threshold value   the frequency distribution of the voltage signals, and characteristic variables thereof etc. and this information is used in the context of a closed control circuit for controlling actuating members of the machine.       

   The sensitivity with which a structure-borne sound sensor  30   1  to  30   6  registers component vibrations, produced by fibre contact, in the audible range is given in V/N (volts per newton). 
   In the embodiment of  FIGS. 7   a ,  7   b , a structure-borne sound sensor  30  is associated with, for example adhesively bonded, screwed or magnetically connected to, a clasp  34 . This clasp is associated with any desired card flat  14  by means of a force-based and/or shape-based connection. The structure-borne sound consequently passes from the revolving card top, by way of the clasp  34 , into the structure-borne sound sensor  30 , where it is converted into an electrical signal. Such attachment of the structure-borne sound sensor provides maximum flexibility with regard to selection of the card flat  14  and the card flat clothing and also of the flat card, because the clasp can be placed on any desired card flat. It also allows the sensor to be attached permanently to a card flat, that is to say the sensor runs around permanently in the card top unit, attached to or on a particular card flat  14 . The clasp has two resilient arms, both of which bear a contact element at the free end, one contact-element-bearing arm being associated with an inner wall and the other contact-element-bearing arm being associated with an outer wall of the carrier member  14   c . The structure-borne sound sensor  30  is located on an arm in the hollow internal space  14   b.    
   In a further embodiment shown in  FIG. 8 , one contact-element-bearing arm of a clasp is associated with one outer wall and the other contact-element-bearing arm is associated with another outer wall of a carrier member  14   c  of a card flat. The structure-borne sound sensor  30  is located outside the carrier member  14   c.    
   In yet another embodiment shown in  FIG. 9 , the functions of measurement data collection and of evaluation can be split between two card flats  14 ′ and  14 ″′, respectively (“measurement flat duo”). This measurement flat duo consists of two flats. With a first, carding flat  14 ′ there is associated the structure-borne sound sensor  30  having a clasp  34 , and with a further flat  14 ′″, which has no clothing, there are associated the necessary electronic components  35 , that is to say they are on-board. The flat  14 ′ having the structure-borne sound sensor  30  is positioned first, seen in the direction contrary to the running direction  46  of the drum  4 , and the flat  14 ′″ having the electronics  35  (without a clothing) follows after that flat. The two flats are connected to one another by measurement data cable  36 . Reference letter  4   b  denotes the running direction of the opposed carding surface whilst the flats  14 ′ to  14 ″″ move in the opposite direction to the arrow  4   b.    
   This measurement flat duo can be used in any desired flat card. It is possible to replace one of the flats of the flat card with the flat having the electronics units and to attach the clasp with the structure-borne sound sensor to a card flat positioned in advance thereof. As a result, measurement of the carding intensity is possible under operating conditions that are as realistic as possible. The measurement equipment is no larger and no heavier than an instrument case accommodating the flat with electronics units and the structure-borne sound sensor with clasp. 
     FIG. 10  shows another embodiment in which both the clasp  34  with the structure-borne sound sensor  30  and also the associated electrical unit  35  are associated with the same card flat  14 . The structure-borne sound sensor  30  and the electrical unit  35  are connected to one another by means of a measurement data cable  36 . The structure-borne sound sensor  30  and the electrical unit  35  are located in the hollow internal space  14   b  of the carrier member. 
   Although the foregoing invention has been described in detail by way of illustration and example for purposes of understanding, it will be obvious that changes and modifications may be practiced within the scope of the appended claims.