Abstract:
To improve the properties of all-steel card clothings, a saw-toothed wire is proposed with a foot portion and a plurality of teeth arranged consecutively in the lengthwise direction of the wire, the teeth issuing from the foot portion and each tooth ending in a single point, and where the interval between the points of two consecutive teeth is different from the interval between the points of other consecutive teeth.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention concerns a saw-toothed wire with a foot portion and a plurality of teeth arranged in linear sequence along the wire, each tooth issuing from the foot portion and ending in a single point; a process and apparatus for the manufacture of saw-toothed wires of this kind; and the use of saw-toothed wires of this kind for the processing of textile fibers. 
     All-steel card clothings made of a plurality of saw-toothed wires of the kind described above that are mounted parallel to each other on a carrier base have almost totally replaced the originally used needle-toothed card clothings in the processing of textile fibers. One reason for this is that all-steel card clothings of this kind are more wear-resistant and, as a consequence, offer the possibility of increasing the processing speed; another reason is the fact that saw-toothed wires of this kind are comparatively simple to manufacture. 
     2. Description of the Related Art 
     A state-of-the-art apparatus for manufacturing saw-toothed wires of the kind described at the beginning is shown in FIG.  4 . This apparatus has a feed mechanism  410  mounted on a machine bed  400 , by which a profile wire  450  is advanced along a given travel path  454 . For this purpose, the profile wire  450  is clamped tight between two feed rollers  418 , one of which is driven to turn about a rotational axis  420  that is perpendicular to the given travel path  454 . 
     For working the profile wire  450 , there is further a machine tool  430  mounted on the machine bed. This machine tool  430  comprises a spindle  436  running in bearings in a spindle stock  434  and driven by a 3-phase AC motor  432  to rotate in the direction shown by the arrow  437 . A blanking tool holder  438  is mounted on the front end of the spindle  436  in a rotationally fixed connection. A blanking tool  440  that is mounted on the blanking tool holder  438  and works together with a blanking die  442  of the machine tool  430  provides the means for producing saw-teeth by blanking material-free portions out of the profile wire  450 . The 3-phase AC motor  432 , the spindle stock  434 , the spindle  436  and the blanking die  442  are mounted together on a base plate  444  which can be swiveled in increments of 5° relative to the machine bed  400  and the feed mechanism  410 , as indicated by the graduation marks of the angular scale  446 . 
     Mounted at the front end of the spindle  436  is a bevel gear  412 . This bevel gear  412  meshes with a bevel gear  414  that is attached in a rotationally fixed connection to that end of a worm gear that faces the machine tool. Thereby, the worm gear is made to turn about a rotational axis whose position is fixed in relation to the machine bed  400  and the feed mechanism  410 . This rotation is transferred to a gear that meshes with the worm gear  416  and turns about the rotational axis  420  extending perpendicular to the given travel path  454 . This allows the pair of feed rollers  418  to be driven by the 3-phase AC motor  432  via the worm gear  416 , the bevel gear  414 , the bevel gear  412  and spindle  436 . This drive mechanism assures that the profile wire  450  is advanced each time by an equal feed interval in the direction indicated by arrow  452  between the individual work steps performed by the blanking tool  440 . 
     Accordingly, the apparatus shown in FIG. 4, using only one drive motor and one machine tool, provides a particularly simple means of producing saw-toothed wires with a constant pitch, i.e., a constant interval between the points of consecutive teeth. The shape and pitch of the teeth of the saw-toothed wire produced in this manner depend on the position of the base plate  444  relative to the machine bed  400  and also on the feed mechanism  410 , the blanking tool being used, and the transmission ratio effectuated by the worm gear  416  in combination with the gear that turns about the rotating axis  420 . 
     When saw-toothed wires made with equipment of the kind shown in FIG. 4 are used in the processing of textile fibers, one observes, particularly at high processing speeds, an increase in damaged staple fibers and accumulations of non-aligned fibers, especially of short fibers (pilling effect). 
     SUMMARY OF THE INVENTION 
     In view of the problems with the existing state of the art, the object of the present invention is to provide a saw-toothed wire of the kind described at the beginning that enables a reliable and gentle processing of fibers while assuring a high degree of wear resistance combined with easy manufacturability, and to further provide an apparatus for the manufacture of saw-toothed wires of this kind. 
     In accordance with the invention, the problem is solved through saw-toothed wires in which the interval between the points of two consecutive teeth is different from the interval between other consecutive teeth, and through processes and devices for the manufacture of saw-toothed wires of this kind. 
     This solution of the inventive problem is founded on the insight that the observed damage of the staple fibers and other defects in the processing of fibers are traceable to the different requirements that a saw-toothed wire used in the processing of textile fibers must meet when penetrating into the fiber fleece, working the fiber fleece and leaving the fiber fleece. With the inventive saw-toothed wire, the tooth pitches of individual segments can be adapted to these different requirements, whereby an overall improvement of the processing result is achieved. 
     In this, it has proven to be particularly practical if the spacing between the points of consecutive teeth along a wire segment of given length changes continuously. To meet this condition, the spacing between the points of consecutive teeth may at first increase continuously, starting from a first given interval up to a second given interval, and then decrease continuously, starting from the second given interval back to the first given interval. From a manufacturing point of view, it has proven to be particularly advantageous if the amount of the difference between consecutive intervals between the points of consecutive teeth along a given wire segment is approximately constant. 
     The desired variation pattern of the pitch of saw-toothed wires according to the invention may be obtained, e.g., by forming material-free portions between the saw-teeth, the saw-teeth being of identical shape, e.g., of a triangular point shape, an arcuate tooth shape, or a truncated triangular point shape. To accomplish this purpose, it is envisaged, for example, to create material-free portions between two consecutive teeth through a number of consecutively performed operations with a machine tool, particularly a blanking tool. As an alternative, however, the saw-toothed wire may also comprise saw-teeth of differing shapes, e.g. of a rhomboid shape, that are separated from each other by material-free portions of identical shape. For the manufacture of saw-toothed wires of this kind, each of the material-free portions can be produced in a single operation. 
     For the manufacture of saw-toothed wires according to the invention, it has proven to be particularly practical if a relative motion of the profile wire in relation to a machine tool device is generated by means of a feed mechanism, and the profile wire, in the course of the relative motion, is subjected to successively performed operations, e.g., blanking operations, for producing the saw-teeth, wherein the feed mechanism is controlled in accordance with a given program for generating different amounts of feed travel between the successively performed operations. 
     In view of the generally expensive construction of the machine tool device, it is particularly advantageous if the profile wire is advanced by the feed mechanism along a given travel path and the individual operations by the machine tool device occur at a given location along the travel path. 
     In this, the attainment of the desired pitch variation pattern can be assured by registering the operating position of the machine tool device and controlling the feed mechanism based on the registered operating position. If the machine tool device has a rotatable milling spindle with a blanking tool attached to it, the angular position of the milling spindle can be continuously registered by means of an angular decoder, and the feed mechanism can be controlled on the basis of the angular position that has been determined in this manner. 
     In order to compensate and thereby eliminate possible spacing errors that could possibly occur with this kind of control, it has proven to be particularly practical if the feed travel of the profile wire, too, is continuously registered and the feed mechanism and/or the machine tool device is controlled on the basis of the registered feed travel. For this purpose, the feed mechanism may comprise a feed roller that is brought to bear against the profile wire and whose angular position is continuously registered by a second angular decoder. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     In the following, the invention is explained in correlation with the drawing, which is also being explicitly referred to with regard to all details essential to the invention that are not closely portrayed in the description. 
     In the drawing, 
     FIG. 1 shows an apparatus in accordance with the invention for the manufacture of a saw-toothed wire, 
     FIGS. 2 a  to  2   d  show embodiments of saw-toothed wires according to the invention, 
     FIGS. 3 a  to  3   c  show pitch variation patterns that can be made with the apparatus according to FIG. 1, 
     FIG. 4 shows an apparatus for manufacturing saw-toothed wires according to the existing state of the art. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The apparatus illustrated in FIG. 1 comprises a feed mechanism  110  and a machine tool  130 , both mounted on a machine bed  100 . The feed mechanism  110  essentially consists of a servo motor  112 , a reduction gear box  114  and a pair of feed rollers  116  between which a saw-toothed wire  150  is tightly held. One feed roller of the feed roller pair  116  is mounted directly on the shaft of the reduction gear box  114 , so that through the rotation of this feed roller in the direction indicated by arrow  152 , the profile wire  150  is advanced along a given feed path  154 . 
     The machine tool  130  essentially consists of a servo motor  132  and a spindle  136  that runs in bearings contained in a spindle stock  134  and can be driven by the servomotor  132  in the direction indicated by arrow  137 . At the front end of the spindle  136 , a blanking tool holder  138  is mounted in a rotationally fixed connection. Fastened to the blanking tool holder  138  is a blanking tool  140  which, working together with the blanking die  142 , serves to punch material-free portions out of the profile wire  150  for the purpose of making saw-teeth. The servo motor  132 , the spindle stock  134  and thus the spindle  136  itself, as well as the blanking die  142 , are mounted on a base plate  144  that can be swiveled in steps of 5° relative to the machine bed and thus also in relation to the feed mechanism  110 , as indicated by the graduation marks of the angular scale  146 . 
     The servo motor  132  of the machine tool  130  is controlled in accordance with a given program by a controller  160  via a control line  166 . At the same time, the angular position of the spindle  136  is registered by an angular decoder  162  and transmitted to the controller  160  via a line  164 . Dependent on the angular position of the spindle  136  as registered by the angular decoder  162 , the servomotor  112  of the feed mechanism  110  is controlled by the controller  160  via a control line  172 . The feed advance of the saw-toothed wire  150  along the feed path  154 , which is caused by the action of the servo motor  112  of the feed mechanism  110 , is registered by an angular decoder  168 . A signal representing the registered feed advance is transmitted from the angular decoder  168  to the controller  160  via a line  170 . This makes it possible to continuously monitor whether or not the feed advance that was determined by the program based on the angular position of the spindle  136  was indeed transferred to the profile wire  150  via the reduction gear box  114 . In case the feed advance deviates from the amount that was determined by the given program, the control of the servo motor  112  via the control line  172  can at once be adjusted correspondingly. In this manner, the angle of rotation of the feed roller pair relative to each turn of the spindle  136  can be adjusted with infinite variability. This makes it possible to effect a feed advance of the profile wire between the feed roller pair in steps of 0.01 mm. With the just described mode of operation of the apparatus represented in FIG. 1, the servo motor  132  of the machine tool  130  serves as “master” and the servo motor  112  of the feed mechanism  110  serves as “slave”. 
     In the inventive apparatus, the known mechanical coupling between the spindle of the machine tool and the advance mechanism is replaced by an electronic coupling. This electronic coupling is effected by means of the controller  160  with the given program, wherein the parallel operation of both servo motors  132  and  112  is of utmost importance, particularly in the start and stop phases. 
     With the apparatus as described, the tooth pitches can be continuously varied. This is accomplished by defining in the given program the period, called cycle length, in millimeters over which the variation is to take place and by specifying the size of the incremental difference per tooth in the variation pattern of the tooth pitch. 
     For the manufacture of different saw-toothed wires by means of the apparatus shown in FIG.,  1  one only has to change the parameters of the tooth pitch in the given program and, if necessary, to swivel the spindle relative to the feed mechanism  110  and, possibly, to exchange the blanking tool  140 . 
     By means of the apparatus shown in FIG. 1, it is possible to produce saw-toothed wires of variable pitch of the kinds shown in FIGS. 2 a ) to  2   c ). 
     Each of these saw-toothed wires  10  has a foot portion  12  with a plurality of teeth  14  that are arranged consecutively in the lengthwise direction of the wire, each of the teeth issuing from the foot portion  12  and ending in a point  16 . In the saw-toothed wires shown in FIG. 2, the spacing between the points of consecutive teeth, i.e., the tooth pitch, increases at first continuously along a first wire segment of given length, whereupon it decreases along a second wire segment of given length. In the saw-toothed wires shown in the FIGS. 2 a ) to  2   c ) with saw-teeth in triangular point shape, arcuate tooth shape, or truncated triangular point shape, this is accomplished by varying the shape of the material-free portion  18  between the individual teeth. To meet this purpose, the apparatus of FIG. 1 can cut the individual material-free portions  18  by performing a corresponding number of blanking steps. 
     In the saw-toothed wire represented in FIG. 2 d ), the continuous variation of the tooth pitch is attained by providing the essentially rhomboid-shaped teeth with a variable shape and separating them with material-free portions of identical shape. To produce saw-toothed wires of this kind, each material-free portion  18 ′ can be cut by the apparatus shown in FIG. 1 with only one blanking step, while between the individual blanking steps, the amount of feed advance of the profile wire is being varied. 
     FIG. 3 shows pitch variation patterns of saw-toothed wires that can be produced with the apparatus of FIG.  1 . For example, according to FIG. 3 a ), it is possible with a given program to produce a pitch variation pattern in which the spacing between the points of consecutive teeth along a wire segment of a given length δ1 increases at first continuously, starting from a first given interval up to a second given interval, and then decreases continuously from the second given interval to the first given interval, with the amount of the difference between consecutive intervals between the points of consecutive teeth being about constant. However, as shown in FIGS. 3 b ) and  3   c ), the pitch variation pattern can also be of an undulating or arbitrarily variable design. 
     The invention is not limited to the embodiments that are represented by the drawing. For example, it is also possible to produce saw-toothed wires in accordance with the invention that have different tooth shapes. As an alternative to the mode of operation shown in FIG. 1, it is also envisaged that the servo motor  112  of the feed mechanism  110  be used as master and the servo motor  132  of the machine tool  130  be used as slave.