Abstract:
A draw frame for textile fiber slivers has a drawing system of successively arranged assemblies of rollers comprising a bottom and a top roller, in which, during operation, the top rollers are pressed against the bottom rollers by weighted pressing devices. When operation is suspended, the bearings of the top rollers are relieved of the weighting by the pressing devices. On interruption to continuous operation the top output roller or the top output rollers is/are capable of being relieved of loading in such a way that no or only slight pressure is exerted on the fiber slivers. To avoid or reduce undesirable formation of windings in a simple manner, resiliently loaded elements that lift the top roller bearings after the pressing devices have been relieved of loading are associated with the bearings of at least one top roller.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application claims the priority of German Patent Application No. 103 31 759 dated 14 Jul. 2003, the disclosure of which is incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   The invention relates to an apparatus on a draw frame for textile fibre slivers with a drawing system of successively arranged pairs of rollers comprising a bottom and a top roller in which a load can be applied to the top rollers. 
   During operation of a draw frame of the above-mentioned kind, the top rollers are pressed against the bottom rollers by weighted pressing elements in pressing arms. When operation is suspended, the bearings of the top rollers are relieved of the loading by the pressing arms and upon interruption to continuous operation the top output roller or the top output rollers are relieved of loading such that no or only slight pressure is exerted on the fibre slivers. 
   During operation, the pressing arms are closed and the pressing devices press the top rollers onto the associated lower rollers of the drawing system. When operation of the drawing frame is suspended, particularly for a longer time period, the pressure cylinders and hence at the same time the top rollers are relieved of load, so that the rollers (roundness) and their resilient coating are protected against deformation. When the pressing arms are pivoted open while the top rollers remain stationary on the lower rollers, the top rollers exert a pressure on the bottom rollers by virtue of gravity. Since the slivers are positioned between the top and bottom rollers, the top rollers, in their idle state, exert a pressure on the slivers. During operation, particularly at high sliver speeds of 1,000 m/min and above, the rollers heat up substantially. The fibres frequently contain substances that become sticky when heated, for example, honeydew in the case of cotton and lubricating agents in the case of synthetic fibres. When the draw frame is at a standstill for a relatively long period—especially for longer than the time required to exchange full for empty cans at the output end of the draw frame—for example, on sliver rupture, when exchanging empty for full cans at the input end of the draw frame, during operational disturbances and the like, the top output roller(s) in particular, at the roller nip with the bottom output rollers, press against the substances clinging to the fibres and the substances become sticky owing to the heat. The disadvantage of this is that the slivers stick firmly especially to the top roller or top rollers and, when operation resumes, are entrained by the rotating roller and wind undesirably around the roller. This causes considerable disturbance to operation, since the drawing system is immediately stopped and the wrapped-round sliver has to be manually removed. In particular, the incident can often not be immediately resolved, which leads to delays and thus to production losses. 
   In a known apparatus (DE 198 39 885 A1), at least one separately controllable pneumatic valve for the pneumatic cylinder is associated with the top output roller and/or the top output rollers and at least one adjustable carrier lever or similar for the top output roller is associated with the pneumatic cylinder. By pulling in the ram, the carrier lever is drawn up and with it, the associated top roller bearing. In order to realise two loading functions of the pressure cylinder, that is, a push function and a pull function, a complicated valve device with corresponding valve control (separately controllable pneumatic valve) is required. 
   It is an aim of the invention further to improve an apparatus of the kind described in the introduction, and to provide a draw frame which avoids or mitigates the said disadvantages and in which in particular the undesirable formation of windings is avoided or reduced. 
   SUMMARY OF THE INVENTION 
   The invention provides a draw frame for textile fibre slivers having a drawing system comprising: 
   a first roller assembly and a second roller assembly, said first and second roller assemblies being arranged one after the other and each comprising a bottom roller and a top roller having first and second top roller bearings; 
   a loading arrangement for applying a load to said top rollers so as to press said top rollers against said respective bottom rollers, which load can be substantially relieved by the loading arrangement; and 
   a lifting arrangement for lifting a said top roller from a said bottom roller when said load is substantially relieved. 
   Advantageously, the lifting arrangement comprises: 
   a first resiliently loaded element associated with a first top roller bearing of a said top roller; 
   a second resiliently loaded element associated with a second top roller bearing of that roller; 
   said first and second resiliently loaded elements being arranged for lifting said first and second top roller bearings when the load applied by the loading arrangement is substantially relieved. 
   Advantageously, the lifting arrangement comprises first and second resilient loading elements for loading said first and second resiliently loaded elements. 
   When operation is interrupted, the bearing pressure of the top rollers on the fibre slivers is absent or substantially absent and, in particular, the top roller engages only slightly or not at all with the fibre material, so that heating of substances in the fibre material, and thus the adhesive effect, are avoided. The fibre slivers are thus effectively prevented from undesirably adhering to the rollers, so that entrainment upon re-start and hence the formation of a winding around the rollers does not occur. Because a resilient element, preferably a mechanical compression spring, is provided to lift the top roller bearing, a substantial structural simplification is achieved. Unlike the known apparatus, a separately controllable valve control for lifting the top roller is not present. A particular advantage is the fact that each time the top roller bearings are relieved of the pressure exerted by, for example, a pneumatic ram (that is, the pressure is reduced or removed), the resilient element automatically relaxes, and as a result, the top roller bearings are lifted from the bottom roller bearings including the top rollers from the bottom rollers. 
   Advantageously, at least one said resiliently loaded element is a driver element. At least one said loaded element is advantageously loaded by a spring, for example, a compression spring. Advantageously, as driver element an angle lever, angled plate or the like is provided. Advantageously, one angle arm of the driver element engages beneath the top roller bearing or the bearing stub. Advantageously, the free end of a resilient element, for example, compression spring, loads the driver element. Advantageously, a resilient element, for example, compression spring, is supported on a fixed bearing. Advantageously, the line of action of the ram and the line of action of at least one resilient element, for example, compression spring, run substantially axially parallel to one another. Advantageously, at least one resilient element, for example, compression spring, is tensioned in continuous operation. Advantageously, each time the pressing elements are relieved of loading, a said resilient element, for example, compression spring, relaxes. Advantageously, the relaxation of the resilient element, for example, compression spring, is effected automatically. Advantageously, lifting of the top roller bearings or the bearing stubs is effected upon extended interruption of continuous operation. Advantageously, lifting of the top roller bearings or the bearing stubs is effected within a short time. Advantageously, upon continuation of continuous operation, the loading of the top rollers and the tensioning of the resilient elements, for example, compression springs, are effected automatically. Advantageously, upon continuation of continuous operation, the loading of the top rollers and the tensioning of the resilient elements, for example, compression springs, are effected simultaneously. Advantageously, a 4-over-3 drawing system is present, the top roller nearest the output—viewed in the direction of travel of the textile fibre material—is relieved of loading. Advantageously, the top roller is a deflecting roller. Advantageously, at least one top output roller is lifted away from the bottom output roller. Advantageously, a spacing is present between the top output roller and/or the top output rollers and the fibre slivers. Advantageously, upon machine standstill at least one top roller is capable of being bought automatically out of contact with the fibres. Advantageously, the last top roller in the material running direction is capable of being brought automatically out of contact with the fibres. Advantageously, upon re-start of the machine the previously lifted roller is capable of being returned automatically into engagement under pressure loading. Advantageously, a mechanical element is provided as resilient element. Advantageously, adjustment devices, for example, threaded pins or the like, are provided for adjustment of the position of the driver element. 
   The invention also provides a draw frame for textile fibre slivers, having a drawing system comprising a roller to which in use a load can be applied, the load being relievable when the draw frame is not in operation, the draw frame further comprising a lifting arrangement for lifting said roller away from a second roller with which it is in co-operation during operation of the draw frame, when the load is relieved. 
   Moreover, the invention provides apparatus on a draw frame for textile fibre slivers with loading of the top rollers of the drawing system of successively arranged pairs of rollers comprising a bottom and a top roller, in which, during operation, the top rollers are pressed against the bottom rollers by weighted pressing elements in pressing arms, wherein the bearings of the top rollers, at standstill, are relieved of the loading by the pressing arms and the top output roller or the top output rollers is/are capable of being relieved of pressure on interruption to continuous operation so that no or only slight pressure is exerted on the fibre slivers, wherein respective resiliently loaded elements are associated with the bearings of at least one top roller and lift the top roller bearings when the pressing elements are relieved of loading. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic side view of the drawing system of a draw frame with an arrangement according to the invention; 
       FIG. 2  shows part of  FIG. 1  in the section corresponding to K-K ( FIG. 1 ) with a pneumatic top roller loading device; 
       FIG. 3  is a front view of a pressing arm with integral housing and two rams, 
       FIG. 3   a  is a perspective view of pressing arm shown in  FIG. 3 ; 
       FIG. 4   a  is a front view, partly in section, of a top roller bearing loaded by a ram on one side and a bearing stub loaded by a tensioned spring, top and bottom roller being located one on top of the other with no gap between them; 
       FIG. 4   b  shows a the top roller bearing of  FIG. 4   a  relieved of loading by the ram and the bearing stub lofted with the relaxed spring, top roller and bottom roller having a gap between them; 
       FIG. 4   c  shows in detail the spring-loaded angle lever shown in  FIGS. 4   a  and  4   b;    
       FIG. 5   a  is a front view, partly in section, of a top roller bearing of the top roller of  FIGS. 4   a  to  4   c , loaded by a ram and a bearing stub loaded with a tensioned spring, top and bottom roller (as in  FIG. 4   a ) being located one on top of the other; 
       FIG. 5   b  shows the top roller bearing relieved of loading by the ram and the bearing stub lifted with the relaxed spring, top roller and bottom roller (as in  FIG. 4   b ) having a gap between them; 
       FIG. 5   c  shows in detail the spring-loaded angle lever shown in  FIGS. 5   a  and  5   b;    
       FIG. 6   a  shows a drawing system of a draw frame according to the invention in operation with the top rollers loaded, and 
       FIG. 6   b  shows the drawing system of  FIG. 6   a  when operation is suspended, with the top rollers relieved of load and with the top output roller (deflecting roller) lifted. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
   With reference to  FIG. 1 , a drawing system S of a draw frame, for example, an HSR (Trade Mark) draw frame made by Trütrutzschler GmbH &amp; Co. KG of Mömonchengladbach, Germany, is provided. The drawing system S is designed as a 4-over-3 drawing system, that is, it comprises three bottom rollers I, II, III (I being the bottom output roller, II the middle bottom roller, III the bottom intake roller) and four top rollers  1 ,  2 ,  3 ,  4 . Drafting of the composite sliver  5  from a plurality of fibre slivers takes place in the drawing system S. The draft is made up from the preliminary draft and the main draft, and the roller pairs  4 /III and  3 /II form the preliminary drafting zone and the roller pairs  3 /II and  1 ,  2 /I form the main drafting zone. The bottom output roller I is driven by the main motor (not shown) and hence determines the rate of delivery. The bottom intake and middle bottom rollers III and II respectively are driven by a variable speed motor (not shown). The top rollers  1  to  4  are pressed against the bottom rollers I, II, III by pressing elements  9   1  to  9   4  (weighting device) in pressing arms  11   a  to  11   d  pivotable about pivot bearings (for example, as shown in  FIGS. 3 and 4   a ), and are hence driven by way of frictional engagement. The direction of rotation of the rollers I, II, III;  1 ,  2 ,  3 ,  4  is indicated by curved arrows. The composite fibre sliver  5 , which consists of a plurality of fibre slivers, runs in direction A. The bottom rollers I, II, III are mounted in bearers  14  (see  FIG. 3 ) which are arranged on the machine frame  15 . 
   Referring to  FIG. 2 , an upper supporting element  12  and a lower holding element  13   a  are associated with the pneumatic cylinder  9 . The pneumatic cylinder  9  forms a cylinder unit having a cylinder cavity  17  comprising two parts  17   a  and  17   b , in which a piston  18  is guided by means of a ram  19  in a sliding bushing  20 . The roller journal  4   a  of the pressure roller  4  passes right through an opening in a holding plate  27   a  and engages in a bearing  22   a . The bearing  22   a  receiving the pressure roller  4  extends into a space between the ram  19  and the roller journal IIIa of the bottom roller III. The bearing  22   a  is mounted on the holding element  13   a . A diaphragm  16  divides the cylinder cavity  17  into pressure regions. In order to generate pressure in the upper part  17   a  of the cylinder cavity  17 , compressed air p 1  can be admitted to this space by means of a compressed air connection  23 . Air is evacuated from the lower part  17   b  of the cylinder cavity  17  through a vent bore  24 . Analogously, air can be evacuated from the upper part of the cylinder cavity  17  and compressed air can be admitted to the lower part of the cylinder cavity  17 . In operation, after a fibre sliver  5  has been guided over the bottom rollers I, II, III, the pressing arms  11  are pivoted into the working position shown in  FIG. 4   a  and fixed in this position by a fixing device (not shown), so that the pressure rollers I, II, III are able to exert pressure. Application of pressure occurs on the one hand as a consequence of each of the rams  19  being located on the corresponding bearing  22 , and on the other hand in that an overpressure is generated in the void above the diaphragm  16 . The ram  19  therefore presses with its other end on the bearing  22 , in order to generate the said clamping between the top roller  4  and the bottom roller (drive roller) III. The ram  19  is displaceable in the direction of the arrows D, E. 
   Referring to  FIGS. 3 ,  3   a , the top roller  4  has associated with it a portal-form pressing arm  11   a . (A corresponding pressing arm  11   b ,  11   c ,  11   d  (not shown) is associated with each of the top rollers  2  to  4 ). In the embodiment shown in  FIG. 3 , the pressing arm  11   a  is in the form of a housing  11  of glass fibre-reinforced plastics and is manufactured by injection moulding. The housing  11  has an inner housing  30  which is an integral component of uniform construction comprising the supporting element  12 , the two bodies of the pressing elements  9   a   1  and  9   a   2  (pressure cylinders), two intermediate elements  31   a  and  31   b , and two holding elements  13   a  and  13   b . The supporting element  12  is in the form of a channel  12   a  of approximately U-shaped cross-section open on one side, pneumatic lines  34  and electrical leads  35  being arranged in the interior of the channel. The open side of the channel  12   a  is closable by a removable cover  36 , which consists of glass fibre-reinforced plastics material, has an approximately U-shaped cross-section and is resilient, such that it is fixed by an interference fit on the channel  33 . The housing  30  is preferably of one-piece construction. The integral housing  30 , which combines all the essential function elements for mounting and weighting the respective top rollers  1  to  4 , can thus be manufactured economically. At the same time, in a simple manner the entire pressing arm  11   a  to  11   d  is rotatable about the centre of rotation  10  and can be locked and unlocked by a locking device  26  (for example, as shown in  FIG. 5   a ). The rams  19   a  and  19   b  are relieved of pressure and hence lifted a distance b 1 , b 2  from the bearings  22   a  to  22   b  of the top roller  4  (see  FIGS. 4   b ,  5   b ). 
   In the embodiment of  FIG. 4   a , on one side of the top roller  4  the top roller bearing  22   a  is pneumatically loaded by the ram  19   a . The top roller  4  and the bottom roller III are located one on top of the other with no gap between them. An angle lever  36   a  having two angle arms  36   a   I  and  36   a   II  projecting at right angles, one at each end, is mounted on the holding element  13   a  as driver element. As  FIG. 4   c  illustrates, the angle arm  36   a   I  engages beneath the bearing stub  25   a  of the bearing  22   a . The other angle arm  36   a   II  is resiliently biased by a compression spring  37 , which is supported on the holding element  13   a . The line of action  38  of the compression spring  37  and the line of action  39  of the ram  19   a  are parallel with one another. The angle lever  36   a  is mounted so that it is displaceable relative to the holding element  13   a  in the direction of the arrows F, G, whereby the position of the angle lever  36   a  is adjustable (when the pressing arm  11   a  is without pressure). 
   According to  FIG. 5   a , on the other side of the top roller  4 , the top roller bearing  22   b  is pneumatically loaded by the ram  19   b . An angled plate  36   b  (see  FIG. 5   b ) is arranged as driver element on the holding element  13   b ; at one end of the angled plate an angle arm  36   b   I  projects at right angles. As  FIG. 5   c  shows, the angle arm  36   b   I  engages beneath the bearing stub  25   b  of the bearing  22   b . The angled plate  36   b  is resiliently biased by a compression spring  40 , which is supported on the holding element  13   b . The line of action  41  of the compression spring  40  and the line of action  42  of the ram  19   b  are axially parallel with one another. The angled plate  36   b  is mounted so that it is displaceable relative to the holding element  13   b  in the direction of the arrows F, G. The reference numeral  43  denotes a latching and unlatching element for the top roller  4 , pivotally mounted around a pivot bearing  44 . A threaded pin  45  acts on the angled plate  36   b , whereby the position of the angled plate  36   b  (when the pressing arm  11   a  is without pressure) is adjustable. 
   In operation, corresponding to  FIGS. 4   a ,  5   a , the rams  19   a  and  19   b  load the top roller bearings  22   a  respectively  22   b  in direction D. In this way, the bearing stubs  25   a  and  25   b  mounted on the top roller bearings  22   a ,  22   b  respectively are also pressed downwards in direction M. Via the angle arm  36   a   I  and via the angle arm  36   b   I , the angle lever  36   a  and the angled plate  36   b , and the bearing stubs  25   a  and  25   b , are pulled downwards in direction F—against the force of the respective compression springs  37  and  40 . At the same time and automatically, the compression springs  37  and  40  are consequently tensioned in direction N. 
   When operation is suspended, corresponding to  FIGS. 4   b ,  5   b , and the rams  19   a  and  19   b  are now relieved of loading in direction E, a gap b 1  respectively b 2  is present between the end of the rams  19   a  and  19   b  and the top roller bearings  22   a ,  22   b  respectively. Because the top roller bearings  22   a  and  22   b  have been relieved of loading, and by virtue of the gaps b 1  and b 2 , the bearing stubs  25   a  and  25   b  are likewise relieved of loading in direction L. Owing to the relaxation of the compression springs  37  and  40 , the bearing stubs  25   a  and  25   b  are pulled upwards or lifted in direction G by way of the angle lever  36   a  and the angled plate  36   b , by means of the angle arm  36   a   I  and the angle arm  36   b   I  respectively. At the same time and automatically, the compression springs  37  and  40  consequently relax in direction O. 
   Referring to  FIG. 6   a , in operation the top output rollers  1  and  2  lie on the bottom output roller I with applied loading, the fibre material  5  running through between the top output rollers  1  and  2  and the bottom output roller I. Upon extended stoppage time—which is detected in the electronics control and regulating device, not shown, for the drive motors—the top output roller  1  is relieved of loading and immediately thereafter, as shown in  FIG. 6   b , lifted by the distance c away from the fibre material  5  and the bottom output roller I. This prevents the fibre material  5  from adhering via foreign bodies and so on, as a result of pressure, to the top output roller  1 . Because the top output roller  2  is now relieved of loading and hence remains in place by gravity, the fibre material  5  remains firmly clamped and held between the top output roller  2  and the bottom output roller I and, upon re-start, can be guided without problem by the top output roller  1  and the bottom output roller I. 
   Except where the opposite is apparent, the same reference numerals are used to indicate corresponding parts in each of the drawings 
   The invention has been described by the example of pneumatic pressing elements (loading elements). Alternatively, mechanical, hydraulic or electrical pressing elements for loading the top rollers  1  to  4  can be used. 
   In practice, many loops appear around the deflecting roller  1 , usually caused by lubricating agents and adhesive particles present on the fibres. After an operational disturbance in the machine (sliver rupture, coiler can change or the like), the machine attendants are often not able to resolve such incidents immediately. The draw frame relieves the drawing system of loading after an interruption occurs, but the hot deflecting roller  1  lies on the fibres  5  under its own weight. If the deflecting roller  1  lies for an extended period on the sticky fibres  5 , these adhere to the deflecting roller  1  and upon restart, the sticky fibres  5  wrap themselves around the deflecting roller  1 . The measures according to the invention enable the deflecting roller  1  to be lifted by means of a resiliently loaded driver element  36   a ,  36   b . By lifting the deflecting roller  1 , the fibres  5  can no longer stick to the roller, and the pressure on the lower roller  1  is reduced, whereby the wrap-round tendency is considerably reduced. The reduction in the wrap-round tendency significantly increases the efficiency of the draw frame when sticky fibres are being processed, because operational disturbances and their elimination are reduced or avoided 
   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 practised within the scope of the appended claims.