GILLBOX

Abstract: A faller bar transfer mechanism is described for a screw type gillbox (10) which comprises at least one cam (34) located at the transfer end of each of the working and return screws (12, 14) to contact the faller bars (24) and move them between the working and return screws and vice versa. The cam has a backwardly directed profile with respect to its direction of rotation. The faller bars on transfer are fully displaced from the horizontal path of the next following faller bar by a vertical movement less than 85 % of the total transfer distance. The profile of the cam is chosen such that the faller bars are displaced 80 % or less of their total transfer distance by the time the cam has rotated through 100 % from the point of initial contact with the faller bar. The cam profile meets the end of the faller bar less than 30 % below the horizontal centre line between the screws. The faller bars are no more than 1 cm (three eights of an inch) longer than the distance between the driving screw spindles. The acceleration imparted to the faller bar by the cam is gradual and the knocking or "hammering" action of the bulk of previous gillboxes is avoided completely. The profile (44a) is preferably shaped so that the faller bar is brought up to a speed in the first portion of the cam revolution which will transfer between the two sets of screws. The profile is thereafter lowered so that, in normal use, the faller bar does not contact the cam at all. By this means it is possible to accelerate the faller bar to the minimum speed necessary for it to effect proper transfer and not continue acceleration beyond this point, thus minimizing the amount of retardation which must be applied to the faller bar when it reaches its destination, and allowing much faster machine operation.

Description: G ______ 13 OX This invention relates to gillboxes and in particular relates to an improved faller bar transfer mechanism therefor. Gillboxes (sometimes referred to as "draw frames" or "pin drafters") are used in the primary processing of worsted or semi-worsted yarn manufacture. The worsted card or converter initially forms random or loose fibres into a rope-like form known as "sliver". A gillbox fulfils the function of opening, straightening and mixing the fibres comprising the sliver to ensure that a uniform and level product is supplied to the spinning frame which produces the final yarn. A conventional gillbox consists of a pair of feed rollers, a pair of delivery or front rollers, and between these a number of bars having pins set into them known as faller bars. The sliver is fed into the nip of the feed rollers and is delivered from the front rollers while the faller bars are moved between the two sets of rollers so that the pins of the faller bars provide a combing and straightening action. The faller bars are moved along the gillbox in the direction from the feed rollers to the front rollers and as each faller bar reaches the end of its travel it is transferred to a return run which brings it back to the feed rollers for re-use in a continuous fashion. It is normal practice for a gillbox to possess a second set of faller bars which operate in an identical manner but are positioned in an inverted fashion above the sliver mass. This type of gillbox is known as an "intersecting" gillbox. There are three main methods used to mechanically drive the faller bars in a gillbox. These are by chains, by cam track or by worm-type screws. The present invention is particularly concerned with gillboxes which employ worm-type screw for moving the faller bars. A pair of screws will drive the faller bars in the working area and are known as working screws, while a further pair of worm screws will be positioned below the working screws for the return cycle and these are known as return screws. In order to transfer the faller bars from the working screws to the return screws, and again from the return screws to the working screws at the beginning of the cycle, it is usual for cam/arm arrangements to be provided at the ends of the screws which strike the ends of the faller bars and knock them from the working to the return run or vice versa. Indeed these cams are sometimes referred to as "hammers" because of the striking action they have. It will be appreciated that such a violent mechanical action imparts a great acceleration to the faller bars which then need to be retarded at the other end, and various means have been proposed to achieve this without causing excessive wear and vibration in the machine. However suffice it to say that none have been completely successful and that this form of mechanical arrangement limits the speed at which the machine can operate. In one proposal to alleviate this problem the hammers are replaced by cams having a backwardly directed profile starting at the root of the worm-type screw. Corresponding retarding cams are located on the ends of the screw to which the fallers are to be transferred. In order for this construction to operate it is necessary that the ends of the fallers have an unusual and relatively complicated profile to correspond both with the accelerating and retarding cams. Moreover the fallers are located considerably below the centre line of the drive screws and are of a length greater than the distance between the roots of the drive screws. This means that the faller bars have poor screw lead control, are relatively expensive to manufacture and cannot easily be removed for cleaning, repair, etc., in use without displacing the saddles of the gillbox. Considering that in a normal days shift the faller bars may need to be removed three or four times this is a considerable disadvantage. Moreover, the co-operation of the accelerating and retarding cams needs to be exact as the acceleration imparted by the accelerating cam is quite large. While this may be achievable in a new machine, wear in the gear trains, etc. soon introduces slack into the system which leads to imprecise handing over from the accelerating to the retarding cam and thus introduce "chattering" which rapidly leads to excessive wear. The invention seeks to provide a form of faller bar transfer mechanism for a screw type gillbox improved in the above respects. According a first aspect of the invention there is provided a faller bar transfer mechanism for a screw type gill box which comprises at least one cam located at the transfer end of each of the working and return screws to contact the faller bars and move them between the working and return screws and vice versa, the cam having a backwardly directed profile with respect to its direction of rotation, characterised in that the faller bars on transfer are fully displaced from the horizontal path of the next following faller bar by a vertical movement less than 85% of the total transfer distance. According to a second aspect of the present invention there is provided a faller bar transfer mechanism for a screw type gillbox which comprises at least one cam located at the transfer end of each of the working and return screws to contact the faller bars and move them between the working and return screws and vice versa, the cam having a backwardly directed profile with respect to its direction of rotation, characterised in that the profile of the cam is chosen such that the faller bars are displaced 80% or less of their total transfer distance by the time the cam has rotated through 100° from the point of initial contact with the faller bar. According to a third aspect of the invention there is provided a faller bar transfer mechanism for a screw type gillbox which comprises at least one cam located at the transfer end of each of the working and return screws to contact the faller bars and move them between the working and return screws and vice versa, the cam having a backwardly directed profile with respect to its direction of rotation, characterised in that the cam profile meets the end of the faller bar less than 30° below the horizontal centre line between the screws. According to a fourth aspect of the present invention there is provided a faller bar transfer mechanism for a screw type gillbox which comprises at least one cam located at the transfer end of each of the working and return screws to contact the faller bars and move them between the working and return screws and vice versa, the cam having a backwardly directed profile with respect to its direction of rotation, characterised in that the faller bars are no more than 1 cm (three eighths of an inch) longer than the distance between the driving screw spindles. The worm drive screws on most gillboxes have two leads and therefore deliver two faller bars per revolution. Thus in this case two cams would be provided 180° apart. If a triple lead screw is employed, it will be necessary to have three cams mounted 120° apart. In this case, of course, the 100° referred to above is reduced in the ratio 120:180; and a similar adjustment would need to be made for any other number of screw leads. The remaining description will be with reference to a double lead screw but it will be appreciated that the invention is equally applicable to screws with single, triple, or higher numbers of leads. The cam profile of the invention is, as already indicated, directed backwardly with respect to the rotation of the cam so that the acceleration imparted to the faller bar is gradual and the knocking or "hammering" action of the bulk of previous gillboxes is avoided completely. The profile is preferably shaped so that the faller bar is brought up to a speed in the first portion of the cam revolution which will transfer between the two sets of screws. The profile is thereafter lowered so that, in normal use, the faller bar does not contact the cam at all. By this means it is possible to accelerate the faller bar to the minimum speed necessary for it to effect proper transfer and not continue acceleration beyond this point, thus minimizing the amount of retardation which must be applied to the faller bar when it reaches its destination. Conventional retarding devices may be employed with the apparatus of the invention. However, it has been found that by employing the cam profile of the apparatus of the invention operating speeds of up to twice those possible with conventional apparatus can be attained and sustained without causing excessive wear enabling a single gillbox to achieve up to twice the normal throughput. In order to co-operate with the cams of the invention the ends of the faller bars need to be modified from the normal square end. It has been found that for both ease of manufacture and efficiency of operation a simple rounding of the ends of the faller bars is preferred. However other profiles of faller bar end may be employed as described more fully hereinafter. The faller bars should be of a size that their profile ends just fit between the roots of the screw drives. Moreover in normal operation it is preferred that the faller bars be located very slightly (1 or 2 mm) below the centre line of the screw drives. While this improves operation in accordance with the invention it is desirable to avoid the faller bars being located too much below the centre line of the screw drives as this introduces unwanted problems including poor faller end/screw control, and the force which is exerted by the fibres on the pins leads to excessive leverage the further the faller bars are positioned from the centre line. While no hard and fast limit can be placed on this, it is preferred that the distance which the faller bars are positioned below the centre line of the screw drives should not exceed approximately 5mm or 6mm, with 8mm being the maximum distance allowable. It is also preferred that the cam rises from the root of the screw. The cam preferably contacts the end of the faller bar at approximately the horizontal position, that is on the horizontal centre line between the screws. While the contact may be up to 30° below the horizontal centre line, it is preferred that the contact point in practice be no more than 15° past the horizontal since this leads to the following advantages: improved faller bar removal; improved screw lead/faller bar end control; reduced faller bar/fibre leverage; and simpler and lighter faller bar construction. These advantages reduce rapidly as the 30° limit is approached, and although the invention will work at this limit, it is preferred to operate below 15°. The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figures 1 to 3 are respectively side, front end and top views of a conventional gillbox; Figure 4 is a partial diagrammatic representation similar to figure 2 in accordance with the invention; Figures 5(a) to (c) illustrate different cam profiles; Figure 6 illustrates a different faller end profile; Figures 7(a) and (b) illustrate the degree of lift given to the faller bar; and Figure 8 is a similar view to figure 4 with a modified cam profile. Referring to the drawings, and initially figures 1 to 3, a conventional gillbox arrangement generally designated 10 is illustrated having two pairs of screws 12 and 14, one pair positioned above the other. The lower pair of screws 14, the "return screws", are connected together by a cross shaft 16 and bevel drive 18. The upper pair of screws 12, known as the "working screws", are driven by spur gears 20,22 from the return screws 14. A plurality of faller bars 24 each having a multiplicity of vertically directed pins 26 are provided (for instance 20 or 30 to a machine). The faller bars 24 are of such a length as to slot into the leads or grooves of each pair of screws as illustrated in figure 3. The faller bars 24 when in the leads of the working screws 12 are supported by a pair of slide bars 28 known as "working saddles". Corresponding slide bars known as "lower saddles" 30 are provided below the return screws 14. At the point where the faller bars 24 are transferred between working and return screws there are situated a pair of outer guides 31 known as "conductor guides". The guides 31 are normally spring loaded from a pivot point and act to restrain and guide the fallers 24 on their passage past the working saddle ends into the opposing screws leads. The downstream ends (adjacent front rollers 32) of the working screws 12 are fitted with cams 34. Similar cams (not shown) are fitted to the downstream ends (adjacent feed rollers 36) of the return screws 14. In operation sliver is fed from the feed rollers 36 across the top of the working screws 12 to the front rollers 32. The pins 26 penetrate the sliver and comb and straighten it. At the same time the screw drives 12 and 14 are driven so that the faller bars 24 move in the direction of arrow A in figure 1, i.e. from the feed rollers towards the front rollers. The speed of drive is generally set so that the speed of the fallers 24 is a little more than the speed of feed of the feed rollers 36. However the peripheral speed of the front rollers 32 is generally set considerably faster, normally four to eight times faster, which results in the fibres being pulled through the pins 26 of the faller bars, imparting a combing action to the fibres. This is commonly referred to as "drafting" the fibres. If we consider a single faller bar 24 moving along the working saddle 28 under the action of the working screws 12, it will reach the downstream end of the screws 12 at which point the outer end of the cams 34 (which rotate in the sense of arrow B in figure 2) will impact onto each end of the faller bar and knock it downwardly towards the return screws 14. The guides 31 guide and to some extent retard the faller which nevertheless reaches the return run with a considerable velocity. It is then picked up by the return screws 14 and transferred back towards the feed rollers 36. At the downstream end of the return screws 14 there are similar cams (not shown) which once again knock the faller bar 24, this time upwardly, to the working run where it is engaged once more by the working screws 12. The cycle is endlessly repeated for the each of the faller bars 24. It will be appreciated by a person skilled in the art that the speed of this mechanism is restricted by the method of transferring the faller bars 24 between the screws 12 and 14. Referring now to figure 4, and using like numerals for like parts, it will be seen that the ends 36 of the faller bars 24 are rounded and sit in close to the roots 38 of the working screws 12, the cams 34(a) are of a profile which is sloped in a backward direction with respect to the direction of rotation shown by arrow B. The cam 34(a) thus contacts the faller bar 24 at or close to the horizontal centre-line position between the two screws, at the lowest and inwardmost portion of the cam profile, accelerating the faller bar in a relatively gentle manner over nearly 180° of the screw rotation, in contrast to the violent hammering action of the conventional gillbox. in practice it is convenient to complete the transfer in approximately 160° of rotation and to have a cam profile portion 40 which holds the faller bar in place through the last 20° or so that it is picked up by the screw thread of the lower screw 14. It will be seen that the first part of the profile 42 is relatively steeper than the bulk of the profile 44. The length of this portion 42 is determined so as to be sufficient to impart to the faller bar 24 sufficient speed for it to safely transfer between pairs of screws. In full speed operation the portion 44 of the cam will not normally be contacted by the faller bar 24 (although if the machine is operated slowly the bar will ride the whole of the cam surface). The cams operating to transfer the faller bars 24 from the lower screws 14 to the working screws 12 operate in precisely the same way. The shape of the cam is such that in the first 100° of rotation (out of the preferred 160° to complete the transfer) , the faller bar 24 has moved less than 80% of the total transfer distance. By this means the slowest speed consistent with proper operation is imparted, reducing wear and vibration to a minimum and enabling the machine to be operated much faster than conventional machines. Also, in accordance with the invention it is not necessary to provide a retarding cam with consequent saving both in manufacturing expense and in maintenance (keeping the retarding and accelerating cams in close synchronization) . Figure 5 illustrates different shapes of cams which may be employed. Figure 5(a) shows a cam similar to that already described while figure 5(b) shows one having a comparatively steeper initial profile 42 from the root 38. This will result in a faster initial motion of the faller bar 24 making it possible to apply fairly severe braking to the bar at the later stages of its flight. Alternatively in figure 5(c), a slower initial movement is imparted keeping the flight speed lower and not allowing as much braking action to be applied to the bar owing to the possibility of the outer profile of the cam impacting onto the bar. In figure 6 it will be seen that an alternative form of profile of the faller end 36 is illustrated. The end profiles of the faller bars are required to be of such a form as to allow the cam profiles to impart a smooth rolling or sliding action to the bar as transfer is performed but their precise shapes may differ. The faller bars are positioned substantially on the centre line with the screws and they must also be able to be easily removed from the screws for cleaning purposes. This restricts the length and position of the bars 24 to substantially within the peripheries of the two screw roots or shafts 38. The use of a normal square ended faller bar would result in a locking action as the cam profiles tried to initially move the bar. A profile as illustrated in figure 6 will give a reasonable rolling or sliding action between the cams without locking the faller bar. Other variations of this form are of course possible but for many purposes the smoothly rounded end illustrated earlier is preferred both for ease of manufacturing and efficiency in use. Turning now to figure 7, it can be seen that in a preferred arrangement the faller bar 24 is mounted so that its centre is slightly below the centre line of the root 38 of the screw 12, e.g. l_mm (l/16th inch). Figure 7(b) illustrates the position 90° of rotation later. In the example shown, the faller bar has moved about 1.75cm (ll/16th of an inch) from its initial position. The total displacement is approximately 3.9cm (1.532 inches) and thus at this point the displacement is just over 45% of the total. At 100° of rotation the displacement is approximately 55%. The faller bars in the working screws are spaced closely together, the spacing being dependent upon the pitch of the screws. In order adequately to "work" and draft the fibres, a screw pitch of 9mm or there abouts is normally used leaving a gap between the faller bars in the working screws of between approximately lmm and 1.5mm. Once a particular faller bar is in position for transfer to the lower (or upper) screws its forward movement ceases and is converted to a vertical movement. At the same time this vertical movement is taking place, the faller bar immediately following is still being carried forward horizontally. It will be appreciated that owing to the close spacing of the faller bars the vertical displacement of the faller bar in transfer must be carried out in sufficient time so that the next following faller bar does not catch it up which would cause the machine to lock or jam. For example in a machine having two-start screws of 9mm pitch, as one faller bar contacts the cams the next faller bar will be in a position more or less level with the end of the saddles. As the screws continue to revolve, this latter faller bar will progressively move forward beyond the end of the saddles until after 90° of screw movement the faller bar will be some 4.5mm beyond the saddle end. After 180° of screw movement, it will be in its own transfer position fully 9mm beyond the saddle ends. It is clear that the preceding transfer faller bar will have had to have been displaced at sufficient speed in the vertical direction to accommodate the forward movement of the following faller bar. Faller bars in accordance with the preferred form of the present invention have rounded ends, but the ends are not cranked as with certain prior art designs. This minimises the faller bar depth. It has been found that in order to keep clearance between faller bars on transfer it is necessary for the transferring bar to have completed full displacement from the next following faller bar in the first 100° rotation of the cam. This requirement applies to most mechanisms using screws of around 9mm pitch. These conditions are easily met when traditional hammer type actions are employed as fast initial faller bar acceleration is in any event a feature of these mechanism. On the other hand, when backwardly directed cam profiles are used in order to impart gradual faller bar acceleration, a faller bar of lesser depth is advantageous since it can be removed vertically from the transfer zone sufficiently quickly, without having to impart a high acceleration. For example, in a preferred form of the invention the faller bar depth is some 55% of the total distance between working and return runs compared to 90% with some prior art designs, particularly those having faller bars with cranked ends. It is therefore necessary, with the invention, only to move the transfer faller bar 55% of its total vertical distance in the first 100° of spindle rotation, compared to 90% of the total distance with the prior art designs. This explains to some extent why the prior art designs impart such high accelerations: it is necessary to physically move the transfer bar out of the way of the next following bar. It should be noted that in the preferred method described above it has been found advantageous to modify the working profile of the cam levers slightly from that illustrated in figure 4(a). Reference has not been made to this previously as it does not influence the faller bar flight in full speed operation. Referring to figure 8 (using like numerals to figure 4) it will be seen that the cam profile surface 44 has been modified (44a) compared to that of figure 4(a). The reason for this modification is to keep adequate faller bar clearance when the machine is operated slowly or by hand, as the bar will ride the whole of the cam surface under these conditions. As previously explained, under full speed operation surface 42 influences faller bar flight speed whilst surface 44 is not contacted by the faller bar during normal operation. If a faller bar of lesser depth was used, this modification would not be necessary. While the invention has been described with reference to one set of faller bars, it is equally applicable to intersecting gillboxes with two sets of faller bars. The apparatus of the invention enables gillboxes to operate at up to twice the conventional speed without excessive wear and without requiring complex or expensive components.

Claims: CLAIMS 1. A faller bar transfer mechanism for a screw type gill box which comprises at least one cam located at the transfer end of each of the working and return screws to contact the faller bars and move them between the working and return screws and vice versa, the cam having a backwardly directed profile with respect to its direction of rotation, characterised in that the faller bars on transfer are fully displaced from the horizontal path of the next following faller bar by a vertical movement less than 85% of the total transfer distance. 2. A faller bar transfer mechanism for a screw type gillbox which comprises at least one cam located at the transfer end of each of the working and return screws to contact the faller bars and move them between the working and return screws and vice versa, the cam having a backwardly directed profile with respect to its direction of rotation, characterised in that the profile of the cam is chosen such that the faller bars are displaced 80% or less of their total transfer distance by the time the cam has rotated through 100° from the point of initial contact with the faller bar. 3. A faller bar transfer mechanism for a screw type gillbox which comprises at least one cam located at the transfer end of each of the working and return screws to contact the faller bars and move them between the working and return screws and vice versa, the cam having a backwardly directed profile with respect to its direction of rotation, characterised in that the cam profile meets the end of the faller bar less than 30° below the horizontal centre line between the screws. 4. A faller bar transfer mechanism for a screw type gillbox which comprises at least one cam located at the transfer end of each of the working and return screws to contact the faller bars and move them between the working and return screws and vice versa, the cam having a backwardly directed profile with respect to its direction of rotation, characterised in that the faller bars are no more than l cm (three eighths of an inch) longer than the distance between the driving screw spindles. 5. A mechanism as claimed in any of claims 1 to 4 in which the cam profile is shaped so that the faller bar is brought up to a speed in the first portion of the cam revolution which will transfer the bar between the two sets of screws. 6. A mechanism as claimed in claim 5 in which the profile is thereafter lowered so that, in normal use, the faller bar does not contact the cam at all. 7. A mechanism as claimed in any of claims 1 to 6 wherein the ends of the faller bars are rounded. 8. A mechanism as claimed in any of claims 1 to 7 in which the faller bars are located very slightly (1 or 2 mm) below the centre line of the screw drives. 9. A mechanism as claimed in claim 8 in which the distance which the faller bars are positioned below the centre line of the screw drives does not exceed 8mm. 10. A mechanism as claimed in any of claims 1 to 9 in which the cam rises from the root of the screw. 11. A mechanism as claimed in any of claims 1 to 10 in which the cam contacts the end of the faller bar at approximately the horizontal position, that is on the horizontal centre line between the screws. 12. A mechanism as claimed in any of claims 1 to 11 wherein the faller bar depth is no more than 55% of the total distance between working and return runs.

Inventors: WALKER MICHAEL, WALKER, MICHAEL
Applicants: GILL SYSTEMS LIMITED, WALKER MICHAEL, WALKER, MICHAEL
Application year: 1996
Main classification: D01H5
IPC codes: D01H5