Webbers for the textile industry
United States Patent Asselin et al.  
 [451 Apr. 15, 1975 1 WEBBERS FOR THE TEXTILE INDUSTRY [76] inventors: Robert Asselin, 10, rue Magenta;  
 Pierre Asselin, Rue Romelot, both of Elbeuf, Seine Maritime, France [22] Filed: June 19, 1974 [21] Appl. No.: 480,927  
 [30] Foreign Application Priority Data June 19, 1973 France 73.22277 [52} U.S. C1. 226/113; 19/163; 226/119 [51] Int. Cl B65h 17/42 [58] Field of Search 226/108, 113, 114, 118, 226/119; 19/163; 28/1 CL [56] References Cited UNITED STATES PATENTS 3,558,029 1/1971 Manns 226/108 3,638,279 2/1972 Swados. 226/108 X 3,682,734 8/1972 Burger 19/163 X Primary Examiner-Richard A. Schaeher Arlorney. Agent, or FirmYoung &amp; Thompson [57] ABSTRACT A webber for folding a fleece delivered by a card to convert it into a web of different thickness from the fleece comprises a fleece feed system, first and second main carriages provided with rollers carrying two endless guide belts adapted to receive the fleece therebetween and move it along a loop-like path, drive means for linearly reciprocating the main carriages in parallel directions, drive means for moving the guide belts relative to the main carriages, a delivery belt for receiving the fleece leaving the guide belts, and drive means for driving the delivery belt along a linear path substantially perpendicular to the direction of movement of the main carriages. At least one auxiliary carriage is provided and comprises rollers carrying the guide belts, such auxiliary carriage being reciproeated in a direction parallel to the movement of the main earriages.  
 15 Claims, 28 Drawing Figures in 21 2 28. C2? 2 in #31117 {5 14 I +25 /3 1 I 11 25&#39; 16 i 5 5H SHE] u m: 12 -877,  
 PATENTEEAFRI mnnwwmms SHEET @HF 12 3,877,628  
 WEBBERS FOR THE TEXTILE INDUSTRY BACKGROUND OF THE INVENTION This invention relates to webbers.  
  This of course is the name given in the textile industry to machines which receive a fleece of reduced thickness and predetermined width as prepared by a card from flock, machines of this kind folding the fleece to convert it into the web which is thicker than the fleece and whose width is, as a rule, different from, and preferably greater than, a width of the fleece.  
  A known webber basically comprises a feed system for a fleece, a guide system receiving the fleece leaving the feed system and causing the fleece to move along a loop-like path, and a delivery belt on which the fleece is placed as it leaves the guide system.  
  The guide system of the known machine comprises two aprons or endless belts which run on rollers carried on upper and lower moving carriages or slides or the like. Through the agency ofa first drive means, the carriages can be given a periodic rectilinear reciprocation in parallel directions,  
  Through the agency of a second drive means, the aprons or belts can be rotated relatively to the carriages and a third drive means is provided to make the delivery belt move at a continuous rate of advance in a direction perpendicular to the direction of movement of the carriages. Consequently, the fleece is placed on the delivery belt in consecutive transverse folds or plies, the relationship between delivery-belt speed and the speed of the lower carriage determining the number of overlapping folds and therefore the thickness of the final web. Web width is defined by the travel of the lower carriage.  
  To obtain a uniformly thick web and to ensure that the fleece is not stretched or compressed while passing through the machine, the speeds of the carriages must of course have definite relationships with the fleece feed speed determined by the fleece feed system.  
  In the known machine it is impossible to provide the necessary speed relationships in practice and, as a result, the web is thicker at its edge than at its centre. Also, there is some stretching or drafting of the fleece as it passes through the machine.  
  Another disadvantage of the known machine is connected with the geometry of the aprons. The reciprocations of the carriages produce air eddying above the delivery belt and there is no protection from the eddying for the fleece which is on the belt. Consequently, the fleece, which is of reduced density, is readily lifted by the eddies, leading to irregularities in the final web.  
 SUMMARY OF THE INVENTION It is an object of the invention to obviate these disadvantages and to provide a webber adapted to produce a web of substantially uniform thickness at appreciably greater outputs than have previously been possible.  
  According to the invention, a webber for folding a fleece delivered by a card to convert it into a web of difi&#39;erent thickness from the fleece comprises a fleece feed system, a first main carriage and a second main carriage comprising rollers carrying two endless guide means adapted to receive the fleece leaving the feed system and move it along a loop-like path, first drive means adapted to impart to the main carriages periodic rectilinear reciprocations in parallel directions, second drive means adapted to impart to the guide means a speed of movement past the main carriages. a delivery belt adapted to receive the fleece leaving the guide means, and third drive means for imparting to the delivery belt a continuous rectilinear motion in a direction substantially perpendicular to the direction of main carriage movements, the webber comprises at least one auxiliary carriage having rollers carrying the guide means, and fourth drive means for imparting to the auxiliary carriage a periodic rectilinear reciprocation in a direction parallel to the direction of main carriage movements; the guide means comprises continuous endless belts each running on rollers carried by the two main carriages and on rollers carried by the auxiliary carriage, the rollers being so disposed that the loop-like path along which the fleece travels extends between portions of each of the two guide belts.  
  Advantageously, the webber has provision for protecting the delivery belt from air eddies arising from carriage movements. This feature is very useful in the case of high speed operation with light-weight fleeces, the eddies then being considerable and tending to lift the fleece laid on the delivery belt.  
  Advantageously, the webber has provision for moving the fleece between its entry and exit without stretching or compressing it, and provision for obtaining on the delivery belt a web which is of constant thickness at its edges as well as its centre, the speed of the second main carriage being so chosen that the curve representing such speed plotted against time has no sharp corner.  
  Such features also help high-speed operation with light-weight fleeces by obviating the risk of tearing or stretching of the fleece, such risks normally tending to be heightened at high speeds. The features also help to provide a web which is of constant thickness over its entire width by deformation at the edges of sharp and precise folds, despite the considerable inertia force applied to the carriage at high speeds and without using for the purpose very large and theoretically infinite forces.  
  Preferably, all the features hereinbefore mentioned are used in combination so that all the conditions for high-speed operation with light-weight fleeces are provided together.  
 BRIEF DESCRIPTION OF DRAWINGS In order that the invention may be readily understood, embodiments thereof will now be described and related to the prior art with reference to the appended drawings in which like parts have like references. In the drawings:  
  FIGS. 1 to 3 illustrate schematically a prior art webber;  
  FIGS. 4 to 6 are diagrammatic views in elevation, in three operating positions, of a first form of the invention;  
  FIG. 7 is a diagrammatic view in elevation of a second form of the invention;  
  FIG. 8 is a diagrammatic view in elevation of a third form of the invention;  
  FIGS. 9 to l I show curves representing the positions, speeds and accelerations of the main and auxiliary carriages respectively in dependence upon time, for a first choice of second main-carriage speed;  
  FIGS. 12 and 13 show curves representing the position and speed respectively of the delivery belt as plotted against time. the conditions of second maincarriage speed being the same as in FIGS. 9 to II;  
  FIG. I4 shows curves representing the speed of rotation of the rollers of the second main-carriage as plotted against time, the conditions for the speed of such carriage being the same as in FIGS. 9 to 13&#39;.  
  FIGS. 15 to 17 show curves representing the positions, speeds and accelerations of the main and auxiliary carriages. plotted against time, for a second choice of second maimcarriage speed;  
  FIGS. 18 and I9 show curves representing the position and speed of the delivery belt. plotted against time. in the same conditions of second main-carriage speed as for FIGS. 15 to 17;  
  FIGS. 20 to 22 show curves representing the posi tions, speeds and accelerations of the main and auxiliary carriages. plotted against time. for a third choice of second main-carriage speed;  
  FIG. 23 is a drive diagram for a main and auxiliary carriage drive facilities;  
  FIGS. 24 and 25 are diagrammatic views, in elevation and plan respectively, of alternative form of the drive facilities referred to in FIG. 23;  
  FIGS. 26 and 27 are views, in elevation and plan respectively. of an embodiment of the main and auxiliary carriage drive facilities in accordance with the diagram of FIG. 23; and  
  FIG. 28 is a diagram showing the drive connections between the elements of FIGS. 26 and 27.  
 DESCRIPTION OF PRIOR ART Webbers of the kind shown diagrammatically in FIGS. I and 2 of the drawings are known.  
  FIG. I is a diagrammatic view in elevation ofa known webber. whilst FIG. 2 is a corresponding side view.  
  Basically. machines of this kind comprise a feed sys tem I for fleece 2, a guide system receiving the fleece 2 leaving the feed system I and causing the fleece to move along a looplike path, and a delivery belt 3 on which the fleece is placed as it leaves the guide system.  
  The guide system of the known machines comprises two aprons or endless belts 4, 5 which run on rollers 6 carried on moving carriages or slides or the like 7, 8. Through the agency of a drive facility (not shown in order not to overload the drawings). the carriages 7, 8 ccan be given a periodic rectilinear reciprocation in parallel directions. carriage 7 moving from the solidline position shown to the chain-line position 7a while carriage 8 moves from the solid-line position shown to the chain-line position 8a.  
  Through the agency of another drive facility (not shown), the aprons or belts 4, 5 can be rotated relatively to the carriages 7, 8, and a third system 9, shown in FIG. 2 is a means of making the delivery belt 3 move at a continuous rate of advance in a direction perpendicular to the direction of movement of the carriages. Consequently. the fleece 2 is placed on the delivery belt 3 in consecutive transerse folds or plies. in the manner visible in FIG. 3, the relationship between delivery-belt speed and the speed of the carriage 8 de termining the number K of overlapping folds and therefore the thickness of the final web. Web width is de fined by the travel of the carriage 8. In FIGv 3 K is 2.  
  To obtain a uniformly thick web and to ensure that the fleece is not stretched or compressed while passing through the machine. the speeds of the carriages 7, 8 must of course have definite relationships with the fleece feed speed V determined by the fleece feed system 1. In the known machines the top carriage 7 moves at a speed 14 having an absolute value V/2 and the bottom 8 runs at a speed w of the same absolute value as V. Consequently, the length of the loop described by the fleece 2 between places A and B remains constant and the fleece is placed on the delivery belt 3 at a speed equal to the feed speed V. Of course. the delivery belt runs at a speed proportional to V.  
  The carriage speed conditions would be satisfactory if only they could be strictly adhered to. For that to be the case. however. the carriages 7, 8 would at each reversal of their movement have to change from one speed to the opposite speed in an infinitely short time. something which is possible only if the carriages have zero inertia or experience infinite forces at the ends of their travels. their acceleration being infinite in both cases. Clearly. it is impossible to comply with such conditions in practice. In fact. absolute carriage speeds decrease gradually at the ends of travel. then become zero. reverse and gradually increase to the new speed.  
  As a result. the web is thicker at its edges than at its centre. Also. there is some stretching r drafting of the fleece as it passes through the machine. These disadvantages can be reduced. but unfortunately not obviated. by restricting the fleece feed speeds and the belt speeds, with a corresponding reduction in output which is limited in practice from to metres/minute in the case of a 1.5 denier fleece.  
  Another disadvantage of the known machines is connected with the geometry of the aprons 4 and 5. The reciprocations of the carriages 7, 8 produce air eddying above the delivery belt 3 and. as FIG. I shows, there is no protection from the eddying for the fleece 2 which is on the belt 3. Consequently, the fleece 2, which is of reduced density. is readily lifted by the eddies, leading to irregularities in the final web.  
  The embodiments of the present invention now to be described obviate these disadvantages and provide a webber adapted to produce a web of substantially uniform thickness at appreciably greater outputs than have previously been possible.  
 DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION In a first form of the invention, a webber comprises (FIGS. 4 to 6) a feed belt I for a fleece 2. a delivery belt 3 and a guide system which receives the fleece 2 leaving the feed belt I and presses the fleece 2 on the delivery belt 3 after moving the fleece move around a loop-like path.  
  The guide system comprises two continuous endless belts. A first belt 11 runs around a flxedspindle drive roller 12, rollers 13 disposed on a first main carriage I4, rollers 15 disposed on a second main carriage l6. fixed-spindle rollers 17. a roller 18 disposed on a first auxiliary carriage l9, and a roller 21 disposed on a second auxiliary carriage 22. Clearly, belt It takes the form ofa main loop between the rollers 12 and 15, loop length being determined by the position of the main carriages l4, 16. Belt 11 also takes the form of two sec ondary loops controlled one each by the auxiliary carriages I9, 22.  
  A second guide belt 23 runs over a fixed-spindle drive roller 24, rollers 25 disposed of the first maincarriage l4, rollers 26 disposed of the second main carriage l6, fixed-spindle roller 27, and a roller 28 disposed on the third auxiliary carriage 29. Belt 23 describes a main loop between rollers 24 and 26, the loop length being determined by the position of the main carriages l4, l6, and an auxiliary loop whose length is determined by the position of the third auxiliary carriage 29. The main loops formed by the two belts ll, 23 extend along parallel paths and co-operate with one another to bound a passage for the fleece 2.  
  Conventional drive means (not shown) drive the two drive rollers 12, 24 at a rim speed equal to the fleece feed speed V, and another conventional drive means (not shown) moves the delivery belt 3 at a constant speed in a direction substantially perpendicular to the plane of the drawing.  
  A flexible connection such as a chain or belt 31 is connected at both ends to the main carriage 14, runs over a fixed-spindle drive roller 32 and is also connected to the third auxiliary carriage 29. A drive means to be described hereinafter drives roller 32 at a periodic alternating rim speed u. All carriages, both main and auxiliary, are guided by systems (not shown in order to overload the drawings) on straight paths which are substantially perpendicular to the direction of movement of belt 3. Consequently, the first main carriage l4 performs a rectilinear reciprocation at a speed u and the third auxiliary carriage 29 moves similarly but at the speed -u.  
  Similarly, a chain or some similar system 33 has both its ends connected to the second main carriage 16, runs over a fixed-spindle roller 34 and a fixed-spindle drive roller 35 and is connected to the first auxiliary carriage 19. A drive means to be described hereinafter drives the roller 35 in a periodic alternating movement at a rim speed w. The main carriage l6 and auxiliary carriage [9 therefore perform a rectilinear reciprocation, the first at a speed w and the second at a speed -w. The speeds u and w have the same period T.  
  A third a chain 36 is connected at its ends to the first main carriage 14, runs over a fixed-spindle roller 37 and a fixed-spindle drive roller 38 and is also connected to the second auxiliary carriage 22. The drive means hereinbefore referred to drives the roller 38 at a rim speed u so that the auxiliary carriage 22 performs a per iodic rectilinear reciprocation at a speed -u.  
  Only some of the chains 31, 33, 36 are shown so as not to overload the drawings.  
  The speed w is such that the curve representing it plotted against time has no sharp corner. Also, its amplitude is such that the second main carriage [6 makes a movement equal to the required width of web in a time corresponding to half a period of operation T/Z. Examples will be given hereinafter of preferred relationships between the speed w and time.  
  Once the speed w has been selected, the speed u can be determined as follows:  
  While the first main carriage 14 makes its movement in the direction of the fleece feed, such movement hereinafter being called its outward travel,&#34; the speed u is equal to V/2. In the travel in the opposite direction, hereinafter called the return travel the speed a is equal to (w+ V/2). The speeds u and w are counted positively in these terms if of the same direction as the speed V of the fleece feed and negatively if not.  
  The delivery belt 3 runs at a speed proportional to the absolute value of the speed W.  
  In contrast to what happens in the known machine described hereinbefore. the fleece 2 is placed on a belt at the speed w of the second main carriage l6 and not at the fleece feed speed V. Accordingly. the length of the loop which the fleece 2 describes in the machine before being placed on the delivery belt 3 is not constant. Abandoning these two totally unnecessary condi tions is a means of so choosing the speed w that. as will be seen in detail hereinafter. it becomes possible to obviate theoretically infinite accelerations and speed jumps.  
  FIGS. 4 to 6 show the carriages, guide belts and fleece in three positions during the outward travel. The first main carriage 14 is finishing a travel which is something like half the travel of the second main carriage 16. From the time it enters the machine until it is placed on the delivery belt, the fleece is always retained between parallel parts of the belts I] and 23 and is therefore protected from the air eddies caused by carriage movements. Also, the bottom parts of the belts between, on the one hand, the rollers 15 and 17 and. on the other hand, the rollers 26 and 27 form a virtually continuous curtain which extends parallel to the deliv ery belt and protects the fleece thereof from eddies.  
  At the end ofthe main loop of the guide belts the rollers 13, 25 and the rollers 15, 26 of the respective two main carriages are separated from one another so that at places of such separation, where the belts bend sharply, the movements of the two guide belts are completely independent of one another and they do not rub together in a manner likely to produce static electricity which would cause irregularities in the fleece. Guide plates (not shown) can also be provided at the two places concerned for improved guidance of the fleece, Also, the carriage 16 can have protective plates disposed in extension of the bottom parts of the two guide belts and co-operating to bound a passage for the fleece, such plates supplementing the protective cur tain formed by the belts ll, 23 parallel to the delivery belt 3.  
  The conditions hereinbefore given for the two maincarriage speeds u and w preclude any compression or stretching of the fleece. for in a time interval d: the length of the loop described by the fleece in the machine varies by the quantity dt(2uw). Also, the length of fleece placed on the delivery belt in the same period of time is lwldl, |w| denoting the absolute value of the speed w. If there is to be no compressing or stretching of the fleece, the sum of these two lengths must always be equal to the fleece length Vdt fed into the machine by the feed belts; this state of affairs corresponds to the equation:  
 Zu-w-l-lwi V It can be readily checked that the solutions of this equation are the values for u hereinbefore given with the sign conventions defined for the speeds u and w.  
  It is also easy to check that the speeds hereinbefore defined for the three auxiliary carriages are such that the total length of the two endless guide belts remains constant.  
  The various parts of the guide belts run at different speeds from one another: the absolute speed of that part of the belt 11 which is between the drive roller 12 and the rollers 13 is V. whereas that part of belt 11 which is disposed between the rollers 13 and the rollers 15 moves at a speed of (V-2u) and the part between the rollers 15 and the roller 17 has an absolute speed of \*-2ir 2w). the speeds u and w being taken with their sign.  
  In the return travel, it is equal to w V/2. Consequently. the absolute value of that part of the belt 11 which extends parallel to the delivery belt 3 is zero during the return travel. and so the fleece portion which has just been laid on the delivery belt 3 has above it a belt part which is moving above it at zero speed. A simi&#39; lar result occurs in respect of the bottom part of the belt 23 during the outward travel. Clearly, therefore, the fleece is very effectively protected from air eddies.  
  During the outward travel the speed u is equal to V/2, and the absolute speed V-2u+2w of the bottom part of belt 11 is 2w. Consequently, the relative speed of such part of the belt relatively to be rollers 15 is always equal in absolute value to This relative speed represents the rim speed of the rollers 15, which speed is therefore always equal to the speed at which the fleece moves on such rollers. There is therefore no slip between, on the one hand, the rollers 15 and, on the other hand, the guide beit and the fleece.  
  The second embodiment of the invention. shown in FIG. 7, differs from the embodiment just described only as regards the path of the first guide belt 11. Instead of the first auxiliary carriage 19 shown in FIGS. 4 to 6, there is a fixed-spindle roller 4!, also, the second auxiliary carriage 22, instead of being connected to the chain 3i imparting to it a speed u, is attached to an independent chain 42 running over a drive roller 43. The drive means for the carriages drives the roller 43 at a rim speed of (wu). The result obtained is, of course, the same as obtained by means of the construc tion shown in FIGS. 4 to 6. The second embodiment saves one moving carriage but at a cost ofa slight complication of the carriage drive means, which is required to provide not only the speeds u and w but also the difference between them.  
  The third embodiment, shown in FIG. 8, is simpler than the first two embodiments since it has just one auxiliary carriage. Each of the two guide belts ll, 23 describes just one main loop and one auxiliary loop, and the length of the auxiliary loops of the two belts is controlled by just a single auxiliary carriage 44, the same carrying rollers 45 for the first belt 11, and a roller 46 for the second belt 23. Carriage 44 is driven by an endless chain 47 associated with a drive roller 48. The carriage drive facility drives the roller 48 at a rim speed of (wu).  
  A disadvantage of this embodiment is that the second guide belt 23 has no portion extending above the delivery belt, and so the fleece is less protected against air eddies than in the two previous embodiments. Also, the first main carriage [4 of FIG. 8 has only a single largediamcter roller 49 for the two guide belts, with a consequent risk of static electricity building up which must be discharged by suitable known means.  
  A description will now be given for the main features of the movements of the moving carriages and of the delivery belt as they arise from some preferred choices for the relationship between time and the speed w of the second main carriage 16.  
  FIGS. 9 to 14 relate to a sinusoidal relationship between the speed w and time. FIGS. 9 to 11 relate to the moving carriages, FIG. 9 showing their positions, FIG. 10 their speed and FIG. ll their acceleration, all plotted against time along the abscissa, just a single period T being shown. The period T is equal to 2C/V, C denoting that travel of the second main carriage 16 which is equal to the required final web width. This relationship, which applies for any speed laws, merely states that the fleece length laid on the delivery belt in one period is equal to the amount of fleece fed into the machine by the feed system during the same time.  
  The chosen speed w is represented by a curve 51 in FIG. I0 which corresponds to the equation w (1 1V/2) sin (gVr/C). The position of the second main carriage [6 is represented by a curve 52in FIG. 9 which also has a sinusoidal relationship to time. Half way through the period the carriage 16 has travelled a distance C, and one-quarter of the way through the period the carriage 16 has travelled a distance C/Z.  
  As already stated, once the relationship for the speed w has been chosen, the speed relationships for the other carriages can be deduced from it by the formulae previously given. The speed it for the first main carriage I4 is in the case represented by a curve 53 in FIG. 10 and the position of carriage 14 is represented by a curve 54 in FIG. 9. Clearly, the travel of carriage 14 is slightly more than C/Z. A curve 55 in FIG. 10 and a curve 56 in FIG. 9 represent, where applicable, the speed and position of auxiliary carriages running at the speed (w&#39;u).  
  The accelerations corresponding to the three speed curves of FIG. 10 are shown in FIG. 11. Of course, the acceleration of the second main carriage (solid-line 57) has a sinusoidal pattern. The sinusoidal accelerations of the first carriage (chain-line 58) and, where applicable, of the auxiliary carriages (heavy chain-line curve 59) have a break in the middle of the travel, such break corresponding to a sharp point in the carriage speed curves. However, all these accelerations have finite values at any time and can be provided by means of physically feasible forces.  
  FIGS. 12 and 13 show the variation in time of the position and speed of the delivery belt 3. As already stated, its speed, represented by a curve 61 in FIG. 13 is proportional to the absolute value of w. More accurately, its speed is given by the formula: V, Alwl/ZKC in which A denotes the width of the fleece entering the machine and X denotes an integer equal to the number of overlapping folds of fleece required to form the web, K being at least 2.  
  As can be gathered from curve 62 in FIG. 12, the position of the delivery belt is not related linearly to the time as in known machines but is so adapted to the position of the second main carriage as to form an even web. Of course, the delivery belt moves by an amount A/K in one period T.  
  FIG. 14 represents, plotted against time, the rim speed of the output rollers 15 and 26 of FIGS. 4 to 6. Curve 63 represents rim speed for zero rotation of the guide belts, and curve 64 represents rim speed of the delivery rollers and the belts are rotating at a speed V. As already stated, in such a case the latter rollers have a rim speed equal to the absolute value of w.  
  The other two speed relationships of the second main carriage as shown in FIGS. 15 to 22 are odd periodic time functions, each alternation of which comprises two sinusoidal portions possibly separated by a constant-amplitude portion.  
  As a rule, if n denotes an integer equal to at least 2, the three portions of an alternation of w are defined as follows:  
 when 0 t rr/na, w w (l-cos nat)/2 natl/2.  
  The second alternation is similar to the first but in the opposite direction. In these formulae, WM nV/(nl) and a &#39;rrV/C.  
  FIGS. to 19 relate to the case in which n is 2. Curve 65 of FIG. 16 shows the variation of w in time. In this case there is no constant-amplitude portion and for the first alternation just have W V[ lcos(21rVt/C)]. Curves 66 and 67 in FIG. 16 shown, plotted against time, the speeds u of the first main carriage and any moving carriages, respectively, whose speed must be (W14).  
  Curves 68 to 70 of FIG. I5 show the positions of the various carriages plotted against time, and curves 71, 72 of FIG. 17 show accelerations of the second and first main carriages. As curve 69 shows, the first main carriage goes slightly beyond its original position near the end of the period; also, as curve 72 of FIG. 17 shows, first-carriage acceleration has a sharp point, but no break, in the middle of the period.  
  Curves 73 (FIG. 18) and 74 (FIG. 19) show the position and speed respectively of the delivery belts, whose speed can be deduced from w by the same formula as above.  
  FIGS. to 22 show the case for n 3. Curve 75 in FIG. 21 has a segment 76 of constant amplitude W 3V/2 between sinusoidal portions 77 and 78. Chainline curve 79 represents the speed u of the first main carriage, and curve 81 represents the difference (w-u) used for auxiliary carriage control in some of the embodiments hereinbefore described.  
  Curves 82 to 84 in FIG. 20 show, plotted against time, the movements corresponding to the three curves of FIG. 19, and curves 85, 86 in FIG. 22 represent accelerations of the two main carriages, such accelerations having sinusoidal portions separated by zerovalue portions.  
  Of course, the speed V, of the delivery belt is related to the second main-carriage speed w by the formula hereinbefore given. The third speed pattern w (curve 75) makes it possible, in relation to the other two patterns hereinbefore described, to reduce the maximum torque and the effective torque which the motor for the carriage drive means is required to provide.  
  As an example, FIG. 23 shows a drive diagram of a drive means for the moving carriages. A motor 9] drives a first cam 92 at the angular velocity n&#39;V/C and, through a chain-and-sprocket system 93, a second cam 94 at an angular velocity of 21rV/C. Cams 92, 94 have guide tracks 95, 96 whose pattern depends upon the pattern chosen for the second main-carriage speed w. For instance, if the latter pattern is a pure sinusoidal time function, track 95 is circular. Engaging therein is a roller 97 driven, via a slide (not shown) perpendicular to the plane of FIG. 23, by a rack 98 which is therefore moved in rectilinear reciprocation. Rack 98 rotates a shaft 99 running at a speed w.  
  Similarly, through the agency of a roller 10] and a rack 102, cam 94 drives a shaft 103. Track 96 in cam 94 has a pattern such that the angular velocity of shaft 103 is equal to (V Iw I). Consequently, when rack 98 makes one complete reciprocation driving shaft 99 at a speed w, rack 102 makes two complete reciprocations driving shaft 103 first at the speed (\/w) and then at the speed (V-l&#39;w) (curve I09 in FIG. I0).  
  The arrangement comprises a first differential I04 having one planet wheel [05 driven by shaft I03 atone speed and in the opposite direction to shaft 103, while the spindle of satellite 106 is driven by shaft 99. The second planet wheel [07 drives through a chain-andsprocket system a shaft 108 at a speed 11. A second differential III has its first planet wheel II2 driven by shaft 103 at one speed and in the same direction as the latter shaft. A spindle of satellite H3 is driven by shaft 99, and the second planet wheel I14 drives via a chainand-sprocket system a shaft at a speed (w-u This is how the three speeds require to drive all the moving carriages are provided from the shafts 99, I08, [15.  
  FIGS. 24 and 25 are views in elevation and plan respectively, of a variant of FIG. 23, making possible rapid and ready adaptation of the carriage drive means to a modification of the travel C and therefore of final web width. As already stated. the carriage movement period T must be 2C/V but the amplitude of carriage movement speeds does not depend on C. In the variant shown, the motor 9] drives the cam 92 at the angular velocity TrV/C and it drives the cam 96 at twice the angular velocity through gears I16, I17 and a chain 118. Through the agency of rollers 97, I01 the two cams 92, 96 are adapted to displace rods 119, 121. As in the previous case, racks 98, 102 drive shafts 99, 103 via gear wheels 122, 123 (FIG. 24), however, the racks 98, 102 instead of being directly driven by the rollers 97, 101, are displaced by the rods 119, 121 through the agency of rocking levers I24, 125 which are pivotally mounted at places I26, 127 and which terminate in forks 128, 129 so that distances between the rods 119, I21 and the racks 98, 102 can be varied. The elements 92, 96, I I9, 121 are disposed on panels 131, 132 whose positioning can be adjusted by means of screwthreaded rods 133 so interconnected by means of gear wheels 134 and chains 135 as to rotate solidly with one another. The rods 133 of the two panels are so interconnected by pairs of bevel gears I36 interconnected by a chain 137 as to rotate solidly with one another.  
  To alter the travel C of the second main carriage 16, one of the rods 133 is operated to shift the two panels 13], 132 and alter the relationship between the travels of the rods 119, I21 and rack 98, 102. The motor 91 runs at a speed which is in inverse proportion to the travel C, the speeds of the moving carriages being independent of C and depending only upon the fleece feed speed V.  
  FIGS. 26 to 28 show an industrial embodiment of a carriage control system of the kind shown in FIG. 23. Motor 91 rotates the first cam 92 which moves a roller along a circular path, the speed law obtained for w is therefore the sinusoidal one, as represented by curve 5] of FIG. 10. The roler slides in a vertical guide 141 which can move on rollers 142 and rails 143 (FIG. 26). Through the agency of a chain or belt 144, guide 141 drives shaft 99, the same running at a speed w. By way of gear wheels 145, 146 the shaft 99 drives the spindle of the satellite of the differential 104 (FIG. 27) and also drives through gear wheels 147, 148 the spindle of the satellite of the second differential 111, gear wheel 147 also driving the roller 35 which drives the second main carriage (FIG. 28). The second cam 94 (not visible in FIGS. 26 to 28) drives the shaft 103; in order not to overload the drawings, shaft 103 is not shown correctly positioned in FIG. 27. Via gear wheels 149, 151 and 152. [53 shaft 103 drives the input planet wheels of the differentials 104, Ill. Through gear wheels 154, 155, the output of differential 104 drives the roller 38 which drives the first main carriage at a speed u. Similarly. through gear wheels 156, 157 the output of differential lll drives the roller 43 which in some embodiments drives the auxiliary carriages at a speed (w-u).  
  The invention is not of course limited to the embodi ments described. which can be varied in many ways. inter alia as regards the drive facilities for the moving carriages. without departure from the scope of the invention. For instance. provision other than the bottom runs of the guide belts can be made to protect the delivery belt from turbulence.  
 I claim:  
  1. A webber for folding a fleece delivered by a card to convert it into a web ofdifferent thickness from the fleece, the webber comprising:  
 a fleece feed system; first and second main carriages; rollers on said first and second main carriages; first and second endless guide means carried on said rollers for receiving the fleece leaving said feed system and moving the fleece along a loop-like path;  
 main carriage drive means operative to impart to said main carriages periodic linear reciprocations in parallel directions;  
 guide drive means operative to impart to the guide means a speed of movement relative to said main carriages;  
 a delivery belt arranged to receive the fleece leaving the guide means; and  
 delivery drive means operative to impart to the delivery belt a continuous rectilinear motion in a direction substantially perpendicular to the direction of movement of said main carriages;  
 in which webber the improvement comprises:  
 at least one auxiliary carriage;  
 rollers on said auxiliary carriage carrying said guide means;  
 auxiliary carriage drive means operative to impart to said auxiliary carriage a periodic rectilinear reciprocation in a direction parallel to the direction of movement of said main carriages;  
 said guide means comprising first and second continuous endless guide belts running on said rollers of said first and second main carriages and said auxiliary carriage;  
 said rollers being so disposed that the loop-like path along which the fleece travels extends between portions of each of said first and second guide belts.  
  2. A webber according to claim 1, comprising means for protecting said delivery belt from air eddies arising from carriage movements.  
  3. A webber according to claim 2, in which said means for protecting said delivery belt comprises bottom runs of said guide belts. said rollers being so disposed that said bottom runs are disposed substantially in a single plane parallel to said delivery belt, said runs co-operating to form a substantially continuous plane curtain extending above said delivery beit over a length at least equal to the width of said delivery belt.  
  4. A webber according to claim 1. comprising means for moving the fleece between its entry and exit without stretching or compressing it. and means for obtaining on said delivery belt a web which is of constant thickness at its edges as well as its centre.  
  5. A webber according to claim 4, in which said carriagc drive means are operative to move the various parts of the guide belts at speeds such that the fleece and the guide belts move without stretching or compression.  
  6. A webber according to claim 5, in which: said main-carriage drive means are adapted to move said first main carriage at half the fleece feed speed when such carriage moves in the feed direction. and at the algebraic sum of the speeds of said second main carriage and half the fleece feed speed when the first main carriage moves in the opposite direction; and said de livery drive means is operative to move said delivery belt at a speed proportional to the absolute speed of said second main carriage.  
  7. A webber according to claim 6. in which said auxiliary carriage drive means is operative to drive said auxiliary carriage at a speed equal to the difference between the speeds of said second and first main car riages.  
  8. A webber according to claim 6 t; mprising a said auxiliary carriage for each of sa first and second guide belts. said auxiliary carriage d i -me means being operative to drive one of such carriages at the same absolute speed as said first main carriage hut in the oppo site direction thereto. and to drive the other auxiliary carriage at a speed equal to the difference between the speeds of said second and first main carriages.  
  9. A webber according to claim 6, comprising first and second auxiliary carriages for said first guide belt and a third auxiliary carriage for said second guide belt. said auxiliary carriage drive means being operative to move said first auxiliary carriage at the same absolute speed as said second main carriage but in the opposite direction thereto. and for moving said second and third auxiliary carriages at the same absolute speed as said first main carriage but in the opposite direction thereto.  
  10. A webber according to claim 4. in which said means for obtaining a constant thickness web comprises means for changing the direction of maincarriage movement by the use of limited forces.  
  It. A webber according to claim 10, in which said main carriage drive means are so devised that the curve representing the variation of second main-carriage speed has no sharp point.  
  12. A webber according to claim II, in which said main carriage drive means are so devised that the speed of said second main carriage is an odd periodic time function.  
  13. A webber according to claim 12., in which said main carriage drive means are so devised that the speed of said second main carriage is in a sinusoidal relationship with time.  
  14. A webber according to claim 12, in which said main carriage drive means are so devised that one of the alternations of the curve representing the speed w of said second main carriage plotted against time I comprises three adjacent parts defined as follows:  
 when t is between 0 and Tr/na. w W l-cos nat )/2;  
 when I is between &#39;rr/na and (n-l)1rfna. w W and when t is between (n-l)1r/na and vr/a, w. I w l] (*1 cos nat]/2.  
 n denoting a positive integer. a corresponding to rrV/C.  
 WM dfilwting V/(ri-1). C denoting the amplitude of the fleece between its entry and exit without stretching or compressing it and means for obtaining on the delivery belt a web which is of constant thickness at its edges as well as its centre.