US2659936A

US2659936A - Fiber drafting

Info

Publication number: US2659936A
Application number: US252692A
Authority: US
Inventors: Olle E Sandelin
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-10-23
Filing date: 1951-10-23
Publication date: 1953-11-24
Anticipated expiration: 1970-11-24
Also published as: BE511546A

Description

Nov. 24, 1953 o. E. SANDELIN 2,659,936

FIBER DRAFTING Filed Oct. 25, 1951 2 Sheets-Sheet 1 IN VEN r022 0L 2 E E. SA NDEL //v BY RIC HE Y, WA rrs, EDGE)? TONJN-IVENNY A TTORNEYS Nov. 24, 1953 o. E. SANDELIN FIBER DRAFTING Filed Oct. 23 1951 2 SheetsSheet 2 INVENTOR. 0L LE E. 59 N041 //v Patented Nov. 24, 1953 UNITED :s'mTE-s PATENT GFFICE DRAFTING fll le E. "Sanaelin, Cleveland; Ohio mfpiieafieirbember zs, 195' '1,-"seria 1 fib. 252,692

v 24 elaims.

application is a eentiri iia111031 in imrftiir hi3? eiipe I epfiiic ni s 'ial N9. 5 1,951-, fi1ea September 30, 1%)48jriow abenqenea.

"This inventidn Le impreve'ihenes in drafting fiber strands, suh as s1 ifiesmbb ngs nii th d1: @Iftifidiail st ple fibers flof in riiiiidl'es" i ee'ereates;

'ifi'wifieh said mating ember has the feign-1 t? a me mg'enmess 'beltwhiehis pertinent a1 e pafrts'f the ftf in head "blqwthe street wiiieh'patses through the drafting head. H v 4 Fig; is view, to an enlarged SeaIef-a's'eetic n 15 1's of Fig; 1 represented as "ciit =5"? m 2 t Fig; 8 i'sfa View in 'perpecti-vepf the suction 1561i i-imbldyed in "the embod-imerit 0f 6.

Fig. 9 is =a arose-Sectional View of a multiple trumpet guide employed in the apparatuspf Fig. '6 represented as cut :by a plane ii-9 indicated in Fig. 6.

Fig. 1'0 a View of a cross seetion through the 'top Wall iii "the sirctib'n box shown in Fig; 8-, t6 ther 'w-iththe upperand lower belts'of Fig.6, rem sifted but by -a plane '1 O l-0, near 'the efitri end (if the beltsa's indiated imFig. :6.

FY. 11 is a fragmentaiiy "erbss seetiona'l 'ViW (td eln mai ged seale') "efthetop wallet the"suc= ti'dii Jobi: 'sh'owii in Fig; 8 tbgetiier with the dipper and iewer b-elts ei E ie. 6't0='exp1am the principle of 'epi ation Hi the invention, represented as "out by a, plane H near'the'exitend 0f the-belts as indicated ih Fig. "6.

Fig; 12; a'view cfirrpdnding t'd Fig 8 with a inbdifie'd fbrih-"of a'per'turi'ng in the suction =box and Fig. 13 is a View 'eorrespbndiiig "to Fig. 1-=1 to illustrate the tiperation of the ihvei'ition in empleyirrg a 'strctien hex such as illustrated in Fig. 12.

R'ferfi'ng' to the drawing and specifi'eally 'to Figs; 1 t6 3, the drafting "head eviiisists "(if three pairs 6f riidt6r=driVen ro'llers l 2, S -Q and 5 -15, respectively, between which a. fiber strand *iii' sliver i to be drafted, "cbnsisting of *na'tui'a'l or artificial stame hb'ers, is passed. The three T6116! pairs are preferably situated at distances from eaeh "other which are somewhat g 'r eater than the lqiig'est fibers included in *the strand dr sliver. The rel-lei pair l'-2 is driven at a eeftainiperipir- 'ralsp'eed, whereas the roller pair 3 4 is'd-riven with a sbiiiewliat gr'eatei' peripheral speed and the iollei 1' "5- 6 'is -'olriveh at a c'dnsiderably reater peri heral speed. It will be iind'erstooii that, if desired, *onl diie 6f the rollers (if each pair iieei bedriveii, 'r nue theranerlpeire i=2 aria ki' 4" niif the fiber straridat the'eiitraii' and exit a fi FSt f tirig rateh, tvliile the rllei entrance rid 'e iiig rlt'h At this drafting of the fiber strand, long fibers that have been "taught by the following roller pair would, but for the employment of theipre'sent invention, have -a tendency of pulling along short fibers that are not held either by the preceding or the following roller pair, so that the distribution of material in the fiber strand would become uneven and consequently the finished strand would present thicker and thinner portions which is very disadvantageous. Different devices have heretofore been proposed for holding the short fibers under control during the passage of the drafting ratch between the successive roller pairs so that these short fibers are not carried along by the long fibers too early. Among these known devices for controlling the fibers there are distinguished two types which at present are used exclusively. One type essentially consists of one or more freely running rollers arranged at one or more points in the drafting ratch and pressing the fiber strand against one or more supporting rollers for holding back the short fibers so that they are not carried along by the long fibers too early. The other type consists of two endless belts which from opposite sides press against the fiber strand along part of the drafting ratch to hold the short fibers under control.

In practice these known devices may be modified and combined in various ways, but have the common disadvantage of not being able uniformly to influence all the short fibers of the fiber strand, as they directly act up on only the fibers lying at the surface of the strand. Besides, these devices have the disadvantage of flattening the fiber strand so that it must often be collected to an approximately round form at one or more points during drafting by passing the fiber strand through a funnel, which presents many disadvantages well known by those skilled in the art.

Th present invention overcomes the abovementioned disadvantages of the known devices by holding the short fibers under control in a new manner in the drafting ratch of the drafting head. In carrying out the invention, the fiber strand is nipped at points spaced a distance exceeding the length of substantially all the longer fibers of the strand to avoid tearing these fibers and, during the drafting process, the fibers are held together by suction which also retains the shorter fibers in the strand parallel to the others and maintains uniform friction between fibers.

This is accomplished by providing a member having a center strip permeable to air and causing this member to travel in an endless path including a pathway along and including a drafting ratch. The side Of this member opposite the fiber strand is subjected to sub-atmospheric pressure. In the embodiment shown in Figs. 13, such a member may take the form of an endless belt 8 which is passed around the roller 4. A suction box 9 is provided, which extends from the roller pair 3- i to a point adjacent the nip of the rollers 5 and 6,. and which suction box forms a guide for the belt in such a manner that the latter has a part continuously contacting and supporting the fiber strand I along substantially the entir drafting ratch between the roller pairs 3-4 and 5-6, while the belt 8 is traveling with the same surface speed as the strand feeding speed of the rollers 3-4.

The belt 8 may be pervious to air over its whole width, but in the embodiment illustrated only a narrow endless middle portion ll! of the belt is pervious to air within the region where the belt comes into contact with the fiber strand l. The suction box 9 is connected by means of a conduit II to a suction pump (not shown) and has a narrow slot l2 (Fig. 3) or line of perforations in its upper wall exactly below the air pervious portion Ill of the run of the belt 8, traveling between the roller pairs 3-4 and 5-6, so that air is sucked through the said run of the belt into the suction box 9 and therefrom to the suction pump through the conduit H. The air flowing through the slot I2 and the air pervious portion H] of the belt 8 sucks the fiber strands i into firm engagement with the belt 8. Part of the air passes through the fiber strand so that every separate fiber of the strand is sucked towards the belt into engagement with the belt and/or other fibers of the strand, so that the adhesion of the fibers to each other and to the belt is promoted. Thus, each individual fiber of the fiber strand is held under exact control in the drafting ratch between the roller pairs 3-4 and 5-6, whereby all short fibers are effectively prevented from being carried along too early by the long fibers already caught by the rollers 5 and 6. Since the air is sucked to the slot l2 also from the sides of the fiber band 1, the air will also have a collecting effect on fiber ends that project from the strand.

If desired, a belt 8 and a suction box 9 may of course be arranged between the roller pairs l-2 and 3-4 also. Moreover, the suction box may be completely open at the top, but it seems to be more suitable to use only a narrow slot i2 or line of perforations in register with the fiber strand 1, since the air pump does not need to have as great a capacity then.

In the embodiment shown in Fig. 4 the drafting head has two pairs of motor-driven rollers l3-Hl and l5-l6 at the entrance and exit ends, respectively, of a drafting ratch for a fiber strand l1. As usual, the strand feeding speed of the rollers l3--l4 is lower than the strand feeding speed of the rollers l5--I6. Between the roller pairs I3-l4 and i5-l5 is mounted a motordriven drum l8 having a narrow peripheral zone continuously contacting the fiber strand 17 along the major part of the drafting ratch between the roller pairs l3-l4 and l5-lfi and being pervious to air. As shown, the axes of the drum l8 and the rollers are parallel. Said peripheral zone of the drum I8 revolves with a surface speed which is preferably the same as the strand feeding speed of the rollers l3li.

The drum It has a bearing sleeve I9 rotatably supported on a suction pipe 20 which is extended into the interior of the drum where it supports a stationary bafile 2i and has an opening within the drum I8 within the space bounded by the baffle 2|. The bafile thus restricts the suction, generated by a suction pump (not shown) connected to the pipe 20, to the arc of the drum contacting the fiber strand ll. The device according to Fig. 4 operates in the same general manner as the device according to Figs. 1-3 so that no special description of the operation is deemed necessary in this connection.

Endless belts 53 with a narrow air-pervious zone lb (Figs. 1-3) may be manufactured and marketed ready for use, but it is also possible to manufacture and put on the market long lengths of belt with a longitudinal narrow zone which is pervious to air so that endless belts 8 of desired peripheral length can be made in the spinning mills. In Fig. 5 is shown a part of such a belt length 22 with an air-pervious zone 23.

In Figs. 1, 2 and 5, there is illustrated an arrangement in which the suction box 9 has a single slot or row of apertures and the belt 8 has a single air prviods one 23 :rsi aeoni'modating a 5111516 fibr :strand 01 sliver 1. It "Will be derstood, however, "that the invention is not limited thereto andithat provisions may be made also for traversinga plurality of sliyers "-1, simultaneously. For example, a as illustrated, in Figs. 6 and-8, a 'suctionbox 'dl maybe employed having -'a plurality of zones 32 consisting of ton tihilbus or interrupted openings adapted to un-- o'er-lie air p'erviou-s zonesst ih a belt In the specific construction illustrated in 8, the aper tured zones 32 in the top plate'or top wall '35 of the suction 100x 31 take the form "of 'continuous slots, althoughinterrupted slots or series of holes may also be employed. As illstrated in Fig. 7, the air 'per-vious zones 33 in the belt :34 consist of rows or staggered apertures 3'5. If desired, the structure including the belts of Fig. 6 may take "the place of the watch rolls and 2 in Fig. "1.

In place of the slots 32 illustrated in Fig. 8, rows 0f obliquely transverse slots or apertures 8"! corresponding 'in'position to the rows of staggere'd apertures 3t in the belt '34 may be provided in the top wall or plate "35 of the suction box '31 as illustrated in the fragmentary diagram of Fig. 12.

'Moreover, the invention is not limited to the use-of a single belt or endless surface member 8 each drafting stageas shown in Figs. 1 and 2, l

as a second belt oritrav'eling surface member'ss may also be employed as illustrated in "Fig. Preferably the-belt38 is relatively thin and flex-- ible, more so than theibelt- 'a l, and the belt 38 is non-pervious to air. In the specific arrangement illustrated there is a multiple trumpet guide 40 through which the slivers l are drawn.

In the embodiment of"l'5ig.-'6 the surface speed of the belt 34 is not intermediate 'between the peripheralspeeds of the pairs of latch and draft rolls. The surface speedof belt 3 1 is the same as thesurface spee'd or the -roller's H-43. In the arrangement illustrated, the surface speed of the belt 34 is less than that of the'rolls '3 and t. However, as illustrated diagrammatically in 'Figs. and 11, as a result of the presence of the upper belt 33, the fibers 1'1 are not merely drawn along the traveling surface member 01' belt "3 4, but are actually drawn throug hspaces dfl formed between the lower and upper belts t l and 278, so that thes'livers become progressively smaller in cross section as shown by comparing cross-sec tional v'iewso'f Figs. l0 a'nd 1 1, 'the latter having an enlarged scale. Inasmuch as the upper belt '38 is intentionally so chosen 'as to be 'quite thin and highly flexible, it conforms in shape very closely to the cross-section of thes'livers i and hugs the'surface of thebe'lt 3 4 at the portions "not occupied 'by the sliver "7. In oonse quence aneven higher and more uniform degree 0f-draftc0ntro1 is accomplished than in thearrangement of Fig. 1. With either arrangement, an unusually high ration of elongation, or draft ratio, is accomplished so that the length of the sliver after passing between the nipr'olls 5 'andt is many times that before entering the 'ratch rolls, and conversely "the weight and thickness of sliver has become very'much less upon reaching the nip rolls 5 and B.

The suction throughout the pervious lower belt '31 draws the'unper belt '38 down into contact with it and, as illustrated, prevents the fibers of the slivers "from spreading as well as producing a functional grip 'on the slivers passing "between the belts 34 -and "38, which facilitates drafting :of the aser's :01 the slivers are held onto the surfaces for "the "belts and more therewith. Pretferably a weighted supporting roll M I is provided for "the upper belt :38. The lower belt '34 hugs the upper belt as 'by reason of suction and roll pressure and pulls it along so that the linear-speeds of the two ibelts are the same. rcr drivingthelower :belt eta drive roll t? is provided.

Suitable guide rollers such as the :rollers 43 are provided ror thelower belt s4, and a forward. end 44 of thesucticn box 31 serves as a guide member for the forward end 'of the lower belt 31%. Preferably, the end E4 is provided with notches M to avoid trapping fibers under the 138133 4. rirheiforwardiend of the upper 'b'elt 38 requires inn guide member ibec'ause the suction holds it in pla ce. ZPreferably, however, a :bar at isiprovidedto bend down the top of the belt 38 and enable theiloop t? to well into the hi of the draft-rollers "3 and '4. Consequently, as shown, idratt control of the

belts

34 and 38 is continued to a :point beyond their intersection with a plane tangent to -the cylindric'al :surfa'ees of both the draftrolls 3 and "4.

The upper, thin, non-pervious belt 38 overlying the air pervious :belt at is drawn by suetion towards the surface of the lower belt and produces frictional resistance to the movements of the fibers of the four slivers passing between said belts. Ennis suction caiise's the thin iipper belt 38 to take on longitudinally directed waves hugging each of the :iour slivers, the edge por tions of the belt and the portions located intermediate the perv ious rows of openings on the lower 'belt 3 3, being forced towards the surface of the lower beltet by act'io'n o'f th'esuc'tion.

As illustrate'd in Fig. 1-1, ii th'eslots 32 'inthe top plate 35of thesuctlon box 3 l are wider'than the'width's ofzt'h'e rows 'ofthe-openings 36 or the air pervious zones 33 inthe lower belt '3fl, and'to some extent even if they are narrower, there might be a slight tendency toward sagging as illustrated at :lBinFig. '11. If desired, the lower belt 3'4 may be caused to remain substantially uniform in a plane by employment of an arrangement of obliquely'transverse slots orape'rtures 31 as in-Figs. I2 and 1-3. 'The transverse dimension iii "the "slots '31, measured "perpendicular to the direction of motion of the belts, approximately equals the width of'each row 33 of apertures 36 in the belt 34, so that someportion of sa slot 31 is always under a belt opening "36, and pulsations'are thereby avoided.

'As explained, more fully 'in my copendin'g applic'ation Serial No. 253,300, filed October 26,

1951, the apparatus illustratedmay form apart of a multistage drafting system with the drafting rolls 3 and 4 of Fig. -6, serving as ratch rolls for a subsequent drafting stage employing an apron or belt 8 carrying the four "strands 7 into "a trumpet formed 'ina condenser plate. "Features disclosed herein, but not claimed are claimed in my said copendin'g application.

The invention may "be used in every kind of textile machine with drafting heads in which a strand'or'sliver, used in the broad senseis to be drafted or stretched as will be clearly understood by those skilled in the art, and thelinvention is not limited to the specific illustrative constructions and arrangements shown and described.

What is claimed is:

1. In a fiber strand draftinglhead of the type having spaced first and second pairs of rollers nipping'the strand at the entrance and exit ends,

respectively, of a drafting ratch, the pair of rollers at the exit end having a higher strand feedin speed than the pair of rollers at the entrance end of the drafting ratch, a member moving in an endless path including a pathway along and within the drafting ratch and continuously contacting the strand along at least part of the drafting ratch and being pervious to air, and a suction device to suck air through said member for sucking the fibers of the strand toward said member to promote the adhesion of the fibers to each other and to said moving member.

2. In a fiber strand drafting head of the type having spaced first and second pairs of rollers nipping the strand at the entrance and exit ends,

respectively, of a drafting ratch, the pair of rollers at the exit end having a higher strand feeding speed than the pair of rollers at the entrance end of the drafting ratch, a member moving in an endless path including a pathway along and within the drafting ratch with substantially the same speed as the strand feeding speed of the rollers at the entrance end of the drafting ratch and continuously contacting the strand along at least part of the drafting ratch and being pervious to air, and a suction device to suck air through said member for sucking the fibers of the strand toward said member to promote the adhesion of the fibers to each other and to said moving member.

3. In a fiber strand drafting head of the type having spaced first and second pairs of rollers nipping the strand at the entrance and exit ends, respectively, of a drafting ratch, the pair of rollers at the exit end having higher strand feeding speed than the pair of rollers at the entrance end of the drafting ratch, a rotating drum continuously contacting the strand along at least part of the drafting ratch and being pervious to air, the axes of the drum and rollers being substantially parallel, and the fiber-contacting portion of the drum lying between the pairs of rollers, and a sucking device to suck air through said drum for sucking the fibers of the strand toward said drum to promote the adhesion of the fibers to each other and to said drum.

4. In a fiber strand drafting head of the type having spaced first and second pairs of rollers nipping the strand at the entrance and exit ends, respectively, of a drafting ratch, the pair of rollers at the exit end having higher strand feeding speed than the pair of rollers at the entrance end of the drafting ratch, a rotating drum having a peripheral surface revolving with substantially the same speed as the strand feeding speed at the entrance end of the drafting ratch and continuously contacting the fiber strand along at least part of the drafting ratch and being pervious to air, the axes of the drum and rollers being substantially parallel, and the fiber-contacting portion of the drum lying between the pairs of rollers, and a sucking device to suck air through said peripheral surface of said drum for sucking the fibers of the strand toward said peripheral surface to promote the adhesion of the fibers to each other and to said peripheral surface.

5. In a fiber strand drafting head of the type having spaced first and second pairs of rollers nipping the fiber strand at the entrance and exit ends, respectively, of a drafting ratch, the pair of rollers at the exit end having higher strand feeding speed than the pair of rollers at the entrance end of the drafting ratch, a moving endless belt continuously contacting the fiber strand along at least part of the drafting ratch and being 8 pervious to air, and a suction device to suck air through said belt for sucking the fibers of the strand toward said belt to promote the adhesion of the fibers to each other and to said belt, said belt moving in a path including a pathway along and within the drafting ratch.

6. In a fiber strand drafting head of the type having spaced first and second pairs of rollers nipping the strand at the entrance and exit ends, respectively, of a drafting ratch, the pair of rollers at the exit end having higher strand feeding speed than the pair of rollers at the entrance end of the drafting ratch, a moving endless belt being pervious to air, and a suction box for guiding said belt in contact with the strand along at least part of the drafting ratch and sucking air through said belt for sucking the fibers of the strand toward said belt to promote the adhesion of the fibers to each other and to said belt, said belt moving in a path including a pathway along and within the drafting ratch.

'7. In a fiber strand drafting head of the type having spaced first and second pairs of rollers nipping the strand at the entrance and exit ends, respectively, of a drafting ratch, the pair of rollers at the exit end having higher strand feeding speed than the pair of rollers at the entrance end of the drafting ratch, a moving endless belt running over one of said rollers at the entrance end of the drafting ratch and being pervious to air, and a suction box for guiding said belt in contact with the strand along the drafting ratch from the pair of rollers at the entrance end of the drafting ratch to a point adjacent the nip of the pair of rollers at the exit end of said drafting ratch and sucking air through said belt for sucking the fibers of the strand toward said belt to promote the adhesion of the fibers to each other and to said belt.

8. In a fiber strand drafting head of the type having spaced first and second pairs of rollers nipping the fiber strand at the entrance and exit ends, respectively, of a drafting ratch, the pair of rollers at the exit end having higher strand feeding speed than the pair of rollers at the entrance end of the drafting ratch, a rotating drum having a narrow peripheral surface zone continuously contacting the strand along at least part of the drafting ratch and being pervious to air, and a sucking device to suck air through said peripheral surface zone of said drum for sucking the fibers of the strand toward said peripheral surface zone to promote the adhesion of the fibers to each other and to said peripheral surface zone, the axes of the drum and rollers being substantially parallel, and the fiber-contacting portion of the drum lying between the pairs of rollers.

9. In a fiber strand drafting head of the type having spaced first and second pairs of rollers nipping the strand at the entrance and exit ends, respectively, of a drafting ratch, the pair of rollers at the exit end having higher strand feeding speed than the pair of rollers at the entrance end of the drafting ratch, a moving endless belt having a narrow endless zone continuously contacting the fiber strand along at least part of the drafting ratch and being pervious to air, and a sucking device to suck air through said zone of said belt for sucking the fibers of the strand toward said zone of said belt to promote the adhesion of the fibers to each other and to said zone of said belt, said belt moving in a path including a pathway along and within the drafting ratch.

10. In a fiber strand drafting head of the type having spaced first and second pairs of rollers geo es c rollers at the exit end having ahigher strand feeding speed the pair of rollers at the entrance end of the drafting ratch, a member moving in an endless path including apath-way along and; within the drafting ratch a-nd continuously contacting the: strand along at least part the drafting ratch and being pervious to air, and a suction device adapted to suck air through a narrow zone of saidmovi-ng member in reg; 6e1- with the strand contacting said moving member for sucking the fibers of the strand toward said moving member to promote the adhesion of the fibers to each other and to said'movi-ng member.

11, The method of drafting a strand containing fibers of various lengths which comprises the steps of nipping the strand at the entrance end of a drafting ratch, nipping the strand. at the exit end of the drafting ratch at a point spaced from the entrance end of the drafting ratch a distance. greater than the length of substantially the greater portion of the fibers of the strand, feeding the strand at the entrance end of the drafting ratch, drawing the strand at the exit end at a greater speed than the feeding speed while passing an air pervious surface along the fiber strand in contact therewith with the same direction of motion, and sucking air through said surface from a side opposite the strand for compacting said strand and maintaining friction between the fibers therein.

12. The method of controlling the fibers in a strand during drafting which comprises the steps of feeding the strand longitudinally of itself within an area referred to as a drafting ratch, passing an air-pervious surface along the strand in contact therewith, with the same direction of motion, within the drafting ratch, and sucking air through said surface from the side opposite the strand for compacting said strand and holding the shorter fibers therein.

13. The method of drafting a strand containing fibers of various lengths which comprises the steps of nipping the strand at the entrance end of the drafting ratch, and nipping the strand at the exit end of the drafting ratch at a point spaced from the entrance end a distance exceeding the length of substantially the greater portion of the fibers in the strand, while passing an air pervious surface along the strand in contact therewith, with the same direction of motion, sucking air in a relatively narrow longitudinal zone through said surface from a side opposite the strand for compacting said strand and maintaining friction between the fibers therein, and causing the longitudinal speed of the strand at the exit end to exceed that at the entrance end for drafting of the strand.

14. The method of controlling the fibers in a fiber strand during drafting which comprises the steps of feeding the strand longitudinally of itself and simultaneously passing an air pervious surface along the strand in contact therewith, with the same direction of motion, and sucking air through the surface in a relatively narrow longitudinal zone from the side opposite the strand for promoting friction between the fibers therein while causing the speed of the strand beyond the air pervious surface to exceed that with which the strand is fed for drafting thereof.

15. In a fiber strand drafting head of the type having a pair of rotating rollers nipping the strand at the entrance end and a second pair of rollers nipping the strand at the exit end of the drafting ratch rotating with greater speed than the first mentioned pair of rollers, a member having a surface moving in a pathway along and within the drafting ratch in adirection from the entrance end toward. the exit end and continuously contacting the strand along at least a part of the drafting ratch, said surface being pervious to air, and a suction device to suck air through said surface for sucking the fibers of the strand on to said member, to promote their adhesion to each other and to said surface.

16. In a sliver drafting head of the type having a pair of rollers at the entrance end and a second pair of rollers nipping the sliver at the exit end of the drafting ratch, a member having" a surface moving in the pathway along and within the drafting ratch in a direction from the entrance end toward the exit end and continuously contacting the sliver along at least a part of the drafting ratch, said surface being pervious to air, a second member having" a surface also moving in a pathway along and within the drafting ratch and continuously contacting the sliver on the side opposite the first such member and a suction device to draw air through said first mentioned surface for holdingthe fibers of the sliver together thus promoting their adhesion to each other and to said first mentioned surface, the second mentioned member being relatively thin and flexible whereby an enclosure of elliptical cross-section is formed for confining said sliver.

17. A drafting head such as set forth in claim 16 wherein the suction device comprises a box with a wall having longitudinally extending slots therein, said box having an outlet adapted to be connected to a vacuum line.

18. A drafting head such as set forth in claim 16 wherein the first mentioned surface member has rows of openings therein to render it pervious and the suction device comprises a plate having rows of openings therein adapted to correlate with the rows of openings of said first mentioned surface member, said plate forming the top wall of a suction box having an outlet adapted to be connected to a vacuum line, and said openings in the plate serving as the inlet thereto.

19. The method of controlling the fibers in a strand during drafting which comprises the steps of feeding the strand longitudinally of itself within an area referred to as a drafting ratch, confining the strand in said ratch between moving surfaces with the same direction of motion, one of which surfaces is air pervious, and sucking air through the air pervious surface from the side opposite the strand for compounding said strand and holding the shorter fibers therein.

20. In a fiber strand drafting head of the type having a pair of draft rolls having a given surface speed and nipping the strand at the exit end of the drafting ratch, a member having a surface moving in a pathway along and within the drafting ratch in a direction from the entrance end toward the exit end with a lower surface speed than that of the said draft rolls and continuously contacting the strand along at least part of the drafting ratch, said surface being pervious to air, and a suction device to suck air through said surface for sucking the fibers of the strand on to said member to promote their adhesion to each other and to said surface.

21. A drafting head as set forth in claim 20 wherein the surface member is formed with a row of staggered holes therein to render it air pervious therealong.

22. A drafting head as set forth in claim 21,

11 wherein the suction device comprises a box having a wall with an air pervious zone therein correlated with the air pervious portion of the surface member, said box having an outlet adapted to be connected to a vacuum line.

23. A drafting head for drafting fiber strand having a pair of draft rolls nipping the strand at the exit end of the drafting ratch, a member having a surface moving in a pathway along and within the drafting ratch in a direction from the entrance end toward the exit end and continuously contacting the strand along at least part of the drafting ratch, said surface member being formed with a row of staggered holes therein to render it air pervious therealong, and a suction box having a wall with an air pervious zone therein correlated with the air pervious portion of the surface member, said box having an outlet adapted to be connected to a vacuum line for sucking the fibers of the strand onto the said surface member to promote their adhesion to each other and to said surface, wherein the air pervious zone of the box wall comprises a row of obliquely transverse slots whereby some of the staggered holes in the surface member come into registry with portions of the oblique slots while others of the staggered holes are covered.

24. The method of drafting a strand of fibers, which comprises the steps of nipping the strand at the exit end of a drafting ratch while passing an air pervious surface along the strand in contact therewith within the drafting ratch, with the same direction of motion, applying a flexible, longitudinally movable surface to said strand on the side opposite said air pervious surface, and sucking of air through said air pervious surface from the side opposite said strand for compacting said strand and maintaining friction between the fibers therein. 1

OLLE E. SANDELIN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,221,025 Campbell Apr. 3, 1917 2,219,356 Dreyfus et a1 Oct. 29, 1940 2,231,526 Casablancas Feb. 11, 1941 2,274,424 Miller Feb. 24, 1942 FOREIGN PATENTS Number Country Date 4,682 Great Britain of 1890