US2818789A - Machines for forming fold lines in boards or sheets - Google Patents

Description

I MACHINES FOR FORMING FOLD LiNEs IN BOARDS OR SHEETS Filed July 6, 1954 Jan. 7, 1958 w. KIRBY ETAL 3 Sheets-Sheet 1 Jan. 7, 195 w. KIRBY ET AL MACHINES FOR FORMING FOLD LINES IN BOARDS 0R SHEETS Filed July 6. 1954 3 Sheets-Sheet 2 1958 w. KIRBY ET AL 2,818,789

MACHINES FOR FORMING FOLD LINES IN BOARDS OR SHEETS Filed July 6, 1954 3 Sheets-Sheet a a fig 110 116 5 38 2 121 130 Y 19 United States Patent MACHINES FOR FORMING FOLD LINES IN BOARDS R SHEETS Wilfred Kirby, London, and Flavius Kingsford Daniels, Dartford, England, assiguors to Vickers-Armstrongs Limited, London, England Application July 6, 1954, Serial No. 441,474

Claims priority, application Great'Britain July 6, 1953 1 Claim. (Cl. 93-581) This invention relates to machines for forming fold lines in boards or sheets composed of fibrous .materials such as used in the manufacture of boxes, containers, cartons and the like.

Machines are already known for producing fold lines in boards or sheets, such machines possess the disadvantage that they either rely upon very large moulding pressures to produce a fold line, or else rely upon the alteration of the physical dimensions of the blank for the purpose of drawing material laterally into the produced fold line. With existing machinery it is therefore difiicult, to operate upon a blank so as to produce therein simultaneously several spaced fold lines.

In accordance with the invention, a machine forproducing fold lines in board or sheet blanks made of fibrous material, includes at least one pair of rotary folding mem-' bers which peripherally inter-engage to form a .nip, the arrangement and construction of said members being such that when a sheet or board passes between the nip a fold line is producedby forming shear slipplanes in the board or sheet along the foldline.

For a better understanding of the invention and to show how the same may be carried into effect, referenee will nowv bemade to the. accompanying. drawings which,

Figure l is a perspective elevation of a bendingand creasing machine,

Figure 2 is apart sectionalelevation to an. enlarged scale of one of the carriages of the machine of Figure 1,

Figure 3 is a part sectional side elevationof the carriage of Figure 2,

Figure 4 is a part section on. IV-IV of Figure 2',

Figure 5 is a part sectional plan takenin the.line-V-V of Figure 3. 7

Referring to the drawingsthe machine shown therein has a b'ed'l from which pillars. 2 (only one of which can be seen in Figure 1), extend upwardly for the support 2,818,189 Patented Jane 71, 1958 annular flange is secured on the rdtherenil of the 1'6 hy alrey fl. Aipihionwheel-23 i's -mounted o'n'th'e bush and is secured thereto by means 'of bolts zl-A- p'a'ssin'g through the flahge '21. The pinion wheel 23 engages with aworm wheel 24 mountedupon a shaft 25. The pin'ion wheel :23 and the worm wheel 24 are located within a housing 26 formed .in the part 18. A plate 27 is provided for. closing the-housing :2'6, =a11d is secured to the walls of th'ehousing by means offbolts 28. The plate 27 has a boss 27A on which is carried a ring 29 having a lever 29A extending laterally .therefro1n. A further plate?!) havin a slot 30A is carried *on theb'oss 27A and this plateissecured to the plate 27 by bolts 30B. 7 The plate 30 ;-has graduations 30C and .the 'graduations 30C '"c'ooperate with the projection 31. The lever 29A carries a projection Iii-which protrudes through "the 'slot A graduated'dial 321s mounted upon the shaft 16 so that it bears against one end of the bushifi g the dial being heldinpositi'on by means of a locking nut '33, screwed onto a threaded part 34 on the end of the shaft 16. The graduations on the dial 32 cooperate with the projection 31.

The'worni wheel '24 iskeyed (by a key 43) to the shaft suchv that the shaft "may m'ove aiiially of-"tli'e worm. wheel; but the latter cannot rotate about the shaft. The shaft 25 is vertical and is mounted on bearings provided in the frame 19. Theuppe'rend of the shaft 25 has a. collar 35, the lower surface 36 of abuts against the bottom of a recess 37 in the frame 19. The lowermost end of the shaft 25 is formed with ananniilar flange 38 in which there is formed a transverse groove 39-. A coiled spr'ing40 is provided upon that part iii the shaft 25 which extends beyond the surface 41 or the frame U: The spring. bears against the upper surface 42 of the annular flange 38 and against the surface 41 soas to the: lower surfaceof the collar" 35 against the bb'ttenh of the recess 37. V p v The lower rackandpinion mechanism- 12B consists of ar'ack .44 secured to the rail 7 bybolts 45 (only dire Bolt beingvshown). A piriion' wheel 46-engagingw'ith the rack 44 is mounted upona shaft 47. The shaft 47 is rotatablymounted in a hearing termed in a part 48 ofth mainframe 49 of the-part 8B.- A pinion wheel 50 secured to the shaft 47 by a key 51, is maintained in positionaby a: locking nut 52 threaded en to a serewee portion 53- 011 theshaf1547;

ofa receivingtablefi. for blanks 4- of fibrous material.

The blanks 4 may be fed'forward over the table 3 towards a horizontal longitudinal opening 5', bordered above by a horizontally;extending rail 6",,and below by a parallel sin-1ilar--rail*(not shown in Figure 1").. The rails serve to suppore'slida-blybetween them" several carriages 8', the carriages'are effectively divided int'o'twoparts; 8A'an'd 813 so that a blank may be fed through the carriage: Each one ofthe carriages-8-supports rotary f'ormingmembers 9, Ithxand 11'. It will sufiice for the present purpose-to describe :the-'.arrangement"of one of 'thesemarriages 8 Qne: suolmcarriage 8z is arrangedtor sliding between theropposedzrails'zfi: and 7.:with the aid of: air rack and pinbmmeehanism lzAz-and' 12B atrtlie;topi and bottom respectively of :.the. -.carriage.-

The rack ,andwpiniomrneehanisme 12A .mounted' upon the upp errailo consists: of api-nion .wheel115v engaging with a .rack.13.se.cured.totherail 6.-by bolts 14' (only -one ofiwhich is-shown) Theapi-nionwheel 15; is-ssecured 12010116 end .of agshaft .16, which. latter isjournalled intaebearin'g The'pinion wheel 5ft meshes with aworm wheel eairried upon a shaft 55; A key way 56 is fanned mega tudinally of the shaft 55 and a key' (not shown is previ-ded which engages in the key way 5G and a cooperating, key way (notshowiiy in the wheel- 54. Hesse the shaft 55 is slidable axially through the Whel54 but must alW-aysr'otatewith the wheel 54.

The shaft" 55 is vertical and is jour'nalledat it's" 11 end in ar-bracket57 formedin the upper pa'r t of the fra e 4'9. The lower end of the' shaft 55 is similarlyjiiuinalled in ar -further bracket 58formed on the lowe'ip of the frame '49. A spring. 59 is threaded upon that pattof the." shaft 55- which is between the brackets 57y aiid 58 The; upper end of the spring.- 59" bears against the" lhwer 17. formeqhin: an upstanding partrlsl ohthe-frameelQ-of the upper part 8A of the carriage 8. A bush 20 having an thespring: 59 beats a'g'ainst the u pee surface- 61*" of" a collar 62 secured tdtheshatfSS-byi-a=pin 631 The spring 59-x-acts soas to urge the collar: 62 i11toabutnient' with the upper surface 64"of-the"-bra'cket 58;i; efthe spring 59' urges. the shaft-55 downwardly.

T-he'upper end of the shaft 55-is formed with a flaii'ge .upon the upper-of which is" formed-a--rib*66': The rib- 664s so dimensioned as to; co-operate'inthe recess 39"it'1 the, flange 38; Thelowermost surface'h'l of 'the flan'g'e 65 -,abuts--.against the upper'surfa'ce of the bracke't 57? The pinion wheel 50 and the worm wheel 54 are enclosed within a housing 68 formed in the frame 49. A plate 69, for closing the housing 68, is secured to the walls of the housing by bolts 70 (only one bolt being shown). The lower end of the shaft 55 is apertured to receive the shank of a plug 55A. The head of the plug 55A serves asan abutment surface for co-operating with a horizontal bar (not shown) disposed immediately below the shafts 55 of all the carriages 8'. The bar is arranged to be moved upwardly by means not shown so that when it engages with the plugs 55A, all the plugs 55A, and hence all the shafts 55 are:n1oved upwardly.

In order simultaneously to traverse the carriage portions 8A and :8B, the lower shaft 55 is moved upwardly with respect to its bearing brackets 57 and 58 until the rib-66 engages with:the recess 39, the parts 8A and 8B thereby becoming coupled together. Rotation of the shaft 25 by means of the handle 107 therefore causes the shaft 55 also to rotate. Rotation of the shafts 2 and 55 turns the worm wheels 54 and 24 andthese rotate the wheels 23, 15, 50 and 46. Rotation of the wheels 15 and 46 causes the carriage 8 to be moved along the horizontal rails 6 and 7.

The extent of the lateral transverse may be measured by referenceto the indicating dial 32.and projection 31.

A main driving shaft 71 passes through the carriage part 8B, such shaft having a longitudinal key-way '72. An annular member 73 is mounted rotatably within the carriage part 8B and is'disposed upon the driving shaft 71 with a key 74 entering the longitudinal key-way 72. A second-annular member 75, similar to the first is also supported rotatably in the carriage part 813 and lies upon the driving shaft 71. The second annular member 75 is not however, keyed to the shaft 71, but is connected rigidly to -the-first annular member 73 by bolts 76 extending between the two members 73 and 75. The annular members 73 and 75 are shrouded by the frame 49 and a side member 76A which are secured together by bolts 7613. Ball races 76C are provided between the member 75 and the frame 49 and between the members 73-and 76A; An annular forming element 77 is located between the two annular members 73 and 75, the bolts 76 passing through the element 77 so as positively to prevent-any movement of the element 77 relative to either of the annular members'73 and.75. The outer peripheral edge 78 of the annular forming element 77 is tapered so --as to be of substantially V-section with the apexof the V rounded. Inthis particular example, the angle of the V is about60degrees. It is however to be understood thatthis angle'is not critical. Two channelsection rings 79 and 80 are located one on either'side of the-forming element 77 in such a way that the channels 81 and 82 of the rings 79 and '80 respectively are opposed and he one on either side of the element 77. The webs .83 and 84 of the rings 79 and 80 lie in planes parallel to the general plane containing the annular forming element 77, and the flange portions 85 and 86 of smaller diameter of the rings engage'upon the flat surface 87 of the element. The flange portions 88 and '89 of greater diameter terminate upon the peripheral edge of the forming element 77 and are themselves bevelled so .as to fit upon the tapering annular peripheral edge 78 of the formingelement 77. Thus the'two rings 79 and 80 shroud the forming element 77 except for the extreme peripheral portion 90, i. e. the-portion near to the rounded tip of the V-section. When the assembly of the tworings 79 and 80 and forming element 77 is viewed from the out side, the outer curved :surfaces of the rings 79 and 80 appear to be in alignment and separated by the projecting peripheral portion 90.01" the forming element 77. Preferably these outer curved surfaces of the rings 79 and 80 slope gently away from the peripheraledge 78 of the forming element77 so that they are of greater radius near to the forming element 77 than in parts of such surfaces more distant from the forming element.

The rings 79 and 80 which-shroud the formingelement 4 77 are forced into intimate contact with the forming element 77 by circular pads 91 and 92 placed directly in contact with the rings and urged into such contact by springs 93. The pads 91 and 92 and the springs 93 are all carried by the described two annular members 73 and 75, so that the assembly consisting of the forming element 77, the two rings 79 and the circular pads 91 and 92 and the springs 93, rotates in accordance with rotary motion imparted to the main driving shaft 71.

The upper part 8A of each carriage 8 has a shaft 94 the axis of which is contained ina plane above and par allel to the horizontal plane containing the main driving shaft 71, the axis of such fixed shaft 94 being however directed perpendicularly to the axis of the main driving shaft 71. The axis of the shaft 94 is contained in a vertical plane which is the medial plane of the described lower forming element 77. Two hangers 95 and 96 are mounted upon the shaft 94 and are adapted to be rocked aboutsuch shaft with-the aid of two upstanding yokes 97 and 98 formed on the hangers 96 and 95 respectively. Movement of each yoke causes corresponding rocking motion of its particular hanger. The two yokes 97 and 98 engage .upon two eccentric portions 108' and 101 respectively of opposite-eccentricity on shaft 99 so that the turning of the eccentricishaft 99 in the one direction or the other, produces motion ofthe yokes 97 and 98 to the same extent, but in opposite directions. The upper carriage-part SA has mechanism 192 for adjustably rotating theeccentiic shaft 99 in either direction. The mechanism 102-consists of a shaft'1ll3 journalled in a bearing 10.4 formed in the upstanding part 18 of the frame 19. The shaft 103 has an annular flange 105 formed at approxi mately the centre thereof. The upper surface of this flange bears against the lower surface 196 of the bracket in which the bearing 104 is formed. A collar 103A is securedto-the shaft 103 by a pin 198. A handle 107 is provided for fitting onto the upper end of the shaft 183, this upper end being of square section. The lower portion 1090f the shaft 103 is threaded, and carries thereon aslideblock 110. The slide block 118 has a square cross section, and is entered in a slot 111 in the frame 19. The slide block ,is dimensioned so that it is a sliding fit within the slot 111. The block 110 has a rectangular recess 112 formed therein, the direction of the recess being transverse to the axis of the shaft 103. A pin 113 is entered in the recess 112, the pin 113 being dimensioned so that it can slide in the recess 112. The other end of the pin 113,is,entered.in one end of a link 114, the other end of the link 114 being secured to the end 115 of the shaft 99, bya pin 116.

. A second link 117 has one end thereof mounted on the endi115 of the shaft 99. The-link 117 is located between the 'link114 andthe frame 19. The other end of link 117-has an arcuate'slot 118 through which a stud 119 projects. The stud 119 is mounted in a plate .120 which is secured to the frame 19 by screws 121. The plate 120 hasa scale 120A engraved thereon, the scale reading from 0 to 8. A pointer 122 integral withthe link 117 cooperates withv the scale. The link117 may be locked relativeto. the plate 120 by means of a nut 124 threaded on the stud 119.

A member 125 is interposed between-the frame 19 and the link-117.- Theshaft 94 is mounted, at one end thereof, in the member 125 and is mounted at its other .end on a yoke 126. The member 125 hasasubstantially rectangular aperture 127 out therein through which aperture 127 the end 115 of the shaft 99 passes. The link 117, has a spigot 117A which is eccentric with respect to that bore of the-link 117 which receives the shaft end 115. The outerdiarneter of the spigot 117A is in contact with the member .125 at the top and bottom of the aperture 127. Byrotatingthe-h'nk 117, within the limits of the slot118, the member 125,- and consequently the shaft 94, canbe movedup or down relative to the shaft end 115. To set admires mi s. thel a s 717 tu 'a diabpl t he Sh ft -l. until h 'Pq i t 'r w per tes wi h desi e raduap he a e 2 A 6: settin up. he aa atamss he af y b oy d'u aad. da re ive is? t 'ber125bymeans of-an' adjusting screw"128'; the latter being intended to be operated by means of aton mylbar. Tha kc is fqrms fl he ramc .2 shaftj94iby means of a pin1 29th 'dir c 2 be n ra v rse o th axis f scan at ym v t l' imemb r tiqnr he a t tt. w n sabq ti ep n 1. 1 he m m oand .1 e-ra s d, r qwe a .withrespect tothe frame 19.

' ,de'pending endcf eachhanger 95hr 96 .is formed s. a bar-l ke s uc re: nd ea x c ives amps.- 'ite ppsr snn nasleinennlland. E is ti y A haa e'rltqsether wi a compo te Zap-Pe f0. gei apt farms e. of the. ot ry f r i embers i; @Qmamher 0hr E2 h compesiteupr r rm e lem n 3: (an 322;) ompris s wd rm s discs. 3 a1 .;1 3 (or ,325 13)r. The ,discslie side byside in their respective boxes Th'e pe r ipheral-outeredges. ofthe-discs forming a, com.- pqsite element are turnedtowards one another so .that-th e assemblyv seems to consistof asingle disc. Each compositeelernent. 131; or 132 hasiits outer. periphery tapered this being. effected ,by bcvelling each of the two-discs forming the composite. 'l he -angleotlbevel of the-twodiscs forming the composite is not the -sameiso that the -one disc a.blunter-edge-thantheother, e.'g., disc,13 3 or 135 hasablunter edge than disc 134,0r 13$ The more sharply bevelled disc 134 or 136 has an outer periphery of slighter greate rdiameter-than the other disc- (133 or 135). Thediscs .135 andlgzh.are mqtlntecl by means of ball races 137-and 138' respectively upona shaft 139. The shaf 1 4- 31 ad ally directedfl n ewhich is-locared a heics i e lithe at,.. hd whi h es o spac apart the discs 135 and 13 ;6. Thje=shaft1l39 is .journalled in bearings 141 and 142, the bearing 142 being formed in a plate 143 secured to-the-hanger-96. The discs 133 an s fi w im larly iwnt di hehoxaof t h n r 95.

Theme-ha ger .5. 11 fiiw htQ tB d'ifIOm the shaft 94 support their respective boxes so that these boxes lie substantially on either side of the vertical plane containing the shaft 94. The axis of rotation of each composite element is inclined with respect to the last mentioned vertical plane so that the portions of said axis remote from the plane are at a lower level than those near to the plane. The inclinations are such that both of the composite forming elements are, at their lowest points, closely adjacent one another and efiectively lie on either side of the extreme peripheral portion 90 of the lower forming element 77.

To move the forming members 10 and 11 towards and away from each other the shaft 102 is rotated by turning the handle 107, whereupon the slide block 110 is moved either upwardly or downwardly depending upon the direction of rotation of the handle 107. In either case movement of the block 110 is transmitted to the link 114 which latter rotates the shaft 99, and causes the yoke arms 97 and 98 to move in opposite directions by virtue of the oppositely directed eccentric portions 100 and 101 so that the members 10, 11 are swung towards or away from each other. A scale 130 is provided upon the frame 19, and a pointer 110A on the block 110 co-operates with this scale. It will be realised, therefore, that the scale 130 and pointer 110A afford a means for indicating the distance between the members 10, 11. It is not desirable that there should be a point common to the co-operating edges of the composite elements 131 and 132 and the lower forming element 77. Hence as shown in Figure 2,

' P t QPW Q l stir er: a as swenrtary lding the vertical plane containing the axis of rotation of the composite element 131 is spaced a horizontal distance "6 awaytromithje'verticalfnlane on a ninathe than d ivin shaft 71 cnthe; ideo,,ff 11c1'1 lah gw ils, thehthet o he maos te lemwt fiz. i s m lat y. hac i n the other side of the vertical plane containing the driving shaft 71.

lathe mplpyment or t e machin ha onwfs $9t bd ca riers 8,, a cord ng; to the thickness. of the board .or sheet; so, th composite forming elements. 131 32am" set. y n the case. Oi.prpgressivelyjncrea ng ressiyelyathehansers 5 m swung apart, and efie'ctive edges of the, composite I i lemejnts 131;and' 1,32, are. both raised from the atig 'lLQWevfiQIhlillQflemfit 77! After anapprp, nr ate adlu tment has. been. made.v ccor ing 'to'board thickness, the blank 4is1fe1 thlQl gh. th ca rier fi-Whilsl the main, driving shaft-7 1 is; IZOtatin g; the. lower forming element 77 In, passing between the. upper, and, lower rotary forming members 9,"10,' 11a fold line is imparted t the-blaplg 4. It, is to .b e noted thatzthe, lower form member. 9,. selflcompensatingfor. differences, of thick,- ness offa single, blanlot, in the sense, that the shrouding rings 7 9, andYSD; can. be forced downwardsbythe blank. 4 itself, thereby revealing,atl rgeripartv of the, edge 7,8-ofi the lower forming element 77.

As, the maehinehas several? of the described carriers arranged side, by, side several fold tlines can a be -s imultane-, ously maderinthe sameblank. It-willbe appreeiatedthat the=carriers need not: be, mounted side by side in-=afline that is transverse, to. thedirection of movements ofi the lank, I o esir dcertain, c merscculd be mounted one behind the'other with reference to, the -intended direction of movementofthe blank.

' When, carriers are mounted one shehind the; other-it. is necessary to align thecarriers with ;respect, toeach 1011161: Thepalignment ofyapy;one-tpairyofcarriers is elfected: as follows The-projection 31;;onthe leverr29-A- ontthe front carrier 8 '(with respect to the direction of movemention the: blank). is, set. to; the: zerosof; the; graduations 30C-on the pi ata-.30, 'Ilhe nut 33-isxloosened and thesdiali 32-is turned, until; its zero ;g;1i@duation coazoperatescwith the projection :31, after which hfinutfl 33 is tightened.

The-lowertpart ofgtbescarriagez (i.-.-e.- part 8B)l iS then setsgthat thegperipheralgpsimian: ofzthe lower forming el ment-:77 i ce trally disposed; between: the composite upper forming elements 131 and 132. When so disposed the rib 66 and the transverse groove 39 are in alignment so that upward movement of the shaft 55 would cause them to engage.

The lower carriage part 8B of the rear carriage (i. e. the carriage disposed behind the said front carriage) is then positioned by aligning the lower forming element 77 thereof with the lower forming element 77 of the front carriage. The upper part of the rear carriage is then set, with respect to the lower forming element 77 of this carriage, so that this element 77 is symmetrically located between its associated composite upper forming members 131, 132, after which the projection 31 on the lever 29A and the dial 32 of the rear carriage are set in the same way as those of the front carriage.

When it is desired to produce two fold lines which are closely adjacent to each other, the front and rear carriages are adjusted along the rails 6 and 7. Thus, for example, if the graduations are in metric measurement, and it is desired to make two fold lines which are 8 mm. apart, the lever 29A of the front carriage is moved so that the projection 31 coincides with graduation 4 on the plate 30. The shaft 55 is then moved upwardly so that the rib 66 engages with the groove 39, after which the shaft 25 is rotated by the handle 107 in a direction such as to bring the zero of the dial 32 into coincidence with the projection 31. Rotation of the handle 107 causes the carriage 8 to move 4 mm. to the right (when viewing the machine in the direction of the movement of the blank 4). The same process is repeated with the rear carriage thereby moving the rear carriage 4 mm,

to the left v (as viewed .fromthe front of themachine). Hence when-the machine .is in -,use twofold lines are produced on ,the,:,blank 4, onebytthe front ..carriage ,8 and .onegby the rear carriage, ,the fold lines being 8 mm. apart.

It is to be understood that the machine, describedabove is subjectto ,modification without departing from .the underlying principle. Thusa simplermechanism could be. employed, if only onethickness and quality of board or sheet'is to be subjected to the fold lineoperation. In this case, the necessity for having two composite forming elements lSl, 132, largelydisappears. It becomes then possible. to use a single upper forming member the periphery of which is of channel section so that the two flanges of the channel canengageion eitherside of the V-shaped lower forming element.

It will also be quite clear that the disposition of the upper and 'lowerforming elements or members could be inverted.

The effect obtained in forming the fold lines isthat shear slip planes are produced in the fibrous sheet or board in a zone along the fold line. Great moulding pressures are not required nor is the blank.diminished significantly in the dimension perpendicular .to the fold line. This seems to be due to the fact that when the material passes between the nip constituted by the upper and lower forming members or elements, a shearing force is exerted over the area of the material located on either side of the fold lineand including the location of the fold line itself. The slip planes produced by the treatment can be seen after a blank has been prepared with the fold lines and experiment shows that if the shearing stress necessary to-produce shear slip planes in a specimen of a board exceeds the tensilebreaking stress of that board, then the particular sample of board in question is not suitable-for the invention. This appears tohe substantially the only limitation to the use of the machine. I

Where fold lines are to be made in board of considerable thickness it is advantageous to make two closely adjacent fold lines for each bend or crease or complete turnback that is to be performed with the material after the fold lines have been made therein. In producing for example a right angle bend, forty five degrees of bend can be taken in. each'fold line so that in the finishedbendthe material existing between the fold lines lies at an angle of a hundred and thirty five degrees .to the walls approaching the right angled bend. By continuing the bending process beyondninety degrees, a turn-down is formed inwhich the intermediate material lies at right angles to the superposed walls approaching the turn-down location.

We claim:

A machine for producing fold lines insheet blanks made of fibrous material, the machine including at least one unit that comprises first, second and third rotary foldline-forming members, ,a peripheral edge on each of the first and second fold-line-forrning members for contacting one side of the sheet blank, a peripheral edge onrthe third fold-line-formin g member for contacting the opposite side of the sheet blank, the peripheral edge of the first member lying in a first plane and the-peripheraledge of the second member lying in a second plane that is inclined with respect to the first plane, the peripheral edge of the third member lying in a third plane and the first and second rotary members lying on opposite sides of the third plane, the third rotary member comprising a disc having a bevelled peripheral portion on each side, the bevelled peripheral portions of the disc meeting to provide the said peripheral edge of the third rotary memher, a sheet-supporting shroud ring on each side of the peripheral edge of the disc and rotatable therewith, the shroud rings respectively abutting against and masking the bevelled portions of the disc apart from its peripheral edge, and spring means supporting the shroud rings and urging them against the disc While permitting deflection of the shroud rings towards the axis of rotation ofthe disc comprising the third rotary member.

References Cited in the file of this patent UNITED STATES PATENTS

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