US1969071A - Apparatus for the manufacture of rubber tubes - Google Patents

Description

ug. 7, 1934. A. A. GLIDDEN x-:T Al.

Filed oct. 1o, 1929 j? W, e z @30745 Z/7fgd .2% mi@ 77:07;

A. A. GLIDDEN ET Ax. 1,969,071

APPARATUS FOR THE MANUFACTURE OF RUBBERTUBES Filed Oct. 10, 1929- 3 Sheets-Sheet 2 Aug. 7, 1934.

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Aug 7, 1934.` A. A. GLIDDEN ET AL 1,969,071

APPARATUS FOR THE MANUFACTURE. OF RUBBER TUBES Filed Oct. l0, 1929 3 Sheets-Shes?l 3 Patented ug. 7, 1934 RUBBER TUBES Alfred A. Glidden and Thomas-'M.Knowland,

Watertown, Mass., ass'ign'ors to Hood Rubber Company, Inc., Watertown, Mass., a corporation of Delaware Application October 10, 1929,

serial No. n 398,629

9 claims. (ci. 18-24) f vThis invention relates to the manufacture of vulcanized rubber tubes, particularly of Vinner tubes for pneumatic tyres, and has for its object the construction of tubes of this character rdirectly from latex, orA its concentrated modication, revertex, by agglomeration of the individual solid particles suspended in the water emulsion by progressive and regulated evaporation of the said Water which conserves'the association of the component of said unit particles, as distinguished from coagulation, as by means of acid agents, which is characterized by extrusion from the rubber coagulumy with the waterr of emulsion, of the proteids, sugars, etc., normally associated with the rubber particles.

The invention presents three aspects, namely: process, product, and apparatus, and is herein described in all three. ances ofthe elements or factors of apparatus, in their lnecessary functional order and succession, are steps of the process. The process or series of steps requires the essential elements of the apparatus,l as described herein, for its performance. The performance of the essential elements of apparatus, and the process therein involved, inevitably results/in the product herein described.

In its process-aspect, the invention is characterized by application of a foundation lm of rubber-emulsion (with usual composition-ingredients distributed through it, such as zinc oXid, sulfur, an accelerator) toa mandrel, the material of which is preferably afmetal inert to latex, and the vsurface non-porous and impenetrable, partially drying the said lm, under conditions which maintain uniform thickness of the film, applying a second lm coating on the foundation film before the exposed surface of the latter has, by loss of Water, reached irreversibility, ypartially drying the second or outer nlm under dation nlm, applying a third film to the still reversible material of the second, and so on, until the desired body or thickness of tube has accumulated, when the tube, supported by the mandrei,` may be thoroughly dried, then stripped from the mandrel, and vulcanized; or vulcanized onV themandrel and afterward stripped.

In its apparatus aspect, the invention is characterized by means for applying, in succession and superposition, upon a mandrel, coatings of a latex composition, means for immersing and. emerging, in alternation, the lower segment or.

limb of the mandrel in a poolr of the emulsion,

and means for changing the rate of rotation lof The respective perform-` conditions similar to those imposed on the founthe mandrel on its axis to s uit the conditions, respectively, for applying and setting each coatf ing of emulsion. Y Y

In its product aspect, the invention is exemplified by a tube of latex rubber (or rubber com,- position) which, though built to desired thickness by accumulation ofsuccessive latex emulsion coatings, is free from lamination, an integer in structure, homogeneous, and free fromv any grain effect; a tube which, when completed, vconserves inrits constitution the Whole of the ingredients in suspension in the original emulsion, and the characters of the original rubber unit particles, altered vonly by aggregation and coalescence, consequent on elimination of the water of4 suspension, and by vulcanization.

Herein, the word latex is employed as meaningreither normal latex, or its reversible concentrate, revertex.

' diagrammatic.

Fig. 1 illustras the modein which successive film coatings of prepared revertex composition are applied in building a tube; Y

Fig. 2 the ltube mandrel removed `from Contact with the composition-supply;

Fig. 3 a segment in section of mandrel and first nlm coating; Y l V Fig. 4 a similar segment-section of mandrel, iirst coating and second coating;

Fig, l5 is an end-elevational view of apparatus comprising the elements illustrated in Figs. 1 and 2;

Fig. 6 is a view, partly in front elevation, partly in section, of the same;

Fig.7 is a section on line 7-,7 of Fig. 5; and

Fig. Y8 isa wiring diagram. 95

First referring to the elementary Figs. 1 to 4, inclusivez-,liquid latexA composition R, (of whatever concentration may be desired, preferablyVv more concentrated than normal latex)v containing, for instance,.-zinc oxidffinely divided sulfur, ,and anaccelerator, isplaced in a trough T. .A tubemandrel, lM, of aluminumor other smoothly Vvpolished surface, isv mounted on cen- ,tersv above thetrough, substantially parallel lwith the levelsurfacey of the composition.

Mechanical adjuncts (not shown in Figs.`

1 andI 2,) l are Aprovided whereby the mandrelv M andA trough T may be r4made to approach or recede from each other While main- 11M]` taining the said parallel relation. Preferably this will be accomplished by raising and lowering the trough T.

The first film coating of latex composition is applied by raising the trough T until a. narrow segmentv of ,they mandrelA is immersed; in the .composition. Before making this contact thesurface of the composition R should be cleared of any skin that may have formed upon it. At or;

just before the contact is made, the mandrel M is started to rotate on its axis, but4 rather slowly, say at a surface velocity about seventy-five inches per minute.

mandrel and composition quickly: broken as by lowering the trough T, and immediately after emersion the mandrel is causedto rotate on itsv axis (which is kept horizontal) at a much higher speed than before; the number of rotations per' minute may vary within `quite wide limits, provided-thealte'rnation of any given point on the mandrel'surace; betweenrascent andv descent, be

sufficiently frequent to prevent the lm or enveiopeof latexlfrom running circumferentially of the mandrel to produce irregularities in thickness ofthe film. For this-'purpose a surface velocity of about one hundred and-'eighty inchesper minute has been found-suitable.Y The coated mandrel is keptrotating-.atV the relatively higlr ratev until theY evaporation of the water fromv ythe coating of composition has so far' reduced the water-percentage astoproduce anv increase of viscosity. and plasticitytherein which practicallyvxes the coating` iii-uniform thickness, but not so far-Vas to produceirreversibility in the composition at andnear` its exposed surface, if, as will'be-almost invariably the case, the composition layeron the mandrel is to be built up`v mandrel, but alsobecause thetime of exposure to drying air can be more accurately determinedv when the extraction offwater from the composition iilm is effectedinoneradial direction-only@ The foundation .coatingv having-beenvset; as

above 'described the' application or"l the nextcoating follows. The mandrel M, now carrying a layer oi composition setto apracticallyirm consistency, which, however,` retains enoughvof the kemulsion liquid l' to preserve f the reversible character at the exposedl surface,` is again broughty into segment-immersion' relation with he composition supply R inl trough T, its rate of-rotation being1 slowedldown to give a surface' velocity of about seventy-iive inches perminute, so that the second lm coating shall be evenly taken up. Just prior to the application oi' the SecOndcGating the condition of-'the rstis as illustrated in Fig.: 3 (the coating-thickness in this gure andi in- Fig. 4'being exaggerated). Thewater of lthe supply-emulsion is migrating inftliedirection of the arrow through the'coat? ing Ll, and the intimacy of agglomerationof the suspended Vsolids in the film increases in the same direction. The applicationV of the 'nextv coatings L2 over L1 (Fig. 4)V stops evaporation-' When the mandrel has made one full rotation, the-'contact between;

from the surface of coating L1', in which the remaining Water proceeds toward uniform redistribution. At the same time water from L2 migrates into L1, reversing the progress of agglomeration of the revertex solids. The mandrelM; being as before immersedirom thegcomposition supply R, and given its higher rate of rotation, water-evaporation from the outer surface of coating L2 begins, and presently the migration of Water inrboth L1 and L2 proceeds centripetally; the momentry reversion ofy migra tion from L2 to L1 will havev integrated the two coatings., so that no-'distinction of lamination will thereafterdevelop between them.

The foregoingialternations of envelope-application andv evaporation having been continued untilthedesired thickness of tube is acquired the agglomerated material o n the mandrel will be dried thoroughly, or until it is in condition `for vulcanization; the mandrel with the uncured tubeon it may then -be placed ina suitable vuieanizingY apparatus, and cured ;v or the tube-may be strippedA rst and vulcanized later. If-thetube is to be 'used'as an inner tube of a pneumatic tyre, the preferred modeof'manufacture will comprise attachment of a valvebase to-the-unvulcanized tube Ywhile on the mandrel, removall of the tube from the mandrel by the aid of compressedair, attachment' of thevalve, splicing the ends ofthe tube, inflation and vulcanization/in any -usual'manner- A Observed advantages of the process above describedl are: That each layer of the supply` emulsion, attachedto the form represented'by the mandrel (with or without previously setk layers) being quite thin, is by the air-drying to-which it is'subjected reduced to avery nearlyl homogeneous condition of agglomerationof 'the latexsolids. (as distinguished from the otherl solids which enterl into 'theivulcanizable comeratingfcolloidal'net of latex-solids) so that .in

a tube-.of considerable wall-thickness, produced by theaccumulation of Vthiny layers, the struc-.

ture is. homogeneous rand the residual Water-v smallin percentage-and uniformly distributed'.

A relatively short period of air drying4 of'the l completedy tube, at temperatures belowA boiling point suiiices.. to` eliminate this rresidual water; thusthe tube is-soon incondition for vulcaniza tion and can becured without danger of any cellular sponge. formation in` its wall. Tubes4 formed in the manner above described are freerom any..""grain are. exceptionally strong and resistantfto penetration, tearing, or checking.

distinction. between agglomerationk and:`V

coagulation of latexiparticles is `well'recognized,v

though` the. twoA changes in physical state' may be. sequent: inr the relatively. abrupt transformation tocoagulation. Transformation of a latex emulsion into. a; virtually solid vconsistency by.

Vagglomerationbyvthe above described agency of spontaneous` evaporationv is a relatively slow andgentle process; its progressive-stagesare. difficult to.v detectv directlybut may Withicon'- iidence be inferrediby observing. thek subsidence z of i Brownian .movement in f test samples f takenr` at successive. intervals. .It is .believe'dj andi the qualities of agglomerated'latex confirm .the'belief-,ithatthis-mode of transformationl of latex to a `virtualV solidA conserves inthe constituent particles-their originally associatedconstituents, and does not break the unit-aggregates of latex particles.V 'The strength` and toughnessjof the resultant product; as in atube made as'aboveA these motors Vreceiving their current from a'= described, as well as other valuable properties, demonstrate a radical difference from like articles of manufacture made from coagulated and milled rubber. Moreover, forced extraction of the water from a latex, as by filtration under I pressure-differential, breaks a considerable pro' portion, if not all, of the original rubber-particle units, and carries. off valuable ingredients associated with rubber in latex.

There are still other methods than simple spontaneous evaporation of its liquid by which a latex may be agglomerated, as by gradually acidifying an alkaline latex .with an acid coagulant; the formation of a tube by agglomeration by such a method would require a technique more delicate and difficult than the evaporation method, which is therefore regarded as preferable.

Referring now to Figs. 5 drawings: In these figures there is illustrated an apparatus which in its essential members and their related operations is the same as the ap-` paratus illustrated in Figs. 1 to 4, inclusive,'but shows adjunctive mechanical environment there- 4of adapted to actuate the principal apparatus elements in the same manner as that described in connection with the explanation of the. process. In the apparatus as morefully equipped, the mandrels are multiplied, but each.

in turn performs its function in relationto the latex trough or reservoir exactly as in the elementary arrangement and manipulation of the single-mandrel. In the intervals also between successive immersions in the latex pool, each mandrel is rotated with relative rapidity and given time adequate to set the `last applied latex coating to the stated condition which is short of that of reversibility of the surface. AThis apparatus is particularly designed to permit the .concomitant manufacture of a plurality of tubes,

thus comprising supporting and conveying means which is arranged to carry a plurality of rotary mandrels about a circuit, one part` of which is in juxtaposition to a dipping vat that contains the liquid lwhich is to be applied to the mandrels in successive lms or layers.- zTo this end the supporting means is preferably arranged to be locked inv a plurality of positions, each one of which corresponds to the location `of one of the mandrels in juxtaposition to the dipping vat, whereby the supporting means may have an intermittent movement and be effective in bringing successive mandrels into a position where the rotary surface thereof may contact the liquid contained in the vat.

Preferably, means are provided to cause the Vat to be lifted to bring the surface of the contained liquid into contact with a'narrow segmental portion of a juxtaposed mandrel.

application of the latex layer or film to the mandrel, the speed of the latter is preferably comparatively low'when its surface is in contact with the liquid; while in order to permit the 4satisfactory drying of the latex or revertex and to permit the applied-layer of the same to maintain a uniform thickness. without the occurrence of bubbles or wrinkles, thespeed of rotation of the mandrel is increased, i. e., preferably factors such as electric motors for the mandrels,

to 8 inclusive, of the v Inl order to permit the effective, even, and uniform common source of 'supply by means of contacts'` engaging circularor segmental conductors which" are arrangedso that the motor'thatdrives the mandrel in juxtaposition to the vat may rotate -at a 'lower speedV than the other motors.

As shown in Figs.' 5 and-6, the supporting and conveying means for the mandrels may comprise a rotary frame or support l which is-provided with an axle 2-having its ends mounted upon supporting frames. or standards 3; the support 1 -preferablypomprises parallel circular platesu 7 and 7a,1which are spaced from each other at a .suitable distancefto permit. the. location of Y substantially rhorizontal cylinder. mandrels M. of suitable length therebetween. I

Preferably each :mandrel M comprises a hol-` low metal cylinder of suitable metal, such as aluminum, and has a comparatively smooth exterior surface. Plugs 12, provided with shoulders 9, are arrangedto interfit withl the ends of the cylindrical ,mandrels, having central openingsv 8 ,for intertting engagement with axial sup-I ports thatare carried by the parallel plates 7 and7axof rotary support 1.` Thus, as shown in Fig. .6, supporting plate 7 may carry a plurality of rotatable elements 18 mounted in and slidable` through openings 17; thesev elements havelieads,v 19 engaging sleeve-like stops 20that are secured to theplate 1... The opposite end of each rotatable ,element preferably has a frusto-conical head 21 that is` urgedby a spring 22 into intertting engagement with an opening 8 in a plug 12.. Each member-2o and opening 17 in plate l cooperate in providing a bearingv in which an axialr support 18 may rotate. Y

At the opposite end of `each mandrel, we prefliov erably provide a rotatable stub shaft 25 exizothrough gearing 26-27 in rotating the corre.

sponding stub shaft 25 and the adjoining manv,dr el.. Obviously a mandrel M may be removed bycompression of the corresponding spring 22 and consequent movement of the. corresponding part 21 out of engagement. with the `plug 12,

ywhereupon the opposite plug may be4 removed from engagement with the member 21e.

AA vatfor trough T is disposed below axle -2 of the rotary support, being mounted upon a suitable frame 31, the ends of which are secured to non-rotatable nuts 33 that-engage jackY screws 34 at either end of the machine. Theseljack screwsI preferably are verticallyY disposed and rotate in Vbearing brackets 36 and 37 that are mounted on the standards 3. The lower end of each jackscrewcarries a beveled gear 39 which meshes witha corresponding gear 40 upon a horizontal shaft 41. Azhandcrank 44 is' ar-A ranged to rotate'shaft 4l .byl means of sprockets 45` and 46. and 'a chain.47. It is thus evident that rotation of crank r44 is 'effective in rotating shaft 41 andthe beveled.gears 39 and 40V to cause the jack screws 34 to turn. in unison, thus lifting .or lowering frame 31 and'trough T.

Means are preferably provided to facilitate the stopping of the conveyor member or rotary .Y

frame yin any one. of a pluralityof positions cor-A respondingto Ythe preferred operative juxtal position of any one'of the rotary mandi-els M 'La position!attheilowestLpontin its.path;. iae;, atv

.mandrel andaprogresses:rapidly 'tortheiother end5.

. locking. block 52 carried. by a.. plunger' 5.3.1 that.

is normally pressedl into; engagement. with. a. lug; by a. compression spring; 514 (Figi: 7);. v-.A bracket 55 upon theirame; member; 3. supports.- tlre spring and plunger, while: a, handle: 56 permits its; movement out'. of'Y engagement; with the. lug. Preferably f the member 5:2.A has a curved.; edge. pOrtion. 52L which.- permits. the ready? engagementoi; the side. of.thelug'withr.the locking block. as: the; frame; is rotated. the; lug snapping into engagement. Witlrthe.. corresponding intermediate recess uponthe face of? the block to.

lock the frame in position; unless the; plunger is jmoved: or; held out. of.; its normalA position..

Ereferably each. of.: the. electric. motorsg29. re.- ceives. its. current. from .a common sourcebeing: connected.; tobrushes: Which-fare; mounted.- on..the.. rotatable plate 6.4:-.andi are resiliently urgediinto.- engagement. with segmental conductors-6.0 and 60.a orclb within a 'xed contaotboxlv 61.. Pref-- erably. the.v inner. conductor 6.()A is: circularu and:

may continually engage a brush=62that V:is con,- nected with. each motor,. the segmental. conduc-i tor. b f ormsthemajor portion of' acircle; the.

. short segmental. conductor Gila'being. located. be'V tweenits. ends; An individuali contact. 63'` forf v each. motor. thus is .normally i'n engagementwith either. the outer, segmental. conductor.r 60??V or the segmental portion.60@;.there being. ashortfgapv of' non-conducting.v material between thesev con-I ductors. Suitable. Variable resistanceszR1 and' R2" may be arranged in series with. the conductors` 6l)a andf. 6.01), .the resistance R21 in seriesl with. the Conductor 60?# being. arranged.I normally: to pro yidea; fairly. high resistance soithat.: the voltage;-

of; the. current. flowing; through. the 'motor' 29 which; hasl its; brush;v 63 in. contact" with: the; conductor 60.a will be. materially less; than. that: passing: to the: remaining. motors; Preferably the; connections are so arranged. thatY less` en I ergy. will.: thus ybe impartedto tl'lef.motorwhich is driving; the' mandrel. that.` has been. stoppedv in juxtaposition. to.: vat.. '12.. Under.y normali operating; condltions' the speed?Y of: each'-4 mandrel will therefore be; materially reduced. as it.v arrives ati a point.:.adjoining thevat'..

Preferably the axisa 2.: off the.- frame.- 7; andi the axes of" the individuali rollers or..mandre1s: M are so disposed'. thati the 1 latter. havefai slight. in

clination to -..the. surface ofi. the-.liquid contained.

Within: vatY T, i. a. slight: inclination: to. thel horizontal;v Thus,` the .lower.mostflimit;. or: longitudinalaprolla. of: the;` mandrel is. slightly dis-- placed from"parallelism.l with thek surface-1 off* liquid composition in thetro.ugl1:on-vat;i and,. wheny the; latter. is raised; to.l effect' immersion. of. the'. lower: sector of mandrel: surface. the. contact; between..y theJ lower liml of; the mandrel and. theY surface.. ofi the; liquid. begins ailone'. endr; ofthe This mode.. of; makin'gi immersioni; isfiless likely.:

, toall'ow inclusioniof bubblesiinithe coating-.thanx immersionnofl the Sentire. lower.' limb mandrel:r at.A the.. same... instant; r.

The; revertexconipositionts.which may: conta-in; forexamplezinc ox'id; nelydivi'ded sulfur'a'nd Y an; accelerator` is; placed: 1in-.the Vat? amfithei frame 1, as shown,A maybe rotated` by.' hand-forA .1

5 immerse;- thez lower.- limbo; ther mandrel in, and remorefitom; the later.: @1191131.51011y in tbetroueh.-

any" suitableI intermittently operableuldriying; means mar beaemnloyed for.thisnurnoseefthe..

support; f1. being; automatically' locked bythe blonli 52fwhenfonefofithe mandrels M is brought.

intog juxtaposition With the vat. T.. Normally,

z thezflatter;r is disposed at. a4 level `which prevents.

thee conta'ct-ofzfsuch. a mandrel with the surface of' the contained; liquid;A YThe crank. Lidrnay then be;J operatedta lift; the; frame 3l and vat. T' so` gressivecontacting of.l the; liquid surface with: the surface off. the mandrel; which is eiective; in

forcing; outzairrfrom between these. surfaces and;

Which'layoidsfthe tendency .of airgclinging to. the

mandrel; to aform. bubbles or. blisters in.. the deifposited; nlm.. The mandrel. preferably is; per;

. initted to rotate for one revolution, thereby' piokingupfathin lm or/acoating. of'. the. latex or.' rei/.ertenf The handle. 44 is then operated, to lowerA the Vatrrom'. itspositionwhere the mandrel.y engages the vliquid surfaoeand. the frame 1r istrotatedso'-tl'iat: the succeeding mandrelr is disposedlfabovethe- .Vat andV so that the coated mandreliis-moved. outaof jurita-position..tov the vat.V

Thisautomatically resultadue to the arrange- Ament ofithe segmental conductors, in the rotary acc'elerationof the last? coated mandrel. Thus thetmandreL while: being coated, may have a comparativelylow. speed-toperniit .the depositing. of' afthinilayerxfofiliquid uponits surface; practioallysas soon. as .it-leaves :the liquid surface, the rotary speedof .the mandrel is'v increased, thus preventing; the formation: of wrinklesror irregu-l lar ridges upon the mandrel, in other wordsinsuringzthe'retention of ,-a-thinunif'o-rm film; The

higher? speed' at'. which ther mandrels` rotate after latex orf-the removal of the excess: moisture;

vleaving the Vat alsolaids: inthe drying of' their Preferably the supportisnotr rotated at such a l `rate asitobring the first' coated. mandrel into performed; there will4 ordinarily be a period ofv delay'betweenathesuccessive mandrel coatings.

While; as` show-n', therotary support 1 andthe vat- SO-may both beiV manually moved or operie ated, it is* evident ftliat automatic means mayr be provided for either orboth of thesejpurposes.

lWe claim: Y Y

1. n apparatusof the character. descrilved,V a horizontal"cylindric'allmandrelrotatably mounted with its. lowerinost. limit: slightly inclined to the .l horizontal, means .tdi-state the same, atrough adapted .to.o'entail/1 .latex emulsion,v said troughv locatedbelow' the said mandrel, rand,means -ier relatively.v movingl the mandrel and .trough lteV immerse. .theflower' limb of; the mandrelv in, .and

renroyei-'itL-fromnthe vlatenerriulsion inthe trough. Y 2:;- Inlapparatusi-.oi' the :character described, a. horizontal cylindricalmandrel rotatably mounted:

with itslowermost` limiti. slightly inclined. to* the looatedf below..I thesaidi mandrel, and. means for.l

relatively' mofa/'ing4 the f mandrel; and. trough to the means for rotating the mandrel adapted to impart different rates of rotation thereto.

3. Apparatus of the class described comprising a plurality of horizontal cylindrical mandrels, a common supporting and conveying means, said means being arranged to move the mandrels about a circuit While permitting their rotation about their individual axes, means for rotating the mandrels, a vat arranged to contain liquid to be contacted by the surface of each mandrel in one portion of its circuitous path, each mandrel having its axis slightly inclined to the horizontal as it is brought into juxtaposition to the vat, whereby its surface is progressively brought into contact With the liquid surface.

4. Apparatus of the class described comprising a plurality of mandrels, a common supporting and conveying means, said means being arranged to move the mandrels about a circuit While permitting their rotation about individual axes, a vat arranged to contain liquid to be contacted by the surface of each mandrel in one portion of its circuitous path, driving means to cause the rotation of the mandrels and control means associated with the driving means, said control means automatically causing the more rapid rotation of a mandrel as it moves out of juxtaposition to the vat.

5. Apparatus of the class described comprising a plurality of mandrels, a common supporting and conveying means, said means being arranged to move the mandrels about a circuit While permitting their rotation about their individual axes, a vat arranged to contain liquid to be contacted by the surface or" each mandrel in o-ne position of its eireuitous path, locking means automatically operable to stop the supporting and conveying means in a plurality of positions corresponding to the location of the respective mandrels in juxtaposition to the dipping vat, driving means to cause the rotation of the mandrels and control means associated with the driving means, said control means automatically causing the more rapid rotation or" a man drei as it moves out of juxtaposition to the Vat.

6. Apparatus of the class described comprising a plurality of mandrels, a common supporting and conveying means, said means being arranged to move the mandrels about a circuit while permitting their rotation about their individual axes, a vat arranged to contain liquid to be contacted by the surface of each mandrel in one portion of its circuitous path, locking means to stop the supporting and conveying means in a plurality of positions corresponding to the location of the respective mandrels in juxtaposition to the dipping vat, individual driving means for each of said mandrels, and control means associated with said driving means and arranged to cause the more rapid rotation of each mandrel as it leaves the vat and a decrease in its speed before being brought into juxtaposition to the vat.

7. Apparatus of the class described comprising a plurality of mandrels, a common supporting and conveying means, said means being arranged to move the mandrels about a circuit While permitting their rotation about individual axes, a vat arranged to contain liquid to be contacted by the surface of each mandrel in one portion of its circuitous path, individual driving motors for each of said mandrels, a common source of current for said motors, and conductors to transmit current from said source to the motors, a resistance in series With one of said conductors arranged to cause the supply of a smaller amount o-f current to the motor that is driving the mandrel in juxtaposition to the vat than to the other motors.

8. Apparatus of the class described, comprising supporting and conveying means, a plurality of rotatable mandrels carried by said means, a dipping vat arranged to contain liquid to be contacted by in turn the respective mandrels, means for rotating the mandrels, said means being arranged automatically to effect the rotation of each mandrel at a relatively low speed when in juxtaposition to the tank, and at a relatively high speed thereafter.

9. Apparatus of the class described, comprising supporting and conveying means, Y said means comprising spaced parallelly disposed portions, a plurality of rotatable cylindrical mandrels spanning Ythe space between said support portions, driving means associated with one of said support portions and comprising elements adapted to interiit With one end of each of the cylindrical mandrels and, axial elements carried by the other supporting portion and arranged to intert with the other end of each of the cylindrical mandrels, said axial elements each having a compressible portion, whereby the opposite end of the mandrel may beimoved out of interfitting engagement With the corresponding driving member by the compression or" the said portion of its axial element.

ALFRED A. GLIDDEN.

THOMAS M. KNOWLAND.

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