US2980290A - Method and device for the formation of a stream of particles of constant layer thickness - Google Patents

Description

April 18, 1961 F. FAHRNI METHOD AND DEVICE FOR THE FORMATION OF A STREAM OF PARTICLES OF CONSTANT LAYER THICKNESS 2 Sheets-Sheet 1 Filed Jan. 16, 1957 uvvavrore Fred Fahrni O O O O O 8y ALMA,

April 18, 1951 F. FAHRNl 2,980,290

METHOD AND DEVICE FOR THE FORMATION OF A STREAM 0F PARTICLES OF CONSTANT LAYER THICKNESS 2 Sheets-Sheet 2 Filed Jan. 16, 1957 Dive/7hr: Fred Fall/Hi By W 9. HALL/724W? United States Patent- METHOD AND DEVICE FOR THE FORMATION OF A STREAM OF PARTICLES OF CONSTANT LAYER THICKNESS Fred Fahrni, Freudenbergstrasse 115, Zurich, Switzerland Filed Jan. 16, 1957, Ser. No. 634,573

Claims priority, application Switzerland Jan. 16, 1956 21 Claims. (Cl. 222-1) used for the formation of a stream of wood particles, such as shavings, chips, and similar particles such as those used in large quantities for the manufacture of hot pressed wood shaving boards.

In conformity with the method according to the invention, the height of the heap of particles lying in front of the measuring means is sensed in diflerent places by several responsive devices distributed across the Width of the transport member, and in addition, when the transversal distribution of the stream of particles is uneven these responsive devices start a distributing device by means of a control means, which device equalizes the diflerences in the dammed up height of the heap of particles. 7

The device for carrying out the method comprises, according to the invention, several responsive devices distributed across the width of the transport member in front of the measuring member in relation to the direction of conveyance of the transport member, and which become active when the height of the heap of particles lying in the region before them attains a determined height. For

- the rest the device according to the invention is provided with control means connected to the responsive devices and cooperating with a motor driven distributing device for equalizing the differences in the dammed up height of the heap of particles transversally to the longitudinal direction of the transport member. r

The use of the principle of the damming measuring member, such as, for instance a rotary spiked drum, a rake having a translatory motion or of a similar device, incombination with a shaking chute or a conveyor belt is, in itself, not novel. n

It is also known to arrange a device for the removal by suction. or otherwise of the particles which have been heaped up in excess in the neighborhood of the damm ing or measuring member, which together with the transport member forms the so-called measuring gap which determines the thickness of the stream of particles formed. Apart from the fact that such devices absorb a relatively large amount of energy and are not particularly s imple in construction, it is disadvantageous, when workingwith wood particles coated with bonding means, to cause particles returned to the container for the reserve. of particles to mix with freshlylcoated particles, because this may prejudice the later bonding of the particles to form a solid body.

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due to small inexactitudes in the system for dispensing the particles from the container containing the reserve of particles (for instance lack of parallelism of the dispensing rollers, etc.) or may for instance be caused by a practically imperceptible lateral inclination of the transport member. These faults add up, and it may then happen that in certain regions the height of the heap of particles is considerably in excess, whereas at other points there are not suflicient particles to fill up eventual gaps in the stream of particles which is arriving.

In the case of the invention these disadvantages are eliminated owing to the equalizing of the differences in the dammed up height of the heap of particles. The responsive devices may also be used advantageously for momentarily stopping a dispensing device of a container for the supply of particles arranged above the input end of the transport member, when the height of the mass of particles dammed up in front of the measuring member exceeds a certain value.

The equalization of the height of the heap of particles may in practice be obtained by local control of the stream of particles flowing from the container for the supply of particles onto the transport member, for instance by means of a swinging guiding plate. An advantageous solution is also obtained by providing a lateral distributing device directly influencing the heap of particles and equalizing the same and fitted with motor-driven toothlike or other members.

The drawing shows a strewing or spreading device in which a stream of particles of constant layer thickness is formed with the help of a shaking chute and a spiked drum. The illustrated machine services to prepare fleeces Fig. 4 shows a cross-section of a varient of a detail of the machine.

Fig. '5 shows another variant of the same detail, and

Fig. 6 discloses the control circuit.'

In Fig. 1 of thedrawing a mould-frame 1 is in the act of running past in thedirection of the arrow beneath the strewing device described lateron. This frame, is essentially composed of a bottom plate 2 and of a frame .part proper 3 which can be lifted off. The frame rests on conveyor chains 4 which are carried on rollers 5 or on continuous wooden supporting battens so as not to sag;

The mould-frame 1 is drawn along by means of a stop 6;

The machine rests on the floor by means of four vertical pillars 7. The whole frame of the machine iscompleted in addition by two longitudinal beams 8 resting on the pillars 7, two cross'bearns 9 and 56 and two U profiles 10. A conical bin to hold the reserve of shavings is fixed to v thejlongitudinal beams 8 and inside this are arranged a If, on understandable grounds, supplementary devices such asthose' which have just been described are eschewed, v

it'may ha'ppen'that the heap of particles dammed up in front of the measuring member is of very uneven height,

spiked drum 12 and a spiked belt 13 for dispensing the shavings. These dispensing means are driven by an electric motor 14 with the help of driving belts 15 and 16.

A transport member, such as, a shaking or oscillating chute 18 surrounded on three sides by vertically project ing edges 19 is hung directly under the exit of the bin 11 by means of links 17. Other types of conventional flat chute is practically horizontal. An electricniotor27 provided to generate the vibratory motion required 16 of this edge,

' 1 11 comb-like plates "set t 90? fr'ofn a emone; and

conveyithe ,tnass of shavings 21 and d ves 7 a shaft 25 by j 7 4 means of a pulley 28 and a belt 29. Anteccentric sheave 26 is secured to this shaft, sothat during the rotation of ing which has not been drawniis; swung ba kf gl, 'f t i and reciprocate s" thesuspended shaking chute 1 8,; sothat themes of shavingsdispensed by the bin 1:1}5 conveyed 1 a'r'rowend forms a' pile offshayin'gs 3011p against this of elec ric mi ctn oxit i y s che e a ageously provided, one of them being placed on the left side and t theotheron the right sideof the shaking chute'18 It theshaft' 25 ,adtivingrod 23'articulatedin 22 a gl which encircles the eccentric sheave 26; by means Qffibflllb??? is thus possible to determineon which side of the" shaking chute the heap of shavings Egtl'fir' strises upto the level limiting drum 43.

1 There exists a possibility that, for some refi n olfoth i the bin ll inay dispense quantities Ofshaving's which ar'e tQWards. a spiked drurn 31,1;otating in the direction of the not equal on both sides. 1111" order to compensate siich irregularities in the delivery of the shavings, the machine is fitted with thefollowingfdevice: A motor 50 drives,

i by means "of a belt 5 1,3 shaft 52 on which 'a re keyed spikes 32 arebent backwards 'jn relation to the direction t t of rotation of the d'rurn. In thisway'it"isjesslikely that t e' h' ins sh u e om i mmedbe wssn he spi es:

a Infaizldition, it isfthis measure-which nzikesit possible 1 e spiked drum: to o n ra e -PfPFIlY w h; V rotarylcornbing member to be fdescribed later, The;

spiked'drum 31 is m'Quntedonf ashaft 33, which ,is carnected tbs bevelgear tand to a shaft 36. bevel ottomlfl, of the shaking'chute'is 'thus ensured. otorQ39 drives the a Z spiked dr'urri 31 by]rneans}of .a belt 49. Owing to the relatively largeldiani'eteipof thel drium,'lt he speed ofithis dtu-nineed not betveryihigh'. 57+ p a t V, "I'hej'spiked dru n '31'fr'otating in'a directionifwhich is; contrary to the direct'ion 'of meson of the'conveyed 's hav- V ing'sthusdams the shavings, fills .inigafisj in thestream of shavings and in Vadditionloosens the tmas'stof shavings.

ness fiowsunder it; (In this manner anfexactlysprede'ter-q V 5 mined'volume of shavings is released per unit oft/dine two bevel gears 53, of which only one, howevenisvisiblef -in tliedra'wingi Shafts 57; runningiin' bushingsQSS carried bya' cross'bean 56 .are'dr iven by means'of bevel gears 54 and carry a foot 58at'their lower 'extrernity.

V 7 Two supports 59 are pivoted'in' the feet 58. tIhey carry atrake 68 provided with anuinber of shoi tspikes'szand with. several long'jspikes 6 1. Thesho-rt spikes are paia'llel 7 1 i' t fiwqe i i i b a in s nd Wheaten erves 20.

"@ 'toi adjust the height of thedrum 31} It isrig dly con-.

to each other and the long spik es' are parallel} l iowevey,

the shorti'spikesfar {slightlyinclined ,up'war dlyidirection, 'whilelthe long spikes are slightly inclinedf in a downwardly direction. When the, moto'rffil is' running, the rak'efit) 'efiects 'a" translatdrytrnotion, indicated byfdtiifiandjda'shes', and'this in one direction orinie bthe n accord ing to the manner in which thePmo tdr is switched on. In

a s way the fl -Pe er p: Shav n s 'w b 'eY- the'left'to'the rightorvice versa V 1 e l f A fu lensha ins hute eS th helm- 64 h hhas a relatively, considerable inclination is arranged to continue' the shaking chute 18; i-Thisfshaking chute',' lwhich serves toeffect the "stfewingfoperation, is hung by: means V V ""s'o ,thata uniform stream of shavings ofc onstant thickv- V In additio The Qm'easuring effect is particularly; good ew'ingtg the '5 bent back "shape-of the spikes32lg ;I tis of course possible V t to'rnount thesha ft 33 exactly. above'the delivery fedgeuof thersh'aking chute, 18; In'certain' cases however i't" will beadvantageons to set this shaftiback, somewhat towards t the biri'll, or even to'niount jit a'srnall'dis tafic' =f-It e' level jofithe shavina ants-lee p a ains the,

spikecl drnmfil were to rise higher-than .theilevelof, the

topre ventjtthis, a, level limiting-drum 43,"domposedjo fl providediwithnotches 44"( Fig. 2) k'eye'd we; shaft} whichis, driven'bygthemotor 3 9 by means ofsga belt The tooth-likeipro'jections 4 5rreach inlbetweenltlie spikes;

e i'that the latter rotatestat very high speed; The

" inging hanging plate 41,16 which isj seeured" till the drawing; A 'fixed 'contact" shaft: 33,: then-the shavings vciuld immediately" bet-"drawn up over'the dru T 'he exactfmeasuringefiect of th; t spiked drum 31 j woulds'thus be rendered void.'; Inorde'r? t me gstwhich flnng'bacl; as indicated; impinge in ,66 which'on thie one en' l is'iartienlated i1 5? end onthe other end closely encircles eccentric sheave. '68

mounted onqthe shaft 25 by'rneans of a ring f69gand of a a ball-bearing-twhichhas not bfififl shown; The two; ec centric sheaves 26j and 6 8 areat from one another," so that'thezforceslof inertia of the two sha king chutes l LIIQQSl'P W l ymwmne t e 411105161 eff ollo win'gis a description of theoperation of the machine the construction of whieh'thas been describedfgj V The shavingscontained a in; the bin ill are .Vdeliv ered ffgm its loweriendj and strewnor spread onto the shak ing" f ehute 1 8. as long as the motor v llisrunning and drivlng theispiked drum 12 zasywell as thefQSPikedbeltB. 1, Owingtothe vibratory motion thr shavingsr are con'vey'ed towai dsithe' deliv'e'ry edge." ,As has already been men tioned a relatively even layer ofqshavings j'fjoft constant thickness passesjthrough under the spiked drum 31; "This mass ofshayings nowffallsfionto the injclined bottom'fi t 9 411 flat; tran p t m m er r strewi lha s hu 63.;"Ifhe task jofthis shakin'g chute,is first lofall to' ac,-

celerate the' conveyancfe.offthe shavingslfissuing from the ,calibrating'gap (gap between thespiked drum 31"and the] ,bdttomifl ,Of the shaking chute) The: thickness bf the layers of .shayings' thusi becomesfle'ss, t which favors the elimination, of strewing'ei'rors. 111 additionpowing to.

the highei-lspeed of conveyance; eventually reinainin'g'bundies of shavings are 'tornaparton-the shaking chute and finallyany predominant direction of the shavings is 'elimi-v. gateg becanse the shavingsiskip, about amongst themselves.j shavings tann m'; the delivery edge of the 'str wing s aking ehuter63iinga tmonldt frame sl i latterico'uldralso be replaced bya conveyor belt It the heap pft shavings;3Q situated on one; sidel of the we .tory of the outer edges of3tl'ie comb" plates Df {the level limiting 'dru'ni 43,"th'en there: beshavings which will be, fl ng b ck agains the P ate 47i ,L- e i sl s pp s h happensjontlierear side theishaking'schute 18 as elongingto an electric circuitzwhich fhas -viewedjnjFig; l; The plate,'whicli hangs freely will be 7 p 7 d zswungftowardsithe rear so thatthe 'contact 48, comes lwo fotm a pairiof contacts; JIWOJSUCh'PZjl' S 3 5 tojttest against the contact 49 and closes a V is not described in detail, for instance the circuitaofa control relay. vThe closing of the pair of contacts indicated in the upper part of Fig. 2 causes the motor 50 to be switched on in such a fashion that the rake 60 now begins to convey shavings to the other side. It effects, for this purpose, a translatory circular motion until the opposite pair of contacts closes, with the result that the direction of rotation of the motor 50 is reversed anew.

The contacts 48 and 49 can also be advantageously used to control the feed delivery motor 14. A timing device could for instance be provided for this purpose, which starts the motor 14 when the time interval between two reversals of the motor 50 exceeds a predetermined value,

i.e. when the heap of shavings 30 piled up against the spiked drum 31 has diminished too much. The motor 14 is switched oif again after a given time interval, for instance under the control of another timing element, which begins to function after the reversing contacts have been actuated the following time. a

Fig. 4 is a partial view of a cross-section of a varian of the device, which, instead of the spiked drum, is pro vided with a plate 70 cooperating with driving means generating a translatory motion and which is moved over the bottom 20 of the shaking chute. In the case of Fig. 5 the shavings are dammed back by means of a rake 72 swinging about an axle 71. The speed of the swinging motion of this damming membermust naturally be very great in order to ensure the regularity of the thickness of the layer of the stream of shavings issuing from beneath it.

It would obviously be possible-and in some cases even more advantageous-to replace the spiked drum by an endless spiked belt. In place of the equalizing means comprising rakes with a translator-y. motion it would also be possible to use means which distribute the supply from the container 11 unevenly across the width of the shak-.

ing chute 18 according to the momentary requirements.-

For this purpose the feed device and the distributing device could be combined, and use be made of a feed spiked drum, which is divided along its length, each individual section of the drum being mounted on the same shaft but being driven independently. Finally, it appears advantageous in this respect, to control the stream of, particles flowing from the container 11 by means of one or more guiding'plates, suspended so as to be able to swing, so that the shaking chute 18 is unevenly loaded across its width. The control of sucha guiding plate,

which owing to the simplicity of its principle has not been shown in the drawing, may in practice be effected by means of a piston connected to it and moved under the action of pressure means, which in its turn is controlled in a known manner by means of electro-magnetically controlled valves.

As to the control circuit containing both contacts which serve to reverse the direction of rotation of motor 50 and the timing relay circuit comprised in the first mentioned circuit, they are shown on the diagram in Fig. 6.

The diagram in Fig. 6 is very simple. However, the circuit shown can only work when contact or is normally opened and contact cl is normally closed.

If the height of the. heap of chips exceeds a predetermined value on the right side, contact cr is closed, whereas if this height is exceeding said value on the left side, contact cl is opened. The process is the following: After contact Start is closed, relay A is energized and a self-holding circuit is established over contacts a1 and cl. The direction of motor MR is reversed by a transfer of contacts a3a4 and time-lag relay T1 is switched on, because of the closing of contact a2. When the heap has reached the predetermined height, contact cl opens, relay A drops out and contacts a3 and a4 transfer to the other position, so that motor MR starts turning in the other direction. The next pick up of relay A is caused by the closing of contact cr. Relay T1 cannot close its contact, 11, if the closing time of contact 7 a2h'as not exceeded a certain duration. If such is the case, time-lag relay'TZ picks up and keeps contact t2 Closed for a predetermined time. Fig. 6 is very simple, but the embodiment described in the patent application in Figs, 1-5 contains two closing contacts 48 and 49, whereas Fig. 6 contains a closing contact er and an opening contact c2.

What I claim is:

1. An apparatus for the formation of a stream of particles of constant layer thickness comprising a'flat trans- 'port member and a measuring member, several sensing responsive devices distributed across the width of said transport member in front of said measuring member in relation to the direction of conveyance of the transport member, said responsive devices constructed to become active when the height of the heap of particles lying in the region attains a predetermined height, control means connected to the responsive devices and a motor-driven distributing device cooperating with the latter for equalizing the differences in the dammed up height of theheap of particles transvers'ally to the longitudinal directionof the I transport member.

2. An apparatus according to claim 1, characterized in that a laterally equalizing device themotion of which is reversible is made use of as distributing device, so that according to the momentary position of the control means, particles are moved from the left hand towards the right hand longitudinal side of the transport member or viceversa.

3. An apparatus according to claim 2, characterized in that the laterally equalizing device comprises a rake having a translatory and circular motion, the direction of this motion being reversible.

4. An apparatus according to claim 1, characterized in that the distributing means provided consist in means which are able to cause a differential feed of the particles to the transport member across the width of this transport member, and this in dependence of the momentary position of the control means.

5. An apparatus according to claim 1, characterized in that a guiding plate is arranged between thetransport member and a container for the supply of particles arranged above the input end of the same, which guiding plate can be swung to one side or to the other under the influence of the control means.

6. An apparatus according to claim 1, characterized in that a guiding plate is connected to a piston, which can be moved underthe action of pressure means tovdeposit particles on a particular transverse section of a transport member.

7. An apparatus according to claim 1, characterized in that the measuring means comprise a continuously moving surface provided with spikes which are bent backwards, in relation to the incident stream of particles.

8. An apparatus according to claim 1, characterized by the said measuring means being provided with spikes, wiping members provided with slots which by means of driving means can be set in rotation about an axis which is perpendicular to the longitudinal direction of the slots, and which reach in between'the spikes of the measuring means in such a fashion that-the transport of particles over the measuring means is prevented.

9. An apparatus accordingto claim 1 wherein said control means comprises two contacts placed on different sides of the longitudinal middle axis'of the transport member and which change their state of contact when the height of the mass of particles on the same side attains a tion of conveyance of the transport member and arranged v fl i A rri ethod for the formatio'ni -o f a'stream' pair ticlesofconstant layer 'tliiclrness oilerc'the width' of the} 7 stream; in particulaf of wood particles snch as shaying's; v

V iiisuch a fashion that they are actuated by the pai'ticles flling'hack bythei wiping'members. T' 1 f 1 lapparatus 7 according to plaimgi; characterized} by ti in; relay in the said control ifiahs cifciiit whi ch clesofic'on's tant layer thicknes s fin particular of 'wood particles such as;shaving's,. chips and similar pa'rticles,'-- ficomprising'f usi ga fiat transport member and mea'snring means" arranged" above the transpqrt'member," dam i g; those" particles Whichlie above the height i corresponding" i latin'g'bhute corriprise -electrical 'contact members; said to the desired layerithickness, sensing 'in diifer'ent places releasir lgr seyer'al responsive sensin'gifnermbers causes the S pp y f fi l it i fi s b itdfbs 0 rnjentarily entirely arrested.

"the height'of'theheap of particles lyingfihifront ofthe- 1 m'eas ir'ing means" and V acrossithe' width oftheftran'spo'igt member, and; equalizing the'ilifierenc'e' in thedamn iedeup V -"hje'ightofthe heap' of particles whenthe t'r'ansiiersal dis; trihiitiori oi the stream ofiparticlesbecorries uneven;

14. A method according to ;lai1ri l3 characteriiedhy said drhnrand associatedfw itii said drun and said rotatable element for" placing garages transversely across said tfanspgi'rt'r'rieniberjso'as to degreas'efthei thickness of said;

streani off articles at certainpoint'sj on said transport rriehiher and; o- 'inci'eas'ecfthe' thickness 'at other pointsan'cl theie yflf Substantially e ualize the thickness qffme nt;

cles across the' tra'nsport member.

;"17.'" Ari apparatus as' set "forth 1, sensing 1 resiionsiveldevieejs being mechanical, and; electric proxim- 1 ity switches distrihnted'acrqss said fiat transport member actuated by saidv sensing responsive devices.

- 18,-" Anapparatus asset 'forth' in claimlfi in'which said flat transport-mernher comprises an oscillating chute. V I9 L A deVice as s 'et f orthi clairn'18 in Whichs'aid rneans' forplacing iparticles transversely arosseziid oscilelectrical contact inemhers' operative'ly""connecteditq an 7 oscillatin'gba'r having fingers V movable tgenerally crosswise n of said chute whereby when said r-finge'rs' are operating said particles are moved transi' erselyto the' right or't otheleft from an area of greater layer thickness toj an' areaof j thinner layer thi cknesslso thatthe thickness across the 120. A- method according :to c1air ncl3 comprising the stp ofmoi'lingparticles laterallyjinf-ront' of the dam 'in relation to theidir'ection of conveyance so that the height I of: the heap of particles lying in 'front of the measuring" member is "equalized.

chips and'similarlparticles, conyeying theparticles e015 fZ'l; A methodfaccording toxlaimt13 coni prising feeding v 3 rann inadirectiontowafds -a n etering- 'pointarranged, '20

particles' frozn a container. for the reserve of particles 'ar'i f'ahove said stream, darnmingthose' particles which lie". abo'ye the' heightfeo'rrespohdingrto .thgd e'sired layer thlick' ness checking at thesameitixne"and iirizli1ferr1tplaces across the'width offthe strean't fthe heightpfthefheab of- 1 particles lying in front of the metering: point and "eqnal 'i'zingth difierence n the: damme up height of'the'lieap ofparticles when the 't'ra'nsvers al dis'tribhtioh Vof'thie st-reanr "gofi p'articles isjtmeven at;thse' level checking pon es;

; I 16. An apparatus for the formation of astr'eam' of'parconstant layer thickness comprising a flat transport'irnrember, a thickness regulating drum] positioned" l V above and" adjacent" to said flat transport member 'fa'nd havingprojectinglelernents thereon, a level limiting rotata 7 ble element positionedto cooperate with said drnr'n,jand

ranged above the transgort niernbenlcontrolling saidfeeding insueh'fa mariner thatthestream of; particles flowing on'tofthe in'put endofTthetralnspdrtvis unevfil, and sabseqnehtly eqiialiiingthe .uneven' heightg -as' seen'acr'ossj 'the width t'the trans p ortjlinember, of the heap of dammednp particlesdyin'g in front of -the na'ezis'uring' membenf I ReferencesCited injthefile of patent in UN I S A E M ENIS. l 1,460,57 3-V "Church etal. 2,162,443 a. i Muller June 13, I939 means above said flat transport member and ihfrontof "T Tf7ff :--f---": 495

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