US2257322A - Sifter - Google Patents

Description

Sept. 30, 1941.

Filed NOV. 15, 1937 Sheets-Sheet 1 IN Z9 I. W i 45 .57 "HI INVENTOR PAUL -J-BARNARD 6/ BY 79 M MLA+M A'TTORNEYS Sept. 30, 1- I P. J. BARNARD 2,257,322

SIFTER Filed Nov. 15, -l93'7 2 Sheets-Sheet 2 INVENTOR PAUL J BARNAED ATTORNEYS Patented Sept. 30, 1941 UNITED STATE PATENT OFFICE 1 SIFTER Paul J. Barnard, Racine, Wis. Application November 15, 1937, Serial No. 174,511

1 Claim.

This invention relates to improvements in sifters. 7

It is the primary object of the invention to provide sifting apparatus which will pass extremely fine material through an extremely fine screen without clogging the screen.

While the invention is of broad application it can best be understood with reference to specific problems. The device hereinafter to be disclosed as an exemplification of the invention, therefore, will constitute a device for sifting powdered resin through a screen or screens ranging to, a fineness of 200 mesh. The process of producing a powdered resin ofthis high degree of fineness has heretofore involved prohibitive cost. Resin will almost instantly clog a fine screen in the sifting devices heretofore known.

More specifically, the purposes of the present invention involve first, the provisionof means whereby the material to be sifted will be deposited in a layer of almost imperceptibly slight thickness on the screen; secondly, the provision of means whereby the portion of the screen through which the material must pass will be not merely vibrated but subjected to sharp impact blows in a direction opposite to that in which the material is intended to pass the screen i thirdly, the provision of means whereby the screen will be automatically cleaned at very short intervals without such abrasion as might destroy so delicate a screen; and, fourthly, pass-v ing a gas (preferably air) through the screen in the direction of the material passage therethrough and preferably concurrently with such passage.

Other objects and advantages of the invention will be apparent from the following disclosure.

In the drawings:

Figure 1 is a view in side elevation of a device embodying the invention. I

Figure 2 is a view showingin plan a fragment Like parts are identified by the same reference' characters throughout the several views.

The ground or otherwise finely divided material is supplied through a hopper 15 which preferably includes a baffle l6 over the feeding wheel I! which is located in the discharge mouth of the hopper and coacts with the wall Hi to deliver minute quantities of the finely divided material from the hopper. For the purposes for which the invention was devised I prefer to cover the feed roll I! witha lambs wool surfacing at 20 and to operate it at a speed of approximately 1 to 2 R. P. M., whereby the material is discharged from the hopper in an almost imperceptible stream upon the sifting screen 2|.

The screen 2|, for the purposes of the present disclosure, may be assumed to be to 200 mesh. A screen of this mesh is so fine that its reticulations are hardly apparent to the touch. The screen is mounted upon a screen frame 22 pivoted at 23 in the open bearing notches of supports, 24.

The entire frame, and the screen 2| therein contained, is set at an angle tothe horizontal as clearly appears in Fig. l. The upper end of the frame is held by tension springs 25 against cams 26 which are mounted on shaft 21 and may cone veniently have square peripheral contours. In actual practice I have found it expedient to turn the cams on shaft 21 at a speed of about 400 R. P. M., but for other materials and designs it will be understood that changes may be made in such details, the example being illustrative only.

The cams do not merely vibrate the screen but deliver to it a sharp impact in a direction such that the inertia of the powder on the screen will tend to cause the powder to flow through the screen into the collector 28 and thence into the bin 29. Any powder incapable of passing the screen will, of course, be discharged through the reduced end portion 3|] of the screen frame 22, or it may be subjected to additional screensin series.

I find that if the powder to be screened is deposited on the screen to any substantial depth a very objectionable clogging of the screen results.

The slowly turning feed roll I! covered with lambs wool takes care of this phase of the problem by limiting the deposit on the screen to an extremely fine and almost impalpable layer. Clogging would still occur, however, but for an arrangement by which the screen is cleaned at extremely short intervals. The use of the screen cleaning device, together with the means which limits the deposit, keeps the material flowing freely and constantly through the screen.

7 material.

screen so that the pressure fluctuation will facilitate the cleaning.

For a cleaner in the construction shown in Fig.

36. Upon this carriage I mount at least one, and

V 1 I prefer to employ a garrjage transversely beneath the screen on the guide IOd'SL'l'd preferably two, suction nozzles 38 of sufficient eic tent longitudinally of the screen frametzttocomprehend the entire width of the screen 2 By using two nozzles I can cover the screen more f en. ndlw a le de r o r c roca i n a rr e 55 than u d-b rq ihleif bat ns nozzle wereused. The twonozzl es are connectedto ac m p pes i a me to; a lQ cr. .9 the means'of producing partial vacuum at the nozzle Flexibility. of the pipes or hoses, 39 is sufficient to accornrnodate the reciprocation of the carriage 35. The discharge from the blower preferably leads to a c'entrifug al vortex separator ll of conventional design wherein the dust is separated from the air, the dust being delivered througha, discharge conduit at 42 into a suitable collector at .43. Since this material has passed the screen it should be of substantially the same fineness as that collected in the container at'29. V i y e A convenient means of operating the. various parts is shown in the drawings but 7 will be understood to be not essential to' the invention The motor lti, throughsuitable chains 45 and 4 1 an d sprockets therefor drives the shaft 21 upon at 48 carried by the shaft drives a speed reducing train 49 from which motion istransmitted by chain 50 to the shaft 5! upon which the feed roll I! is mounted inthe discharge throat of the hopper l5... 'H

From'pinicn 53 on the cam shaft 21 another chain at54 drivesa conventional speedreducing gear set 55 from which motion is delivered through the crank 5.6 and link 57 to a lever 53 pivoted at 5'9 andfconnected to thelpin 50 on the reciprocable' carriage35 for. the reciprocathe size of mesh becomes such that the special arrangements herein described are no longer necessary.

It will be noted that the vacuum nozzles 38 are required to move across the lower surface of the screen 2| in very intimate relation thereto. In view of the delicate nature of the screen it is therefore important to protect the screen against abrasive wear.

I have found that I can protect the screen without appreciably affecting the degree of vacuum or the pull exerted by the nozzles on the .material tending to clogthe screen if I provide 'on the under surface of the screen two strips of 'the material ordinarily used in making shims. The strips are shown at 65 and have a thickness which in actual practice need be only one or two thousandths of an inch. They support the screen some of the principles of this invention may be 'which the cams 26 are mounted. A small pinion tion of the carriage. .Theblower tii maybe pro- 7 vided with, its own motor at 6|.

Each nozzle is narrow and the highpressure areaproduced thereby isof limited extent. The carriage may be moved at the rate of about" fifty reciprocations per minute to shift the elongated pressure areas over the entirescreen acrossthe path of material discharge therethrough. c

It will, of course, be understood to be well known in this art to pass siftable material from one screen to another, the screens usually increasing in size of opening to producea series of products of graduated sizes. 'I contemplate such an arrangement in connection with this invention but'have. notillustrated it because it is believed that the arrangement would be obvious in View of the. foregoing disclosure. The succes sive screens may befed and operated andcleaned in' exactly the manner already disclosed. until employed. Ilhave shown such a device in the accompanying drawingsin which a shaft 10 turns in bearings H which carry stationary heads 12 closing the ends-ofa rotatable screen cloth cylin der 15 which constitutes the screen. Material is fed into the device throughthe: hopper spout passing through the head 12.. Inthe course of rotation .of'the inclinedlscreen cylinder 15 the- 5 material islsifted through the screen in the col-I lecto-r. TI a'nd the coarsegrains, incapable of passing'the screen, will pass through the opening '18 in the lower screen head 12 on to the discharge table.l9. 1

The sharp impacts desirable for expediting progress of the material through the screen may qonveni'ently'be delivered by means of small hammers pivotally carried on one or more shafts at 8| rotatable to cause the hammers to impact the bearings "l l in'the desired direction.

'Thecleansing of the screenmay be accomplished by astationary vacuum nozzle at 83 from which vacuum pipe 84 leads to any suitable source of vacuum such as that already disclosed.

I claim:

- In a device of the character described, the combination with an inclined screen and means for the vibration thereof, of a feed hopper arranged for the discharge of material on to the screen, a feed roller controlling. delivery from said hopper, a nozzle reciprocable across said screen substantially in face contact with the underside thereof, means for reciprocating said nozzle,'and means connecting said nozzle with asource of vacuum for the cleansing of said.

said nozzle to draw air through said screen while relieving said; screenof the friction of said nozzle.

PAUL ;J; BARNARE,"

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