US791782A - Screen. - Google Patents

Description

10.791382 n v1 Am-mn JUNE-6,1905.

is. E. HBNDRIGK.

SCREEN APPLICATION IvILED DEO.17, 17902 lnvenfr Witnesses UNITED lSTATES Patented June 6, 1905.

ELI E. HENDRICK, OF CARBONDALE, PENNSYLVANIA.

SCREEN.

SPECIFICATION'fOrmIng part of Letters Patent No. 791,782, dated :rune e, 1905. Y Application filed December 17, 1902. Serial N- 135,473.

' and useful Improvement in Screens, of which the following is a description.

This invention relates tov screens of the character employed in the separationvof particles of coal into various sizes. Screens of this character are of two types, the revoluble type and hthe shakingtype, the latter employing a flat perforated surface to which aY shaking or gyrating movement is given and the former employing a cylindrical screen-jacket pitched from end to end and revolved by suitable power, the coal being fed to the interior thereof. In the latter the Eperforated jacket may be continuous, but for convenience is preferably .made up of a series of segments having imperforate side and end margins, the latter for attachment to the spider-bands of thc screen-barrel. The mesh of the separatingsurfaces used in both types of screens is also generally divisible into two classes, in one of which the interstices are arranged in rows both longitudinally and transversely, (this description being known as opposite Inesh,) while in the other the interstices are arranged in rows in one direction, but only alternate interstices are arranged in rows in the direction at angles thereto, (this description being known as staggered mesh.

first place, excessive crimping or curving of the web-bars tends to weaken the mesh either 4at the junctions between the longitudinal and transverse webs or at the apices of the curvatures, and, second, where it has been sought vto crimp the webs or bars of a staggered-mesh,

. uniformity in size of the interstices.

surface this has commonly resulted in the distortion of such mesh, by reason of which improper sizing of the coal has resulted.y

The present invention relates particularly to a screening-surface of the staggered-mesh type in that it employs interstices which are arranged in rows longitudinally of the screen, while of the interstices arranged transversely or circumfercntially of ,the screen only the alternates are in rows, the center of each interstice being opposite a web or bar dividing the two interstices ofthe next adjacent longitudinal rows. l

The objectof the invention is fourfold: first, to so fashion the screening-surface as to avoid weakening thereof in the crimping operation; second, to avoid excessive fracture of the particles of coal; third, to economize screening-surface by assuring the proper separation of the particles early in their travel across the perforated surface and without permitting them to slide in mass beyond the point where by reason of ltheir size such separation is possible, and, fourth, to give the screeningsurface suflcient ourvatures of the web-bars to properly agitate and turn the particles of coal, without, however, interfering with the In carrying out my invention to meet these requirements I employ a, staggered-mesh surface in which the longitudinal web-bars separating those rows of interstices which lie in the longitude of the screen are undisturbed in the crimping operation, being allowed toremain in the general plane of the end margins of which they form an integral part. The trans- Verse'webs, however, which connect these longitudinal webs, are curved or crimped, all in the same direction and toward the axis of the screen-in other words, the transverse webs on the working surface of the mesh presenting a series of convexities. In thisconstruction the first requirement is met by leaving the longitudinal webs undisturbed and by crimping the transverse webs all in the same direction-w1. e., toward the center of the screen. There areno sharp angles or abrupt curvatures; but the longitudinal webs are permitted to contribute maximum strength to thetransverse webs which they support. The

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`line y2 201 Fig. l.

second requirement isY met, since the particles of coal next to the screening-surface'are acted upon by-each Vof the transverse webs, which tends to oppose the passage of such particles across the surface. In other crimped and staggered screening-surfaces heretofore employed only thealternate transverse `webs-were curved or crimped inwardly toward the axis of the screen, the other transverse webs being curved in the opposite direction. Asa result of this, only the alternate webs-2'.. e., those presenting convexities--acted upon the particles of coal, so that such particles were permitted to travel just twice the distance before such travel was interrupted by a convex web,andtheforceof the impact was therefore twieelas great, resulting commonly in splittingfthe particles of coal ork chipping off edges, which being too line for commercial use foundtheirwvay eventually into the culm. Even Awhere the'fracture did not produce this wasteful result the chipping or excessive breakingl of the particles of coal has ha'd the effect of decreasingthe value of the product, coal of fthe larger-sizes commanding higher prices than coal of smaller sizes. The third requirement is met in the construction which I have here described, since the particles of coal 'l passing over the surface of the screen are acted upon at each interstice, each transverse 'row of interstices extending obliquely to the longitudev of the surface, presenting a'series-of convexities which catch and turn the particles, sliding close to thel mesh in such manner as that if a particle presented in a certain direction at one interstice prove of too great-size to pass therethrough it will be caught by one ofthe convex websfand turned so Aas to present another side to the-next diagonally adjacent interstice and, moreover,

guided to that interstice, in view of the height of the convex transverse web a-nd the 'depression (in the original plane of the plate) ofthe adjacent longitudinal web separating thetwo interstices referred to. The fourth requirement is met in the construction herein referred to, `since-every interstice in the screening-surfaceV is of the same size no matter in what direction vthe particles of coal be presented tofthe-samefor separation. This feature-will be hereinafter alluded to.

For convenience I shall describe the invention as embodied in a segmental plate designed Vto be attached tothe spider-bands of la revolublevscreen, although it is obvious that such invention may be embodied `ina continuous jacket for such a screen or in a flat plate designed for use in a shaking screen.

In the drawings, 'Figure l is a perspective View `of a -screen-segment employing my invention. Fig. 2 is a transverse section on the Fig. 8 is a longitudinal section'on the line 3 '3 of Fig. l; and LLis an --enlargeddetail view, hereinafter to be referred to.

means of which `the -plate .may be secured to the spider-bands of a revoluble screen. 'Ihe interstices A are substantially quadrlateral inform, those lying in the longitude of the -plate being in straight rows, but only the alternate interstices being in rows transversely of the plate. In other words, the center of eachinterstice is opposite a transverse web bounding two interstices of the next adjacent row. The longitudinal webs B, orthose lying lengthwise of the screen-segment and barrel, are left undisturbed in the crimping operation,remaining, therefore, in the original plane of the end margins of the plate. The transverse webs C are all crimped or curved inwardly toward the axis of the screen, so as to presenten the working surface ol" the segment a series of convexities designed to catch and turn the particles of coal passing over such surface. 'It will therefore be seen that each quadrilateral interstice is bounded by four webs, two opposite 'websl being parallel and flat, while the remainingrtwo opposite webs are parallel and convex. It will also be seen that in a screen mesh as here arranged eaeh interstice is of exactlyxthe same size as every other intrstice, and this regardless of the direction in which a particle of coal may be presented'thereto for separation. To appreciate the improvement madey in this respect, attention iscalled to the construction illustrated in Letters PatentNo. 632,201, illustrating a form of crimped and staggered mesh surface heretofore introduced for the separation of coal. In this construction, as in the present case,the.longitudinal webs are llat and in the plane of the end margins, of which they form an integral part. The transverse webs, however, are alternately convex and concave. This arrangement presents serious objections realized in the commercial use of mesh so fashioned. `The first .of these is lthe fact that by the alternate crimping of the transverse webs in opposite directions the uniformity of the mesh is destroyed. .Thisxis -made clear by the diagrammatic View, Fig.

4, abovereferred to, illustrating a section througha screening-surface in which, as in that illustrated `in Ia'ent No. "632,201, ther longitudinal webs D are straight, while the transverse webs -E F are alternately convex and concave. Vere these transverscwebs arranged in the plane of the longitudinal webs D the size of the interstice would be thatindicated by the dotted line Gr. By the arrangement of these webs alternately above and below the plane of the longitudinalwcbs, therefore, the size of the interstice longitudinally is represented by the dotted `line 1I, the size L IOO of the interstice in a direction at right angles thereto, however, remaining that indicated by the dotted line G. In other words, instead of a substantially square interstice this methodof crimping results in an interstice which has a greater dimension longitudinally than laterally. Again, by reason of the alternate ele- I vation and depression of the transverse webs particles of coal of too great size to pass through an interstice if presented in one direction would pass therethrough if presented in another direction. f If, therefore, the interstices 'were of a size to separate half-inch particles, larger particles intended to be separated from the vmass only at a distant point in thescreen-barrel would also passv through at this point with particles of smaller size, the result being imperfect sizing of the coal in the bins below the screen.

Another defect of the previous construction here referred to and one which is removed in the invention herein described arises out of the direction of travel of the mass of broken coal. This direction'is not in the exact longitude of the screen, but, because of the pitch of the screenbarrel and of the movement of the screening-surface,which tends to carry the coal up the side of said barrel, is in a direction oblique to the longitude of the screen.A A particle of coal,therefore, passing over the surface of the screen shown in the patent referred to would impinge against a convexity and be turned thereby so as to fall not into the next diagonally adjacent interstice, but upon the next diagonally. adjacent concave transverse web, from which the movement of the screen and the pressure 0f other particles of coal against it would move it either through the next longitudinal interstice or up upon the next longitudinal web only to cause the same to fall upon the next concave transverse web, all the time precluding its passage through the screen. In the screen herein shown and described this operation is impossible. A particle of coal impinging l against a convex web and of a size precluding the chief respects in which the screen of the present invention constitutes an advance upon screens heretofore in use, the former, being not only of higher eficiency and economy of screening-surface, (and therefore of the space occupied by the screen,) but also making it possible in the use of a screen of staggered mesh to obtain absolutely reliable separation of the various sizes of coal.

What I claim, and desire to secure by Letters Patent, is

1. An integral screen of staggered mesh, all of the longitudinal webs whereof are parallel and straight and all of the transverse webs whereof are parallel and curved or crimped inwardly toward the axis of the screen, substantially as set forth. i

2. An integral screen having substantially quadrilateral interstices, each interstice being opposite a transverse web separating two transverse and adjacent interstices, all of the longitudinal'webs of such interstices being' Witnesses:

E. D. YARRINGTON, J. R. VANDERFORD.

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