US2235653A - Screen cloth for high speed vibrating screens - Google Patents

Description

L. E. SOLDAN March 18, 1941.

scnmm CLOTH FOR HIGH SPEED VIBRATING SCREENS Filed July 21, .1958 2 Sheets-Shae; l

' INVENTOR. LEW/6 E. 50LDAN 4 ATTORNEY.

March 18, 1941.] SQLDAN 2,235,653

- SCREEN CLOTH FOR HIGH SPEED VIBRATING SCREENS I Filed July 21, 1938 2 Sheets-Sheet 2 Fig. 7

cknnnnnonnnnnnn INVENTOR. LEW/J E. SOLDAN Patented Mar. 18, 1941 UNITED STATES watts PATENT OFFICE SCREEN CLOTH FOR HIGH SPEED VIBRATING SCREENS Lewis E. Soldan, Chicago, 111. Application July 21, 1938, Serial No. 220,441

1 Claim.

to provide a screen cloth adapted to minimize or 5 eliminate the binding of the cloth by the piling up of the material placed on the screen. I

Qther objects and advantages of the invention will appear in the specification, drawings, and accompanying claim.

The screen cloths in use today have a pronounced tendency to blind or become clogged up because of the piling up on them of the material placed on the screen. This tendency is especially pronounced when the material to be screened is damp, oily, or otherwise sticky.

Screen cloth used for screening devices is usually made of long wires which are secured or fastened to cross pieces or spacers, which in turn are secured rigidly to a frame. These cross pieces or spacers are used to separate the wires and hold them at a uniform distance from each other to insure uniformity of size of the material which passes through the screen. The long wires may be kept at a uniform distance from each other by other wires which are woven across the long wires in the same manner that cross or woof threads are woven across the long or warp threads in the weaving of textiles.

The size of the material passing through the screen cloth can be made more uniform by separating the long wires in a manner more positive than is had by the weaving of the cloth. This is done by fastening or securing the long wires to spacers or cross pieces of more substantial nature than the cross Wires used in weaving. The wires are usually fastened to these spacers or cross pieces by putting the wires into slots cut into the cross pieces or spacers, welding the Wires onto the spacers, crimping flanges on the spacers or separators over the long wires, and soldering or brazing the-long wires onto the spacers.

An objection to the use of the screen cloths now in use which are made in the manner described above is the tendency to blind which they all have.

In the case of woven screen cloth, the material placed on the screen piles up because the cross wires hinder the passage of the material placed on the screen as it slides along the wires. This coupled with the reduction in the springiness of the wires resulting from the weaving renders such screen cloth subject to blinding. a

Screens whichtoday are made by fastening the long wires onto the spacers have a pronounced tendency to blind, because the material placed on the screen piles up at the spacers. In screen cloths of this variety, the material to be screened is supposed to slide along the long wires and fall through. The material too large to be screened is supposed to slide along the wires and fall ed 5 of the end of the cloth. Part of the material, which is too large to pass through the screen, will usually extend through the opening between any two wires and come into contact with the spacer as it passes along the wires. If the material cannot rise up and slide over the spacer, the material behind it will pile up and blind the screen cloth. One object of the invention is to minimize or eliminate the tendency to blind of screen cloth resulting from piling up of the material placed 15 on the screen by reducing or eliminating barriers to the passage along the screen of material placed upon it.

In screen cloth made by holding the long wires in slots in the spacers, the tendency to blind 20 is very pronounced. This results from the fact that the tops of the spacers extend above the surface of the screen and present a barrier to the passage along the wires of the material placed upon the screen.

The same objection is found in connection with screen cloth made by crimping flanges on the spacers over the long wires. The crimped flange extends above the surface of the cloth and presents a deterrent to the passage along the wires 30 of the material placed upon the screen.

In screen cloth made by soldering or brazing the long wires to the spacers, a great deal of emphasis was placed on the necessity of maintaining a uniform distance between the Wires. This emphasis resolved itself into the practice of solidly filling the spaces between the wires over the spacers with solder. Such practice opens the cloth to two objections. The first is that the solder presents a barrier to the passage along the Wires of the material placed upon the screen and the second is that the solidity of the layer of solder in which the wires are held serves to dampen the springiness of the wires which is so essential to the performance of a screen cloth. The above conditions are objectionable as they render the screen cloth subject to blinding.

In screen cloth made by welding the wires to the spacers, the barrier to the passage along the 50 wires of the material placed upon the screen which is found in the other screens described, is avoided. However, in making screen cloth for high speed vibrating screens, welding is not a practical method of fastening the long wires to 55 the spacers. To make a practical and serviceable screen cloth for a high speed vibrating screen, wires must be used which are springy, tough, and which have a polished or smooth surface. The smooth or polished surface allows the material placed upon the cloth to slide freely and without hindrance while the springiness prevents the material placed upon the screen from wedging itself between the wires and enables it to pass or jump over any obstructions to its passage along the wires. Welding requires such an amount of heat that the temper of the wire is destroyed or at least impaired to such an extent that the necessary springiness is destroyed. Also the heat impairs the smooth or polished surface of the metal and leaves it rough, which roughness acts as a deterrent to the passage of material placed upon the screen cloth. In these ways, the screen cloth made by Welding wires to spacers is rendered subject to blinding.

The screen cloths which are made in combination with a frame are rendered subject to blinding because the springiness of the wires and spacers are dampened. The sturdy longitudinal members commonly used, to which the spacers are firmly secured, operate to materially reduce the resilience of the screen cloth and thus reduce its effectiveness.

The invention consists of fastening or securing long, smooth or polished wires of hard carbon steel which are springy and tough to spacers in such a manner that the tendency to blind is eliminated or reduced.

In the accompanying drawings, Fig. I represents a screen cloth to which the invention is adapted to be applied. Fig. II is an enlarged cross section of said screen cloth, and Fig. III is a cross section of a spacer of the screen cloth. Figs. IV and V represent a method of making screen cloth by attaching wires to projections on spacers. Figs. VI and VII represent a side and end view respectively of a high speed vibrating screen in which a screen cloth like that shown in Fig. I is used.

In Fig. I is shown one type of screen to which the invention is adapted to be applied. The screen cloth consists of long, smooth or polished wires of hard carbon steel is and spacers l2 to which the wires 18 are attached. The wires may be made of any hard carbon steel, but it has been found that music wire is well adapted to use in such a screen. Such wire is springy and tough, and at the same time has a smooth or polished surface. Both of these qualities are desirable in wire for screen cloth. The springiness and toughness of the wires allow the wires to vibrate, which vibration prevents the material placed on the screen from wedging itself between the wires, and enables the material placed on the screen to pass over the spacers. The vibration of the wires is imparted to the material placed on the screen and in this way such mate rial is enabled to slide along the wires and over the spacers easily because the imparted vibration changes the contact between the material placed on the screen and the wire, from line contact to point contact, thereby reducing the effective friction surface. A smooth or polished surface is desirable for wires used on screen cloth because it presents a minimum resistance to the passage along it of the material placed on the screen. The spacer i2 is made of metal and is made strong enough to provide a solid support for the long wires l0, but resilient and springy enough that the vibration of the wires will not be dampened, but will be reinforced by vibration imparted to them by the vibrating spacer. The spacers are adapted to be placed at such distances from each other that the inherent frequency of the wires may be increased by resonance resulting from the vibration of the spacers operating in harmony with the vibration of the Wires. The wires H] are secured to the spacers I2 by a holding means Hi.

In Fig. II is shown an enlarged cross section of the screen near a spacer 12. The holding means [4 is shown to be much in the nature of a. fillet. It is substantially thinner at the center of the space between the wires than it is where it contacts and holds the wires. Such a holding means is desirable because it presents a minimum deterrent to the passage over it of the material placed on the screen. Because a minimum resistance is offered to the passage over the spacer of the material placed on the screen, the Wear on the holding means I4 is minimized, the life of the screen is lengthened, and the material placed on the screen easily slides over the spacer.

In Fig. III, a cross section of a spacer i2 is shown near a long wire Iii. There the spacer is a rectangular bar to which some material has been attached on the sides, but the spacer may be made from a solid piece of metal. The holding means I4 is seen to be thinner at the edges of the spacer than it is at the center. This condition in combination with the curved sides of the spacer enables the material placed on the screen to easily pass over the spacer. When the material placed on the screen contacts the spacer and the holding means, it gradually rises and slides over the spacer. The use of a holding means like that shown in Figs. II and III reduces the dampening effect on the vibration of the wires which is found in other screens using solder for a holding means. The old types which used a solid filling of solder to hold the wires, considerably dampened the amplitude of the vibrations of the wire. This in turn reduced the efflciency of the screen. By use of such spacer and holding means, the resistance to passage over the spacer of the material placed on the screen is minimized and this coupled with the vibration imparted to the material placed on the screen by the vibration of the wires renders this screen free from any tendency to blind.

The wires Ill must be held to the spacers l2 by soldering, brazing, or some similar process. Welding is not desirable because the high heat required in the process destroys the temper of the wires and destroys the smooth or polished surface of the wires. When the temper of a Wire is gone, it is useless for screen cloth because its springiness is essential to its good performance, as is the smooth or polished surface. Such surface presents a minimum hindrance to the sliding along the screen of the material placed on it. Soldering, brazing, or any similar process does not require excessive heat and is adapted to use as a holding means for screen cloth because such process does not destroy the temper or the smooth surface of the wire.

In Figs. IV and V, is shown a construction which further reduces obstructions offered to the passage over the spacer I2 of the material placed on the screen. The member [6 is formed on the spacer l2 and processed to provide support for the wire Ill. The wire I0 may be held securely in place by soldering, brazing, or other means. A cloth made with this type of spacer would elimihate the piling up of material at the spacers and thus increase the screens efficiency. The construction shown is one way by which the wire may be held, but the invention is not limited to this one construction.

To secure added resilience in the screen cloth, the invention dispenses with longitudinal members of sturdy nature which are found in the frames of ordinary screens. The elimination of such non-resilient members tends to promote the vibration so necessary to prevention of blinding. The screen cloth is adapted to be attached to a high speed vibrating screen by a plurality of tensioning clamps.

In Fig. VI is shown one type of cloth to which the invention is adapted to be applied, held in an ordinary high speed vibrating screen of which side IB is shown. The spacers, 12 on which the wires I!) are mounted are formed in such manner as to lock with member 20 which can be pulled up by a suitable tightening means represented here by bolt 24 and nut 26. The tightening means may be used to create tension in the spacers I2. Because the cloth is held at only a few points by clamps, the spacers are freer to vibrate than those found in screen cloth made in combination with a frame. This increased ability to vibrate, in combination with the adjustable tension possible in the cloth, combine to render it free from any tendency toblind.

, By means of the above or similar constructions, screen cloth may be had which will minimize or eliminate the blinding of screen cloth even when the material placed on the screen is wet, oily, or otherwise sticky.

What I claim is:

In a high speed vibrating screen having longitudinal side members, a vibrating screen cloth comprising a series of parallel spaced tong, smooth springy wires 'of hard carbon steel, a series of transverse spacers of tough springy resilient metal, said spacers being attached to said wires transversely thereof and at such regula rly spaced distances as not to: interfere with the natural vibration of said wires, said wires and spacers being attached to each other at their points of intersection by means of solder so placed as to leave open spaces between the Wires above the spacers of substantially the diameter of the wire and to permit free vibration =of the spacers, said spacers being connected to the side members of the frame under tensile stress to permit natural vibration of the screen cloth as a whole.

LEWIS E. SOLDAN.

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