US1710795A - Screen - Google Patents

Description

April 30, 1929. R. w. ARMS 1,710,795

SCREEN Filed Jan. 14, 1928 2 Sheets-Sheet 1 Int/@7260?" April 30, 1929. R w, ARMS 1,710,795

SCREEN Filed Jan. 14, 1928 2 Sheets-Sheet 2 Patented Apr. 30, 1929.

UNITED STATES 1,710,795 PATENT OFFICE.

RAY W. ARMS, OF CHICAGO, ILLINOIS, ASSIGNOR TO ROBERTS AND SCHAEFER COM- PANY, or CHICAGO, ILLINOIS,

A CORPORATION OF ILLINOIS.

SCREEN.

Application filed January 14, 1928. Serial No. 246,719.

My invention relates to improvements in screens and has for one object to provide means for electrically heating the screening element by utilizing the screen wires as resistance means whereby the material contacting surface of the screen is heated to a point only sutlicient to prevent the deposit of moisture on the surface, the idea being that if the surface is heated sullicient to prevent moisli) ture forming on the screen itself the screen will not blind and wetmaterial can successfully be screened.

Experience shows that it this heating is going to be accomplished at low voltages as is done particularly in connection with coal handling where high tensions and resulant possible spark formations will be dangerous and also where commercial voltages would push too much through the screen wire, itis necessary to provide a resistance circuit of considerable length always longer than the overall lengths of the screen. My solution of this problem takes the form then of dividin the screen body longitudinally into a plura ity of separate sections side by side as far as the screening is concerned but in series so far as the electric current is concerned. We may divide the screen into two parallel sections side by side, provide a bus bar at each end in each section, close a section between two adjacent bus bars at one end of the screen and close a circuit through the power source through the two opposed bus bars or if necessary we may divide the screen into three or more sections. In any event all the screen sections will be in series with each other on the electric circuit.

In doing this the screen panels must be separated by insulating means which will not appreciably interfere with the screening capacity of the screen. Preferably this is done by cutting the screen, longitudinally separating the opposed edges of the screen sections and clampin these edges together between insulating plates which are given suflicient strength so that the gripping of these plates on the screenwill be sutficient to support the transverse tension calculated to hold the screen members in place on the frame. If it is a screen where the screen members are under no transverse tension then the sole purpose of the insulating strips is to insure insulation of the screen sections and to prevent escape of material between adj acent sections.

It will be noted that the heating of the screen wire or the screen material results in greatly increased life of the screen independent ot the prevention of blinding because the heating of the screen prevents the deposition of water on it and therefore avoids corrosion and chemical action. Perhaps also the vaporization of the water as it comes in contact with the screen surface serves to some extent as a cushion between the screen wires and the material upon which they work so as to very definitely prolong the life of the screen beyond the life which may be expected when the heating does not take place.

Experience shows that when the wire is heated in the manner indicated by acting as a resistence element the wire is heated from the inside out. There is no successful or appreciable heatin the wire while the wire is operating under a burden of coal but the heat in the wire nevertheless is sufficient to prevent formation of moisture film on the wire which results in corrosion and which results in blinding the screen. Too great heat would cause oxidation ofthe wire, would have a deleterious effect on the coal and would absorb a needlessly great amount of electric power but when the heat is controlled by arranging a group of separate screen sections in series to provide a long resistence path and when the amperage is properly related to the resistence to build up a relatively small amount of heat in the wire, this results in protecting the wire against blinding and against corrosion.

My invention is, illustrated more or less diagrammatically in the accompanying drawings, wherein Figure 1 is a side elevation of a screen embodying my invention;

Figure 2 is a plan view;

Figure 3 is a diagrammatic showing of the screen cloth and electric contacts;

Figure 4 is a section along the line H of Figure 2;

Figure 5 is a section along the line 55 of Figure 2;

Figure 6 is a diagrammatic showing ofthe electric circuits;

Figure 7 is a detail of the flexible conductors.

Like parts are indicated by like characters throughout.

A is a supporting base. Projecting upwardly from it are a plurality of rigid drive head supporting posts A. On these posts are bearings A" A which carry the crank A which may be driven by means 01 a pulley A" and belt A from any suitable source of power. A is a connecting rod adapted to be driven by the crank.

B B are the side bars and B B the end bars of a rectangular screen frame. This frame is driven by the connecting rod A pivoted on the brackets B on one of the end bars B and is supported free to oscillate longitudinally on the pivot links B 'B. These links are shown at diii'erent lengths so that there is a downward slope at the discharge end but it will be understood that under some conditions the length of the links might be the same. Material is discharged onto the screen through the chute 13, passes over the screen and the oversize is rejected, bein discharged to the chute B. Material whicdi passes through the screen may be caught by any suitable trough not shown beneath the screen fabric.

The screening body or screen fabric is made up of a pluralityot' separate metallic screen Sections C C \Ve have shown them for the purpose of illustration side by side divided along the longitudinal center of the screen. There might be more of these separate screen panels or they might extend transversely instead of longitudinally of the screen. These panels are joined at the discharge end by metallic strips C which serve both as-bus bars to place the longitudinal screen wires of each section of screening in electric contact with the longitudinal wires of the other section and also serve to hold the screen and give them physical support as a part of the supporting frame. At the other end ofcach screen section are two separate pairs of bus bars C 0", there being one pair for each screen section. The two screen sections are joined together to furnish a continuous screen by insulating strips C C held together by rivetsC to gri opposed edges of the screen section and ma (e a physically continuous screen without electric connection between the screen sections except at their ends. It will be noted that the bus bars C C and C C are gripped upon the screens by means of rivets C as shown.

' Bolted to the bus bars C C are rigid conductors I). These conductors extend up over the side frames B and bridge laterally thereover. Each conductor makes an electrical contact at its end with a flexible lead D which lead is generally semi-circular in shape and is anchored at its other end on supporting bars D D projecting from the transformer D to which are connected leads D D from any suitable source of electric power. These flexible conductors D are made up of a series of separate laminated flat spring strips D D preferably bound by a flexible wrapping D of electricians tape, rubber or the like. The thin cross section of each such strip associated with the arcuate shape of the strip provides a flexible conductor which will maintain electric contact with the screen during its operation and such flexible conductor being supported as it is by the wrapping to hold the separate strips in proper relation gives a conductor of large cross section sufficient to carry the current without appreciable voltage drop and without heating while at the same time providing a conductor which does not break or crystallize during oper tion. It will be understood that the shape, cross section and arrangement of the parts that make up the flexible conductor is such that the conductor carries its own weight and does not sag appreciably away from the semi-circular shape during operation.

In Figure 6 is'shown a diagrammatical lay out of a series of screens with means for heating all of them. In this case there are a series of separate screen panels E E E E E" E" E. Each pair of screen panels forms a single screen element. There are thus four screens in thesystem, each panel has at each end a bus bar E, excep the panels E E and E E which at their outer ends are joined by a single bus bar E which completes the circuit between the screens E E and E E The bus bars on screen panels E 13 ,19 E, E E, E E and E E are joined by the flexible conductor strips E E. The bus bars at the free ends of screens E and E are connected by means of flexible conductors D to the conductor strips E which lead to a transformer E to which electric power is supplied through the conductors E Thus the current for heating all the screens in the battery passes through all of the screen sections in series. There may, of course, be more or less of these sections and under such conditions as this only screens which are always used at the same time would be coupled together. The arrangement illustrated is one which is appropriate in coal handling machinery where the separate screens are used to treat coal, some part of the coal passing over each of the screens. Under these conditions whenever one screen is being used all of them are being used and it is desirable to heat all of them.

In Figure 7 is shown in detail the arrangement of the flexible conductor strips. The mechanism supporting the screens and the mechanism adapted to feed material to and receive it from the screen is not here shown as it forms no part of my invention as shown in Figure 6 through the detail of the mechanism for one screen is shown in Figures 1 to 5 inclusive.

I claim:

1. A screening system comprising a plurality of separate screen panels, means for connecting them together electrically in series and means for supplying electric current to said screens with the screen panels in series on the line. Y

2. A screen comprising a supporting framework, a lnrality of metallic screen panels carried tliereby insulated from one another and electric connection between the ends of said panels, a source of electric power and connections between such ower source and the free ends of the panels w ereby the screens are in series on the line.

3. A screen comprising a frame, a plurality of metallic screen panels carried thereby, insulating strips joining the adjacent edges of said screens and ada ted to hold them structurally together while insulating them one from another, a bus bar joining two 0 posed ends of said screens', separate bus bars or the free ends of each screen panel and means for closing an electric current through the screen panels from one of the separate bus bars thro h the bus bars joining them to the other 7 us bars.

4. A screen comprising a vibratory frame, a metallic screen panel carried thereby, a source of electric power and a connection between the wer source and the metallic screen pane comprising a flexible conductor.

5. A screen comprising a vibratory frame, a metallic screen panel carried thereby, a source of electric power and a connection between the power source and the metallic screen panel comprising a flexible conductor, the flexible conductor com risin a plurality of relatively thin lamina tee to d and to slide one with respect to the other.

6. A screen comprising a vibratory frame,

a metallic screen panel carried thereby a source of electric power and a connection tween the wer source and the metallic screen pane comprising a flexible conductor, the flexible conductor com risin a plurality of relatively thin lamina ree to nd and to slide one with respect to the other, a flexible insulating binding for the laminae.

7. A screen comprising a vibratory frame, a metallic screen panel carried thereby, a source of electric power and a connection between the Fower source and the metallic screen pane comprising a flexible conductor, the flexible conductor com risin a plurality of relatively thin laminae ree to d and to slide one with respect to the other, the condnctor being arcuate in shape, one arm of the arc bein connected to the screen, the other arm to t 10 source of electric power.

Signed at Chic county of Cook and Sgtge of Illinois, t is 4th day of January, 1

RAY W. ARMS.

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