US1713144A - Screen - Google Patents

Description

y 1929- G. A. OVERSTROM 7 1,713,

. SCREEN Original Filed Sept. 28, 1920 risk 3 awwemtoz M 2551 .12) flbtomuf Patented May 14, 1929.-

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Original application filed September as, 1920, Serial no. 413,376. Divided and. this application filed March so, 1925.

My invention relates particularly to screens where a very high frequency of vibration is employed to accomplish the desired results. This application is a division of my application Serial N 0. 413,376, filed September 28, 1920, for vibrating screens, and relates particularly'to means forfastening andholding the screening cloth securely in place and wherein the screening cloth is quickly and easily replaced.

Other objects will appear hereinafter and I attain these objects by the construction illustrated in the accompanying drawing in which: a

Figure 1 is a cross section of a portion of a screen box illustrating the'principles of my invention as applied to the stretching and fastening the screen cloth.

Fig. 2 is a sectional view in detail showing a method of fastening fine screen cloth to the stretching beams. v

Fig. 3 is a cross sectional view of a part of a screen box illustrating another mode of 2e stretching and fastening the screening cloth.

Fig. 4 is a'transverse section taken'near one end of the screen box.

The same numerals refer to like parts throughout the several views.

In the operation of vibrating screens I have found that the longest life of the screen cloth, as well as the greatest capacity per square foot of screening surface and the least blinding of the screens-is obtained when the. as-screen cloth is stretched tight between the sides of a vibrating box, and rigidly held to such box at the sides and ends only, allowing a clear unobstructed-flow over the screening surface without bolts, rivets or otherpbstructions to hold the screen cloth to the vibrating member. j 1

I have found also that where the sides of the screen cloth were rigidly held to a stationary frame, and the 'central'part of the wire-screen cloth was attached to a vibrating member, not alone did the wires soon break near the vibrating connection bolts, but the whole screen cloth wore rapidlypwhere the wires were in contact witheach other. Undoubtedly-this was caused by the-mechanical wreckingaction and abrasion due to the distortion of the position of the wires.

.I therefore naturally reached the conclu- .sionthat the wires comprising the cloth must not be disturbed in relation to each other, but

Serial No. 19,201.

B0 ter of the screencloth prevented the even distribution of the material to be screened, especially 'if the feeddid not land exactly uni formly each side of such connections.

As argeneral rule, I operate my screens from 1500 to 2000 vibrations per minute,- and the vibrations may be about 1/16-inch diameter on fine material, 1/8-inch on medium size and 3/l6-inch'or slightly over on coarse as well as on moist material, on which less num-. ber of vibrations and greater movement gives better results.

To effectively meet these and various other conditions under which the screening operations are conducted and to permt ready replacement of the worn-out screens, I provide the construction herein disclosed. My inven- 'tion accordingly includes special fastening devices which are capable of being variously utilized. As a specific example, however, illustrative of the principles of my invention applied toa screen box which fulfills the above and other conditions, the screen box is made up of sides 1, to which are attached the top rails-'2 and the bottom rails 3 provided withtie rods 7 on which are pipe struts 8 to hold the sides securely braced. The frame is held togther by nuts 9 on the ends of rods 7 The end ties 5 and 6 hold-the sides 1 and the tie pieces firmly together. The supporting pipe 12 is held by clamps 11 and collars 13 are shrunk onto pipe 12. To the ends of pipe 12 arepressed spiral springs 14, which are held in place by check nuts 15 on the ends of pipe 12. The spiral springs 14are clamped 5 fast in the spring clamps 16 which are rigidly secured onto the stationar 'beams 18.

The screen cloth 52 is astened to stretching beams 53. .Stretching bolts 54 serve to draw the beams 53 toward the sides 1 or bottom rail 3, thereby pulling the screen cloth drum tight.

In cases where wood is desirable for stretching beams, the construction shown in Fig. 4 is used. The edges of the screen cloth are turned at right angles and the cloth held between cleats 55 and stretching beams 53, the cleats being screwed on to the beams, thereby clamping the cloth between the two. The turned sides of the cloth are also tacked to stretching beams 53 in case of the finer clot-h.

For stretching coarser and heavier cloth, steel channels and angles are more frequently used, as shown in detail in Figs. 1, 2 and 3. In the upper part of Fig. 1 and in the lower part of Fig. 3 I have shown independent wire stretchers, and in the lower part of Fig. 1 and the upper part of Fig. 3, I have shown twin stretchers for stretching, respectively, a single screen or double screens. In case of independent stretchers a single spacer 56 may be used. When the channels are used, they themselves form spacers.

Inside liners 57 serve to protect the sides 1 from wear, and also to hold down solidly the stretching beams 53 to the bottom rails 3-. The wedges 58 which bear against the top rails 2, serve to press down the liners 57 The wedges are not driven home solidly until the screen cloth is stretched.

When heavy screen cloth is used, it is only necessary to bend the sides of the cloth over double or U-shaped, then slip the U over the flange of the channel or angle. When lighter cloth is used, I employ one or two U clips, one 59 fitting inside the other 60, outside of the U-shaped side of the screen cloth. This method effectually prevents slipping of the screen cloth when stretching, but also allows of easily slipping the flimsy screen cloth into place without removing the stretching beams from the screen box. In case of very fine bronze and brass screens, I sometimes only use the inside U clip and solder screen cloth 52 to the inside U Fig. 2.

clip 59 asshown at 61,

7 Where twin stretching is used in triple deck screens with sizes in tandem or more as shown in diagram, Fig. 1, the cloths cannot be slipped in when stretching beams are in position, but the screens must be put on to the beams outside the box and then dropped in place. In that case a nut 62 is riveted or welded to beams 53 and a tap bolt 63 employed for stretching. It would be impossible to put in bolts 54 in such a situation.

Having set forth the object and nature of my invention and various constructions embodying the principles thereof, what I claim as new and useful and of my own invention and desire to secure by Letters Patent, is:

1. In vibrator structuresya screen box, a plurality of U-beams extending longitudinally of said box. screen cloths overlapping the edges of said beams and means for drawing said beam toward the sides of said box to draw said cloths taut, the width of said means forming means for accurately spacing the cloths.

2. In a vibrator structure, a screen box having beams extending longitudinally thereof near the top and bottom, flanged beams extending parallel to said beams, screen cloths overlapping said flanged'beams and means connected to said flanged beams for drawing said cloths tight, the width of said means forming means for accurately spacing the cloths.

In testimony whereof I have hereunto set my hand on this fourth day of March, A. D.

GUSTAVE A. OVERSTROM.

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