US1937274A - Screen plate - Google Patents

Description

Nov. 28, 1933. A. D. HOYLE Er AL I 1,937,274

2 Sheets-Sheet l Filed March 12, 1931 Nov. 28, 1933. A. D. HOYLE ET AL 1,937,274

2 Sheets-She SCREEN PLATE Filed March 12, 1931 Patented N... 28, 1933' UNITED STATES SCREEN PLATE Alfred D. Boyle and Frederick B. Olson, Berlin, N. 11., assignors to Brown Company, Berlin, N. 11., a corporation of Maine Application March 12, 1931. Serial No. 521,939

8 Claims.

In the making of paper it is customary to run the aqueous suspension of pulp through a screen to strain out foreign particles, lumps of fiber, etc. which would cause irregularities in the paper sheet. This is usually done just before the pulp is run onto the Fourdrinier wire on which the pulp is formed into a sheet or web. The screen through which the pulp suspension is passed is customarily in the form of a rectangular plate 'through which a number of slits from .004 to .025 inch in width have. been cut. The actual width employed in each instance depends on the kind of pulp which is to be screened. The pulp fibers are washed through these slits, leaving on the upper face of the screen particles or lumps too great to pass through a slit. In making screen plates, grooves are customarily milled in the under face and the slits are then sawed through from the bottoms of these grooves to the upper face bf the plate. Owing to the narrowness of the slits, the saw blade must be thin and the plate itself: must be of a material sufilciently soft to be sawed. Bronze is widely used for this purpose. When in use the upper edges of the slots wear more or less rapidly according to the nature of the pulp passing through the slots, the amount of abrasive grit carried by the pulp, and the presence or absence of acid, etc. in the water. It is necessary to keep the slot edges sharp as the wearing of the upper edges widens the slot at the top so that foreign particles, slime, etc. are liable to be wedged in the widened portions of the slots, clogging them. To remedy this the face of the plate may be ground down if the metal forming the slot walls is thick enough. This renews the sharp upper edge and uniform top width of the slots.

The present inventionrelatesto an improved screen plate and a method of making the same. According to the invention, small bars with cross sections resembling a keystone are assembled side by side with spacing shims between their ends, and are securely joined together. This structure affords several advantages. The bars themselves may be economically drawn or rolled to shape and may be made of relatively hard metal so that the rate of wear of the plate is greatly reduced. The bars can be rapidly, assembled and accurately spaced, doing away with the tedious and costly sawing of slots. For pulp stock containing acids or other corrosive ingredient, the bars may be made of acid resistant metal such as chrome-nickel steel, or of bronze plated with an inert metal such as chromium. If plated bars are used, they are preferablyplated prior to being assembled, so that they may be readily inspected for flaws in the plating. The bars should be joined together in any desired manner, as by welding, since the plate is usually subjected to severe vibration or agitation when in use.

Figure 4 is a fragmentary plan view of the plate'shown in Figure 1.

Figure 5 is a section on the line 5-5 of Figure 4. Figure 6 is a section on the line 6-6 of Figure 4. Figure 7 is a fragmentary perspective view of a pair of bars ready for welding.

Figure 8 is a fragmentary plan view of a portion of the plate adjacent to the center line.

Figure 9 is a section on the line 9-9 of Figure 8. Figure 10 is a fragmentary plan view of a modified form of the invention.

Figure 11 is a section on theline 11-11 of Figure 10.

Figure 12 is a section on the line 12-12 of Figure 10. I t

Figure 13 is a section on the line 13-13 of Figure 10.

Figures 14, 15 and 16 are sections, respectively on the lines 14-14, 15-15 and 16-16 of Figure Figure 17 is a fragmentary plan view of another modified form of the invention.

Figure 18 is a section on the line 18-18 I Figure 17.

Figure 19 is-a fragmentary. plan view of a further modification oi. the invention.

Figure 20 is a section on the line 20-20 01' Figure 19.

Figure 21 is a fragmentary perspective view of a bar such as may be used in the plate illustrated in Figure 10. a

Figure 22 is a fragmentary perspective view of a bar such as may be used in the plate shown in Figure 17.

Figure 23 is a fragmentary perspective view 0 I a cellulosic pulp suspension of wood fiber or the i stock is fed. The screen plate 30 is provided with a series of slots 32 through which the pulp fibers and water freely pass. These slots, however, are carefully regulated in width so as to catch foreign particles, thus to avoid specks and lumps in the paper which is made from the pulp fibers. Heretofore it has been customary to construct the screen plates in one piece by milling out grooves in the under face thereof and then sawing slots of desired width from the bottoms of the grooves to the upper surface of the plate.

According to the present invention, the plates are constructed of a large number of individual pieces which are securely fastened together as by welding or otherwise. These pieces for the most part may be formed by cold rolling suitable metal such as non-corrodible steel, bronze or any other metal having the characteristics desired, the bars being rolled into a shape somewhat similar to that illustrated in Figures 6 and '7. As therein shown, the finished bar 31 may have a cross section resembling a keystone or T-shape, including an upper, substantially rectangular portion 33 and a reduced portion 34 extending downwardly therefrom and preferably tapering as shown. The upperpc-rtion has a top face 35 and a pair of side faces 36 which are preferably parallel to each other, or approximately parallel, the lower portion 34 projecting from the lower face of the upper portion in the form of a heavy rib or fin, as illustrated in Figure 7. In Figure '7 the bars are shown in their inverted position ready to be welded together. After the bars have been thus joined to form a screen plate, the plate is inverted to the position indicated in Figure 1 with the ribs or fins 34 projecting downwardly so as to present a plane upper face 35 interrupted by the slots 32. In making a bar 31, it may be first cold rolled to the proper cross sectional shape, after which the side faces-36 are preferably ground and polished. These side faces, as is evident from Figure 6, ultimately form the side walls of the slots 32 so that by careful grinding and polishing of these faces, the slots 32 are assured uniform width and smooth sides which offer nothing on which fibers may possibly catch to clog the slot.

In making screen plates by milling and sawing as has been heretofore done, the choice of metals is limited to those whichcan be cut by fine saws. Thus the harder metals, such as steel, cannot be used in the manufacture of plates by milling and sawing. Thesemetals are available for screens made according to the present method and add greatly to the'life of the screen plate, since they are not so quickly worn away by the friction of the pulp fibers passing through the slots. Since the choice in metals according to the present invention is not limited, we are able to make a screen plate of such material as chromium nickel steel which, besides being hard, is also resistant to corrosion by acids. Such a plate is particularly valuable for use with pulp stock having acid or other corrosive material therein. The present invention can also be employed in the making of screen plates of bronze or other metals. In order to protect the bronze, the bars 31 may be plated with a protective metal such as chromium. These plated bars may be easily and thoroughly inspected for defects in the plating before the bars are assembled to form the screen plate. Thus a plate of plated bronze made according to the present invention is more reliable than a sawed bronze plate which is plated with chromium or the like as a last step in the manufacture, since in the latter case it is impossible sixths, etc. of a plate.

to inspect effectively the side walls of the narrow slots 32. Furthermore, if a defect in the plating of a one-piece plate is discovered, it is necessary to replate the entire plate.

In assembling thebars 3 1 to form a screen plate, we may employspacing elements such as shims 40. These shims may be of any desired thickness and can readily be obtained in the open market in the form of strips of steel. They may be easily and frequently tested for correct thickness by micrometer calipers, thus insuring slots of accurate and uniform width, free from errors which have heretofore been occasioned by the wearing of saw blades and other similar causes. In making a screen plate 30, we may form a bar 31 of indefinite length and may cut off the sections therefrom of desired length. This length may be conveniently equal to the width of the screen plate itself. The sections of bar may be assembled upside down in side by side relation as illustrated in Figure 7, the successive sections of bar being spaced by three shims, one at each end and one in the middle, these shims being between the adjacent faces 36 of successive bars. When the requisite number of bars has been assembled to form a plate of the desired length, the structure may be clamped tightly in a suitable jig and may be secured together as by welding along the edges and down the center line. In order to prevent the spreading of the welding material along the slots 32 and the channels between the fins 34, we may insert a suitable dam 41 of copper or other suitable material, a series of these dams being mounted together in the form of a sort of comb, if desired. The space between the dams 41 and the side of the jig is filled up with welding material. as at 42, so that a solid rim of metal is thus formed along the sides of the plate. Similar dams may be used adjacent to the center line of the plate to permit the filling up of the channels, as at 43, without undue spreading of the metal along the channels between the fins 34. The resulting plate thus built up is a rigid unitary structure having slots 32 which are uniform in Width and have polished side walls, offering no point of vantage for the catching of fibers thereon. As shown on the drawings, the slots 32 are of uniform width from top to bottom, so that'when the upper edges of the slots eventually become worn and it is necessary to grind away the face of the plate to provide sharp upper edges again for the slots, the slot width be ween the upper edges is just what it was when the plate was new.

Instead of building a one-piece plate as described, we may build plates in sections, sufiicient bars being assembled to form sections of desired or convenient size such as halves, quarters, or

made, may be secured together as by bolting, welding, spot-welding, etc. to form a whole plate.

The dimensions of the bar 31 may be varied as desired. By way of illustration, the total height of the bar may be about three-eighths of an inch, the height of the upper rectangular portion 33 being about one-twelfth of an inch so, as to provide material sufficient to permit grinding off the top face when the upper edgesof the slots become worn. The Width of the bar 31 on its top face may be about one-sixth of an inch, 'and the width of the rib or fin 34 may taper from about one-tenth of an inch down to about one-seventeenth of an inch. As hereinbefore stated, these dimensions are approximate and may be varied as desired.

Instead of assembling the sections of bar in a Such sections, after being rectangular frame, illustrated in Figure 10. This I frame may comprise an end piece 50 to which are permanently fixed a pair of side members 51, 52, a second end piece 53 being detachable so as to permit the insertion of sections of bar between the side members 51 and 52. We may also providea central member 54 having one end-permanently secured to the end mcmber'50. As shown, the free end of the central member 54 may be mortised into the inner wall of the end member 53. As shown in Figures 12, 14 and 18 the ends of the sections of bar may be mortised into the inner side walls of the members 51 and 52 and place, the tenons 56 on the ends of thebars slid-- ing in suitable grooves 57 in the side walls of the longitudinal members of the frame, or, if the other modified form of structure is used, the recesses 58 in the ends of the bars fit on tenons or ribs 59 formed on the side walls of the longitudinal members 51, 52 and 54 of the frame. When the bars spaced from each other, the end member 53 is placed in position on the ends of the side members 51 and 52 and is secured thereto as-by rivet pins 60, these pins being reinforced, if desired, by welding at the comers of the frame and at the point where the central member 54 meets the end member 53. As 'shown in Figure 16, the end member 53 may be fitted to the side members 51 and 52 by mortised joints.

In spacing the bars'whichare assembled in a frame such as that illustrated in Figure 10, shims may be employed, as described, in connection with the making of the plate illustrated in Figure 1. If shims are thus employed, the bars may al be welded to the longitudinal members 51-, 52

and 54 of the frame so as to insure a permanent correct spacing of the bars from each other. Instead of employing shims to space the bars, we

may shape the end portions of the individual I sections of bar so as to form thereon spacing lugs 65 which project laterally from one or both side faces thereof. These lugs may be formed by drop forging individual bar sections, preferably cold, after the sections have been cut from the rolled bar of indeterminate length. If a tenon 56 or a mortise 58 is to be formed on each end of 1 the bar, this also may be formed in a single operation with the formation of the spacing lugs 65.

By this process the lugs 65 may be quickly and acber 54 and one of the side members so as to strengthen the assembled plate against a spreading of the central portions of the side members 52 and 53. When a plate is made thus, the bars are replaceable with little difllculty so that after a plate has been worn to such an extent that the upper face will stand no more grinding down, the

, r, 3 bars may be removedfrom the frame and be replaced by a fresh set of bars. Instead of mortising the bars to the longitudinal members of the frame, the bars may be made with plane ends, as

shown in Figure 23, spacing lugs 65 being also provided in the form therein illustrated. These bars may be assembleddn the frame as shown in Figure 19 and are preferably welded in place to hold them in proper alinement.

We claim:

1. A method of making a screen plate, which comprises assembling a plurality of metal bars side by side with uniform spacing elements adjacent to their ends, and welding the bars rigidly together at their ends 2. A method of making a screen plate, which comprises forming a metal bar having an upper portion with a substantially rectangular cross section and a reduced tapering lower portion, grinding and polishing the side faces of the upper portion, cutting oiT sections of the bar of equal lengths, assembling said sections side by side with top faces flush and polished side faces uniformly spaced to form slots of predetermined width between consecutive sections, and welding said sections rigidly together at their ends.

3. A method of making a screen plate, which comprises assembling strips of hard metal stock side by side with uniform spacing elements between successive bars at their ends, inserting dams in the spaces between said bars near their ends and welding between said dams andthe ends of the strips to unite the strips and elements into an integral structure.

4. A method of making a screen plate, which comprises assembling side by side strips of hard metal stock having a cross-section consisting .of a substantially rectangular portion with a fin projecting from one side, said strips being arrangedwith their fins parallel and with spacing elements between them at their ends, inserting dams in the channels between successive fins at points near the ends of the strips, and welding between the dams and the ends of the strips to poin the strips and elements into an integral structure.

5. In the papermaking art, a screen plate comprising a series of hard non-corroding steel bars having a T-shaped cross-section and uniformly spaced side by side, said bars being solidly-joined together by welding between their end portions.

6. In the papermaking art, a screen plate comprising a series of hard non-corroding steel bars having a T-shaped cross-section and uniformly spaced side by side, said bars being solidly joined together by welding between their end portions and central portions.

'7. In the papermaking art, a screen plate comprising a series of hard non-co'rroding steel bars having a T-shaped cross-section and arranged side by side, and a pair of spacing shims between the end portions of each pair of successive bars, said bars and shims being joined together in a rigid unitary structure by welding between the .end portions of said bars.

8. In the papermaking art, a screen plate comprising a series of chrome-nickel steel bars having a T-shaped cross-section and uniformly spaced side by side, said bars being welded together at their end portions into a unitary structure.

ALFRED D. HOYLE. FREDERICK B. OLSON.

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