US2004507A - Flat screen frame - Google Patents

Description

June ll, 1935.

J. J. MORAVEC FLAT SCREEN FRAME Filed June 27, 1934 4 Sheets-Sheet l June 1l, 1935. J, MORAVEC 2,004,507

FLAT SCREEN FRAME Filed June 27, 1934 4 Sheets-Sheet 2 .Inu @n fb f': away/7 .IMO/'avec June 1l, 1935. 1 J, MORAVEC l 2,004,507

FLAT SCREEN FRAME Filed June 27, 1934 4 SheetsSheet 3 June 11, 1935. J. J. MoRAvEc FLAT SCREEN FRAME Filed June 27; 1934 4 Sheets-Sheet 4 Patented-June 11, 1935 UNITED STATES PATENT OFFICE,

23 Claims.

My invention relates to devices commonly known as vibratory at screens used for the refining of wood pulp in paper making, and, in particular, for the separating of ne wood fibers suitable for further steps in the processes of paper manufacture, from wood slivers, bark, dirt and other extraneous matter. As is well known, this separation or screening of the fine fibers is accomplished by drawing the pulp thru flat metal screen-plates provided with fine slots, generally about 1/100 of an inch wide an'd about 4 inches long, and, as the pulp passes over these screen-plates, the fine bers are drawn thru the slots, 'while the coarser fibers and undesirable particles pass over the top of the screen plates and are later either worked over or wasted. To aid in drawing the ner fibers thru the slots, a suction is established by placing a flexible sheet, called a diaphragm and usually made of heavy rubber under the screen-plate supports, and causing this diaphragm to be vibrated by arms bearing on a revolving cam, or by other means.

The screen plates are supported in a shallow rectangular vat or trough, usually about 31/2 feet wide, having a gentle slope longitudinally from the inflow to the outflow end. It is customary to make the screen-plate supports, the cross pieces, sides of the vat, braces and other supporting frame members of wood. Heretofore the heavy metal screen plates were supported onA longitudinal bars or beams and transverse bars, generally made of hard wood, and the screen plates were secured to these transverse bars by screws and other means arranged to hold the screen plates firmly in place, but to permit them to be taken up or removed when necessary. However, the continuous vibration of the rubber diaphragms causes a sympathetic vibra'- tion to be imparted to the screen plates, transverse bars, and other supporting frame members, with the result that the screws gradually work loose, the surfaces of the screen supporting members fray and chip off, wood splinters frequently drop into the refined pulp below the screens, and repairs are necessary at frequent intervals. Furthermore, the continual water logging action to which the transverse wooden' bars are subjected, together with the deteriorating action of the chemicals in the pulp, causes these bars to go to pieces much more rapidly than would ordinarily be the case. These wooden bars also become coated with slime, and, unless they are scraped 01T regularly, this slime mixes with the refined pulp below the screen plates.

The object of my invention is to overcome these objectionable features, and to provide a. nat-screen frame and supports of suitable con- 5 struction and material to resist the deteriorating effects of constant vibration and chemical action.

I attain my object by providing a screen frame built in sections, each section comprising a uni- 10 tary structure, or, if built up of separate parts, the parts so arranged that they will, when assembled, constitute unitary sections, so that individual frame sections can readily be removed, thereby facilitating inspection and repairs of separate sections when required without necessitating the taking apart of the vibratory atscreen as a whole.

A further desirable result attained by my invention is that all surfaces which come in contact with the refined pulp are of metal and thus the sloughing off into the refined pulp of the undesirable coatings and portions of Wood surfaces is avoided.

Another feature of my invention is that the means provided for locking the screen frame members in place is so housed as to exclude all pulp material therefrom, which pulp material would otherwise interfere with, and cause deterioration of the operative parts of said means.

The above mentioned as well as other features of my invention are hereinafter fully described with reference to the accompanying drawings, in which Fig. 1 is a sectional view of the vat containing 35 my screen-plate supports taken longitudinally along the center line of the vat; the screen frame as here shown consisting of longitudinal and transverse members cast into one piece for each section or suction chamber;

Fig. 2 is a transverse section across the sam vat but drawn to a larger scale;

Fig. 3, sheet 2, is a drawing, in a diagrammatic isometric perspective, of my vat, screen plates and screen frames, with some of the screen plates removed and portions of the supporting frame members broken away to show details of their construction, the screen frames being of the s ame construction as shown in Figs. 1 and 2;

Fig. 4, sheet 1, shows a block-bar holding the frame;

Fig. 5, sheet 1, is bar taken on line used in screen plates down on the screen a cross-section of the lock- 5 5 of Fig. 4; 55

portion of my one-piece frame, illustrating specifically an optional means of fastening adjacent frames together;

Fig. '7, sheet 4, shows a longitudinal sectional view of the vat, similar to Fig. l, but with screen plate supports made up of individual, removable transverse bars and spacing plates;

Fig. 8, sheet 1, shows the spacing plate employed with the individual removable bars in the construction illustrated in Fig. 7 for wooden vats;

Fig. 9, sheet 4, is a larger sc'ale, vertical section of a portion of the side of the wooden vat, showing, partly in section, used for holding down lock-bars and screen plates on the screen frame;

Fig. 10, sheet 4, is a view of the rear face of my lock-screw-clamp, that is, the face adjacent to the side of the vat;

Fig. 1l, sheet 4, is a horizontal section on the line lI--II of Fig. 10, looking down;

Fig. 12, sheet 4, is a side view of my lockscrew-clamp;

Fig. 13, sheet 4, is a horizontal section on the line i3-I3 of Fig. 12 looking up, with the nut and screw inside the lock-screw-clamp removed;

Fig. 14, sheet 4, is a plan view of the nut in the interior 'of my lock-screw-clamp;

Fig. 15, sheet 3, is a fragmentary view, in perspective, of a side of one of the transverse bars used in the construction illustrated in Fig. 7 for wooden vats;

Fig. 15a, sheet 3, is a fragmentary view, in perspective, of a side of one of the middle bars used in the same construction;

Fig. 16, sheet 3, is a vertical section of the side of a metal vat corresponding to the section of the wooden vat shown in Fig. 9;

Fig. 17, sheet 3, is a longitudinal section of a metal vat with part of the screen plates broken away and the middle bar, lock-bar and lockscrew-clamp removed;

Fig. 18, sheet 3, is a the middle bar of the a metal vat;

Fig. 18a, sheet 3, is a similar view, on reduced scale, of one of the other transverse bars adapted for use i'n a metalvat;

Fig. 19, sheet 2, is a fragmentary longitudinal section of a vat containing a modied construction of part of my screen frame; and

Fig. 19a, sheet 2, is a cross section of two adjacent side bars of my screen frame illustrating another modified construction.

Referring rst to Figs. 1, 2 and 3: a, a' and a2 are longitudinal beams, and b, b are transverse beams in the supporting frame of the vat. c and c' are the sides of the vat. The bottom of the vat is closed by series of rubber diaphragms d.

In my screen frame as illustrated vby Figs. 1, 2 and 3, which I designate as my one-piece construction, each frame is rectangular in shapeabout 2 feet wide and 31/2 feet long-is made to hold two screen plates n, and is composed of three integral, transverse bars e, f and e' spaced apart by integral end members g, and intermediate braces h, h and i, fi', which elements together constitute one frame unit. The sides e', e and the end portions g of the frame are made with flanges as e2 at the bottom, so as to provide broad bearing faces resting firmly on top of the rubber diaphragm d, which in turn is supported on the transverse beams b, and

view on reduced scale of frame adapted for use in my lock-screw-clamp.

Fig. 6, sheet 3, shows, in perspective, a cornerthe longitudinal beams a, a'. The bottom edges of the middle bar f, and the intermediate braces h, h', and 7', a" are spaced from the bottom of the frame so as to provide ample clearance space above the diaphragm d within the cham-4 ber formed by each screen frame. The sides e and e and ends g of the frame are made with a ange 7cv at the top on which the screen plates n rest. The middle bar f of the frame is made with opposite lateral anges m and m', level with the top ange Ic of the ends g, and surmounted by overhanging beveled shoulders o and o'. The sides e and e' are made with vertical iianges k2 (see Fig. 1 and Fig. 6) adapted to be engaged by the heads of bolts k3 extending thru the side of the vat, as shown in Fig. 2. This construction eliminates the use o! the iron tie-rods heretofore employed and extending across the vat to prevent any spreading of the sides. These former tie-rods, which were ordinarily made of wrought iron, and passed thru the suction chambers between screen plates and diaphragms, became coated with rust as a result of their contact with the wet pulp, and the scaling off of this rust into the refined pulp was a troublesome feature of the customary type of wooden frames. This objectionable feature I have avoided by substituting the bolts k3 and keeping these bolts out of contact with the wet pulp.

The screens are rectangular metal plates, portions of which are shown by n in Fig. 3, provided with narrow parallel transverse slots n', the slots thus extending longitudinally along the top of the vat. These slots are generally about 4 inches long and 1/100 of an inch wide, as previously mentioned. The side edges o! the screen plates n are beveled; one beveled edge of each screen plate is engaged by the beveled edge of one of the shoulders o or o of the middle bar f, and the other beveled edge of each screen plate is engaged by the head p' of a lock-bar p (see Figs. 4 and 5). The lockbar p, which has a T-shaped cross-section, as shown in Fig. 5, has the edges ofits head p beveled to correspond to the beveled edges of the screen plates.

'I'he exterior faces o1` the sides e and e' of the frame are provided with lugs q to keep adjacent frames spaced suiiciently from each other so as to permit lock-bars to be inserted between them. Holes may be drilled thru these lugs and thru the sides of the frames, and screw bolts q' inserted in these holes for the purpose of bolting adjacent frames together in the vat,

or adjacent frames may be fastened together by external locking lugs, as will be explained later on. After the screen plates n have been placed in position on the top of the frames the lock-bars are dropped into place, and the screen plates cannot be removed or lifted out of place without lifting up the lock-bars.

The lock-bars p are heldl in place by means of a lock-screw clamp r placed at each end of the lock-bars p. The details of my lock-screwclamp are shown in Figs. 9 to 14, sheet 4. The lock-screw-clamp comprises a screw s on which is threaded a clamping nut t, having a lip l. The screw s is rotatably supported in the housing u and the top of the screw, which extends thru the top of the housing v, has a head w of hexagonal cross-section, or similar convenient shape, to facilitate the turning of the screw. A bearing ring a: is placed between the bottom of the screw head w and the top of the housing v. A pin y is inserted in the neck oi the housing v and is engaged by a circumferential groove s' in the shank of the screw. The pin y is held in place by a ferrule or sleeve z dropped over the neck of the housing v. The clamping nut t, which is raised or lowered by the turningof the screw s, is shaped as shown by the plan view in Fig. 14, and the side views in Figs. 9 and 11. It is square, with two sides cut away as at 2 and 3, Fig. 14, and provided on one side with a projecting lip 4 the top surface of which extends obliquely upward. The lock-screw-clamp housing u encloses the clamping nut t on three sides I4, I9, I5. 'I'he interior of the housing v corresponds to the square shape of the clamping nut t and permits the clamping nut to move up and down on the screw s'but prevents any rotation of the clamping nut. 'Ihe interior of the housing is made with two rectangular guide ribs 5 and 6 (Fig. 11) on which the clamping nut t slides. Figs. 11 and 13 show horizontal cross-sections of the housing from which it will be seen that one face thereof is open to permit free vertical movement of the projecting lip 4 of the clamping nut. At regular intervals, corresponding A to the location of the lock-bars p, indentations are cut into the sides of the vat to accommodate recessed plates 'I (see Fig. 9), which are fastened to the vat sides by bolts 1a. These plates are 'provided with a recess 1b, to accommodate the projecting side'portions I4, I5 of the housing v, and with a downward projecting locking flange 9 adapted to engage the projecting lip 4 of the clamping nut t.

vThe bottom of the housing v of the lockscrew-clamp is made with a lug I 0 tapered at its ends and projecting downwardly a distance slightly less than the thickness of the screen plate n and adapted to slide between the beveled edges of the screen plates. The lock-bar p is made slightly shorter than the frame or the screen plates so that the end of the lock-bar will extend under the bottom of the housing v of the lock-screw-clamp up to the lug I0. 'I'he end of the lock-bar p thus prevents any movement of the lug I0 and consequently any movement of the bottom of the housing v out away from the adjacent vat side. A gasket II of rubber or other packing material is inserted in the cavity I2 at the bottom of the housing v for the purpose of making the connection between lockscrew-clamp and lack-bar p absolutely tight.

The front side I3 of the lock-screw-clamp housing (see Figs. 10, 11 and 13) extends out beyond the 'side faces I4 and I 5, as at I3a, and the tops of the side faces have pendent flanges I6 and I'I (Fig. 10). 'I'he ends of the screen plates n are held down by wooden bars I8, see Figs. 1 and 3. These bars are made with a longitudinal groove on the bottom in which is inserted a gasket II a, similar to and in line with the'gasket II in the bottom of the hous'n" If the lock-screw-clamp r, and another longitudinal groove and gasket IIb on the side adjacent to the side of the vat. The purpose of these is to make the connections between the bars I8 and the screen plates and between the bars and the vat sides absolutely tight when the lockscrew-clamps are tightened. The ends of the bars I8 are cut out at the top and front faces, as shown at I8a in Fig. 1, to fit into the sides of the lock-screw-clamp housing, so that the front face of the wooden bars I8 will be flush with the front face of the lock-screw-clamps r,

iand the pendent flanges I6 and I'I will flt over the ends of the bars I8.

By the turning of theA screw s of the lockscrew-clamp, the clamping nut t is raised and its lip 4 is interlocked with the flange 9 of the plate f 'I, the end of the lock-bar is held down firmly, and the sides of the screen plates engaged by the lock-bar are held down on top of thescreen frame. Simultaneously the flanges I6 and I I of the housing v bear down on the ends of the engaged bars I8, causing the latter to bear down on top of the ends of the screen plates. The

.sloping adjacent faces of the lip 4 of the clamping nut t and flange 9 of the plate 'I pull the lock-screw-clamp r firmly against the vat side and hold it there. Thus, no pulp can get inside the housing of the lock-scre'w-clamp, which formerly was one ofy the chief difficulties in the use of the screw -clamp heretofore employed.'

The front faces ofthe lock-screw-clamps, engaging the adjacent ends of the bars I8, hold the bars I8 tight against the sides of the vat. As a result of this sealing of joints there is no suction loss in the suction chambers below the screens and it is impossible for any pulp to get into the suction chambers except thru the narrow slots in the screen plates.

The lock-bar p is slightly concave longitudinally, as shown on exaggerated scale in Fig. 4. However, when the ends are pressed down by the lockscrew-clamps the top becomes straight. Having the top made slightly concave insures the firm pressing-down of the screen plates by the lock-bar along their entire side edges.

Each frame, as described, constitutes an individual suction chamber with a rubber diaphragm for the base and a pair of screen plates for the top. A rod or plunger :c attached to the center of the diaphragm d, and reciprocated by a cam, or other means, not shown, causes the diaphragm to vibrate up and down and, as well known, the suction resulting from such movement of the diaphragm draws the fine pulp fibers through the slots of the screens.

Instead of fastening adjacent frames together by bolts such as q' the outside faces of the frame sides e, e' may be made with interlocking lugs 42 as shown in Fig. 6, by which means adjacent frames are-held firmly together when two frames are dropped into position side by side in the vat. Of course, when the frame sides are made with these interlocking lugs the bolts q' are dispensed with and the holes which would be drilled for them are omitted.

The advantages of my frame, as now will be apparent, are: First of all, there is no wood to splinter and wear away, no screws to be replaced, or other parts to work loose with the constant vibration. Secondly, the removal of the screen plates is a very simple matter, especially as compared with the amount of work required in removing the screen plates of the ordinary flat vibratory pulp screens. Further, the removal of the entire frame is quite simple, and particularly the removal and replacement of the rubber diaphragm can be done easily, and requires removal of one frame only. My one-piece frame is suitable for use in the ordinary and when so installed constitutes a metal lining for the vat since the wooden sides of the vat are protected from contact with the pulp. But, while my screen frame is especially adapted for use with the present type of Wooden vats, of course it is not limited in use to any particular type of vat.

The foregoing description covers my metal flat screen frame made as a one-piece or unitary. structure. It may, however, bebuilt of separable members, and this construction has advantages in the transportation of frame members from the place of manufacture to the place of use.

When so 'designed my screen frame sections entail certain differences in construction readily seen by comparison with my one-piece sections shown by Fig. 3.- My built-up frame sections consist of end members 26 (Fig. 8), the equivalent.of end members g of Fig. 3, side members 26 (Fig. 15), the equivalent of members e and e' of Fig. 3, and middle bars equivalent of members f of Fig. 3.' In this construction whereby screen frame is\built up of separable parts, I do not considerthe braces such as h, h. of Fig. 3 necessary.

The end members 2D (Fig. 8) have rectangular cut-out portions or notches 2| at the bottom and other cut-out portions or notches 22 at the top. The end members 20 are designed to serve as liner plates for the inner sides of the vat. The side members 26 (Fig. 15) are formed at their ends with projecting lugs 44 at the top, and the middle bars 23 (Fig. 15a) are formed at their ends with projecting lugs 43 at the bottom. The lugs 43 fit into the bottom notches 2| of the end members 20. The upper notches 22 of the end members 20 are made exactly large enough to accommodate the lugs 44 of a pair of bars or side members 26.

This built-up frame assembly is shown by Fig. 7, representing a -longitudinal section of a wooden vat in which screen frame assembly is installed. The side members 26, like their equivalents e and e', have external lugs 21, for keeping the sides of adjacent sections spaced from each other suiliciently to allow lock-bars 28 to be dropped between them, and they have end flanges 46 adapted to engage the heads of bolts Ic1 extending thru the sides of the vat. Adjacent side members 26 may be held together either by bolts 29 or by interlocking lugs similar to the lug 42 of Fig. 6. The middle bars 23 are provided with screen plate engaging elements 24, similar to the elements m, m and o, o' of the integral middle bar f of Fig. 3. The screen plates 25 are also held down by the lockbars 28 andby the bars I6' extending over the ends of the screen plates. The bars I6 and lock-bars 28 are held down by lock-screw-clamps r already described. The end members 20, which act as spacer plates for the side members 26 and middle bars 23 as well as liner plates for the vat sides, may be made in convenient lengths, for example, as shown in Fig. 8, in lengths corresponding to the width of each screen frame section.

My screen frame, when constructed 0f separate members; possesses the same advantages over the old fashioned Wooden screen frames as already pointed out with reference to my onepiece screen frame. It is further suitable equally as well for a metal vat as for a wooden vat.

Fig. 16, sheet 3, shows a vertical section of a side of a metal vat; and Fig. 17 shows a longitudinal section of the metal vat with portions of the screen frame removed and part of the screen plates broken away. The sides 30, which may be made in sections of convenient length joined together in any suitable manner so long as the joints areabsolutely tight and the inside of the sections are flush with each other, are

23 (Fig. 15a), thev preferably made with vertical ribs or webs 3| on the back, with top and bottom flanges 32 and 32' (see Fig. 16), and a longitudinal ridge 33 on the bottom surface adapted to engage a shoulder on the beam 34 of the supporting frame for the vat. Figs. 18 and 18a show a middle bar and a side member, respectively, of my built-up screen frame as adapted for the metal vat. The lower portion of the vat sides is of greater thickness than the upper portion, making a ridge 38 between upper and lower portions. In the lower portion of the vat sides, at points constituting the location of the middle bars of the frame sections, grooves are made by pairs-of blocks 39 just wide enough to accommodate the ends of the middle bars 40. At the ends of the middle bars 40 (see Fig. 18) the bottom iianges 4| are cut away so as not to interfere with the blocks 39. Thus, when the middle bars are dropped into place, they are securely held in the vat sides. The side members (Fig. 18a) are made with vertical flanges 41 and with external spacing lugs 48, and adjacent side members are held together either by bolts or by interlocking lugs (such as 42 in Fig. 6) in the manner already described. The vat sides are made with rectangular depressions or wells 35 containing downward projecting flanges 36 at the top, said flanges being adapted to engage the projecting lip 4 of the lock-screw-clamp previously described. The vat sides are also provided with holes located below the wells 35 thru which bolts 31 are inserted, and the heads of these bolts are engaged by the flanges 41 at the ends of the side members 45. The method of locking the screen plates in place is exactly the same as that described before.

In the specification thus far the screen plates have been described as 'having beveled side edges, with the middle bars provided with locking heads to engage adjacent edges of the screen plates; and lock-bars are provided to engage the other sides of the screen plates. This construction, however, may be modified if desired; 'the screen plates may be made with straight, instead of beveled edges on one side, and the locking head of the middle bar may be dispensed with. Also the lock-bars may be modified or dispensed with entirely.

One such modification is illustrated in Fig. 19 (sheet 2)', showing a fragmentary longitudinal section of a vat, in which 5| represents the diaphragm, 52 is the middle bar having opposite lateral flanges 53 at the top. The related ends of the screen plates have straight edges 56, and the screen plates ends are fastened to said flanges 53 of the middle bar by screws 51.

58 is a modified form of lock-bar. As apparent, this lock-bar has no pendent shank. The lock-bar 58 is secured in place by tie rods 59 extending down thru the transverse frame member of the vat support, such bolts being spaced, for example, about l0 inches apart.

A still further modification of the means for securing the screens in place is shown by Fig. 19 (sheet 2). Here the lock-bar has been entirely dispensed with, the edges of the screen plates over the side bars 54 are made straight instead of beveled, and adapted to touch each other, and are fastened on the top flanges of the bars 54 by screws 49. In such cases the top flanges of the bars 54 are made broad enough to touch each other.

In all other respects my screen frame construction would be the same as above described,

including longitudinal bars extending along the vat sides over the ends of the screen plates and the lock-screw-clampsfor holding the longitudinal bars, screen plates and screen supporting frame sections rmly in place.

I claim:

1. A flat screen assembly comprising adjacent rectangular all metal sections, each composed of sides, ends, a transverse middle bar, and screen plates, said middle bar being spaced from the bottom of the frame, the middle bar provided with a locking head for engaging adjacent screen plates, means-for connecting the opposed sides of adjacent frame sections so spaced as to receive a screen plate lock-bar between them, a screen plate lock-bar adapted to be inserted between said opposed frame sides, said lock-bar provided with a head adapted to engage the sides of adjacent screen plates, and means for securing said lock-bars in place.

2. A flat screen assembly comprising adjacent rectangular all metal, one-piece sections, each composed of sides, ends, a transverse middle bar, braces and screen plates, said middle bar and braces being spaced from the bottom of the frame, the middle bar provided with a locking head for engaging adjacent screen plates, means for connecting the opposed sides of adjacent frame sections so spaced as to receive a screen plate lock-bar between them, a screen plate lockbar adapted to be inserted between said opposed frame sides, said lock-bar provided with a head adapted to engage the sides of adjacent screen plates, and means for securing said lockbars in place.

3. In combination with a vat a at screen assembly comprising adjacent rectangular all metal sections, each composed of sides, ends, a transverse middle bar, and screen plates, said middle bar being spaced from,the bottom of the frame, the middle bar provided with a locking head for engaging adjacent screen plates, means for connecting the opposed sides of adjacent frame sections so spaced as to receive a screen plate lock-bar between them, a screen plate lock-bar adapted to be inserted between said opposed frame sides, said lock-bar provided with a head adapted to engage the sides of adjacent screen plates, means for securing said lock-bars in place, the side walls of the vat provided with recessed plates having a lockange, and said lock-bar securing means including a screw operated locking lip engaging with said lock-flange.

4. In combination with a vat a flat screen assembly comprising adjacent rectangular all metal sections, each composed of sides, ends, a transverse middle bar, and screen plates, said middle bar being spaced from the bottom of the frame, the middle bar provided with a locking. head for engaging adjacent screen plates, means for connecting the opposed sides of adjacent frame sections so spaced as to receive a screen plate lock-bar between them, a screen plate lock-bar adapted to be inserted between said opposed frame sides, said lock-bar provided with a head adapted to engage the sides of adjacent screen plates,`means for securing said lock-bars in place, the side walls of the vat provided with recessed plates having a lock-flange, and said lock-bar securing means including a screw operated locking lip engaging with said lock flange, a series of overlying bars extending over the ends of said screen plates, said lock-bar securing means including a housing forming with said overlying bars continuous wall surfaces constituting the inner sides of a trough over the screen plates.

5. In combination with a vat a fiat screen assembly comprising adjacent rectangular sections, each composed of sides, ends, a transverse middle bar, and screen plates, said middle bar being spaced from the bottom of the frame, the middle bar provided with a locking head for engaging adjacent screen plates, means for connecting the opposed sides of adjacent frame sections so spaced as to receive a screen .plate lock-bar between them, a screen plate lock-bar adapted to be inserted between said opposed rame sides, said lock-bar provided with a head adapted to engage the sides of adjacent screen plates, -means for securing said lock-bars in place, such means comprising a vertical, rotatable screw inclosed by a housing having an opening towards the adjacent side wall of the vat, the latter provided with a recessed plate having a lock ange, a clamp nut threaded on said screw and provided with a locking lip projecting thru said opening for engaging with said lock iiange.

6. The combination described by claim 5 with the base of said housing adapted to bear on said lock-bar and means for holding said housing firmly against the adjacent side wall of the vat.

'7. In combination with a vat a flat screen assembly comprising adjacent rectangular sections, each composed of sides, ends, a transverse middle bar, and screen plates, said middle bar being spaced from the bottom of the frame, the middle bar provided with a locking head for engaging adjacent screen plates, means for connecting the opposed sides of adjacent frame sections so spaced as to receive a screen plate lock-bar between them, a screen plate lock-bar adapted to be inserted between said opposed frame sides, said lock-bar provided with a head adapted to engage the sides of adjacent screen plates, screw clamps for securing said lock-bars in place, the side walls of the vat provided with -recessed plates having a. lock-flange, and said screw clamps including a screw operated lockinglip engaging with said lock ange, the base of said housing provided with a lug adapted to be inserted between adjacent screen plates and bearing against the end of said screen lock-bar, whereby to prevent the tilting of the screw clamp by the engagement of its said locking lip with said lock-flange of said wall plate.

8.,In combination with a vat a flat screen assembly comprising adjacent rectangular sections, each composed of sides, ends, a transverse middle bar, and screen plates, said middle bar being spaced from the bottom of the frame, the middle bar provided with a locking head for engaging adjacent screen plates, means for connecting the opposed sides of adjacent frame sections so spaced as to receive a screen plate lock-bar between them, a screen plate lock-bar adapted to be inserted between said opposed frame sides, said lock-bar provided with a head adapted to engage the sides of adjacent screen plates, screw clamps for securing said lock-bars in place, the side walls of the vat provided with recessed plates having a lock-flange, and said screw clamps including a screw operated locking lip engaging with said lock-flange, a series of overlying bars extending over the ends of said screen plates adjacent the sides of the vat, each of said screw clamps being provided with a housing interposed between and connecting the adjacent ends oi said overlying bars, adapted to hold down said overlying bars, and to form therewith continuous wall surfaces constituting the inner sides of a trough over the screen plates.

9. The combination described by claim with with the base of said housing adapted to bear on said lock-bar, means for holding said housing rmly against the adjacent side wall of the vat, and aseries of overlying bars extending over the ends of said screen plates adjacent the sides of the vat, the housings of said screw clamps being interposed between and connecting the adjacent ends of said overlying bars, adapted to hold down said overlying bars, and to form therewith continuous wall surfaces constituting the inner sides of a trough over the screen plates.

10. In combination with a vat a flat screen assembly comprising adjacent rectangular sections, each composed of sides, ends, a transverse middle bar, and screen plates, said middle bar being spaced from the bottom of the frame, the middle bar provided with a locking head for engaging adjacent screen plates, means for connecting the opposed sides of adjacent frame sections so spaced as to receive a screen plate lock-bar between them, a screen plate lock-bar adapted to be inserted between said opposed frame sides, said lock-bar provided with a head adapted to engage the sides of adjacent screen plates, means for securing said lock-bars in place, such means comprising a vertical, rotatable screw inclosed by a housing having an opening towards the adjacent side wall of the vat, the latter provided with a recessed plate having a lock ange, a

clamp nut threaded on said screw and provided with a locking lip projecting thru said opening for engaging with saidlock flange, the base of said housing adapted to bear on said lock-bar, the base of said housing provided with a lug adapted to be inserted between adjacent screen plates and bearing against the end of said screen lock-bar, whereby to prevent the tilting of the screw clamp by the engagement of its said locking lip with said lock flange of said wall plate, a series of overlying bars extending over the ends of said screen plates adjacent the sides of the vat, the housings of said screw clamps being interposed between and connecting the adjacent ends of said overlying bars, adapted to hold down said overlying bars, and to form therewith continuous wall surfaces constituting the inner sides of a trough over the screen plates.

11. The combination described by claim 10 with the sides of said overlying bars provided with sealing packing strips on their bottom face and also on their face adjacent to the vat side, and withthe housing of said rotatable screw adapted to enter said recessed plate in the adjacent side wall of the vat and to form therewith a complete inclosure for said screw clamp.

12'. In a flat screen assembly a rectangular metal frame section consisting of interttin'g side members, end members, and a middle bar, said middle bar provided with a screen plate holding head, and means for connecting the opposed sides of adjacent frame sections in spaced relation.

13. In combination with a vat, a at screen assembly comprising rectangular metal frame sections, each consisting of intertting side members, end members, an'd a middle bar, said middle bar provided with a screen plate holding head, and means for connecting the opposed sides of adjacent frame sections in spaced relation.

14. In a iiat screen assembly rectangular metal frame sections, each consisting of intertting side members, end members, and a middle bar, said middle bar provided with a screen plate holding head, and means for connecting the opposed sides of adjacent frame sections in spaced relation, a lock-bar adapted to be inserted in the space and to engage the sides of adjacent screen plates, and means for securing said lock-bar in place.

15. In combination with a vat, a flat screen' assembly, comprising one-piece, rectangular metal frame sections, each consisting of intertting side members, end members, and a middle bar, said middle bar provided with a screen plate holding head, and means for connecting the opposed sides of adjacent frame sections in spaced relation, a lock-bar adapted to be inserted in the space and to engage the sides of adjacent screen plates, means for securing said lock-bar in place, such means comprising a vertical, rotatable screw inclosed by a housing having an opening towards the adjacent side wall of the vat, the latter provided with a recessed plate having a lock flange, a clamp nut threaded on said screw and provided with a locking lip projecting thru said opening for engaging with said lock flange.

16. In combination with a vat, a flat screen assembly comprising rectangular screen frame sections adapted to support screen plates, said a rotatable screw inclosed by a housing having' an opening facing the adjacent side wall of the vat, a nut threaded on said screw, said nut provided with a locking lip projecting thru said opening, the side walls of the vat provided with a recessed plate having a flange adapted to be engaged by said locking lip.

17. The combination described by claim 16 with two sides of the housing of said screw clamp adapted to enter said recessed plate in the side wall of the vat.

18. The combination described by claim 16 with the base of said housing provided with a lug adapted to be inserted between adajacent screen plates and bearing against the end of said screen plate lock-bar, whereby to prevent the base of said housing sliding away from the adjacent side wall of the vat when said locking lip is forced against said iiange.

19. A flat screen assembly comprising a vat and a diaphragm, screen frame supportingv members, and screen plates, all surfaces of the vat and supporting members which come in contact with the pulp below the screen plates being of metal, means for fastening the screen plates on the said frame members, means for sealing the ends of screen plates with the sides of the vat, and screw clamps for securing said sealing means in place and for holding down said screen plates and said frame supporting members, each of said screw clamps being inclosed in a metal housing having an opening facing the adjacent side of the vat, said housing adapted to form a complete inclosure for said screw clamp with the vat side, whereby to prevent any pulp coming in contact with said screw clamps.

20. A lock-bar-screW-clamp for a iiat screen assembly of the character described, the clamp comprising a screw vertically journaled in an enclosing housing having an open side adapted to be fitted against the interior face of a side of the vat, to prevent pulp entering said housing thru said open side, a nut threaded and axially movable on said screw in said housing, said nut provided with a lip projecting thru said open side of the housing for engagement withv an abutment provided on the interior face of the vat side, whereby to cause the base of said housing to bear rmly on the adjacent end of the lock-bar.

21. A lock-bar-screw-clamp for a flat screen assembly of the character described, the clamp comprising a screw vertically journaled in an enclosing housing having an open side adapted to be tted against the interior face of a side of the vat, to prevent pulp entering said housing thru said open side, a nut threaded and axially movable on said screw in said housing, said nut provided with a lip projecting thru said open side of the housing for engagement with an abutment provided on the interior face of the vat side, whereby to cause the base of said housing to bear firmly on the adjacent end of the lock-bar, the base of the housing provided with a lug adapted to be inserted between adjacent screen plates and the lock-bar end to hold the base of said housing in place.

22. A lock-bar-screw-clamp for a at screen assembly of the character described, the clamp comprising a screw vertically journaled in an enclosing housing having an open side adapted to be tted against the interior face of a side of the vat, to prevent pulp entering said housing thru said open side, a nut threaded and axially movable on said screw in said housing,

said nut provided with a lip projecting thru said open side of the housing for engagement with an abutment provided on the interior face of the vat side, whereby to cause the base of said housing to bear rmly on the adjacent end of the lock-bar, said housing provided at the top with lateral projections adapted to be engaged rmly with the tops of the ends of longitudinal bars lining the sides of the vat, by the engagement of said lip projection with said abutment of the vat side.

23. A lock-bar-screw-clamp for a flat screen assembly of the character described, the clamp comprising a screw vertically journaled in an enclosing housing having an open side adapted to be tted .against the interior face of a side of the vat, to prevent pulp entering said housing thru said open side, a nut threaded and axially movable on said screw in said housing, said nut provided with a lip projecting thru said open side of the housing for engagement with an abutment provided on the interior face of the vat side, whereby to cause the base of said housing to bear rmly on the adjacent end of the lock-bar, the base of the housing provided With a lug adapted to be inserted between adjacent screen plates and the lock-bar end to hold the base of said housing in place, said housing provided at the top with lateral projections adapted to be engaged firmly with the tops of the ends of longitudinal bars lining the sides of the vat, by the engagement of said lip projection with said abutment of the vat side.

JOSEPH J. MORAVEC.

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