US1787047A - Pulp-filtering machine - Google Patents

Description

Dec. 30; 1939. E. c. LOETSCHER PULP FILTERING MACHINE Filed Spt.

12, 1929 2 Sheets-Sheet 1 WMM k 1930. E. c. LOETSCHER 1,787,047

PULP FILTERING MACHINE Filed Sept. 12, 1929 2 Sheets-Sheet 2 flnuew/iol JnbCZ Patented Dec. 30, 1930 mm. c. Lonrsmn,

or nervous, IOWA PULP-FILTEBILIG MACHINE Application fi led September 12, 1 .29. Seriallo. 892,081.

This invention relates to improvementsin pulp filtering machines, and more articu- Iarly to machines for use in the initia preparation of cellulose fibrous materials to be 5 eventually fabricated into boards, panels,

' and the general run of millwork stock. p In general the process (if manufacturing such materials consists in forming-a pulp of theparticular fibrous substance to be used,- such as corn'stalks or other vegetable fibre, and thenreducing the pulp to a mat of uniform thickness from which an excessof the water has been removed by a partial compression, and subsequently to be compressed to the required thickness and density and otherwise treated to give it the characteristics and prop erties of natural wood. I

An essential step in the process of manufacture is thepreparation of the mat, and it '20 is the object of the present invention to provide a machine which will fulfill the commercial requirements, both as to uality and quantity. Among the -desirable,i not necessar qualities, may be mentioned'uniformity in. ensity'and thickness of the mat as well as the texture of arrangement of the fibrous structure of which it is composed. Again, its I production in a form suitablefor subsequent treatment isessential to economical production, not to mention its production in quantities which will keep pace with the output of the finished material.

So far as I am-aware, the apparatus here- I tofore used for this-purpose has been in the form of a cylindric'screen turning in a vat into flwhi'ch pulp is introduced, a partial vacuum being maintained within the cylinder so that a layer'is gradually built up around the'rotat-ing cylinder, which is then peeled Jofi". Aside from the fact that this method is not continuous, it isopen to other objections, the chief of which are,the limited thicknessof the mat produced and the tendency toward non-uniformity in thickness, due primarily to the fact that the suctionbeing the only 'impelling force, becomes increasingly less effective as the fibre mass is deposited on the screen, so that the limit of thickness is soon reached, or being more effective in some areas than others, the mat will vary in thickness.

In the present machine gravity is utilized largely and suctionbut secondarily, and hence the mat can bebuilt up to any desired thickness, depending on the speed at which the machine is operated. Other advantages in the use of a machine embodying the features" of the invention will be apparent fromthe following description of my preferred em- 1 bodiment, as disclosed in' the accompanying drawings, in which Figure 1 is a top plan view of the machine.

Figure 2 is a view in vertical longitudinal section of the machine taken on line 2-2 of Figure 1.

Figure 3 is an enlarged detail view through the tank and screenas taken on line 3-3 of Fi ure 1.

igure 4 is a to plan View of a section of the filter belt and .t e supporting bars thereof.

Figure 5 is a detail view in vertical section taken on line 5-5 of Figure 2 showing the racks at one end of the tank for supporting the dividing bars; and

igure 6 is a perspective view of one end of a dividing bar.

An elongated open rectangular tank 1 is elevated from the floor and rests upon a low supporting frame 1a. The tank is preferably so constructed of sheet steel suitably braced and reinforced. The len h and width of the .tank may be varied ut in general proportions its length would'be about two and onehalf times its width, the latter dimension 3 being determined by the maximum width of mat to be, produced. The interior ofthe tank is divided vertically b a continuously moving belt 2 carried on diums or pulleys 3 and 4-located adjacent eachend of the tank and journalled in bearings carried by bearing standards 5 and 6 forming the end.portions of the supporting frame 1a. The belt 2, of

a construction presently to be described, is slightly wider than the tank and its upper lead passes lengthwise from one end to the other in a plane slightly inclined to the hori- I zontal, the direction of travel of the belt being from the head to the tailor discharge end of the tank, namely, from right to left in Figure 1, and its inclination being upwardly in the same direction.

The belt 2 consists of an endless band or strip of thin steel 7 perforated throughout with relatively large circular holes 7 a, preferably arranged in staggered rows as shown in Figure 4. Applied over the top'face of the perforated band is a covering of fine wire mesh 8 although if preferred the perforated band may be interposed between two layers of fine wire mesh, the two or three layers, as the case may be, forming the complete belt. The belt supporting drums 3 and 4 are positioned a short distance beyond the ends of the tank and the upper leadon leaving .the drum at the head or lower end, passes through the tank, thence around the drum at the tail end and returning to the head end beneath the tank.

To provide for the passage of the upper lead of the belt through the tank, the latter is constructed in two sections, namely, lower and upper sections 9 and '10, respectively. The lower section consists of bottom, sideand end walls, the upper edges of said side and end walls conforming to the inclination of the plane of travel of the belt, and provided with outwardly projecting flanges 9a. The

upper section of the tank consists of'end and side walls having their lower edges'inclined also to the plane of the belt travel, and hav-' ing flanges 10a complementary to the flanges 9a of the-lower tank section. The two sections are bolted together with their flanges in registerbut spaced apart by a strip or gasket 11 of resilient material, such as rubber extending along the outer edges of the flanges and bolts 12 passing through the same (Figure T e longitudinal spacing strips or gaskets 11 are narrower than the edge flanges 9a and 10a, thus leaving inwardly opening slots 2a along the inner side walls of the tank of a width to receive the edges of the travelling belt 2, as shown in Figure 3, said belt as before stated being slightly wider than the tank. In order to forman air sealaround the edges of the belt 2,! flexible sealing strips 13 are secured to the side walls of the upper tank section along the line of the belt, with their-free lower edges curving inwardly and resting on the top side thereof. At the head or lower end of the tank is a narrow entrance slot 13 for the belt 2, suitably acked so that a watertight-connection is ma e between the entrance slot and the moving belt. At the upper or discharge end, a considerably wider slot 14 is provided, the width thereof being equal to the combined thickness of the belt.

mounted immediately below it, t e same consisting of a plurality of parallel bars 15a nally of the tank and inclined to the same angle as the plane of the belt. These bars are supported at their ends against the end walls of the tank, and as will be observed from Figure 4, the bars although parallel with each other, are arranged slightly oblique to the travel of the belt, the reason for this being to avoid the wearing of grooves; in the belt, as would occur if the bars were parallel with the line of travel of the belt.

At the head end of the tank and above the belt 2 is a separate compartment 16 extending crosswise the end of the tank, the same being formed by a vertical front and a curved bottom wall 16a, 166, respectively, which terminate short of each other to form a discharge opening along what would be the inner lower edge of the compartment. This opening is dimensioned for a maximum dischar e, and for regulating its size two gate.-

to control the size of the discharge opening formed between their edges.

Within the compartment and extending -crosswise of the tank is an agitator 19 consisting preferably of a shaft19a journalled in bearings at each end of the compartment, and rows of paddles or agitating fin ers 19b projecting therefrom. As shown in figure 1,- the agitator shaft is driven by a belt 20 from a small pulley 21 on said shaft to a large pulley 22 on the shaft 3a of the belt drum 3 at the headend of the tank. Opening into the compartment is a large suppl pipe 23 leading from a source of pulp supp y and regulated by a suitable valve; Located centrally above the tank is a water pipe line 24 divided into branches 24a extending crosswise of the tank, and from which depend several spray heads 25. By means of valves, the water is controlled to direct a spray of water onto the material deposited on the traveling belt, as will be described later and in more detail.

Beneath the tank is another pipe 26 opening upwardly through the bottom wall of the lower section at its central point. This pipe leads to a wet vacuum pump (not shown),

Extending lengthwise of the tank and just above the belt are several thin dividing bars 27 supported on edge by plates 28, 28 'secured atwise againsfithe vertical end wall at the tail end of the tank and vertical wall 15 of the compartment, these plates being slotted at short intervals throughout their clear of the top surface of the belt-and act to divide the material as it is being formedthereon into sections of different width, ranging from the full width of the belt to numerous narrow strips, depending on the number of dividing bars used, which are removable and adjustable to any width of material desired.

This'completes the tank and parts associated therewith. Ashort distance beyond the tail or discharge end of the tank is the supporting standard 6 previously referred to as supporting the bearings for the tailend belt drum 4. This standard, it Willgbe observed, is higher and longer than the drum supporting standard 5 at the head end of the tank and serves tosupport a set of presser rolls 'and belts presently to be described.

Just below the tail end belt drum 4 which is journalled at the end of the standard 6 adjacent the tank, is a motor 29 bolted to the floor and directly connected through a flexible coupling 30 to a worm gear speed reducing unit 31 which drives the tail end belt drum 4 at a relatively slow speed through sprocket wheels and chain 32.

Mounted on the standard 6 just beyond the 1 end ofthe filter belt is an arrangement of pressure rolls and belts, their purpose being to partially com ress the material as it leaves the filtering tan and thus remove a portion of the water contained in the pulp. There are two pairs of rolls 33, 33 and 34, 34, one below and *the other above the horizontal path ofthe material, and carried by each air of rolls are belts 35 and 36 of heavy felt. hese pairs -.of pressure rolls are journalled at the ends of bearing arms 37 supported by side frame members 38, 38 mounted upon the standard 6.

The lower pair of rolls is mounted so that the upper lead of the lower belt 35 is horizontal, while the upper pair of rolls is offset vertically so that the upper belt 36 is slightly inclined thus forming a rearwardly tapering space between the belts. By preference the upper rolls and belt are mounted in a sliding carriage regulated by ad ust1ng screws 39 so that they maybe ad usted vertically.

Between the'forward end of the filter belt and the pressure rolls is 'a short table 41 erected on the supporting standard 6 to support the material in its travel across the interveningspace. Beyond'the pressure rolls is a long table 42 for supporting-a removable caul 43 onto which the material is dis charged on leaving the pressure rolls. The table and cauls are dimensioned to the lengths to which the material is to be cut for conremoved and another placed on the table to receive'the next length. a Referring now to the formation of th mat within the filter tank, the operation is .7

as follows: Acontinual supply of pulp of the desired grade and consistency is supplied to the agitator compartment 16 through the supply pipe 23 and kept. in a constant state of agitation by the rotor 19. From the compartment the pulp is continually discharged downwardly and forwardly into the space above-the lower end of the filter belt 2 which is moving slowly in a forwardly and upwardly'inclined directionjas indicated by the arrow in Figure 2. 'The amount of pulp discharged into the tank proper is regulated by the position of the two gate members 17 and 18, the purpose being to maintain a certain pulp level substantially throughout the space above the lower half of the belt surface, as indicated by the horizontal line a in Figure 2. In other words, the, pulp is not discharged directly onto the belt, but rather the belt emerges from a mass of pulp kept in a continuous state of movement and agitation, and in a relatively fluid condition by the water b ing constantly sprayed from the sprinkler heads 25. In this way the pulp is deposited or deposits itself onto the filter belt in a uniform layer or mat A, and furthermore, since the pulp is in solution by reason of the water being continually added, the separate fibres tend to arrange themselves so that as they are picked up by the advancing belt they extend :more or less uniformly in ,the same direction, that is, parallel with the directionof movement of the belt.

- Inasmuch as the-filter belt is perforated, thereis arontinual passage of the water through the belt, this being promoted by the reduced pressure in the space below the belt and maintained through the suction pipe 26. The suction acting'on the under side of the belt' manifestly draws or pulls the fibres toward the surface of the belt,

with the result that the greater the suction the more rapid the deposit and the thicker the layer or mat to be produced, hence by regulating the suction the desired thickness of mat can be obtained. Once the layer has been deposited on the belt and passes beyond the pulp level in the lower end of the tank, its thickness and texture remains reduced in its passage therebetween and more of the water pressed out, so that on leaving the rolls it contains from 40% to 50% of moisture.

While this disclosure does notdeal with the subsequent processing of the material, it may bestated that it is utilized in the making of various kinds of finished materials, by further pressing and drying processes which eventually reduces it to'a density equal to that of natural wood.

In the manufacture of difierent materials various widths of mats are required and this is the purpose of the dividing bars 27 tion,

' outlet from the space in said tank below said which may be placed in the tank in any number and spacing, so that instead of a mat of the 'full width of the belt being formed, it maybe divided into several narrow sections of the same or diflerent'widths, as requirements demand.

Having set forth the novel features of the machine or apparatus embodying my inven- I claim; V -1. A pulp filtering apparatus comprising a tank, an endless screen belt adapted to travel in an upwardlyinclined direction through said tank, means for continuously feeding pulp' into said tank above said belt whereby the fibres are deposited on said belt in a mat of predetermined thickness as said belt emerges above the level of said pulp.

2. A pulp filtering apparatus comprising an elongated tank, a filterbelt adapted to travel in an upwardl lengthwise through sai tank above the bottom thereof, means for .continuously"feeding pulp into said. tankabove said belt, and means for draining. the tank below'said belt.

3. A pulp filtering apparatus comprising an elongated tank, an-endlessbelt of filtering material travelling'lengthwise through said tank in a plane mclin'ed u wardly in the direction of its travel, an ag1tator compartment insaid, tank having a discharge opening above the belt, means for supply ing pulp to said com artment, and a water belt.

4. A ul filtering apparatus comprising an elongatdd shallow tank, an endless filter belt adapted to travel lengthwise through said tank and divide the space therein along an inclined plane, means for continuously feeding ulp into said tank above said filter belt, an" means for discharging the water assing through said belt from the space heow the same.

5. A pulp filtering apparatus comprising an elongated tank, a filter belt mounted beyond each end of said tank, means for driving said belt whereby its upper portiontravels lengthwise through said tank in a plane inclined upwardly in the direction ofits travel, and means for maintaining a predetermined inclined direction,

level of pulp at the end-0f the tank above the enteringportion of said belt.

6. A pulp filtering apparatus com rising an elongated shallow tank, a filter belt of substantially the width of said tank passing lengthwise through said tank in an inclined plane spaced above the bottom thereof, means for driving said belt in a direction to travel upwardly in said inclined lane, means for feeding pulp into the end oi said tank above the entering portion of said belt, and means ,for maintalning a partial vacuum in the ment, and means for removing water from i the space in said tank below said belt.

8. A ul filtering apparatus comprising .1

relative y s, allow elongated tank, a filter belt having its upper lead passing through said tank from end to end and sloping upwardly in the direction of its travel, a rack supporting: said belt within said tank, a compartment at the'end of said tank and connecting with the space above the lower entering portion of the belt, an agitator in said compartment, a

atefor controlling the discharge of pulp rom said compartment, means for supplying pulp to said compartment, and means" for removing water from the space in said tank below said belt.

9-. yApulp filtering apparatus com rising a relatively shallow elongated tank, a lter belt moving through said tank from end to end and sloping upwardlyin the direction of its travel, means for feeding pulp into said tank at a rate to maintain a predetermined pulp level substantially throughout the lower portion of the belt, and means for maintaining the space below'said belt at less than atmospheric pressure.

10., A pulp filtering apparatus comprising atank, a filter belt traveling through said tank from end to end in a plane inclined upwardly in the direction of travel, means for continually supplying pulp to said tank above said belt,'1neans for spraying water on to the belt beyond the point of pulp supply, and

means for maintaining the space below said belt at less than atmospheric pressure.

11. A pulp filterin r apparatus com rising a tank, a filter belt adapted to travel engthwisethrough said tank in an upwardly inclined direction, said tank having openings at each end through which said belt enters and leaves, and inwardly facing channels along the sides into which the margins of said belt extend forming a support for said belt, means for sea'lin the edges of said belt with the side walls 0 said-tank above said belt, means for supplying pulp to said tank above said belt, and suction producing means communicating with the space in said tank below I said belt. 1 12. A pulp filtering apparatus comprising an open tank, a filter belt adapted to travel lengthwise through said tank in an upwardly inclined direction, drums journalled beyond each end of said tank for supporting said belt, said belt entering said tank through a liquid tight slot and having its edges engaging in inwardly facing channels in the side walls of said tank, means for sealing the edges of said belt with the side walls of said tank above said belt, means for maintaining a predetermined level of pulp at the end of said tank adjacent the lower entering portion of said belt, and means for draining the space in said tank below said belt and for maintaining the same 5 at less than atmospheric pressure.

13. A pulp filtering apparatus comprising a tank, an endless filter belt moving lengthwise through said tank, means for supplying pulp to said tank to be deposited on said belt, and a'dividing bar supported edgewise above said belt and extending longitudinally thereof.

14. A pulp filtering apparatus comprising an elongated tank, an endless perforated belt 5 having a portion extending lengthwise through said tank and supported therein to travel in an upwardly inclined direction, means for supplying pulp to said tank, a Y dividing bar adapted to be removably sup ported edgewise in said tank with its lower edge adjacent to the upper surface of said belt, and transverse racks at each end of said tank adapted for supporting the ends of said 22111 in several positions transversely of said A! e v i Signed at Dubuque, Iowa, this 7th day of September, 1929.

E C. LOETSCR.

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