US2658426A

US2658426A - Machine for pulping paper stock

Info

Publication number: US2658426A
Application number: US296680A
Authority: US
Inventors: Cowles Edwin
Original assignee: COWLES CO
Current assignee: COWLES CO
Priority date: 1952-07-01
Filing date: 1952-07-01
Publication date: 1953-11-10
Anticipated expiration: 1970-11-10

Description

Nov. 10, 1953 E. COWLES MACHINE FOR PULPING PAPER STOCK 2 Sheets-Sheet 1 Filed July 1, 1952 INVENTOR.

A TTORNE Y-f Nov. 10, 1953 E. COWLES MACHINE FOR PULPING PAPER STOCK 2 Sheets-Sheet 2 Filed July 1, 1952 ATTORNE I:

m T N w A I Patented Nov. 10, 1953 Edwin Gowles, Cayuga, N. I, assignor to The 'Gowles .Gompany, Princeton, N; 5:, a cnrporae t on o N w Jerse evnlisat aa'rlr finial 19- tr-6 6!!!) 5 Gla.ims. 1

This invention relatesto machines for pulping paper stock, and pertains more particularly to machines of the general type illustrated in my prior Patent No. 2,351A92, in which a varied impeller mountedfor rotation in the bottom of a tank discharges stock outward-1y to defiber the stock, and at the sametime creates a vortical circulation of the stock in the tank which tends to submerge floating stock and repeatedly brings all portions of the stock into the zone of action of thefimpellen Experience with said machines in actual day to day operation in paper mills has demonstrated that if good vortical circulation of the entire contents of the tank is to be maintained, the diameter of the impeller should be at least one iourth, and preferably one third to one half the diameter ofthe tank. However, it has been iound that in such machines, and more particularly in the larger sizes of said machines in which'the tank diameter is frequently as much as2 0 and in which the impeller diameter should befrom 6' to '19 for good circulation, the mechanical and engineering requirements of a drive adequate to transmit the required power input and to main- .tain the desired-peripheral speed of the impeller are quite severe. order to insure reliability .of operation over extended periods gear reducing units have been employed to transmit power to the impeller shaft and such units have added considerably to the lcost of such machines.

Experience with said macl'rineshasalso demonstrated that for any given horsepower input, a small diameter impeller produces more efficient ,defibering action than a larger diameter impeller. For example, a 4' diameter impeller rotatingata speed to consume 100 horsepower is morelenicient than an 8' diameter impeller of the same vane design rotating at a speed to consume 100 horse,- power as shown by the act that the horsepower pe tqn he d vwnsumed by theis ller imp ller to produce ,a given amount of defibering is less than that consumed ,by the larger impeller .to produce an equal amount of .defibering. However, the l impeller cannot be relied upon to maintain adequate vertical circulation in a 20 tank, and larger impellers have been required in large, diameter tanks tort-his reason. It .is anobjectiof the present invention to providea machine-having atank of large capacity in which ,a relatively small impeller may seemployed, said impeller and tank being so constructed and arranged as to makeit possib e 'f or asmallimpelleritocreate and maintain ad ate circulation of all portions of'the stock in the tank and adequate sribmerging action in the manner hereinafter described, but without the necessity of maintainihg'vortical circulation of all portions thereof. Such impellers, because of their relatively small diameter not only operate at higher efiiciency,'but also makes possible'the use of smaller, lighter, cheaper gear reducing units, and in many cases makes possible'theuse of a simple V --belt drive at a cost considerably less than the cost of a gear reducing unit.

This application isfiled as a continuation in part of 'my cope'nding applications Serial No. 72,868, filed January 26, 1949, and No. 146,965, filed March 1, 1950; both now abandoned.

Other objects and advantages of theinventicn willappear hereinaiter. l

A preferred embodiment of the invention selected for purposes of illustration is shown in the accompanying drawings,in which:

Figure 1 is a .top plan view.

Figure .2 is a section on the line 22 of Fig- ,ure 1. w

EigureB .a front view.

Figure 4 is a perspective view of the interior of .the tank, looking .upward from the bottom.

Referring to the drawings, the invention is illustrated as embodiedin a tank of modified cylindrical contour having a flat iron-t wall I and curved side and rear .wall sections 2 and B. The Yflat front wall ms tangent to the curved side Wall section 2 and section 2 merges smoothly into section 3 which, as shown, is preferably ona radius somewhatlarger ,than the lradius of wall 2'. Wall 3 terminates .a short flattened section 3a which ioinswall to form .a corner A. .The radius ,of ,cpr vatulte .of the section 2 is less than the length of the front wall 1. A tank of this type cause 9 elect to fol ow a na ura low pat.-

a ee s a s ia ammq esistance t c cua oe what 6 ext nsal be n serrate in te s a ene a a ies J ther losed my wall surrounding a portion only of the periphery of the impeller is utilized to intercept and deflect a portion of the peripheral discharge from the impeller and to redirect the intercepted discharge in the direction of a portion of the peripheral discharge which is not intercepted.

Thus, at the bottom of the tank, adjacent the corner 4, a curved bafiie I0 extends around a portion of the periphery of the impeller, rougly one quarter thereof, which said baflle is preferably of volute form. The baffle is located between the front wall I on one side and a wall I I on the other side so that the stock which is intercepted and deflected by the bailie is confined and redirected in the direction of the discharge from an adjacent quadrant of the impeller, thereby creating a powerful current moving parallel to the fiat wall I. This current, which constitutes the dominant circulating current within the tank, is, in turn, deflected by the

curved walls

2 and 3, producing and maintaining a constant clockwise (viewed from the top of the machine) circulation of the entire contents of the tank which tends to bring all submerged portions of the stock repeatedly into the zone of action of the impeller. Due to the manner in which the wall 3 forms a corner with the front wall I, the stock moves directly toward the face of the impeller.

The second requisite of a successful machine is the ability to submerge pieces of stock which tend to float on the surface. When dry stock is first introduced the problem is particularly acute, but it exists throughout the operation due to the fact that a large part of the energy introduced by the impeller is dissipated below the surface and the surface is relatively quiescent, particularly at the higher stock consistencies.

For this purpose a cover I2 is provided above the impeller to intercept the upward discharge from the impeller. The said cover is preferably horizontally disposed and extends along the flat wall I of the tank. Adjacent the corner 4 it has a section I3 which curves downwardly and joins the side wall 3a.

A wall I4, parallel to wall I, and lying in a plane between the wall I and wall I I, extends downwardly from the cover I2. The said wall is relatively narrow except near the point where it joins the wall 3a where the section I4a is somewhat wider and has a lower edge I4b which is located at the maximum operating level of the machine. That is, the machine may be operated at lower levels, but for the best performance should not be operated at a level above that of the edge I417.

The stock which is intercepted by the cover I2 is redirected thereby. Some of the stock follows a path more or less parallel to the wall I and, as indicated by arrow I 5, is deflected downwardly by the curved section I3 and wall 311 to augment the main circulating current. Some of the stock, however, moves laterally, as indicated by arrow l6, toward wall I4 where it is again intercepted and deflected downwardly against the surface of the stock, leaving the wall in the form of a curtain of a volume and velocity sufficient to submerge floating pieces of stock which move into its area.

This curtain is particularly effective because of its location immediately above and in front of the impeller. The submerged region in front of the impeller is a region of low pressure into which stock is being drawn from all sides. The velocity and volume of the curtain of stock is sufiicient to penetrate well below the surface and to push 4 floating stock into the low pressure region where it is immediately carried toward the impeller.

It will now be understood why the bottom edge of the wall I4 should not extend below the operating level of the contents of the tank, for to whatever extent it may be allowed to do so, it destroys the effectiveness of the curtain of stock to submerge floating stock.

Moreover, it is important to prevent a reverse or counterflow below the surface of the stock such as might produce an eddy or dead area below the wall I4 near the wall 3. For this purpose a vertical fin I1 is mounted on the wall 3a parallel to wall I and located between that wall and wall I4. It should extend downwardly a substantial distance from a level near that of the edge I 4b. This fin prevents stock discharged by the impeller and intercepted by the wall 3a from moving laterally in a direction counter to the main circulatory movement.

It will be noted that while a portion of the discharged stock is diverted and utilized to insure submergence of floating stock, a considerable portion of the stock so diverted is returned to the main circulatory current, adding its energy thereto.

In order to provide for the removal of finished stock, either to empty the tank on the completion of a batch operation or continuously during a continuous operation the bottom of the tank is provided with a grating I8 through which stock may flow to an outlet chamber IS. The grating is located adjacent the flat wall I, below and somewhat offset from the impeller in a position to be swept by the main circulating current. The ribs of the grating extend parallel to the flow of the current and the force of the current tends to keep the grating clean and unobstructed.

It has been found to be highly desirable to provide a sloping bottom section 20 near the bottom of the curved wall section 2 having a surface which intercepts and deflects upwardly the stock moving along the wall I hear the bottom of the tank, thus aiding the mixing of stock from the upper and lower levels of the tank. It also aids the transfer of energy to the body of stock at the end of the tank and improves the circulation of the main body of stock throughout the tank. Preferably said slope extends close to the end of the grating I8 and a second sloping bottom section 2| extends from the wall section 3 close to the side of the grating to facilitate emptying of the tank.

It will be understood that the invention may be variously modified and embodied within the scope of the subjoined claims.

I claim as my invention:

1. Apparatus for treating paper stock, comprising, in combination, a tank having a fiat front wall, and having a curved wall section joining one end of said flat wall and tangent thereto, said curved wall section joining another wall section curved on a radius greater than the radius of the first section, said second section joining the other end of said flat wall, the radius of curvature of said first wall section being less than the length of said flat front wall, and an impeller mounted for rotation on a horizontal axis extending through said front wall at right angles thereto and discharging stock outwardly from the periphery in directions substantially parallel to said front wall.

2. Apparatus as claimed in claim 1 in which said tank has a sloping bottom section near the bottom of said first named curved wall section which said sloping bottom intercepts and deflects upwardly stock moving along the bottom of said front wall.

3. Apparatus for treating paper stock, comprising, in combination, a tank having a front wall, an impeller mounted for rotation on a horizontal axis extending through said front wall at right angles thereto and discharging stock outwardly from the periphery in directions substantially parallel to said front wall, a curved baflle surrounding a portion of the periphery of said impeller below the axis thereof to intercept and redirect stock in the direction of the discharge from an adjacent portion of the impeller which is not intercepted, a cover lying above said impeller and above the level of the stock in the tank, and a wall extending downwardly from said cover and spaced from said front wall, said wall having its lower edge above the level of the stock in the tank so that some of the stock intercepted 20 and deflected by said cover is again intercepted and deflected by said wall and discharged downwardly against the surface of the stock in the tank.

4. Apparatus as claimed in claim 3 in which said front wall is fiat and said tank includes curved side and rear walls, said flat front wall joining one of said side walls at a tangent thereto and joining the other side wall to form a corner.

5. Apparatus as claimed in claim 3 in which said tank includes a side wall which joins said front wall to form a corner, which said side wall intercepts and deflects stock discharged in the region between said baflle and said cover, and a vertical fin extending downwardly along said side wall below the bottom of said downwardly extending wall and lying in a plane between said wall and said front wall.

EDWIN COWLES.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 232,460 Cooke et al. Sept. 21, 1880 520,680 Hibbert May 29, 1894 2,485,368 Dodge Oct. 18, 1949 2,557,174 Cowles June 19, 1951