US 3853694 A
A mechanism for generating turbulence in a fiber stock flow including a flow chamber such as a headbox for a paper making machine having a flexible plate mounted on one wall at its upstream edge and extending in a downstream direction with a more rigid second plate mounted downstream from the first plate and extending toward the first with the first plate being flexible so as to vibrate due to hydrodynamic forces on the plate.
Claims available in
Description (OCR text may contain errors)
United States Patent [191 Parker, deceased Dec. 10, 1974 1 PAPER MACHINE FLOW CHANNEL WITH A FLEXIBLE PLATE PROJECTING INTO THE FLOW STREAM TO ACT AS AN OSCILLATOR  Inventor: Joseph 1). Parker, deceased, late of Roscoe, 111. by Dorothy C. Parker, executrix  Assignee: Beloit Corporation, Beloit, Wis.
 Filed: Apr. 24, 1973  Appl. No.: 354,110
 ILS. Cl. 162/216, 162/341  Int. Cl. D2lf 1/02  Field of Search 162/216, 336, 341, 342,
 References Cited UNITED STATES PATENTS Hyde 162/341 X 3,103,463 9/1963 Justus 162/341 3,547,775 12/1970 Bossen et 211.... 3,769,153 10/1973 Hill 162/216 Primary Examiner-S. Leon Bashore Assistant Examiner-Richard H. Tushin Attorney, Agent, or FirmHil1, Gross, Simpson, Van Santen, Steadman, Chiara & Simpson  ABSTRACT A mechanism for generating turbulence in a fiber stock flow including a flow chamber such as a headbox for a paper making machine having a flexible plate mounted on one wall at its upstream edge and extending in a downstream direction with a more rigid second plate mounted downstream from the first plate and extending toward the first with the first plate being flexible so as to vibrate due to hydrodynamic forces on the plate.
10 Claims, 4 Drawing Figures PAPER MACHINE FLOW CHANNEL WITH A FLEXIBLE PLATE PROJECTING INTO THE FLOW STREAM TO ACT AS AN OSCILLATOR BACKGROUND OF THE INVENTION The present invention relates to improvements in paper making machines and more particularly to improvements in headboxes and flow dispersion devices which aid in the dispersion of fiber networks and provide for an improved fiber distribution in a paper web.
In the manufacture of paper by discharging a fiber containing stock onto a traveling forming surface, the uniform dispersion of fibers through the headbox and onto the wire is essential for uniform paper. Many structures have been tried to maintain uniform fiber distribution throughout stock as it flows through the headbox to the slice opening. Other devices have been employed to aid in generating a turbulence in the stock to aid in fiber dispersion. Generally, uniform distribution of the fibers must be maintained at all stages of flow through the headbox and onto the wire. It is essential that this be maintained by fine scale turbulence in the stock as it approaches the slice opening so as to avoid nonuniform dispersion and flocculation of the fibers, or to avoid uneven forming if large scale agitation continues.
It is an object of the invention to provide for improved paper web formation by providing an improved method and mechanism for generating fine scale turbulence of the fibers within the stock as it passes through the headbox. 1
A further object of the invention is to generate a fluctuating pressure wave field in flowing fiber suspensions in the headbox or in other locations in the stock supply to the headbox or to the slice opening in order to aid in the dispersion of fiber networks.
A feature of the invention is to provide a mechanism for generating such a fluctuating pressure wave field in a manner similar to vibrating elements in sonic whistles. The desired frequency of the pressure wave is expected to be in the higher acoustic and super-acoustic range. 7
It is also an object of the present invention to provide a device which will generate a high acoustic frequency in a fiber flow stream wherein the device is not fouled by fibers in suspension flowing past the device, and the mechanism is constructed with no sharp protruding leading edges on which the flowing fiber will gather or will staple.
Other advantages and features, as well as equivalent structures and methods which are intended to be covered hereby, will become more apparent with the teaching of the principles of the invention in connection with the disclosure of the preferred embodiments thereof in the specification, claims and drawings in which:
DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic vertical sectional view taken through a headbox or other flow channel showing a structure constructed and operating in accordance with the principles of the present invention;
FIG. 2 is another schematic view of FIG. 1 showing the elements at a different position during operation;
FIG. 3 is a fragmentary schematic sectional view showing another form of the invention; and
FIG. 4 is another view of FIG. 3 showing the parts in a different position during operation.
DESCRIPTION FIGS. 1 and 2 show a flow channel 10 defined between an upper horizontally extending wall 11 and a lower horizontally extending wall: 12. The walls may be the top and bottomwalls of a paper machine headbox conducting stock flowing therethrough in the direction of flow shown by the arrowed line 13.
In a headbox the flow is toward :a slice chamber and slice opening with the slice chamber shown schematically at 14, and a slice opening at 1.5, of the type which directs a flow of paper making stock in the nip between two opposed looped continuous forming wires.
Positioned in the flow stream is a thin plate extending across the headbox in a direction transversely of the flow, with the plate being shown at 16. This plate is made of a thin resilient material such as a stainless steel and is of a thickness that will vibrate due to the flow of stock past the plate with the vibration being of a higher acoustic and super-acoustic range.
The plate 16 is cantileverly mounted along its upper edge 17 to the wall 12 such as by being welded or soldered thereto. The plate extends in a downstream direction with its downstream edge 18 moving up and down rapidly as the plate vibrates.
A heavier second plate 19 is mounted downstream of the first plate 16 and is cantileverly supported at its downstream edge 20 by being mounted on the lower wall 12. The edge may be soldered, welded or otherwise suitably attached to the wall.
The downstream plate 19 extends with its free edge 21 toward the first plate. The free edge 21 is positioned so that it is substantially in alignment with the free edge 18 of the first plate when the first plate is deflected at the lowermost point of its movement in its vibration. Because the downstream plate 19 does not vibrate but maintains its position, it may be formed of a heavier material and may be of extruded plastic epoxy cemented to the lower wall 12.
The upstream plate has a slight curvature with its convex portion facing upwardly toward the stream, and this curvature is accentuated as the plate bends downwardly to the force of the stream flowing thereby. The
downstream plate 19 is also somewhat arcuate in shape with its convex surface facing upwardly. With the plates thus shaped, they form between them a pocket beneath the plates, and the liquid within the pocket varies in pressure to cause the vibration of the first upstream plate 16. The downstream plate has a series of holes 22 therethrough which connect the inner cavity or pocket 23 with the flow stream in the chamber 10.
At the unstressed position of the plate 16 of FIG. 1 as the flow stream cascades off of the free downstream end causing turbulence, the pressure in the pocket or cavity 23 is lowered. As the plate tends to bend downwardly toward the position of FIG. 2 as it is moving downwardly during the cycle of its vibrational move ment, the pressure in the cavity 23 is high. The opening 22 relieves pressure in the cavity and prevents fibers from being entrapped.
With flow in a downstream direction, there is a separation in the flow from the downstream edge of the plate in the manner indicated by the eddies or whirls at 24in FIG. 1. When the plate is bent sufficiently toward the second plate 19, that is, so that the edges are substantially in alignment, it assumes a shape shown in FIG. 2. As it bends back upwardly in its vibrational cycle, it assumes the shape shown in FIG. I. In effect, the upstream plate 16 moves up and down so that it moves between a position of substantial attachment or continuation of the downstream plate as shown in FIG. 2 and a position of separation from the downstream plate as shown in FIG. I. As the plate cycles in its high speed vibration from the position of nonattachment of FIG. Ito the position of simulated attachment of FIG. 2, the
- pressure in the cavity 23 fluctuates, and this pressure together with the bending stresses changing in the upstream plate 16 cause it to vibrate back and forth from its substantially unstrained position of FIG. 1 to its strained position of FIG. 2. As it moves from the position of FIG. 2 to the position of FIG. 1, flow separation occurs, and in this manner steady oscillation of the plate position and consequent corresponding oscillation of the pressure downstream of the plate is achieved. This generates fine scale turbulence throughout the stock insuring uniform distribution and avoiding flocculation in the paper web formed therefrom.
The frequency of oscillation of the plate is determined principally by the velocity of flow and also by the stiffness of the thin plate. The plate will operate for a range of flows and stock consistencies, but different plates of different stiffness can be provided for different operating conditions. For this purpose the section of the flow channel wall 12 may be removable and replaceable with different sections carrying vibrating plates of different stiffnesses and/or sizes.
The opening through the second downstream plate 19 maintains some flow through the cavity 23 and eliminates the possibility of fiber accumulation within the cavity and underneath the second plate 19. In operation as the paper making machine begins operation and the flow of stock proceeds in the direction shown by the arrow 13 in FIGS. 1 and 2 through the headbox to the slice opening 15, vibration of the upstream plate 16 will occur with the plate moving from the position of FIG. 1 to the position of FIG. 2 and back again. This vibration will cause shear and high speed fine scale turbulence in the stock aiding in dispersion of the fibers. While the channel is shown with a single high frequency oscillator, it is understood that a similar oscillator may be positioned on the upper wall 1 1 either opposite the one on the lower wall or slightly upstream ordownstream therefrom. Also, additional oscillators may be positioned each extending across the headbox. Further, similar oscillators may be positioned if desired on the lower end or upper walls of the slice chamber. Variations in size of the mechanical oscillators may be provided depending upon the size of the flow stream and the viscosity thereof.
As stated above, the frequency of oscillation of the plate is determined principally by the velocity of flow and the stiffness of the thin plate. The broad frequency range covered is from 1,000 herz to 18,000 herz. The frequency may vary and advantages will be obtained at different frequencies, but optimum performance may be obtained by checking performance when the velocity and stock consistency is known. A range from 10,000 to 15,000 herz will be frequently found to be useful. Accordingly, the principles of the present invention do not require a specific limitation of a range of vibration frequencies. Reference to high acoustic to super-acoustic shall be herein considered as the range from 10,000 to 18,000, and useful vibration frequency will most often be found within that range, but under certain circumstances of stock velocity and stock consistency, other frequencies will be found to to optimum.
I claim as my invention:
1. A mechanism for generating turbulence in a fiber stock flow stream for improved dispersion comprising in combination:
a flow chamber through which a stream of fiber containing stock flows having a wall member and extending in the direction of flow;
a flexible plate extending away from the wall member in a downstream direction and cantileverly mounted on the wall at the upstream edge of the plate with the downstream edge spaced from the wall member in an unstressed position so that its downstream edge will flex and vibrate with flow of stock along said wall member.
2. A mechanism for generatingturbulence in a fiber stocck flow stream for improved dispersion constructed in accordance with claim 1:
wherein said plate is curved with its convex surface facing the flow stream.
3. A mechanism for generating turbulence in a fiber stock flow stream for improved dispersion constructed in accordance with claim I:
wherein said plate extends transversely along the wall for substantially the entire width of the flow chamber.
4. A mechanism for generating turbulence in a fiber stock flow stream for improved dispersion constructed in accordance with claim 1:
including a secondplate mounted on said wall at one edge and having the other edge position to be in alignment with the first plate at its bent position to form a pocket between said plates.
5. A mechanism for generating turbulence in a fiber stock flow stream for improved dispersion constructed in accordance .with claim 1:
- and including means forming an opening through said second plate communicating between the space between said plates and the flow stream in stock flow stream for improved dispersion constructed in accordance with claim 4:
wherein said second plate has a greater rigidity than the first plate. v 9. A mechanism for generating high frequency oscillation in a fiber stock flow stream for improved dispersion comprising in combination:
a flow chamber through which a stream of fiber containing stock flows having a wall member;
and a flexible resilient oscillatable plate mounted at its upstream edge on the wall member and projecting in the direction of the flow stream with its downstream edge positioned spaced from the wall in an unstressed position and having a flexibility so that the wall will vibrate at a range extending from the high acoustic to superacoustic frequency with the flow of stock through the chamber.
10. The method of generating fine scale turbulence in the flow stream of stock for a paper making machine comprising:
positioning a continuous plate in a headbox mounted quency.