Headbox having pivoted bridging cover

A headbox for a paper making machine having a slice chamber with a vertical tube bank supplying the slice chamber and a distributor chamber behind the tube chamber tapering from a larger size to one side of the machine to a smaller size at the other side of the machine with the lower floor of the header chamber sloping upwardly and a pivotal cover extending over the tube bank and header chamber openable for access to the tube bank and header chamber.

BACKGROUND OF THE INVENTION 
The present invention relates to improvements in paper making machines, and 
more particularly to an improved headbox for supplying paper stock from a 
supply conduit from a fan pump and distributing the stock across the width 
of a machine to a slice chamber. 
In the formation of a traveling fibrous web by depositing fibers in a 
slurry onto a porous forming surface, the stock is distributed onto the 
surface from a slice chamber through a slice opening. In order to maintain 
uniform velocity of flow and fine scale turbulence in the stock, it is fed 
into the slice chamber through a plurality of tubes forming a tube bank 
with the tubes essentially uniformly distributed across the machine. In 
one form of such construction for compactness, the unit is arranged so 
that the distributor tube bank feeds downwardly directly into the slice 
chamber and the tube bank is conventionally supplied with stock from a 
header extending across the machine positioned above the tube bank. To 
maintain a uniform velocity of flow of stock across the header, the stock 
is supplied to the header from a conduit leading from a fan pump at one 
side of the machine and the header tapers to a small end at the other side 
of the machine and excess stock may flow through a recirculating line 
leading off from the small end of the header. In this arrangement in order 
to maintain the distributor tubes at a uniform length, the top wall of the 
header chamber slopes in a downward direction. The downwardly sloping wall 
of the header chamber tends to cause air bubbles to form and tends to 
cause the fibers of the stock to gather along a wall. Also, the fibers 
will tend to conglomerate and nonuniform flow will result so that the 
stock gets dirty as these conglomerates of fibers are released and flow 
further along the header or down through the distributor tubes. Such dirty 
stock or conglomeration of fibers will cause marked defects in the 
resultant paper. That is, in order to produce uniform paper, the stock 
must continue to flow uniformly at all locations and cannot slow down, the 
fibers cannot conglomerate and air bubbles cannot be permitted to form. 
A feature of the present invention is to provide an improved headbox 
arrangement where the advantages of a compact tube bank which leads 
immediately directly down into the slice chamber are retained, yet the 
disadvantages of stock defects and gathering air bubbles are avoided. 
It is accordingly an object of the present invention to provide an improved 
headbox construction with a tube bank leading downwardly into a slice 
chamber and a header chamber for supplying stock to the tube bank wherein 
the header chamber does not have any downwardly sloping surface. 
A still further object of the invention is to provide an improved headbox 
construction of the type described with improved clean-out features 
wherein easy and immediate access to the header chamber and tube bank is 
readily afforded. 
A still further object of the invention is to provide an improved headbox 
construction with a unique cover arrangement which forms a chamber wall 
for the distributor tube bank and the header chamber.

DESCRIPTION 
As illustrated in FIG. 1, a traveling fibrous web is formed by dewatering a 
stock slurry deposited onto a forming surface 10 such as a fourdrinier 
wire. The stock flows through a slice chamber 11 out through a slice 
opening 12 onto the wire 10. 
The slice chamber is formed by a slice chamber floor 13 and a movable slice 
chamber roof 14. The roof of the slice chamber is pivoted at 15 onto 
headbox framework. For pivoting the slice chamber roof up and down to 
change the size of the opening 12, a connecting rod 16 pivotally connects 
to the forward edge of the roof 14 and is moved up and down by an 
adjustment nut mechanism 17 for small adjustments. For major adjustment of 
the slice opening, a Duff Norton jack 19 is mounted on a bracket 12a on 
the headbox and connects to an arm 8 which supports the small adjustment 
mechanism 17. Within the slice chamber are a plurality of flexible 
trailing elements 24 anchored at their upstream end to a plate 23 and 
trailing at their downstream ends receiving flow from distributor tubes of 
a tube bank 22. 
The headbox framework includes a vertical wall 21 which provides a mount 
for the bracket 12 and the arm 8 for the slice roof adjustment mechanism. 
A fiber stock slurry is fed down into the slice chamber 11 through a 
distributor chamber means, such as preferably the tube bank 22 having a 
plurality of vertical distributor tubes relatively uniformly distributed 
across the width of the machine. These tubes are suitably supported to 
extend through holes in the plate 23 at their lower ends leading into the 
slice chamber and in a plate 25 at their upper ends, which plate 25 has 
openings for the stock to flow in the upper ends of the distributor tubes. 
For supplying stock to the upper ends of the distributor tubes, a header 
chamber 26 is positioned immediately behind the tube bank 22. The header 
chamber extends along the full width of the machine, as generally 
indicated in FIG. 2, and is tapered from a larger end 30 to a smaller end 
31 for the purpose of insuring uniform flow velocity across the header 
chamber 26, as the stock flows out of the header chamber up into the upper 
ends of the tube bank across the width of the machine. 
For supplying stock to the header chamber, a stock supply conduit 27 
connects to the larger end 30 supplied by fan pump 28. A recirculation 
line 29 connects to the smaller end for carrying away excess stock which 
does not flow into the distributor tubes. 
The stock flows uniformly out of the top of the header chamber across a 
space indicated at 33 provided beneath a pivotal wall or bridging cover 32 
which extends over the top of a header chamber and over the top of the 
distributor tubes thereby bridging the space over the header chamber and 
the entry to the distributor tubes. The cover 32 will have suitable seals 
around its edge and have dogs or fasteners with a gasket arrangement to 
insure that the stock which is under pressure does not leak out around the 
edge of the cover 32. The cover will have a lip to seal at its side edges 
and to seal at its front edge against the upper wall 25 of the tube bank 
and to seal against the rear wall 36 of the header chamber. 
A unique and important feature is the structural and functional arrangement 
of the cover 32 which permits to be moved from a closed position, shown in 
a solid line position of FIG. 1 to an open position, shown in the dotted 
line position of FIG. 1 wherein full access is afforded to the top of the 
header chamber and to the tube bank for servicing and cleaning. The 
undersurface of the cover 32, shown at 38, tapers or slopes in an upward 
direction for smooth flow of the stock and to prevent the collection of 
bubbles and accumulation of fibers. A strengthening framework 37 is 
positioned above the cover and rigidly secured thereto. 
A preferred mount for the cover provides a pivotal support at its rear edge 
at 34 where it is supported on a bracket 35 mounted to the wall 36 of the 
header chamber. This permits pivotal movement of the cover between its 
solid and dotted line position of FIG. 1. The cover may be moved manually 
or suitable power mechanism may be provided for this movement of the cover 
between its closed position and its open servicing position. 
Thus, it will be seen that I have provided an improved headbox construction 
which provides a very compact unit requiring a minimum of space in the 
mill. The compact space promotes ease of cleaning and servicing, and the 
arrangement attains the objectives and advantages above set forth.