Apparatus for shredding and dry-defibrating compressed cellulose pulp and forming a batt of the resulting cellulosic fibrous material

A method and apparatus are provided for shredding and dry-defibrating compressed cellulose pulp, and depositing the resulting fibrous material on a foraminous support to form a batt of relatively uniform density while controlling the feed of cellulose pulp material through the shredding and dry-defibrating operations to the foraminous support according to the output rate of the batt-forming operation, to ensure a relatively uniform density in the batt withdrawn from the foraminous support.

The feed of cellulose pulp material to a dry defibrator normally requires 
that the pulp be in a loosely compressed form, such as in rolls of loosely 
compressed cellulose pulp, or loosely compressed pulp sheets. It is 
necessary that the pulp be only loosely compressed because of the heat 
developed when tightly compressed or moderately compressed pulp is 
defibrated. The heat liberated in the course of processing such materials 
may be so great that the pulp fibers are ignited. Moreover, particles of 
tightly compressed or moderately compressed pulp may jam the grinding 
members of the defibrator. However, loosely compressed pulp is much more 
expensive than tightly compressed or moderately compressed pulp. 
Therefore, this is a considerable disadvantage, which the art has sought 
to avoid. 
In order to make it possible to utilize tightly compressed or moderately 
compressed sheet pulp in a defibrator, it has been proposed that the pulp 
be first dry-shredded to pieces from 1/2 to 11/2 inches in diameter, which 
pieces can then be fed to the defibrator, such as, for example, a disc 
defibrator. When this is done, however, it is very difficult to achieve a 
uniform and constant discharge rate of defibrated pulp fibers from the 
defibrator, with the result that it is not possible to discharge the 
defibrated pulp material directly to a batt-forming machine. If the feed 
of defibrated material to the batt-forming machine is not uniform, the 
batts that are formed have varying proportions of fibers per unit area, 
with a resulting variation in density. 
Why it is difficult to obtain a uniform discharge rate from a defibrator 
when using shredded pulp as the starting material is not easy to explain. 
The pulp particles from the shredded do tend to have a variable 
consistency, possibly because friction in the shredder imparts varying 
electrostatic charges to the particles. The particles as a result have a 
variable tendency to adhere to one another to form clumps, and the 
resulting clumps have differing degrees of coherence. 
In any event, the fiber batts obtained in such processes have varied 
considerably in density from one portion to the next, which in turn has 
resulted in varying uniformity in the products made therefrom, such as 
diapers, sanitary pads, compresses, and the like. 
In an attempt to counteract the variations in density, it has been proposed 
that a peg-roller or similar milling member operate in contact with the 
surface of the batt, to smooth the batt to a uniform thickness, and give 
it an even surface. This has not been successful in increasing the 
uniformity of the batt material, because the cellulose fibers have a 
tendency to adhere to the roller between the pegs, and wind up on the 
roller, with the result that eventually the pegs are completely buried in 
a mass of fibrous material, and can no longer function to pick up fibrous 
material from the surface of the batt. This problem is particularly 
serious when an excessive amount of fibers is fed to the batt-forming 
machine, which excess is removed by the peg roller. Moreover, a peg roller 
cannot of course compensate by adding fibers to the batt surface when an 
insufficient proportion of fibers is fed to the batt forming machine, a 
condition which is equally responsible for variations in the density of 
the batt. 
In accordance with the present invention, a method and apparatus are 
provided which make it possible to control the feed of shredded, 
defibrated cellulose pulp material to a batt-forming machine according to 
the rate of output of batt from the machine. This output rate is adjusted 
according to the amount of fibrous material removed from the surface of 
the batt, determined, for example, in terms of the loading on a milling 
member such as a peg roller during removal of fibrous material thereby. It 
is apparent that when an excessive proportion of fibers is fed to the 
batt-forming machine, the loading on the milling member, such as a peg 
roller, will increase, and when the proportion of fibers fed to the 
batt-forming machine decreases, the loading on the milling member, such as 
a peg roller, will decrease. 
Accordingly, in accordance with the invention, apparatus is provided for 
sensing the load of fibrous material removed by the milling member, such 
as a peg roller. When this load increases beyond a predetermined amount, 
the rate of feed of shredded defibrated cellulose material to the 
batt-forming machine is decreased correspondingly. When the loading on the 
peg roller decreases below a predetermined amount, the rate of feed of 
shredded defibrated cellulose material to the batt-forming machine is 
increased correspondingly. Thus, the rate of feed is controlled according 
to the loading on the milling member, with the result that a more uniform 
batt is produced, and variations in the rate of feed from the shredder and 
the defibrator are automatically compensated for by an increase or a 
decrease in the rate of shredding and/or defibration, respectively. 
The method and apparatus of the invention are particularly adapted for use 
with moderately compressed and tightly compressed cellulose pulp material, 
such as moderately compressed or tightly compressed cellulose pulp rolls 
and sheets, but are of course applicable to loosely compressed cellulose 
pulp material as well, although application to such material is obviously 
less economic, and therefore such material would not be used except under 
unusual circumstances. 
The process of the invention includes the steps of dry-shredding tightly 
compressed or moderately compressed cellulose pulp material to reduce the 
material to particulate form; feeding the shredded cellulose pulp material 
to a dry-defibrating stage; dry-defibrating the shredded particles; 
feeding the shredded and defibrated cellulose pulp material to a 
batt-forming stage; and forming a batt from the resulting material on a 
foraminous support; reducing the resulting batt to a uniform thickness and 
surface smoothness by removing fibers from the surface thereof; sensing 
the amount of fibrous material thus removed; increasing the rate of feed 
of shredded cellulose pulp material to the defibrating stage whenever the 
sensed amount is below a predetermined limit, and decreasing the rate of 
feed of shredded cellulose pulp material to the defibrating stage whenever 
the sensed amount is above a predetermined limit. 
The apparatus in accordance with the invention comprises a dry-pulp 
shredder; a dry pulp defibrator; means for feeding at a selected rate 
dry-shredded cellulose pulp material from the dry-pulp shredded to the 
dry-pulp defibrator; means for feeding dry-shredded dry-defibrated 
cellulose pulp material to a foraminous support and depositing the 
material on the support to form a batt; milling means for removing 
cellulose pulp fibers from the surface of the batt; sensing means for 
determining the loading on the milling means while fibrous material is 
being thus removed; control means responsive to a sensed load below a 
predetermined minimum, to increase the rate of feed of shredded cellulose 
pulp material, and to a sensed load above a predetermined maximum, to 
decrease the rate of feed of shredded cellulose pulp material; and means 
for drawing off the resulting fibrous batt material. 
In order to control the rate of feed of shredded and defibrated cellulose 
pulp material to the batt forming stage, there can be controlled any one 
or all of: 
(1) the rate of feed of compressed cellulose pulp material to the shredder; 
(2) the rate of feed of shredded cellulose pulp material to the dry 
defibrator; and 
(3) the rate of feed of the shredded and dry defibrated cellulose pulp 
material to the batt-forming stage. 
Normally, however, it is sufficient to control only the rate of feed of 
compressed cellulose pulp material to the shredder, since a change in this 
rate of feed automatically results in a corresponding change of the rate 
of feed of the cellulose pulp material in all of the later stages. 
The load sensing means can sense the amount of fibrous material removed 
either directly or indirectly, in any of several ways. 
The means can, for example, measure directly the weight of material removed 
from the fibrous batt, and, when this weight is below a predetermined 
minimum or exceeds a predetermined maximum, adjust the feed rate of 
cellulose pulp material to the batt-forming stage accordingly. 
Although indirect, it is equally accurate and somewhat less cumbersome to 
sense the torque required to rotate or drive a milling means such as a peg 
roller while it is removing excess fibrous material. As the load on the 
means increases, the amount of power required to operate the means also 
increases. Consequently, upon appropriate calibration of the torque in 
terms of power applied to operate the roller, one can note from the torque 
required to operate the means when the load is too light, indicating that 
too low an amount of fibers is being removed, and therefore too low an 
amount of fibers is being fed to the batt-forming stage, as well as when 
the load is too high, indicating that too large an amount of fibers is 
being removed, and therefore the rate of feed of defibrated fibrous 
material to the batt-forming machine is too high. This torque can be 
measured electrically, or electronically, or mechanically, and compensated 
for by changing the rate of feed correspondingly, reducing it or 
increasing it, as required, according to the load sensed. Such a device is 
illustrated in the embodiments shown in the drawings. 
Although the defibrated fibrous material can be supplied to the forming 
conveyor in any suitable known manner and by any suitable known means, it 
is particularly suitable to supply said material by means of a stream of 
air initially in surplus quantities. Normally, the fibrous material is 
supplied to the forming conveyor from above while the surplus material is 
removed in a direction opposite to the direction in which the forming 
conveyor moves, the removed surplus material being subsequently returned 
to the forming conveyor as freshly supplied fibrous material. By 
continuously circulating surplus fibrous material in the supply zone above 
the forming conveyor, variation in supply can be compensated for in part 
by said surplus material. However, it has now been found particularly 
favorable to supply the fibrous material to the forming conveyor according 
to a preferred embodiment of the present invention, in a direction which 
coincides at least substantially with the direction in which the surplus 
material is removed from the web. In this way, removal of the surplus 
fibrous material from the fiber web is greatly facilitated and the 
admixture of surplus fibers and the fibrous material conveyed to the 
housing by the air streams is rendered more effective. This more effective 
admixture of the fibers means that variations in supply of fibrous 
material to the perforated web are equalized by the circulating surplus of 
fibers in a particularly effective manner while using particularly simple 
means.

The apparatus of FIGS. 1 to 3 has three stages: shredding stage A, 
defibrating stage B, and batt-forming stage C. 
Air-borne shredded defibrated fibrous material from the defibrating stage B 
is carried to the batt-forming stage C via conduits 8a, 8b, to and through 
the hood 1, which opens out towards the foraminous batt-forming support 2, 
in the form of an endless conveyor belt. The belt 2 travels around the 
rollers 3,4,5,6, of which roller 3 is driven and rollers 4,5 and 6 are 
idler rolls. A suction box 7 arranged beneath the foraminous belt 2 draws 
a flow of air through the belt, and thereby draws the air-borne fibers 
through the hood down upon the belt, forming a fibrous batt 24 thereon. 
Adjustment of the amount of suction applied in the box 7 according to the 
flow of air through the feed tube 8b is made possible by the air inlet 16 
in the hood 1, which can be opened or closed, as required, to control the 
proportion of bleed air and thereby adjust the amount of suction to the 
required degree. 
The defibrator 9 in the defibrating stage B feeds the defibrated cellulose 
material through the tube 8a to the fan 13, where it is entrained in a 
stream of air and blown through the tube 8b, into the hood 1, where it is 
carried by air flow down onto the belt 2. The dry defibrator 9 is, for 
example, of the disc type. 
Coupled to the defibrator 9 and driven by the motor 10 is a screw conveyor 
11, which carries the shredded pulp from the shredding stage A. The 
shredder 12 is of conventional type, and is designed for shredding tightly 
compressed or moderately compressed cellulose pulp, in roll or sheet form, 
or in bales 15, the form illustrated in the Figure. A conveyor 14 is 
provided for feeding the bales 15 of cellulose pulp to the shredder 12. 
Adjustment of the rate of travel of the conveyor 14 adjusts the rate of 
feed of bales of compressed cellulose pulp to the shredder 12, stage A, 
and whether this is fast or slow of course to some extent controls the 
rate of feed of cellulose pulp material to each of the following stages B 
and C of the system. 
Similarly, control of the rate of feed of shredded pulp material from 
shredder 12 is controlled by the motor controlling the rate of rotation of 
the screw conveyor 11, and control of the rate of feed of shredded and 
defibrated pulp material through the lines 8a, 8b is controlled by the fan 
13. 
Provision is made for reducing the fibrous batt 24 formed on the foraminous 
support 2 beneath the hood 1 to a uniform thickness in the form of the peg 
roller 17, which is rotatably mounted in an antechamber 1a at the exit end 
of the hood 1, in the manner shown in FIG. 2, extending across the 
conveyor belt 2. The motor 18 (see FIG. 3) is arranged to drive the peg 
roller 17. The axle 17a of the roller 17 is journaled in the bearing 
supports 19 (of which only one is shown in FIG. 2) which are movable 
vertically within the guide members 21,22 by the cams 20. The pegs 17b 
pluck fibrous material from the batt 24, and throw the fibers back out 
into the hood 1. 
A second conveyor belt 23 receives the fibrous batt 24 after milling by the 
peg roller 17, and carries it on for further processing or storage. 
The electrically operated control system for the apparatus controlling the 
rate of feed of fibrous material to the batt-forming stage C is best seen 
in FIGS. 3 and 4. In this embodiment, the control system controls the rate 
of rotation of the screw conveyor 11, and thereby the rate of feed of 
shredded pulp material from the shredding stage A to the dry defibration 
stage B. However, one could also control the rate of movement of conveyor 
14, or of fan 13, alternatively or together. 
The control system, as is best seen in FIG. 3, includes a current 
controlling means 25, provided with a rectifier in electrical connection 
with the motor 10 of the screw conveyor 11, and an electric power supply 
26 via the switch 30. The current controlling means 25 may, for example, 
be of the type ASEA QALB 200. 
The current controlling means 25 is also in electric connection with a 
current transformer 28, which in turn is coupled between the peg roller 
motor 18 and an electric power supply 27 via the switch 31. 
The current controlling means 25 is also in electric connection with a 
potentiometer 29, which is manually adjustable so as to control the speed 
of the screw conveyor 11. The switches 30,31 put the motors 10,18, 
respectively, in connection with the power supply 26,27, and thereby start 
and stop the motors. 
Operation of the apparatus is as follows: First, there are started, in 
order, the suction box 7, the peg roller 17, the fan 13, the defibrator 9, 
the conveyor 11, the shredder 12, the conveyor 2, the conveyor 23, and the 
conveyor 14. A starting feed rate for the screw conveyor 11 is established 
with the aid of the potentiometer 29, manually, such that the loading of 
the peg roller 17 is less than capacity. Pulp bales 15 are sent to the 
shredder 12 via the conveyor 14, where they are shredded into pieces from 
one half inch to one inch in diameter (1 to 2.5 cm). The shredded pulp is 
conveyed by the conveyor 11 to the defibrator 9, where it is defibrated 
and then discharged via line 8a to the fan 13, and then entrained in air 
and blown through the conduit 8b into the hood 1. The suction box draws 
the air and air-borne fibrous material down onto the foraminous conveyor 
2, where the batt is formed by straining fibrous material out of the air 
flow. The control valve 16 is set to reduce the degree of suction to the 
desired value, usually established with a view to the density of the 
fibrous batt on the belt 2. The air in the suction box 7 is vented through 
the suction exhaust system, which is not shown. 
The rate of feed is sufficient initially to always maintain and circulate a 
certain surplus between the peg roller 17 and the belt 2, such that the 
fibrous batt formed is slightly thicker than required, as a result of 
which some fibrous material is drawn off the top by the rapidly rotating 
peg roller 17, reducing the fibrous batt to the desired thickness, and at 
the same time smoothing it. The removed fibrous material is thrown back 
into the hood. The resulting batt is withdrawn from the hood and carried 
on the conveyor 2 onto conveyor 23, for further processing or storage, 
such as, for example, subdivision into absorbent pads for diapers, 
sanitary pads, compresses, and the like. 
At the beginning of this operation, the current controlling means 25 
receives a current from the current transformer 28 indicating a loading on 
the peg roller below a predetermined minimum. This loading however 
gradually builds up as the fibrous batt is formed, and increases in 
thickness, and eventually the loading on the peg roller falls within the 
range of normal operation (for which the potentiometer 29 is set), above 
the predetermined minimum, and below the predetermined maximum. 
While the loading is below the predetermined minimum, the current 
controlling means delivers a signal corresponding to a below normal 
loading and as a result the rectifier increases the supply of current to 
the motor 10 of the conveyor 11, which increases the speed of the conveyor 
11, which increases the rate of feed of shredded and defibrated fibers to 
the batt-forming stage C, and this in turn increases the rate of loading 
on the peg roller 17, so that it reaches a value above the predetermined 
minimum, less than the predetermined maximum. When this point is reached, 
the rate of feed is slowed to within the normal range by slowing down the 
conveyor 11, as the result of a reduction in current flow of the motor 10. 
If the supply of fibrous material to the hood 1 increases, such that the 
loading on the peg roller 17 and consequently on the peg roller motor 18 
exceeds the predetermined maximum value set on the potentiometer, the 
current controlling means 25 delivers an above-normal signal, following 
which the rectifier reduces the supply of current to the motor 10 of the 
conveyor 11, which reduces the speed of the conveyor 11, and results in a 
reduced flow of fiber material through the defibrator 9 and to the hood 1. 
In this way, the rate of feed of shredded fibrous material to the 
defibrator is controlled exactly according to the loading on the peg 
roller 17, so that the loading of the peg roller 17 is held essentially 
constant, above the predetermined minimum and below the predetermined 
maximum. 
The rate of feed of fibrous material to the conveyor 2 can of course be 
controlled in other ways. 
In another embodiment, the torque required to rotate the peg roller at the 
desired speed is used directly to control the speed of the conveyor 10 
through the control member. An example of such a system is shown in FIG. 
4, in which the peg roller motor 18 is movably supported in a stationary 
frame 32. A torque arm 33 is rigidly fixed to the motor. The arm 33 is 
connected to a control resister 34, which through a rectifier 35 controls 
the current supplied to the conveyor motor 10 in response to the angular 
movement of the motor 18 in the frame 31. As this angular movement is 
substantially proportional to the loading on the motor 18, an automatic 
control of the speed of the conveyor 11, as a function of the loading on 
the peg roller, is obtained. 
FIGS. 5 and 6 show a second embodiment of the apparatus of the invention. 
In these drawings, some portions of the structure are the same as the 
structure of FIGS. 1 to 4, and consequently, these portions have been 
identified by the same reference numerals. 
In this embodiment, the entry of the air-borne shredded defibrated fibrous 
material into the batt-forming stage is by way of the conduit 8b, which 
directs the flow of air-borne fibers substantially horizontally, rather 
than vertically, beneath the hood 1b. At the inlet 36, there is a nozzle 
37, which ejects the air-borne fibers substantially horizontally at 
considerable velocity into the hood, in a trajectory over and beyond the 
peg roller 17. 
A baffle 38 serving as a guide plate may be arranged beside the peg roller 
17, and receives and guides fibers which are thrown off the roller 
following their removal from the batt 24. The removed fibers proceed at 
some velocity along the surface of the baffle 38, and are thrown into the 
rapidly moving stream of air-borne fibers emerging from the nozzle 37 at 
the inlet port 36, and are thereby reentrained in the air flow, and 
redeposited on the foraminous support 2. It will thus be evident that the 
trajectory of the fibers thrown off the peg roller 17 follows the same 
general direction of flow of the air-borne fiber stream from the nozzle 
37, which greatly facilitates reentrainment of the removed fibrous 
material into the air stream. 
This apparatus operates in the following manner: A number of bales 15 of 
compressed pulp are placed on the conveyor 14. A reduced pressure is drawn 
on the suction box 7, and the valve 16a is opened to the desired degree. 
The peg roller 17, the shredder 12, the defibrator 9, the conveyors 2, 11, 
14 and 23, and the fans 13 are then turned on, in that sequence. The bales 
are then fed in sequence into the shredder, where they are shredded into 
pieces from 1/2 to 11/2 inches in diameter. The shredded pulp is carried 
by the screw conveyor 11 to the defibrator 9, where the pulp is 
defibrated, and the fibers released. The defibrated pulp is discharged 
through the conduit 8a to the fan 13, and then entrained in an air stream 
blown through the conduit 8b, nozzle 37, and inlet port 36 into the hood 
1b. 
The air-borne fibrous material is drawn down with the air carrying it onto 
the foraminous support 2, while the air passes through the support. Before 
doing so, the fibers may strike and bounce off the rear wall 1c of the 
hood 1b, but the fibers are nonetheless eventually deposited on the 
foraminous support 2 to form a batt 24. According to the degree of opening 
of the valve 16a, the degree of suction applied for drawing the fibers 
down on the foraminous support can be adjusted so as to avoid drawing an 
excessive suction, with a resulting disturbance in the fiber deposition. 
The air drawn into the suction box 7 through the support 2 is discharged 
continuously therefrom. 
In the start-up of operation, surplus fibrous material is charged to the 
housing 1b. This fibrous material together with the air-borne fibrous 
material is laid down on the foraminous support. The rotating peg roller 
17 removes excess fibrous material above a predetermined thickness, and 
throws such fibrous material outwardly toward the baffle 38, whence it is 
carried into the airborne fiber stream from the nozzle 37, where it is 
returned to the air-borne fiber stream fed to the foraminous support 2, 
where, once again, the fibrous material is drawn down upon the conveyor. 
As the peg roller 17 removes excess fibrous material from the batt 24, it 
smooths the surface of the batt to an even thickness, and breaks up any 
clumps of fibers which may have formed. 
In the same manner as in the apparatus of FIGS. 1 to 3, the speed at which 
the conveyor 11 moves is automatically controlled by the electrical 
circuit shown in FIG. 3, in a manner such that the load on the peg roller 
is kept substantially constant, and within the limits of above the 
predetermined minimum, and below the predetermined maximum. 
After passing the peg roller 17, the batt 24 is discharged from the housing 
1b, and transferred from the support 2 to the conveyor belt 23, whence it 
passes to a processing station, where it can for example be either wound 
up or cut into absorbent pads, diapers, compresses, and the like. 
An excess of fibrous material is intially charged to the housing 1 in order 
to provide a circulation of excess material within the hood. This assists 
in maintaining uniformity of density of the batt formed, and compensates 
for any irregularities in the feed of shredded defibrated cellulose pulp 
material to the hood 1b. The result is an improved uniformity. 
Moreover, in this embodiment, since the trajectory of the air-borne fibers 
from nozzle 37 intersects the trajectory of the fibers from roller 17, the 
circulation path of the fibers within the hood 1b is very short. This, 
taken in conjunction with the automatic control of the load on the peg 
roller, affords the additional advantage that the amount of power required 
for effecting circulation of the excess fibers is correspondingly low, and 
the circulation of excess material can in fact be obtained solely by means 
of the peg roller and the flow of air-borne fibers through the nozzle 37. 
It will be apparent that in lieu of one peg roller, two or more peg rollers 
can be provided. Moreover, the roller need not be provided with a 
plurality of pegs, but any milling means can in fact be provided, with any 
kind of surface that can engage, pluck or otherwise remove fibers from the 
surface of the batt, such as a brush surface, a toothed surface, a knurled 
surface, or a grooved surface. 
It is also possible to divide the suction box 7 into separate compartments, 
each with separate suction means, and each if desired with its own peg 
roller or similar milling means. This serves to prevent variations in 
thickness and density of the batt on the foraminous support 2, upstream of 
the peg roller, from causing corresponding changes in the suction box, and 
thereby local variations in the density of the batt. 
In the embodiment of the invention illustrated in FIG. 7, the foraminous 
support 2 is replaced by a hollow drum 41, rotatably mounted with a 
foraminous cylindrical surface. In this case, as seen in FIG. 7, the hood 
1e is of an arcuate configuration, and is arranged above the drum 41 so as 
to extend substantially from one end of the drum to the other end, and 
encloses an arc segment of the cylindrical surface of the drum, with the 
inlet opening 36a oriented for introduction of a flow of air-borne fibers 
in the direction of rotation of the drum. This device also includes a peg 
roller 17, and a baffle 38, operating in the same manner as the device of 
FIGS. 5 and 6. While the embodiment illustrated has only one peg roller, 
several peg rollers can be provided, as described above. 
The suction box 42 is arranged within the drum, directly beneath the hood 
1e, and, like the hood, is fixed against rotation. The suction box can be 
divided into separate chambers, each provided with independently operated 
suction means, if desired. 
The formed batt after milling to reduce it to a uniform thickness and 
surface smoothness is discharged from the drum surface onto the conveyor 
23 at a portion of the drum beyond the suction box, so that the batt is no 
longer held down on the drum surface. 
In this embodiment, also, an excess of fibrous material is initially 
charged to the hood 1e, and circulates therein throughout the batt forming 
operation. 
In other respects, the operation of the device is as described in 
connection with the previous embodiments. 
While it is particularly suitable to carry the defibrated fibrous material 
air-borne to the foraminous support, and form the batt thereon by 
deposition from the airstream, the shredded defibrated fibrous material 
can also be carried to the foraminous support in other ways, such as, for 
example, by a screw conveyor, and then dropped upon the foraminous support 
by gravity. Deposition can be expedited by a flow of air through the valve 
16, as shown in each of the embodiments, the air aiding in carrying the 
fibers down onto the surface of the foraminous support. However, air-borne 
fibers are more advantageous in obtaining a uniform distribution of fibers 
throughout the surface of the foraminous support, during laydown.