Method and apparatus for laying up strands

Strand lay-up system produces a layered strand lay-up from separate feed bins and then deposits incremental lengths of the so formed layered lay-up over discrete selected area to form a more homogenous lay-up.

FIELD OF THE INVENTION 
The present invention relates to the method and apparatus for producing a 
lay-up, more particularly, the present invention relates to an apparatus 
for producing a more uniform density lay-up. 
BACKGROUND OF THE INVENTION 
In the manufacture of oriented strand board (OSB) panels or the like, it is 
generally preferred to produce a lay-up having a core that has distinctly 
different characteristics from that of the two surface layers either for 
strength purposes, i.e. if the surface layers are stronger in bending than 
the core layers, this strength is more effectively used close to the 
surface of the panel. In other cases, it is desired to have a particular 
surface finish which requires the positioning of the particles that will 
produce that finish adjacent to the faces of the finished product. 
In most cases, the less desirable material is contained in the core where 
it is not directly visible and does not contribute significantly to the 
strength of the panel in bending. 
In the manufacture of lumber products using oriented strand board (OSB) 
technology, it is more desirable to have a uniform or homogenous 
cross-section in the resultant composite product which may be obtained in 
part by using essentially the same furnish in each of the layers used to 
form a lay-up for an OSB product. In any of these processes, depending on 
the pressing, there is likely to be a hardened skin or surface layer 
produced during the pressing operation. These skin or high density surface 
areas contribute significantly to the Modulus of Elasticity (MOE) or 
stiffness of the end product in bending when tested via forces applied 
perpendicular to the face or surface of the panel. 
In the manufacture of oriented strand lumber (OSL) the degree of 
orientation of the strands to the longitudinal axis of the product plays a 
significant role in defining the strength characteristics of the resultant 
product. Orientation of the strands is obtained generally by passing them 
through orienting passages. In some conventional orienters, parallel 
rotating disks define the sides of the orienting passages and the spacing 
between disks defines the passage width which contributes significantly to 
the degree of strand orientation, i.e. the smaller the spacing, the better 
the orientation. However, the degree of strand orientation is also 
dependent on the height of the disks above the mat or lay-up being formed 
and a number of other factors. Normally, the strand orientation in the 
manufacture of ordinary OSB products is done using a single deck of 
parallel disks adjacent to the surface of the mat and passing the strands 
between the disks. Those strands that do not immediately fall between the 
disks are carried along the surface of the disks towards one end of the 
orienter. See for example, U.S. Pat. No. 3,115,431 issued Dec. 24, 1963 to 
Stokes or U.S. Pat. No. 4,666,029 issued May 19, 1987 to Burkner. In the 
devices described in both of these patents, the rotary disks carry the 
longer strands that do not pass directly between the disks along the top 
of the disks toward one end of the orienter. 
U.S. Pat. No. 5,325,954 issued Jul. 5, 1994 to Crittenden et al. describes 
an improved strand orienter that facilitates orientation and production of 
a more homogenous mat. However, the decks still tend to carry the longer 
strands toward one end of the orienter. 
U.S. Pat. No. 5,487,470 issued Jan. 30, 1996 to Barnes describes an 
orienter that overcomes many of the problems of the prior art with respect 
to producing a more uniform density mat with the oriented strands. 
However, the density of the mat is obviously dependent on the uniformity 
of infeed to the orienter and the relative uniformity of the dispersion of 
the strands over the area of the infeed end of the orienter as the strands 
tend to pass substantially directly downward therethrough. 
WO96/15299 published May 23, 1996 by Barber, discloses independently driven 
conveyors in sequence, each with a weighing means and each having its 
speed controlled based on the weight sensed thereon to meter the flow of 
material. 
BRIEF DESCRIPTION OF THE PRESENT INVENTION 
It is an object of the present invention to provide an improved lay-up 
system for producing a more homogenous lay-up of oriented strands into a 
mat. 
Broadly, the present invention relates to a system for producing a lay-up 
of strands comprising a plurality of lay-up heads, a receiving conveyor 
for receiving a layer of strands formed by each of said lay-up heads to 
produce layered lay-up, a distributing conveyor having a variable length 
upper reach terminating at a free end, means to move said free end between 
an extended position and a retracted position and deposit selected lengths 
of said layered lay-up over selected distances and means for collecting 
said strands discharging from said free end of said distributing conveyor. 
Preferably, an orienter will be positioned between said distributing 
conveyor and means for collecting to orient said strands passing to said 
mean for collecting. 
Preferably, a preorienter will be positioned between each of said lay-up 
heads and said receiving conveyor. 
Preferably, said system will further comprise means for continuous by 
weighing discrete lengths of said layered lay-up and computer means for 
controlling movement of said free end based on said weights of said 
discrete lengths of lay-up to control the rate of discharge per unit 
movement of said free end to provide the desired distribution by weight of 
said strands on said means for collecting as said free end moves between 
its extended position and its retracted position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The system shown in FIG. 1 shows a collecting and receiving conveyor 10 
that receives strands or the like as indicated by the arrows 12 from a 
plurality of feed bins or lay-up heads 14, in the illustration four are 
shown (there may be fewer or more) and are indicated at 14A, 14B, 14C and 
14D. The strands from these bins or lay-up heads 14A, 14B, 14C and 14D 
form layers A, B, C and D respectively of the layered mat or lay-up 16. 
Preferably, each of the feed bins 14 will direct the strands through an 
orienter schematically indicated at 18 (A, B, C and D respectively). 
Thus, each of the bins 14A, B, C and D preferably deposits strands as 
represented by arrows 12A, B, C and D through an orienter 18A, B, C and D 
respectively onto the conveyor 10 to form the layers A, B, C and D 
respectively of the stratified or layered lay-up 16. Each of the layers A, 
B, C and D is preferably oriented in a desired direction. The lay-up 16 is 
then transferred to a distributing conveyor 20 which wraps around a 
plurality of rolls including a movable dancing roll 22 and a movable front 
or nose roll 24 movement of which adjusts the length of the upper reach 26 
of the conveyor 20 between the rolls 28 and 24 thereby changing the 
effective length of the conveyor 20. Suitable means schematically 
illustrated by the arrows 30 and 32 impart the required movement to the 
rolls 22 and 24 respectively and thereby adjust the effective length of 
the conveyor and the location of the off feed point (roll 24) relative to 
a collecting surface 34. 
The collecting surface or conveyor 34 onto which strands leaving the free 
end of the conveyor are dropped as indicated by the arrows 36 is 
positioned below the free end roller 24. It will be apparent that as the 
roll 24 is moved to the left, the drop off or off feed point from the 
conveyor 20 above the platform or conveyor 34 is changing. It will further 
be noted that the front face of the lay-up 16 is dropping off the end of 
the conveyor 20, i.e. along the front of the roll 24 so that each of the 
layers A, B, C and D are mixed and deposited on the platform 34 over a 
corresponding incremental length of the final lay-up 38 formed on the 
collecting surface or platform 34. 
When the end roller 24 reaches its extreme left hand position (retracted 
position 25 (see FIG. 2)), i.e. adjacent to the roll 28, the system may be 
operated in at least a couple of ways. One way is to advance the roll 24 
preferably at a speed equal to the speed of the upper reach 26 of the 
conveyor so that in effect, the conveyor 26 and the roll 24 have 
essentially zero relative speed and since the roll 24 is advancing as fast 
as the layered lay-up 16, there is no movement of strands off of the 
conveyor 20 and onto the platform 34. This continues until the roll 24 
reaches its extreme right hand position (extended position) 25 (see FIG. 
2). This position 27 is sensed by any suitable movement such as sensor 70 
(to be described below). The roll 24 then begins to move in the opposite 
direction, i.e. back towards the roll 28 and to disperse the strands from 
the lay-up 16 onto the final lay-up 38. The final lay-up 38 may be formed 
by collecting a number of different layers until the required thickness of 
the lay-up or feeding, for example, to a press, if one is making a strand 
board. 
The timing of movement of the lay-up 38 when it is compiled to the required 
thickness preferably by removing the lay-up while the upper reach 26 of 
the conveyor 20 is being extended by moving the roll 24 from its extreme 
left-hand 25 position to its extreme right-hand extended position 27 and 
then commence the formation of a second lay-up 38 from this position. 
When oriented strand board is being produced, it is preferred to provide a 
further or second orienter schematically illustrated at 40 to improve the 
alignment of the strands as they fall as indicated at 36 towards the 
collecting surface 34 so that the strands in the lay-up 38 are relatively 
accurately aligned. 
The degree of alignment of the strands and the lay-up 38 is determined by 
the widths of the passages in the orienter 40 and the height of the 
orienter 40 from the upper surface of the partially formed lay-up 38 as 
the lay-up is being produced and is also significantly influenced by 
preorienting the strands via the orienters 18, i.e. if the strands in the 
layers A, B, C and D of the lay-up 16 are preoriented, the orienter 40 may 
be made with fewer decks since the orienters 18 have done a preorienting 
job, i.e. if the orienter 40 is an orienter as described for example in 
U.S. Pat. No. 5,487,460 issued Jan. 30, 1996 to Barnes because the strands 
and lay-up 16 have been at least partially oriented, the width of the top 
passages in the orienter 40 may be narrower and thus, it may be possible 
to reduce the number of decks required for a given orientation of the 
strands in the lay-up 38. To maintain a short spacing between the top of 
the lay-up 38 and the bottom of the orienter 40, the collecting surface is 
shifted away from the orienter 40 as each layer of the lay-up 38 is 
completed (as schematically indicated by the arrows 66 in FIG. 2). 
Another mode of operation, the system to deposit strands on the receiving 
surface or conveyor 34 is to control the movement of the roll 24 in the 
manner different than that described above in that strands continue to be 
dispensed as the roll 24 at the rate the mat 16 is being advanced by the 
conveyor 20 less the movement of the roll 24 toward the extended position, 
i.e. when the roll 24 is moving. From the extended to the retracted 
position movement of the roll decreases the mount of weight of strands per 
unit area or length of the receiving surface 34, i.e. per square foot or 
per lineal foot. Similarly, increasing the velocity of the roll when 
dispensing strands and when movement of the roll is from the retracted to 
the extended position, decreases the number of strands dispensed per unit 
length of the receiving surface 34. 
Dispensing strands when movement of the roll is alternatively in both 
directions, obviously simply doubles the number of layers for a given 
output from the receiving conveyor 10. 
The calculation of the feed rate will be discussed in more detail 
hereinbelow. 
It will be apparent that when the required height or thickness of lay-up 38 
is obtained, it will still preferably be removed from the surface 34 as 
the roll 24 is being extended from its retracted to its extended position, 
preferably at a rate equal to the rate of movement of the upper reach 26 
of the roll 24 so that no partial layer is formed during the removal. 
In the preferred arrangement shown in FIG. 2, the mat or lay-up 16 is 
formed in essentially the same manner as described above. However, 
incremental lengths of the lay-up 16 are weighed as indicated at 42 to 
provide a weight indication 44 which is delivered to a computer 46 and 
operates a controller 48 to control the movements 30 and 32 of the rolls 
22 and 24 respectively as indicated by the control lines 50 and 52. 
The system illustrated in FIG. 2 is able to account for some fluctuation in 
the weight or density of the mat 16 along its length. 
This is schematically represented in FIG. 2 by showing the curve M 
indicating the actual mass of the mat 16 along its length and M indicating 
the average or mean weight over preferably the full length from the weight 
scale 42 to the free end 24 with the roller 24 extended to the right as 
far as possible. It will be apparent that the instantaneous mass is 
indicated by the mass M0, M1, M2, M3 passing over the end of the conveyor 
24 is dependent on the velocity of the belt indicated as V.sub.1i and the 
velocity of the roller 24 indicated as V.sub.2i and the distance over 
which the mass is deposited is based on V.sub.2i multiplied by the time 
increment. 
Thus, the feed off the end of the moving roll 24 from the retracted 
position 25 toward the extended position 27 is equal to 
EQU F.sub.1 =(V.sub.2i +V.sub.1i)M.sub.i (1) 
where 
V.sub.1i =the velocity of the belt 20 
V.sub.2i =the velocity of the roll 24 toward the retracted position, i.e. 
toward the roll 28 
M.sub.i =the mass for the instantaneous increment of the mat 36 passing 
over the end of the roll 24 in lb/ft.sup.2 and 
F.sub.1 =the rate of flow in lb/min of the strands on the belt 20. 
It will be apparent that when movement of the roll 24 is from the retracted 
position 27 toward the extruded position 25, the velocity V.sub.2i is 
negative. 
The amount of material deposited per unit length of the collecting surface 
34 is determined by the formula 
EQU F.sub.2 =F.sub.1 /V.sub.2i (2) 
where F.sub.2 =flow per unit length, i.e. lb per lineal foot of the 
platform 34. 
By substituting for F.sub.1 in Equation (1), it is apparent that F.sub.2 is 
equal to 
##EQU1## 
which may be then manipulated to indicate the instantaneous set point 
value for V.sub.2i as a function of M.sub.i as follows: 
##EQU2## 
It will be apparent that in the above described system, the velocity 
V.sub.1i will be substantially constant. F.sub.2 represents the weight per 
unit length of strands received on the collecting surface 34 per pass or 
per layer being laid down which may be set as desired. Obviously, the 
velocity V.sub.1i and the rate of feed which determines the average flow 
rate of materials, i.e. M are related and if the mass flow on the conveyor 
V.sub.1i is too high for the desired weight to be applied per unit length 
of the receiving platform 34 the system will not work to deliver the 
required flow. Also, if the fluctuations are too steep, the instantaneous 
change of velocity of the roll 24 may have to be too great to obtain the 
desired result. If the flow rate and velocity V.sub.1i is too high, the 
movement of the roll 24 will reach a maximum and stay there. If the flow 
rate fluctuations are too rapid, i.e. too high in amplitude, the reaction 
of the roll 24 may not be sufficiently rapid to accommodate significant 
changes in mass on the conveyor 20. Generally, the mass flow rate on the 
conveyor 10 will be coordinated with the desired flow to the upstream 
equipment and to the density of the mat or lay-up 38 to be formed on the 
collecting surface 34. 
On the other hand, if the flow rate on conveyor 10 is too slow, i.e. mass 
flow M is very low, the rate of movement of the roll 24 will simply be 
very slow and the production rate will be reflected accordingly. However, 
the mat formed on the receiving conveyor 34 will still have a relatively 
uniform weight profile near the desired F.sub.2 lb per lineal foot. 
To implement the above control, the weight scale 42 (or volume sensor) will 
determine the weight as indicated at 44 and input a shifting register 60 
with the various incremental weights M.sub.p, M.sub.p-1, M.sub.p-2, . . . 
M.sub.p-n etc. of the mat 16 measured, for example, as pounds per 
incremental length along the upper surface or reach 26 of the conveyor 20 
(see FIGS. 2 and 3) in sequence and recorded as measured. 
The location of the roll 24 may be determined in a number of different 
ways. The sensor 70 determines when the roll 24 is in extended position 
and this information may be used as a base position of the roller 24 over 
the surface 34 and the position is calculated as the roll 24 is moved 
relative thereto. If desired, a second sensor 72 may be provided to 
determine and notify the computer controller 46 that the roll 24 is in 
retracted position. The position of the roll 24 is determined as indicated 
at 62 based on input from the sensors 70 (and/or 72) via line 74, the 
velocity V.sub.2i and elapsed time from the base point 72 to give distance 
from the base point and thus, the location of roll 24, i.e. the then 
current position L.sub.i. The corresponding measured mass per unit length 
of the mat M.sub.i at location L.sub.i is known since the particular 
register at the location L.sub.i is known and the mass M.sub.i is inputed 
to the velocity V.sub.2i set point control 48. 
The shifting register 60 shifts to the next register in the sequence based 
on the velocity V.sub.1i of the conveyor 20, i.e. velocity V.sub.1i after 
the time to travel the distance d equivalent to the length on conveyor 20 
of one register or increment M.sub.i of weight, i.e. 
##EQU3## 
The position of Mi on conveyor 20 is deemed calculated based on velocity 
V.sub.1i and time and position of the end point 24 by velocity V.sub.2i 
and time or each may be individually sensed or determined by encoders or 
the like. 
The set point velocity control 48 is operated in accordance with Equation 
(4) to define the set point velocity V.sub.2i that will dispense the 
required mount of material off the end of the conveyor 20 adjacent to the 
roll 24 over a selected length of the collecting conveyor or surface 34 to 
obtain the required amount or weight of material per lineal foot of the 
surface 34. 
It will be apparent that the above system normally lays down a number of 
different layers as indicated by Pass 1, Pass 2, Pass 3, Pass 4, to 
produce the required thickness of mat 38. To do this and maintain maximum 
alignment, it is preferred to move the platform 34 as indicated by the 
arrow 66 to maintain space between the top of the mat 38 and the lower 
edge of the orienter 40 small so that the strands falling from the 
orienter do not lose too much of their orientation. 
The collecting conveyor, when a lay-up is completed, must remove the lay-up 
and be in position to collect the first layer of the next lay-up in the 
time the roll 24 is moving to extended position 27. 
The above description has dealt primarily with the dispensing of material 
while roll 24 moves toward the roll 28. If desired, and as above 
described, by setting V.sub.2i as a negative value, when the roll 24 is 
moving from retracted 25 to extended position 27, the system may be 
operated to dispense the required amount of material per unit length of 
the receiving conveyor 34 as the roll 24 is moved from its left hand 
position 25 to its extreme right hand position 27. Thus, the system may 
lay the mat 38 either with the roll 24 moving to the left or to the right 
or both to provide layers of the desired density as set by the value 
F.sub.2. 
The above description has also been directed to weight, it could equally 
well be applied to volume by using a suitable sensor to sense the volume 
(height) of material on the conveyor 26 along incremental lengths and 
operate the control of the movement of the roll 24 to apply the 
appropriate volume at the appropriate location to form a lay-up with the 
desired volume at the selected locations along the collecting conveyor 34. 
While the above description has primarily been concerned with forming a 
uniform distribution on the collecting conveyor 34, it will be apparent 
that, for example, if a non-uniform depth mold were to be filled, the 
movement of roll 24 could be programmed accordingly to distribute material 
as required to fill the mold, say, to a uniform height or level relative 
to the conveyor 26. 
Having described the invention, modifications will be evident to those 
skilled in the art without departing from the scope of the invention as 
defined in the appended claims.