Non-woven fibrous glass mat and a method and apparatus for efficiently producing same

A non-woven fibrous mat of generally random fiber orientation with built up lines or strips of fiber formed therein directionally oriented to enhance the strength and/or appearance of a mat and a method and apparatus for efficiently producing the same by differentially controlling dewatering in a wet mat process.

BACKGROUND OF THE INVENTION 
This invention relates to a non-woven fibrous mat, and more particularly to 
a non-woven fibrous mat manufactured from a wet mat process. In such a 
process staple and nonstaple glass fibers, natural fibers or synthetic 
fibers, or blends of these fibers dispersed in chemically treated water 
are transferred to the forming section or headbox of a wet mat machine and 
applied to a continuous moving forming belt traveling through the forming 
section or headbox of the wet mat machine by the flow of liquid from the 
headbox through the continuous moving forming belt. The flow of the liquid 
is controlled by means such as a vacuum applied from vacuum boxes located 
beneath the continuous traveling forming belt which causes the liquid to 
flow from the headbox and through the forming belt, and the dispersed 
fibers to be deposited onto the top of the continuous traveling forming 
belt forming a continuous non-woven web of fibers thereon. After leaving 
the headbox, the continuous non-woven web of fibers is conveyed onto a 
moving belt and transported to a binder applicator where binder is applied 
and the continuous nonwoven web of fibers is transported to a drying oven 
to dry the binder. 
More specifically, this invention relates to a nonwoven fibrous glass mat 
of generally random fiber orientation having formed therein some fibers 
oriented in specific directions and in specific patterns for the purpose 
of enhancing both the appearance and the strength of the mat. 
In addition, this invention relates to a method and apparatus for 
manufacturing a non-woven fibrous glass mat having the properties and 
characteristics of the mat described above. 
Prior to the present invention, all of the fiber in a non-woven glass fiber 
mat produced in the manner described above was oriented in a random 
fashion and a woven scrim fabric was often laminated onto the mat to 
enhance its appearance and strength. 
It is an object of the present invention to provide a non-woven fibrous 
glass mat of the type produced from a wet mat process described above in 
which some of the fiber forming the mat is formed in specific 
configurations to enhance the strength and appearance of the mat. 
It is a further object of the present invention to provide methods and 
apparatus for efficiently producing the mat described above. 
SUMMARY OF THE INVENTION 
The present invention is based on the discovery that the most efficient 
manner in which to enhance the appearance or strength of a non-woven 
fibrous mat is to form portions of the mat wherein the fiber contained 
therein is built up and oriented in a particular direction, so as to 
provide reinforcement and enhanced appearance therefor. This discovery is 
coupled with the further discovery that by differentially controlling the 
flow of the liquid through various areas of a continuous traveling forming 
belt in a wet mat process, one can control the thickness and orientation 
of the fibers of the continuous non-woven web belt.

DESCRIPTION OF THE INVENTION 
Referring to the drawings, in FIG. 1 there is illustrated a forming section 
or headbox, generally identified by the reference numeral 2, of an 
apparatus known as a wet process non-woven fibrous mat making machine. As 
shown in the drawing, glass or synthetic fibers, or blends of glass and 
synthetic fibers 3 dispersed in chemically treated water 4, are 
transferred to the forming section or headbox 2. In the forming section 2 
a continuous traveling or moving forming belt 8 passes through the 
dewatering headbox or forming section 2. A vacuum applied by a series of 
vacuum boxes 10 located beneath the traveling forming belt 8 removes the 
water from the dewatering area 7 of the headbox 2 through the continuous 
traveling forming belt 8 and the dispersed fibers 3 are deposited onto the 
continuous traveling forming belt 8 forming a continuous fibrous web 6 
thereon. After leaving the headbox 2 the fibrous web is conveyed on a 
moving belt and transported to a binder applicator 12 and then to a drying 
oven 14 to dry the binder. 
The fiber orientation of the wet-laid non-woven mat produced by this 
process is random resulting at times in a mat having less than desirable 
tensile strength. 
However, in the present invention this deficiency is overcome by producing 
a mat with greatly increased tensile strength. This is achieved by forming 
portions of the mat wherein the fiber contained therein is built up and 
oriented in specific directions. 
As illustrated in FIG. 2 a flat water resistant sheet 16 is fastened to the 
headbox 2 covering a portion of the dewatering area. The sheet 16 has a 
number of longitudinal slots formed therein and is positioned in close 
proximity to the continuous traveling forming belt 8 as it passes through 
the headbox 2. As a result of the continuous forward movement of the 
traveling forming belt 8 as the vacuum from the vacuum boxes 10 is applied 
to the bottom of the continuous traveling forming belt 8 drawing the water 
from the headbox 2 through the continuous traveling forming belt 8, the 
dispersed fibers 3 are deposited through the slots 18 of the flat slotted 
sheet 16 on the top of the continuous traveling forming belt 8 and 
oriented to the shape and size of the slots 18. Since the continuous 
traveling forming belt 8 is in continuous movement the fibers deposited 
within the slotted areas 18 of the sheet 16 are oriented in the direction 
of travel of the continuous traveling forming belt 8. The fibers deposited 
in the dewatering area 7 of the forming section or headbox 2 not affected 
by the sheet 16 are deposited on the continuous traveling belt 8 in a 
random manner. The net effect on the non-woven fibrous mat produced from 
the embodiment of the invention shown in FIG. 2 is, as illustrated in FIG. 
3, the appearance of built up lines or strips of fiber reinforcement 22 in 
the non-woven fibrous mat 20 oriented in the same direction as the 
direction of movement of the continuous traveling forming belt 8. The 
strengthening effect to the non-woven fiber mat 20 in the machine 
direction is dictated by the design of the slots 18, that is the width of 
the slots, the thickness of the slotted sheet 16, and the spacing of the 
slots over a given surface area. The thicker the slotted sheet 16, the 
thicker the built up lines or strips of fiber reinforcement 22 will be. 
Turning to FIG. 4, there is illustrated another embodiment of the present 
invention. In this embodiment a second traveling or moving forming belt 24 
traveling at the same speed and in the same direction as the continuous 
traveling forming belt 8 travels through the dewatering section or area 11 
of the headbox 2 in contact with the continuous traveling forming belt 8. 
The moving forming belt 24 functions in a similar manner to the slotted 
sheet 16 previously discussed. The moving belt 24 as illustrated in FIG. 5 
contains a number of slots 26 formed perpendicularly to the line of travel 
of the continuous traveling forming belts 8 and 24. It should also be 
noted that the traveling forming belt 24 and the traveling forming belt 8 
essentially form one forming belt and could be combined into one belt with 
slotted depressions therein. 
As the continuous traveling forming belt 24 and traveling belt 8 pass 
through the dewatering area 7 of the headbox 2, the partial or head vacuum 
applied against the bottom of the continuous traveling forming belt draws 
the water through the continuous traveling forming belts 8 and 24 and 
deposits a build up of dispersed fibers 3 onto the top of the continuous 
traveling forming belt 24, forming a continuous non-woven web of fibers 6. 
The fibers 3 passing into the slots 26 build up and orient themselves in 
accordance with the patterns of the slots 26 in the traveling belt 24 
aligned in a direction perpendicular to the line of travel of the 
continuous traveling forming belts 8 and 24 and the fibers 3 passing into 
the slots 18 build up and orient themselves in accordance with the 
patterns of the slots 18 in the slotted sheet 16. The continuous non-woven 
web of fibers 6 is then conveyed to the binder applicator and drying oven 
and is ready for use. 
As shown in FIG. 6 in the fibrous non-woven mat 28 produced by the 
embodiment of the invention illustrated in FIGS. 4 and 5, parallel built 
up lines of fiber reinforcement 30 oriented in the same direction as the 
direction of travel of the continuous traveling forming belt are formed. 
These built up lines of fiber reinforcement 30 are formed by the action of 
the slots 18 in the sheet 16. Parallel built up lines of fiber 
reinforcement 32 oriented in a direction perpendicular to the direction of 
travel of the continuous traveling forming belt 8 are formed by the slots 
26 of the traveling belt 24. 
While in the embodiment of the invention illustrated in FIGS. 4 and 5 the 
traveling forming belt 24 is positioned on top of the forming belt 8 it is 
recognized that the position of the traveling belts 8 and 24 can be 
reversed and the web formed on top of the unslotted belt 8. 
It should be noted that a non-woven fibrous mat containing parallel 
reinforcement in the machine direction and cross-machine direction 
produced from the process described above will have the appearance and 
strength similar to that obtained by laminating a scrim or continuous 
sliver or yarn to a preformed non-woven fibrous mat. 
While the illustrations have shown parallel built up lines of fiber 
reinforcement oriented in the same direction as the direction of travel of 
the forming belt 8 and parallel built up lines of fiber reinforcement 
oriented in a direction perpendicular to the direction of travel of the 
forming belt 8, it should be apparent that the invention is not limited to 
such configurations and various designs may be produced including arced, 
curved, and other patterns of reinforcement and/or texture using the same 
technology. 
As illustrated in the various embodiments above the portions of the forming 
belt 8 experiencing a greater flow of water therethrough in the dewatering 
process will have a greater build up and orientation of fibers deposited 
thereon. 
In addition to the embodiments shown in FIG. 6 there is illustrated in 
FIGS. 7 and 8 another embodiment of the invention wherein the desired 
fiber orientation pattern is designed directly into the forming belt 38 at 
the time the forming belt 38 is fabricated so that it controls and varies 
the flow of water through the various segments of the forming belt 38 and 
thus uses this means to control the deposit and orientation of fibers on 
the forming belt. 
Another embodiment for achieving the results of this invention to control 
the flow of water through the forming belt, is to make the forming belt of 
fabric and control the flow of water through the belt by using fabrics 
with areas of different drainage rates, so that as the non-woven web is 
formed more material is collected on the areas of the forming fabric where 
the drainage is greater. Such a forming belt may be constructed by varying 
the strands per unit length, e.g. fewer strands in areas where greater 
drainage is needed and more strands elsewhere, or by varying the diameter 
of the filaments used to construct the fabric in the areas where greater 
drainage is needed and/or by varying the weave pattern of the forming belt 
to achieve the desired result. 
Other approaches to controlling the flow of the water and thus the amount 
of fibers deposited on various segments of the forming belt and orienting 
the fiber in the direction the forming belt travels include adding a 
restrictor under the forming belt and over the vacuum boxes or source of 
partial or head vacuum or inserting blocks or other devices to control the 
differential flow of water through different segments of the forming belt. 
From a reading of the foregoing specification and a study of the attached 
drawings, it should become apparent that many changes in details can be 
made without departing from the spirit and scope of the invention as 
expressed in the specification and accompanying drawings and the invention 
is not to be limited to the exact manner shown and described, as the 
preferred embodiments have been given by way of illustration only.