Apparatus for production and cutting of glass fibres

Apparatus for drawing newly-spun and dressed glass filaments from a bushing comprises, in combination, a rotary cutter constituted by a blade roll with radially directed blades projecting from its surface and a second, back-up roll having a resilient surface, said rolls being mounted with their axes substantially parallel and with at least the tips of the blades in contact with said resilient surface to define a cutting zone for the cutter, together with an auxiliary, independently driven start-up roll, variable speed drive means for accelerating said auxiliary roll to a surface speed at least equal to the surface speed of the back-up roll under production conditions, and guide means operable to divert a bundle of filaments being wound on said auxiliary roll to the surface of the back-up roll and thereafter into the cutting zone of the cutter, whereby the filaments are cut into staple fibres. A method of manufacturing staple fibres based on the use of above apparatus is also disclosed.

TECHNICAL FIELD OF THE INVENTION 
This invention relates to the manufacture of staple glass fibres by cutting 
newly-formed filaments drawn directly from a bushing. 
THE PRIOR ART 
Glass filaments are produced by rapid attenuation of cones of molten glass 
formed at the orifices of a heated bushing. It is usual to produce a 
relatively large number of filaments simultaneously; these are drawn off, 
treated with an aqueous dressing/size which may contain up to 10% by 
weight of solids and then collected by winding as a bundle into a package. 
This package may then be converted into staple fibres, in a separate 
operation, by unwinding the filaments and passing them through a cutter. 
This is a dry or partially dry cutting process because the dressing/size 
applied to the newly-spun filaments to facilitate winding and handling is 
usually at least partly dry by the time the material reaches the cutter. 
The filaments may, however, be converted to staple fibres in a rather 
different manner, by cutting the newly-spun and dressed filaments directly 
from the bushing, without any intermediate winding step. In this case, the 
cutter is used to draw/attenuate the filaments from the bushing. Normally 
a single cutter is used to cut simultaneously all of the bundles of 
filaments from a plurality of bushings, in the interests of maximum 
productivity. Because it is inconvenient to start up several bushings at 
once, the usual procedure is to start up the first bushing and then run 
the cutter up to full production speed to attenuate and cut the filaments 
from that bushing. Thereafter, the remaining bushings are started up in 
turn and in each case the respective bundles of filaments have to be 
progressively accelerated and introduced to the cutter, which is of course 
already running at full speed. Means for achieving this progressive 
acceleration to production speed are known; U.S. Pat. No. 3,815,461 
discloses one example in which a tapered or conical pressure roll is used 
to progressively accelerate a bundle of filaments to the speed of the 
cutter. 
It has also been proposed that a separate, auxiliary cutter should be used, 
with the object of progressively accelerating the filaments to the normal 
production speed of the bushing, whilst at the same time chopping the 
filaments to form waste. Once accelerated, the filaments are diverted to 
the main cutter to join the, or any other filaments already being chopped 
there. This proposal (published after the priority date of this present 
application) calls for the accelerating filaments to be chopped into waste 
and as the prosposal itself points out, these filaments are relatively 
thick and difficult to chop, so that the auxiliary cutter is subject to 
rapid wear. 
By contrast to the prior proposal the present invention provides a simple 
and effective start-up procedure, without the need for a tapered roll 
arrangement or an auxiliary cutter. 
BRIEF DESCRIPTION OF THE INVENTION 
According to the present invention apparatus for drawing newly-spun and 
dressed glass filaments from a bushing comprises, in combination, a rotary 
cutter constituted by a blade roll with radially directed blades 
projecting from its surface and a second, back-up roll having a resilient 
surface, said rolls being mounted with their axes substantially parallel 
and with at least the tips of the blades in contact with said resilient 
surface to define a cutting zone for the cutter, together with an 
auxiliary, independently driven start-up roll, variable speed drive means 
for accelerating said auxiliary roll to a surface speed at least equal to 
the surface speed of the back-up roll under production conditions, and 
guide means operable to divert a bundle of filaments being wound on said 
auxiliary roll to the surface of the back-up roll and thereafter into the 
cutting zone of the cutter, whereby the filaments are cut into staple 
fibres. 
The auxiliary, independently driven start-up roll may be mounted for 
rotation about the same axis as the back-up roll, but spaced a short 
distance axially therefrom, or it may be mounted for rotation about an 
axis parallel to the axis of the back-up roll and spaced therefrom in the 
general direction of travel of the filaments approaching said roll. The 
guide means is preferably constituted by a pulley displaceable in a 
direction parallel to the axis of the back-up roll from a first position 
in which a bundle of filaments is presented to the auxiliary start-up roll 
for winding thereon to a second position in which said bundle is presented 
to the back-up for forwarding into the cutting zone of the cutter. 
Preferably the cutter is of the kind set forth in our co-pending 
application of even date wherein the projecting portions of the blades 
engage the resilient surface of the back-up roll so as to be fully 
embedded therein at the point of contact between the rolls. 
The invention also provides an improvement in the method of manufacturing 
of staple glass fibres by drawing a plurality of glass filaments from a 
bushing and chopping them directly into staple fibers without intervening 
winding and storage, the improvement comprising the steps of initiating 
said drawing by forming said filaments into a coil on the circumference of 
an auxiliary roller, forming an initial winding thereon by rotating said 
roller with a progressively increasing surface speed until the filaments 
advancing towards said roller attain the normal production drawing speed 
for said bushing, then diverting said filaments, whilst still travelling 
at said speed and without breaking them, into driving contact with a 
cutter back-up roll driven with substantially the same surface speed as 
said production speed, advancing said diverted filaments by means of said 
roll into a cutting zone whereat they are both severed from said initial 
winding and continuously chopped into staple fibers, followed by stopping 
said auxiliary roller and removing the initial winding therefrom. 
In particular, the method just recited is preferably applied to bundles of 
filaments from a plurality of bushings, each bundle in turn being 
accelerated to production drawing speed and thereafter diverted into a 
single, common cutting zone. It is particularly preferred that the bundles 
of filaments are diverted into a nip defined between a press roll 
co-operating with the cutter back-up roll to advance the diverted 
filaments into the cutting zone, whereby the degree of driving contact 
between the diverted filaments and the back-up roll is enhanced.

Referring to both figures, a main drive unit 3 supports a blade roll 4 and 
a back-up roll 5, the latter having a resilient surface 6. The blades of 
the cutter roll are shown at 7 in FIG. 2. The drive unit also supports a 
main guide 8 axially reciprocable between its indicated position and the 
position 8' shown by dotted lines. An auxiliary guide 9 is provided below 
the main guide 8; the auxiliary guide is reciprocable between its 
indicated position and a second position 9' shown by dotted lines. 
Mounted coaxially with the back-up roll 5 is an auxiliary start-up roll 10 
which is independently driven by variable speed drive means (not shown) 
contained within the main drive unit 3. The roll 10 is of slightly smaller 
diameter than the back-up roll in order to accommodate a paper, plastics 
or metal sleeve 18, as discussed below. It is spaced axially from the 
back-up roll so as to be completely freely rotatable with respect thereto, 
but the axial gap between the two rolls is effectively closed by means of 
a skirt portion 11 on the back-up roll extending towards and into the 
interior of the auxiliary roll so that a small radial clearance exists 
between said rolls. 
Spaced from the apparatus are a number of further guide rolls 12, one for 
each bushing. Five such guide rolls 12 are shown although this number will 
naturally be varied to suit the number of bushings. In the interests of 
simplicity, the bushings themselves are not shown, although the filaments 
therefrom are shown in FIGS. 2 and 3 at 13, 14, 15, 16, and 17 
respectively. The operation of the apparatus is as follows. A disposable 
paper sleeve 18 is fitted to the auxiliary roll 10 thereby increasing its 
effective diameter to roughly that of the back-up roll. The cutter is 
thereafter started and run up to its operating speed. The first bundle of 
filaments 17 is brought under the auxiliary guide 9 and given an initial 
wrap around the paper sleeve 18 and the auxiliary roll is set into motion, 
wrapping the filaments 17 onto it to form a small cake 19, whilst the roll 
is accelerated to the surface speed of the back-up roll, 5. As it 
approaches this speed, the auxiliary guide 9 is traversed towards its 
dotted line position, thereby dragging the bundle of filaments laterally 
sideways (17') and onto the back-up roll and into the cutting zone 19 of 
the cutter, where the bundle is cut into staple fibres 20. The cutter 
itself and its operation is fully described in our co-pending application 
of even date and need not be further discussed here. As soon as cutting 
begins, the small cake 19 and its paper sleeve 18 is redundant; the 
auxiliary roll 10 can be stopped and the paper sleeve replaced by a new 
one, prior to repeating the cycle with a second bundle of filaments. 
However, before doing so the running bundle of filaments 17 is manually 
diverted from the auxiliary guide 9, to the main guide 8, which has a 
plurality of circumferential grooves 21 in its surface, one groove for 
each bundle of filaments to be simultaneously processed into staple 
fibres. This guide is continuously reciprocated parallel to the axis of 
the back-up roll so as to even out the wear on the latter and on the 
cutter blades by causing the filaments to be traversed over at least a 
major part of the width of the latter. 
The acceleration and subsequent introduction of each successive bundle of 
filaments to the cutter is carried out in like manner to the first bundle, 
until all five bushings are feeding the cutter, the bundles of filaments 
then following the approximate line 22 from the guide pulleys 12 to their 
respective groove on the main guide 8 and thence side-by-side into the 
cutting zone 19 of the cutter. It will be appreciated that the same 
procedure can be used to re-introduce a bundle of filaments following the 
interruption due to a "break-up" at one or more bushings. It should be 
noted that although an ancillary press roll 23 is shown in running contact 
with the back-up roll to hold the filament bundles down onto the latter, 
this is not an essential feature of the apparatus and it can be omitted, 
exactly as discussed in our aforesaid co-pending application. The blade 
roll and ancillary press roll are at least partly enclosed by a housing 
24.