Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Dustfree cutting of a mineral wool web
In the production of mineral wool products for isolating purposes
the formed mineral wool is collected on a transport band, whereby
the velocity of the band determines the production capacity. The
mineral wool is forming a mat, which is also called a web, which
mostly contains a thermocuring binding agent. After the curing
which takes place in a special curing oven and the subsequent
cooling the edges of the web are so uneven that they must under-
go some sort of a levelling operation. Additionally the web must
be cut in longitudinal and transversal directions in order to ob-
tain mineral products of a desired and easily handled form.
The technique generally used today for the said dividing or cut-
ting operations in the production of mineral wool products is saw-
ing with rotating toothed blades furnished with cutters of hard
metal or with fast rotating abrasive wheels. This technique is,
however, undesirable because of the dust being formed and which
is difficult to overcome in order to get an acceptable working
atmosphere. This technique is also causing a waste of material
which in the long run becomes considerable.
The purpose of this invention is to develop a new process for cut-
ting mineral webs where the development of dust and ma~or waste of
material are eliminated.
In order to obtain this purpose cutting with rotating knives has
been tried on mineral webs in the known way which is used in the
textile industry. Characterizing for this technique are partly
the form of the edge of the rotating knife blades, which is such
that the edge is slitting or cleaving the staple of fabric layers,
and partly the very high rotating speed of the knife blades. These
characteristics are very suitable for products constituted of flex-
ible fabric layers and the result is consequently good, which means
that the trace is smooth and the development of dust insignificant
and that the blade can be used for a long time without sharpening.
Using the same technique on mineral wool webs which are relatively
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dense and hard and have a considerable thickness between about 10
to 300 mm has not been successfu]. The development of dust and
waste of material have in fact essentially decreased but the fric-
tion heat grows high and causes deformation of the blade and un-
sharpness after a short use thereof.
Considering these negative experiences another process has been
tried, that is levelling and longitudinal and transversal cutting
of a moving mineral wool web with stationary blades of the same ~-
form as above. Surprisingly enough such a technique has been
adapted on stiff mineral wool webs with a satisfying result. When
adapting the same process on more flexible webs the tearing actions
is, however, too big. The conclusion that also these flexible webs
can be cut with the same knife-formed tool provided the blade is
given a cutting movement, preferably a rotating movement, the
velocity of which is somewhat higher than the velocity of the
material web, has, however, been reached through tests. There
exists no development of dust in this technique.
The new process is thus characterized in that the cutting is per-
formed with a knife blade having a peripherical speed in the di-
rection of the movement of the web which is somewhat higher than
the velocity of the mineral wool web and in that edge of the knife
blade has a form with a cleaving, not a cutt.tng effect, which
latter action means that chips are formed during the cutting.
The essence of the new process is constituted of the fact that
the knife blade has a smooth edge tapering towards the top of
the edge and having a slitting or cleaving effect contrary to
the toothed edge of a sawing blade wherein the teeth are formed
to cut chips during the sawing. As mentioned above saw toothed
blades have been used until now for the cutting of mineral wool
webs and it is therefore quite unexpected that a smooth cleaving
edge with a relatively low rotation rate is able to cut these
webs and produce a clean trace without the development of dis-
turbing dust.
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In a preferable embodiment of the process the knife
blade has a rotating movement and further it is preferable that
the peripherical rate of the knife blade is about 1.1 - 10 times
the rate of the mineral wool web. This relation is empirically
determined for each web and is primarily dependent on the thick-
ness and the density of the web, the amount of binding agent in
the web and on the degree of hardness of the web.
The velocity control of the peripherical speed of the
knife blade is preferably performed synchronically with the velo-
city of the wool web, for example, with a continuous-current
motor.
As compared with the prior known sawing process the
following advantages are obtained
- the development of dust is so insignificant that the apparatus
for removing of dust by suction are superfluous,
- thanks to the very small friction heat the tendency for deform-
ation of the blade is eliminated,
- the amount of working hours for one blade without sharpening
between the work:ing times has increased about tenfold.
In the following a preferable embodiment of the inven-
tion will be described with reference to the enclosed drawings,
in which:
figure 1 is disclosing an apparatus for the performing of the
process of the invention, in a side view,
figure 2 is disclosing the apparatus of figure 1 in section along
the line II - II, and
figures 3a, 3b, 4a, 4b, 5a, and 5b are disclosing segments of dif-
ferent knife blades and sections therefor for performing the pro-
cess of the invention.
The mineral wool web 1, which is coming from the
curing oven and
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subsequent cooling is moving forwards on the conveyor 4 towards '
the knife blades 2 which are cutting the unlevel edge region from
the web. The height of the axles of the knife blades is arranged
to barely reach the lower face of the mineral wool web. The peri- `
pherical moving direction of the knife blade is the same as the
moving direction of the web. The peripherical speed of the knife
blade is empirically determined on the ground of the velocity of
web and of its thickness, density and stiffness. The relation
between the peripherical speed of the knife blade and the linear
velocity of the web will lie between 1.1 and 10, a higher rela-
tion value being normally applied with thinner and softer webs.
By means of continuous-current drive and known transmission de-
vices the knife blade 2 and the conveyor will obtain the linear
moving velocities determined beforehand. When cutting webs of
one and the same type the velocities are maintained constant.
The edge of the knife blade can be formed for example as disclos-
ed in the fiugres 3-5. Normally the simplest form according to ;~
figure 3 is used which has no discontinuities in the peripherical
direction of the edge, while the embodiments of the figures 4 and
5 containing in the peripherical direction inwardly half-circle
formed and interrupted outwardly circular discontinuities respect-
ively are used with webs having inferior cleavability. A common
feature for these embodiments of the edge is naturally, as is re-
vealed in the sectional views, the cleav.tng or slitting edge in
stead of a chips cutting edge.
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