Note: Descriptions are shown in the official language in which they were submitted.
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This application is a divisional of parent applicatîon Serial
Number 2~6,037.
The present invention relates to braking devices suitable for use in
unwinding thin elongated material from bobbins. The present invention has
been found to be particularly suitable for use with apparatus of the type
described in parent application number 286,037, i.e. apparatus for laying up,
or helically winding together a plurality of fine filaments.
Herein the term "fine filaments" means filaments having a very
low capacity for resisting the mechanical stresses to which they are conven-
tionally subjected during the laying together procedure, such as for example,
torsion, traction and flexing, which is due either to the dimensions of the
said filaments, for example, their very small diameters, or else due to the
very nature of the material out of which they are composed, e.g. glass yarn
fiber.
Apparatus are well known for laying up a plurality of wires. Under
normal operating conditions, such apparatus generally subject the wires to
torsional, tractive and bending stresses from the moment the wires unwind from
the bobbins which carry them, until they are layed-up together.
The braking devices used in the known apparatus, give rise to ten-
sion stresses on the wires that are variable in a wide range of values. If,
therefore, these braking devices are used for laying together fine filaments,
as defined above, deformations can take place which may lead to some break-
ages in said filaments.
It is the general object of the present in~ention to provide an
improYed braking device suitable for use in unwinding thin elongated material
from bobbins.
It is a further object of the present invention to provide an im-
proved ~raking device suitable for use ~ith apparatus of the type described
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in parent application Serial Number 286,037, i.e. apparatus for laying up,
or helically winding together a plurality of fine filaments.
According to the present invention there is provided braking means
for bobbins which are mounted for rotation about a bobbin axis and have a
winding of a filament thereon. The braking means comprises a disc co-axial
with the bobbin axis and adapted to be coupled to a bobbin for rotation there-
with, a braking lever mounted for pivotal movement around a first lever axis
parallel to the bobbin axis and having an end engaging the disc at different
radial positions thereon with pivotal movement of the lever, adjustable means
urging the end of the lever against the disc, a control lever mounted for
pivotal movement toward and away from the winding and having an end thereof
urged toward and engaging the winding, and means interconnecting the control
lever and the braking lever for causing the end of the braking lever to move
nearer the bobbin axis as the winding decreases in radius.
The present invention will be better ~mderstood from the following
erc/'~
1~ detailed description of a preferred embodiment thereof~ when
D Figures lard2 are, respectively, side elevation and plan views of a
bobbin braking apparatus;
Figure 3 is an enlarged, fragmentary cross-sectional view of the
bobbin supporting apparatus shown in Figures land2 and is taken along the
axis A-B indicated in Figure 2.
Referring to Figures 1 and 2 there is shown a support 9 on which
a bobbin 10 is mounted. Said support 9 comprises a body 30 from which two
parallel arms 31 extend, the arms being spaced apart from each other and having
a length such as to contain the above said bobbin 10.
Referring to Figure 3, in each of said arms 31, there is formed a
through-hole with its axis A-B perpendicular to the longitudinal axis of the
support 9 itself. In said through-holes, there are disposed bushings 32 and
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33 respectively, in which are situated bearings 34 and 35 spaced apart from
each other by means of the spacers 36 and 37 and maintained in position by
means of circlips 38 and 39. The shafts 40 and 41 are mounted respectively,
on bearings 34 and 35, and each has, on its extremity facing the longitudinal
axis of the support 9, the cylindrical covers 42 and 43 that are received in
the ends of the hollow core 44 of the bobbin 10.
In particular, the cover 43 is provided with teeth 45 which engage
with the walls of corresponding holes in the bobbin 10. The bobbin 10, held
by means of the said cover, is locked or unlocked axially, by means of the
locking nut 46, which is joined to the end of shaft 40 by means of a spring
washer 47. The nut 46 is screwed on a body 48 causing axial movement of the
shaft 40 which serves for locking, or unlocking, the said bobbin 10, without
preventing the bobbin 10 itself from rotating around its own axis. The shaft
41 cannot accomplish any axial displacement, but it can rotate around its own
axis together with the bobbin 10. The rotation of the cover 43 is trans-
mitted to a disc SQ by means of the shaft 41.
Referring to Figures 1 and 2 the support 9 is provided with holes
52 and 53 which are spaced apart from each other and which have their ohn axes
parallel to one another and perpendicular to the longitudinal axis of support
9. In these holes, the braking means 19 of the bobbin 10 are mounted.
Inside the hole 53 in the support 9 is situated a shaft 60, hav-
ing a greater length than the hole 53, so as to protrude with respect to
hole 53. Near to one end of said shaft 60 are mounted arms 62. The arms
62 carry, on their facing surfaces, at their free ends, pads 63 which are in
contact with the opposite surfaces of the disc 50 together with which they
form the braking elements of the system.
The shaft 60 passes through the central holes of a series of
Belleville washers 65, through the holes in the arms 62 and through the
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central hole of the cover 66 and is secured by a threaded nut 68. The nut
68 controls the compression forces of the washers 65 by means of the cover
66. This force is transmitted to arms 62 and thence, to the pads 63. The
above arms 62, disposed as aforesaid, constitute a lever and can accomplish
angular displacements by rotating around the shaft 60 on which they are
pivotally mounted.
In the hole 52 there is mounted a shaft 69 which has its own axis
parallel to the axis of the shaft 60. Gn this shaft 69 at its inner extremity
there is mounted an element which is sensitive to the variations of the un-
winding radius of the fine filaments 11 wound around the bobbin 10. This
element is, an arm 70 which carries a roller 71 which idles about its axis
and has a length such as to substantially cover the entire axial length of
the surface covered by the fine filament 11. This roller is held in con-
tact with said surface by means of a spring 72, the extremities of which are
fixed respectively to the support 9 and to the free extremity 70' of the
arm 70.
The shaft 69 on its extremity external to said support 9 is pro-
vided with an arm 73 which is disposed in such a way as to be an extension of
the arm 70. The arm 73 and the arms 62 are pivotally connected to a tie-rod
74 which interconnects them.
Since in general fine filaments to be laid up should not be sub-
jected to stresses exceeding 100 gr., the contacting elements of the braking
system ha~e been selected to have a friction coefficient not greater than 0.1.
In order to obtain such coefficient a coupling of material commonly known in
the market by the name of "Teflon" with chromium-plated steel, i.e. pads 63
made of "Teflon" and the disc 50 made of steel with the surfaces specular
and plated with chromium, may be used. This combination of braking means
guarantees an insignificant static friction and an insignificant inertia
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force which follows when the apparatus is stopped.
In operation the bobbin 10 is braked by braking means 19 during
its rotation around its own axis. The operation of braking means 19 is such
that the arm 70 responds to the continuously diminishing radius of the
winding of the fine filaments 11 by means of the roller 71.
As the filament 11 unwinds, the arm 70 moves towards the axis of
the bobbin 10, helped in its displacement by the action of the spring 72. At
the same time, this displacement is transmitted, in a way that is proportional
to the lever constituted by arms 62, by means of the tie-rods 74 which connect
the arm 73 to the free extremity of the said segments 62. The pads 63 are
pressed against the disc surface 50 with a predetermined force, by means of
the washers 65 con,pressed by the shaft 60, and the arm 70 through the tie-rod
74 chan~es the dimension of the radius of application of the braking force
by the segments 62, said segments 62 moving said pads 63 from the edges to-
wards the axis of the disc 50.
It will be apparent that the braking of bobbin 10 is such that the
braking moment varies according to the variations of the dragging moment,
which in turn, depends upon the variations of the unwinding radius of the
filaments 11 on the bobbin 10. By diminishing the unwinding radius of the
fine filaments 11, the application radius of the braking force is also
diminished, thereby obtaining a substantially constant tension on the fine
filaments 11 from the time the bobbin 10 is full until the time when the
bobbin 10 is emptied. Accordingly, the fine filaments ll do not suffer any
~ariable stresses which could cause them to break. Another aspect which is
relevant to this type of braking is that the brake itself renders negligible
the difference between the friction value of the static friction, and the
friction values in motion which determine the forces along the axis of the
fine filament and during the stopping. Also, when starting the apparatus,
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little inertia is present which could otherwise cause abnormal stresses on
the fine filament 11.
A ~
