Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to braking devices.
In many industries, when material of indefinite length is
being drawn off holding members such as spools or reels, braking
mechanisms are used to control tension in the materidl. The braking load
imparted by such mechanisms is adjustable as demand for the material at a
downstream position along a processing line increases or decreases. The
adjustment in the braking load has the object of maintaining constant
tension in the material as it is fed along the processing line. An
increase in demdnd is reflected by an incredse in the pulling load upon
the material. It might be found that while the braking mechanism operates
effectively to control tension at relatively slow feedspeeds, at faster
feedspeeds the mechanism may be too insensitive. This lack of sensitivity
may result in intermittent, total brake release, instead of a varying
small braking load, so that substantially constant tension is impossible
to achieve at fast feedspeeds. In contrast, intermittent total brake
release causes the sudden application and release of a small but
significant end load upon the mdteridl. This sudden, on and off,
a~plication of !oad is known to be damdging for some materials which tend
to tear upon the application of sudden tensile load. Also, it results in
the avoidance of constant tensile load which is essential for qual~ty
control of some products. For instance in the telecommunications cable
field, insensitive operation of a braking mechanism during the automatic
winding of paper material to form a layer around a cable core may have
deleterious effects upon the electrical properties. Changes in tension
upon the paper as it is being wound may cause changes in the diameter of
the wrapping upon the core and this will have an effect upon the desired
mutual capacitance of the conductors in the cable during use. This may
render cables unacceptable. Apart from this, during manufacture if the
tension upon the paper material is suddenly increased by an insensitive
braking mechanism, then resultant breakages in the wrapping material will
affect the operating speed of the machine~
The present invention provides a braking device having two
braking members which are operated in such a way that one of the braking
members varies its braking effect under low-pulling loads and the other
braking member varies its braking effect under higher-pulling loads. With
such a braking device, the two braking members thus have diFferent
operational sensitivities and the second braking member may be more
sensitive to operation than the first operating member.
Accordingly, the present invention provides a braking device
comprising a rotatable member having a brake engaging surface and a
braking means comprlsing:-
(a) two braking menlbers for frictionally contacting said
surface and
(b) a brake release linkage comprising a part which is
pivotable about two positions and means to cause
pivotal movement of the part ln a First sense relative
to the two spaced positions upon the application oF an
initial brake release load upon the linkage part to
effect reduction and then release of the braking load
by the first braking member upon said surface and to
cause pivotal movement of said part in a second sense
relative to the two spaced positions upon the
application of an additional brake release load upon
the linkage part to effect reduction and then release
of the braking load by the second braking member upon
said surface.
Ideally, there is no commencement in the release of the
second braking member ~rom the engaging surface until the first braking
member has been totally released from the surface. In a practical
construction the first member is acted upon by a spring to release it from
the brake engaging surface and the spring action causes pivotal movement
of the linkage part about the First load application position. Upon the
first member being released, its movement is stopped and further movement
of the linkage part takes place about the second load application location
to cause the second braking member to move away from the brake engaging
surface.
The first and second load application locations and their
relationship to points on the linkage where the brake release load is
applied to each of the braking members is advantageously such as to
provide a mechanical advantage and produce an operation of the second
meMber which i5 more sensitive to changing load than that for the
operation of the first member.
One embodiment of the invention will now be describe~ by way
of example with reference to the accompanying drawings in which:-
Figure 1 is a side elevational view of a taping apparatusshowing paper tape being applied to a telecommunications cable;
Figure 2 is a view similar to Figure l w1th a spool for the
tape being omitted for clarity;
Figure 3 is a cross-sectional view through the apparatus
taken along line "III-III" in Figure 2 and on a larger scale;
Figure 4 is a multi cross-sectional view o, the apparatus
taken in the direction of arrow IV in Figure 3; and
Figures 5, 6 and 7 are diagrammatic side elevational views,
taken in the same direction as Figure 2 and showing geometrically
different positions of a braking mechanism of the apparatus during
operation.
As shown by Figure 1, there is provided a taping apparatus
10 for applying tape 12 as a core wrapping material 14 around a core 16 of
a telecommunications cable as the cable is being passed along the feed
path 18 d~ shown in the direction of arrow 19. The feed path 18 passes
through a box structure 20 of the apparatus and a sponl 22 holding the
tape 12 is secured to a spindle 24 which projects from and is rotatably
mounted upon one side of the box structure 20. The rotational movement of
the spindle and spool is restricted by a braking mechanislll indicated
generally at 26, which applies a braking load controllec! by the feed or
draw off speed of the ~aterial 12 as will now be described.
As shown by Figures 1 and 2 the hraking mechanism is varied
in its braking effect in a conventional manner by the use oF a dancing
roll 28 mounted upon the free end of an arm 30, which is pivotally mounted
at 32 to the structure. The tape 12 is Fed from spool 22 around the
roller 28 and is held in a position around the roller by two guiding
rollers 31. From the rollers 28 and 31, the tape 12 is Fed around a
non-rotatable guide finger 33 which is inclined and changes the plane of
the material, as shown, to enable it to be wrapped around the core as the
core is fed along the pass line 18. The core is stranded from an upstream
position (not s~own), by conventional means.
The braking mechanism is shown in detail in Figures 2, 3 and 4.
The braking mechanism 26 incorporates a brake release
linkage which comprices a shaft 36 which extends with its axis parallel to
that of the spindle 24 at one side of the box structure 20. The shaft 36
is mounted at one end between the ends of d link which comprises two
parallel spaced link plates 38~ The plates 38 are pivotally mounted at
their upper ends to a vertical arm 40 depending from the structure 20
about axis 74 spaced radially from the shaft 36. The pivotal connection
at axis 74 is such as to allow for radial swinging movement of the shaft
36 at its other end about the arm 40. A brake rod 42 extending from the
arm 30 is pivotally connected to the lower ends of the arms 38 at position
44. Movement of the dancing roll to pivot the arm 30 in a clockwise
directlon ~n Figures 1 and 2 will, of course, move the brake rod 42
towards the left to pivot the link plates 38 about their pivotal axis 74
in a brake release sense. A spring means comprising tension spring 45 ~s
provided for urging the link plates 3~ in a braking direction and thus
aga~nst the release action of the brake rod 42. This spring 45 acts upon
the link plates 38 at a position 43 intermediate the shaft 36 and the
position 44.
The spring 45 is held at another end by a vertical plate 47
which is pivotal7y mounted at 50 to the structure 20. An adjustment screw
52 acts between a stop 54 and the plate 47 to adjust the position of the
plate and thus the amount of tension applied by the spring~
As shown by Figure 2, the braking device includes two
braking members 48 and 49. The member 48 is a brake shoe pivoted at its
upper end 51 ~o the box structure 20 and having a tens70n spring 53
secured to its lower end to urge it towards a "brake-off" position in
which a brake liner 54 lies out of enyagement with a brake engaging
surface 56 of a brake drum 58 coaxially secured to and rotatable with the
spindle 24. In the "brake-off" position, the shoe 48 engages with a stop
pin 59 which is moun~ed on the structure 20. The braking member 49 is
also a brake shoe pivotally mounted at its upper end 60 to the structure
20 and has a brake liner 62 engageable with the surface 56.
The brake release linkage further comprises a moun~ing link
64 (see particularly Figure 3) which is pivotal about two spaced
positions. At d first position 66, the link 64 is secured to a depending
bracket 68 of the frame 20. At a lower position 70, the link 64 is
pivotally connected to an upstanding flange 72, which is secured to the
shaft 36 in a position axially spaced from the link plates 38 as shown by
FitJure 3. Hence at flange 72, the shaft 36 may be pivoted ahout either
the upper or lower positions 66 and 70. It should be noted that in the
"brake-on" position, i.e., with the braking members 48 and 49 in full
engagement with the engaging surface 56 to provide a braking effect upon
the brake drum 58, the axes of the pivotal positions 66 and 70 are
v~rtically in alignment with the pivotal position 74 at the top of the
link plates 38. Also it should be noted that the axis at position 70
(Figure 3) lies slightly below the axis of the position 74, while the
axis of position 66 is spaced by a larger distance above the axis of
position 74.
The brake release linkage also provides part of linkage
which connects the shaft 36 with each of the brake shoes 46 and 48. As
shown particularly by Figure 3, an operating link in the form of a
vertical pair of spaced link plates 76 is provided at the end of the shaft
36 remote from the plates 38. These plates are connected at two spaced
pivotal positions 78 and 80, respectively, to brake rods 82 and 84 which
are in turn pivotally connected to the lower ends of the shoes 48 and 49.
It should be noted at this stage that the pivotal connections 78 and 80 in
the "brake-on" position shown in Figure 2 are also in vertical alignrnent
with the position 74 and tha~ the axes of the positions 78 and 80 are
respectively slightly below the axes of positions 70 and 66.
In use with the spool 22 mounted upon the apparatus as shown
in Figure 1, the wrapping material, which in this case is made from paper,
is fed around the rollers 31 and 28 and is changed in direc~ion around
inclined finger 33 to be wrapped around the core 16 as previously
described and shown ln the drawing. Normally, with little or no tension
applied to the roller 28, the two brake shoes 48 and 49 are applied fully
against the brake engaging surface 56 by spriny ~5. This position is as
shown in ~igure 2 in full outline and also by the geometry of the pivotal
points in Figure 5. However, upon the wrapping rnaterial 12 becoming
tensioned, the dancing roller 28 is pulled so as to urge the arm 30
clockwise under an initial brake release load and thus pull the link
plates 38 ~n a clockwise directioll as viewed ~n Figure 2. This causes the
shaFt 36 to pivot around the position 74 from the vertical in-line
position, as shown in Figure 5, towards that shown in full outline in
Figure 6. This turning of the shaft 36 and the inclination of the link
plates 38 to the vertical shown by dotted outline 38 in Figure 6 is
accompanied by an equal angular movement of the torsionally rigid shaft 36
at its other end. The effect of this is to allow the spring 53 to pull
the shoe 48 in a clockwise direction so that it tends to move away from
~he brake engaging surface 56. At the same time, the pull rod 82 acts
upon the pivotal position 78 in a horizontal direction to urge that end of
the shaft 36 towards the shoe 48. In consequence, the brake rod 82 also
pulls against the brake rod 84 to retain the brake shoe 49 firmly in
engagement with ~he surface 56 and the pivotal position 80 is thus
maintained substantially in vertical alignment with the pivotal position
74. The effect of this is ~hat the linkage at the right hand end of the
shaft 36 (as shown in Figure 3) is caused to pivot about the upper pivotal
position 66 of the link 6~ and also about the pivotal position 80.
The pivoting action is effected as the plates 76 tilt about position 80 to
an angle of orientation substartially equal to that of plates 38 which
causes a certain angular movement of flange 72r This movement of f'lange
72 effects a certain angular movement of the link arm 64 around position
66. Movement about the two non-aligned pivotal positions 66 and 80 is
possible because position 80 is not rigid'ly fixed relative to the frame 20
and moves slightly in a substantially vertical manner to accommodate for
movement around fixed position 66. The shaFt 36 thus becomes inclined
towards the brake shoe 48. This is shown by the dotted outline position
for the shaft 36 in Figure 6. The move~ent of the brake shoe 48 away from
the surface 56 continues under the appllcation of a relative'ly small brake
release load, which is below a certain limit, until the shoe engages the
stop 59 as shown in dotted outline in Figure 2, At this position, the
relative locations of the pivotal positions 66 to 80 are shown in Figure
6. Also in this Figure the relative dispositions of the link 64 and ~he
link arms 76 are shown.
After the brake shoe 48 engages the stop 59, if the speed of
drawing off of the material 12 increases thus causing the dancing roller
to move further to the right~ then an additional brake release load is
applied. Should this occur/ then upon further movement of the link
p!ates 38 in a clockwise direction in Figure 2, a diFferent action at the
right hand end of shaft 36 (Figure 3) then takes place. This increase in
load cannot act by moving the brake shoe 48 any further because the stop
59 prevents pivotal position 78 from movin~ towards the left as in Figure
6. Thus any further clockwise movement takes place around position 70 as
a pivot with spring 53 pu11ing upon shoe 48 and brake rod 82. This
pivotal movelnent is allowed for by slight anti-clockwise movement of the
link 64 about the pivotal position 66 until the brake release linkage is
in the position shown in Figure 7~ During this movement~ the pivotal
position 78 moves vertically slightly to allow for a pivotal movement of
the pivot position 70 around the pivotal position 66. The brake links 76
are turned clockwise so that pivotal position 80 moves towards the brake
shoe 48. This also is shown in Figure 7. This movement of pivotal
position 80 acts upon the brake rod 84 to move the brake shoe 48 in a
counterclockwise direction and away from the surface 56.
As can be seen from the above description, a single
mechanism enables the release of two brake shoes in succession from a
brake engaging surface. It will be appreciated that the spring 53 in
conjunction with stop means 59 act as a means to cause pivotal movement of
the operdting link plates 76 in both the first sense during application of
the initial load and in the second sense upon application of th,e
additional load. It should also be noted that the mechanical advantage
offered by the mechanism is such that the brake shoe 49 is released more
slowly under a particular load increase than is the case for brake shoe
48. On this point as will be noted from Figure 3 particularly, and also
from Figures 6 and 7, the relative locations of the various pivotal
positions are such as to enable this to take place. As can be seen from
0~
Figure 6, the initial movement o-F the link arms 38 in the clockwise
direction is accompanied by substan-tial movemen-t o-f the pivotal
position 78 towards the left as viewed in that figure. This is
because of the ratio of the distances of the axis of the shaft 36 and
the axis of the pivotal position 78 from the pivotal posi-tion 66,
which is the primary position about which movement takes place during
initial loading. Upon continuation of the loading when movemen-t of
the brake shoe 49 takes place, it is noticeable from Figure 7 that the
movement of the brake shoe 49 is a more delicate operation than the
shoe 48 because of the location of -the pivotal posi-tion 70 in relation
to the centre oF shaft 36 and pivotal position 80. Therefore, there
is a greater control of the change in braking load on the surface 56
by the shoe 49 upon a certain degree of movement of the arm 30. Thus
this control enables extremely small and controllably changeable
braking loads to be applied upon -the rotatable member 58 for
relatively high feedspeeds of the wrapping ma-terial 12. Sudden
application and release oF braking load leading to its sudden increase
or decrease is thus avoided, thereby reducing any tendency for the
paper wrapping material 12 to break. ~lso there is a greater degree
of control upon the finished tension oF the material when wrapped
around the cable core with the result that there is greater control in
the wrapped diameter of the material around the core. This, of
course, leads to a greater control in the mutual capacitance between
the conductors of a cable.
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