Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a take-up and pay-out
device for the tow cables of tow lifts having a return spring
for the tow cable that is wound onto a tow cable drum and a
centrifugal brake for the tow cable drum, this brake having at
least one centrifugal weight, in connection with which the
distance between the axis of rotation of the centrifugal weight
and the point of application of the centrifugal weight on an
interior wall of the housing of the take-up and pay-out device,
that is preferably provided with a brake lining, is automatically
variable according to the direction of rotation of the tow cable
drum,such that when the tow cable is being paid out the point
of application of the centrifugal weight is closer to the
rotational axis of the centrifugal weight than when the tow
cable is being taken up.
In a known device based on this principle, a brake
- shoe that is rotatably mounted about an axis parallel to the
axis of rotation of the centrifugal weight is arranged between
two stops, this brake shoe having two braking surfaces that are
nclined towards each other and which extend beyond the outer
edge of the centrifugal weight (see Swiss Patent No. 502,214).
However, this device has the main disadvantage that when the tow
cable is being taken up and paid out there are only insignificant
differences with respect to the point of application of the
rotatable brake shoe on the brake lining bonded to the inside
wall of the housing and accordingly the resulting differences
in the braking effect are far too small.
In another device based on the above principle, it is
true that the requirement that there be a higher braking
moment when the tow cable is being paid out than when the tow
cahle is being taken up can be better satisfied. However, this
device has the disadvantage that in order to vary the lever arm
of the centrifugal weight the axis of the centrifugal weight is
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guided in a slot (see Swiss Patent No. 348,176). Compared to
a fixed axis of rotation this does not provide a sufficiently
secure mounting for the centrifugal weight about its axis of
rotation, so that the centrifugal weight can tilt and topple,
this being prejudicial to the desired function.
The present invention thus provides a take-up and pay-
out device for tow cables of tow lifts in accordance with the
aforesaid principle by which a sufficiently large difference in
the braking effect during pay-out of t,he cable vis-a-vis the
taking up of the cable is ensured without the stable position-
ing of the centrifugal weight being in any way impaired.
According to the present invention there is provided
a tow rope pull-out and retracting device, comprising a housing
havin~aninternalsurface,areeldisposedwithinsaidhousingfortakin~up and
payingout atowrope,a retracting spring coupledtosaidreel,at least
one flyweight pivotally mounted on said reel about a first axis,
said flyweight having a protruding braking surface near said
axis adapted to engage said internal surface in one direction of
rotation and a brake shoe pivotally mounted about a second axis,
remote from said first axis, and adapted to engage said inter-
nal surface in an opposite direction of rotation, whereby a dif-
ferent braking force is produced in opposite senses of rotation.
Thus according to the present invention, an area fur-
thest from the axis the centrifugal weight has a brake shoe
that is rotatably mounted about an axis, parallel to the axis
of
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rotation of the centrifugal weight, between two stops that are
provided and which, in that area close to the axis, has a
braking surface that extends preferably in the manner of a cam.
Using the device according to the invention it is
possible to obtain a considerable difference in braking
performance when the cable is being taken up, on the one hand,
and when the tow cable is being paid out on the other, because
the braking surface that protrudes preferably like a cam that is
effective when the tow cable is being paid out and the braking
shoe that is in its operating position when the tow cable is being
taken up are located a relatively grea, distance from each
other. In addition, the device according to the present
invention has good stability because in that place where the
loading is particularly great, namely, in the area of the
centrifugal weight that is close to the axis a stable braking
surface preferably in the form of a cam-like projection is formed,
this contributing to the direct transfer of force to the axis of
the centrifugal weight. The rotatable brake shoe is located
in the area furthest from the axis, that is to say, where the
loading is significantly less. Thus neither the brake shoe
nor its mountlng are subjected to excessive loads.
The present invention will be further described by
way of the accompanying drawings, in which:-
Fig. 1 is a cross-section through the axis of the
cable drum according to I-I of Fig. 2 of a pay-out and take-up
devlce according to one embodiment of the present invention;
Fig. 2 is a cross section in the line II-II of the
device of Fig. 1 with the centrifugal weight being in the
position for paying out the tow cable;
Fig. 3 is a similar cross-section to Fig. 2 when the
tow cable is being taken up;
Fig. 4 is an enlarged cross section on the line IV-IV
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of Fig. 3;
Fig. 5 is a vertical cross section on the line V-V
of Fig. 6;
Fig. 6 is a cross section on the line VI-VI of Fig. 5
with the centrifugal weight being in the position adopted when
the tow cable is being paid out;
Fig. 7 is a similar section to Fig. 6 of a further
embodiment of the device of the present invention when the tow
cable is being taken up;
Fig. 8 is a vertical section on the line VIII-VIII
of Figs. 9 and lO;
Fig. 9 is a cross section on the line IX-IX of Fig. 8,
with the centrifugal weight in the position for paying out the
cable;
Fig. 10 is a similar cross section when the tow cable
is being taken up, in a further embodiment of the device of the
present invention;
Fig. ll is a vertical section through the axis of the
cable drum;
~ig. 12 is a normal section of a variation for Figs.
8 - 10; and
I Fig. 13 is a normal section of a variation for the
cam-like braking surface of the centrifugal weight.
The take-up and pay-out device according to Figs. 1 - 4
comprises a housing 1, connected through the clamping bracket 2
and the suspension column (not shown) to the circulating device.
The housiny l is extended laterally by the spring housing 3,
this containing the return spring 4. The spring 4, in the form
of a coil spring, is secured at one end to the housing 3 and
at the other to a coiling stud mounted on the shaft 5, this
being connected through a coupling to the cable drum 6 for the
tow cable. Two studs 8, 9, arranged on the cable drum 6, carry
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the two centrifugal weights 10, 11. A brake lining 12 is on the
inside wall of the housing 1. In the areas closest to the axis
the centrifugal weights 10, 11 each have a braking surface 24
that extends in the manner of a cam. In the areas furthest
from the axis each centrifugal weight 10, 11 has a brake shoe
25 mounted about an axis 26 parallel to the axes 8, 9 of the
centrifugal weights, between two stops 27, 28. When the tow
cable 7 is paid out in the direction indicated by the arrow 17
(Fig. 2) the cable drum 6 together with the centrifugal weights
10 and 11 rotates in the direction indicated by the arrow 18.
The braking surfaces 24 thereupon come into contact with the
brake lining 12. The level-like brake shoes 25 lie against
the stops 27 and are inoperative. Because of the proximity
of the studs 8 and 9 of the centrifugal weights 10 and 11,
respectively, the brake surfaces are pressed extremely hard
against the brake lining 12. This results in an extremely
high braking moment when the tow cable 7 is paid out. This in
its turn results in a very smooth acceleration of the skier as
he or she starts off.
When the tow cable 7 is taken up with the empty tow
stirrup the cable drum 6 together with the centrifugal weights
10, 11 rotates in the direction of the arrow 19 (Fig. 3). The
brake shoes 25 contact the stops 28 and their braking surfaces
are pressed against the brake lining 12 whereas the braking
surfaces 24 of the centrifugal weights 10, 11 that are close
to the axis are lifted away from the brake lining. The force
with which the brake shoes 25 press against the brake lining
is relatively slight. For this reason the braking moment is also
slight, and this results in a rapid but easily slowed taking-up
of the tow cable. In the embodiment according to Figs. 5 - 7,
the housing 1 of the take-up and pay-out device has a drum-like
extens'~on 35, this forming a part of the inner wall of the housing
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and having a brake lining 36. As in the case of the embodiment
according to Figs. 1 - 4 there is a braking surface 24 that
extends in the manner of a cam provided on the centrifugal
weights 10, 11 in that area of the said weights nearest to the
axle, but which, in this case, is now opposite the drum-like
extension 35 of the inside of the housing. In the same manner
as in the embodiment according to Figs. 1 - 4 in that area
furthest from the axes there is on each centrifugal weight a
brake shoe 25, that is rotatably mounted about an axis 26
parallel to the centrifugal weight axes 8 and 9. When the tow
cable is paid out in the direction of the arrow 17 and the
cable drum 6 together with centrifugal weights 10 and 11 rotates
in the direction of the arrow 18 the braking surfaces 24 are
pressed extremely hard against the brake lining 36. This
results in a great braking moment when the tow cable is paid
out. The brake shoes 25 then abut against the stops 27 and
are inoperative. When the tow cable 7 is taken up the cable
drum and the centrifugal weights 10, 11 rotate in the direction
of the arrow 19. The brake shoes 25 now lie against the stops
28 and are pressed somewhat less strongly against the brake
lining 12. The result of this is a smaller braking moment
when the tow cable is taken up. The effect of the high braking
moment when the cable is paid out and the smaller braking moment
when the tow cable is taken up can be increased if the brake
lining 36 has a nigher coefficient of friction than the brake
lining 12.
For all practical purposes the embodiment of the device
according to Fig. 8 - 10 differs from the embodiment according
to Figs. 1 - 4 only in the formation of the rotatable brake
shoes 25 in the form of wire stirrups of steel wire. Thus the
brake shoes 25 can be produced in a particularly economical
manner and, in addition, can be mounted in a very simple manner
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on the centrifugal weights 10, 11, respectively. In this
respect, all that is required is a simple hole in the centrifugal
weight 10, 11, respectively, into which one arm of the wire
stirrup is inserted as an axle 26.
In the embodiment of the device according to Figs. 8
and 10 there are once again stirrup-like rotatable brake shoes
in the area of the centrifugal weights 10, 11, furthest
from the axis, these lying between two stops 27 and 28, whereas
in the area of the centrifugal weights 10 and 11 adjacent the
axis there is in each case a brake surface 24 that extends
in the manner of a cam. The function of the take-up and pay-
out device àccording to Figs. 8 and 10 is the same as in the
embodiment of the device according to Figs. 1 - 4.
The effect of the considerably greater braking moment
of the centrifugal brake when the tow cable 7 is taken up in
comparison with the braking moment when the tow cable 7 is paid
out can in all embodiments of the device be increased, e.g.,
by the fact that the cam-like braking surface 24 has a higher
coefficient of friction than the braking surface of the
rotatable brake shoe 25. This is the case if the centrifugal
- weights 10, 11 are of grey cast iron, and brake surfaces 24
that extend in the manner of a cam are also of grey cast iron,
whereas the rotatable brake shoes 25 or their braking surfaces,
respectively, are of steel, because grey cast iron has a
greater coefflcient of friction than steel. This effect can be
increased even further by coating the braking surfaces of the
rotatable brake shoes 25, for example, with plastic, or by
forming the rotatable brake shoes 25 themselves or plastic.
In the case of the stirrup-like brake shoes 25 according to
Figs. 8 - 10, the provislon of a bearing sleeve on the arm of
the stirrup-like brake shoe that works with the inside wall
of the housing 1 or a brake lining 12 applied thereto,
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respectively, when the tow cable 7 is taken up, is also possible.
In the embodiments illustrated, the stops 27, 28 to
limit the movement of the brake shoe 25 are formed on the
centrifugal weights 10, 11, themselves. However, there is an
equivalent solution in the fact that at least one of the two
stops, particularly the stop 28, can be formed on the cable
drum 6. On the basis of a variation of the embodiment according
to Figs. 8 and 10, Figs. 11 and 12 show the arrangement of both
stops 27, 28 for the rotatable brake shoes 25 on the cable drum
6.
The braking surface 24 that is close to the axis does
not necessarily have to be formed by a cam of the centrifugal
weight 10, 11, respectively, that is limited on both sides
by step-like notching. As can be seen from Fig. 13, the braking
surface 24 that extends in the manner of a cam is formed in the
area close to the axis, for example, if in the braking surfaces
24 that lie against the inside wall of the housing or the brake
lining on the inside wall of the housing, respectively, (as is
the case when the tow cab~e is being paid out), the edge areas
of the centrifugal weights 10, 11, respectively that are adjacent
to the braking area 24 in the vicinity of the axis slope
gradually away from the inside wall of the housing (at least
in the direction towards the free end of the centrifugal
weights 10, 11, respectively).
In most instances, the pay-out and take-up device is
for tow cables used on tow lifts, usually have two centrifugal
weights, as has been shown in the illustrations. In this case,
both centrifugal weights, or only one of the centrifugal weights
may be provided with cam-like braking surfaces 24 and rotatable
brake shoes 25 as described in this invention.
It is not essential that the centrifugal weights 10,
11 respectively are formed in each case as a single component,
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as has been shown in the drawings, on which the cam-like
braking surface 25 is formed and on which the brake shoes 25 .
are mounted in such a manner as to be rotatable. It is also
possible to use centrifugal weights that consist of two or
several parts, for example, in such a manner that a main body
that forms the principal mass of the centriEugal weight may be
connected to one or more additional components in such a manner
that also rotate with the main body when the tow cable drum is
rotated, in which connection the cam-like and projecting brake
surface 24 is formed on these additional,components of the
centrifugal weight and/or the rotatable brake shoe furthest
from the axis~is also mounted on it.
