Note: Descriptions are shown in the official language in which they were submitted.
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CABLE-OPERATED EMERGENCY SWITCH
The invention relates to a cable-operated emergency switch to be coupled to a
cable, so that when
the cables moves along a movement path an emergency switching signal can be
triggered, comprising
a coupling element and a housing with emergency switching triggering means
arranged therein and
with an emergency switching element, whereby the coupling element is
operatively connected to the
emergency switching triggering means, so that the emergency switching element
can be switched to
trigger the emergency switching signal by means of the movement of the
emergency switching
triggering means. The invention further relates to a safety device with a
cable-operated emergency
switch of this type, in particular to be arranged connected to a conveyor belt
system.
Cable-operated emergency switches for example are arranged as shutdown devices
at specific
intervals along extended conveyor belt systems to shut down the system in case
of an emergency.
Usually connected to the coupling element is a cable, which runs in both
directions and extends
alongside the conveyor system, and which allows shutting down the conveyor
system from any point
by pulling on the pull cable.
DIN EN 620 specifies guidelines for emergency stop switches with ripcord
systems for ascending
conveyors and systems, safety, and environmental requirements for stationary
belt conveyors for bulk
cargo. It requires that emergency stop switches with ripcord systems are
arranged in a way so that
the associated switching devices are actuated if the ripcord is pulled in any
direction or tears. Further,
ripcord systems must be designed so that the failure of only a single one of
the springs tensioning the
ripcord will trigger the connected switching devices.
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The ripcord switch must be triggerable by the action of a horizontal force
acting upon the pullcord of
less than 125 Newton, in the center between two guide rings and perpendicular
to the cable. The
lateral movement of the rope must be less than 300 mm.
PRIOR ART
Known from DE 696 19 128 T2 is a cable-activated switching device that by
means of a switch can
interrupt the power supply to machines. Disclosed is that a horizontal
displacement of a coupling
element effects a rotation of switching triggering means, which in turn
activates a switching element.
Due to a lever arrangement between the coupling element and a structure
supporting the switching
triggering means, a relatively small movement of the coupling element effects
a comparatively large
angular movement of the switching triggering means.
A further cable-operated emergency switch is known from DE 1 159 074. A cable
being pulled
activates a switching element that is activated by switching triggering means,
which in turn shuts down
a conveyor belt. It is further disclosed that a latching element latches the
switching elements in an
emergency switching position and that in addition to an emergency switching
signal, a switching
contact is provided to output an optical and acoustic signal. This facilitates
determining whether the
switching element has switched.
EP 2 043 117 A2 describes a quick-clamping device for a cable-operated switch,
that can be used to
detect the expansion and tension of a cable. A signal can be generated when
the tension deviates
from a nominal value range. Thus variations in the cable tension can be
detected and remedied at an
early stage.
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DE 29 35 420 C2 discloses an electrical switching-off device, in particular a
cable-operated emergency
switching device. The cable-operated emergency switching device is coupled
with a cable, so that
when the cable moves along a movement path an emergency switching signal can
be triggered, and
comprises a coupling element and a housing, with emergency switching
triggering means arranged
therein, and with an emergency switching element, whereby the coupling element
is operatively
connected to the emergency switching triggering means, so that the emergency
switching element
can be switched to trigger the emergency switching signal by means of the
movement of the
emergency switching triggering means. It is further disclosed that switching
elements are arranged in
the housing and are activated by a cylinder. These switching elements may also
be arranged
distributed at various angular positions on the circumference of the cylinder.
The above-described cable-operated emergency switching device is intended to
provide a higher level
of safety due to its redundant design with several switches and the decoupling
between the coupling
element and the cylinder. However, due to the complex design with numerous
components, the
manufacture of the cable-operated emergency switching device is expensive and
susceptible to failure
during operation.
DISCLOSURE OF THE INVENTION
Consequently it is the objective of the present invention to provide a cable-
operated emergency switch
and a safety device embodied with a cable-operated emergency switch, which in
a cost-effective and
reliable manner ensure a smooth and in particular continuous operation of a
conveyor belt system
without unnecessary emergency shut-downs.
This objective is met on the basis of a cable-operated emergency switch
according the preamble of
claim 1 in connection with the characterising features as well as a safety
device in accordance with
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claim 13. Further embodiments of the invention are described in the dependent
claims.
The invention specifies that in addition to the emergency switching triggering
means in combination
with the emergency switching element there are provided warning switching
triggering means and a
warning switching element, whereby the warning switching triggering means are
operatively
connected to the warning switching element, and whereby the warning switching
element can, with
respect to the movement of the cable, trigger a warning signal before the
emergency switching signal
is triggered.
Issuing the warning signal allows carrying out cable readjustments or for
example the removal of debris
such as for example dropped conveyed goods, which put the cable under
additional tension, before
an emergency switching signal is triggered and the conveyer belt system is
stopped. This allows
achieving a higher delivery rate and a better economy of the conveyor system.
In an advantageous embodiment of the cable-operated emergency switch, the
emergency switching
triggering means and/or the warning switching triggering means are arranged on
at least one cylinder.
This provides a particularly reliable and inexpensive switching means for
activating the emergency
switching element and/or the warning switching element at a precisely defined
switching point.
Advantageously, the emergency switching triggering means is embodied as an
emergency switching
track and/or the warning switching triggering means is embodied as a warning
switching track,
whereby the warning switching track and/or the emergency switching track are
embodied in the at
least one cylinder. This facilitates a particularly space-saving and compact
design of the cable-
operated emergency switch.
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Advantageously, the emergency switching track is of greater length than the
warning switching track
and/or the warning switching track is of greater depth than the emergency
switching track. The warning
switching track and the emergency switching track are embodied as indentations
in the cylinder. In
this, the length of the warning switching track and the emergency switching
track is determined by the
length of the indentation along the circumference of the cylinder. The
respective depths of the warning
switching track and the emergency switching track are determined by how far
the indentation extends
from the circumference of the cylinder in the direction towards the rotational
axis, Le. how close the
indentation approaches a rotational axis of the cylinder. The different
lengths of the tracks facilitates a
simple design, without the need for additional complex mechanisms for
switching the emergency
switching element or the warning switching element. Alternatively, providing a
single track with various
depths facilitates a very compact construction, in which the warning switching
element and the
emergency switching element are realized integrated in a so-called two-stage
switch that is switchable
in dependence on the various depths of the indentations in the cylinder.
In a further embodiment of the cable-operated emergency switch, the emergency
switching triggering
means and the warning switching triggering means are arranged on the at least
one cylinder
adjacently, joined, or nested within each other. This configuration simplifies
the design. In addition,
synergies and a reduced number of manufacturing steps during production of the
cylinder can reduce
manufacturing costs.
In a further embodiment of the cable-operated emergency switch, the cylinder
is connected directly to
the coupling element and in dependence on the movement path of the cable is
rotatable about a
common axis of rotation. In addition, starting from a center position of the
coupling element, a switching
path to an emergency switching point of the emergency switching triggering
means is greater than a
switching path to a warning switching point of the warning switching
triggering means.
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The direct coupling provides a simple and reliable solution with few component
parts. This prevents
any errors or malfunction due to gear ratios, levers, or play between
component parts.
Advantageously the coupling element of the cable-operated emergency switch can
be held in the
center position by means of a spring. In particular, the cylinder may be
operatively connected to the
spring, so that the coupling element is retained in the center position. Thus
the cylinder fulfills several
functions, eliminating the need for additional component parts. Using a spring
allows a simple
readjustment and customization of the force that counteracts the cable tension
or deflection with
respect to the cable's movement. This prevents erroneous shutdowns due to
cable tensions or cable
deflections below a threshold value.
In a further preferred embodiment of the cable-operated emergency switch, a
latching element is
provided to engage and retain the emergency switching triggering means in an
emergency switching
position upon output of the emergency switching signal. Also provided is a
return element for
unlatching and returning to the center position. The latching element ensures
that after triggering of
the emergency switching signal and the associated shutdown of the conveyor
belt system an
inadvertent restart can be ruled out. Expediently, the return element ensures
that the operation of the
conveyor belt system is only possible after an intended return to the center
position.
Alternatively, the warning switching triggering means, the emergency switching
triggering means, and
the latching element may be embodied in other shapes and designs that fulfill
the required function,
such as for example cams, pegs, tracks, hooks, etc.
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The invention further relates to a safety device for a conveyor belt system
with a cable and with a
cable-operated emergency switch to be coupled to a cable, so that an emergency
switching signal and
a warning signal can be triggered in case of a movement of the cable along a
movement path, and
with a control module that is designed to issue a warning message when the
warning signal is output
and to stop the conveyor belt system when the emergency switching signal is
output. Issuing the
warning signal allows carrying out cable readjustments or the removal of
foreign objects such as for
example dropped conveyed goods, which increase the tension of the cable,
before an emergency
switching signal is triggered and the conveyor belt system is stopped. This
leads to a higher production
rate and efficiency of the conveyor system. Alternatively, the use of a
control module can be foregone
and a drive can be stopped or the conveyor belt system can be shut down by
means of the emergency
switching element. Moreover, the warning switching element can issue a warning
signal directly.
Advantageously, the safety device is provided with a cable-operated emergency
switch in an
embodiment in accordance with the above-described characteristic features as a
constituent
component of the safety device.
PREFERRED EMBODIMENT EXAMPLE OF THE INVENTION
Further measures improving the invention are described in the following
together with the description
of a preferred embodiment example of the invention with the help of the
figures. The figures show:
Fig. 1 shows a perspective view of a cable-operated emergency switch without
the housing cover;
Fig. 2 shows a top view onto the open cable-operated emergency switch;
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Fig. 3 shows lateral views of the section along the section line A-A of the
cable-operated emergency
switch of Fig. 2 with an emergency switching track and a warning switching
track embodied on a
cylinder as well as an emergency switching element;
Fig. 4 shows lateral views of the section along the section line B-B of the
cable-operated emergency
switch of Fig. 2 with the warning switching track embodied on the cylinder and
a warning switching
element;
Fig. 5 shows the cable-operated emergency switch in a center position, an
emergency switching
position, and a warning switching position;
Fig. 6 shows a portion of the emergency switching track with the emergency
switching element in the
center position and the emergency switching position;
Fig. 7 shows a lateral view of the cylinder with the emergency switching track
and the warning
switching track nested within each other;
Fig. 8 shows a schematic representation of a conveyor belt system with a
safety device, comprising
the cable-operated emergency switch as well as a control module.
Figs. 1 and 2 show in a perspective view and top view respectively a cable-
operated emergency switch
100 with a cylinder 30, which is arranged in a housing 29 and on which are
provided warning switching
triggering means 10 embodied as a warning switching track 11 as well as
emergency switching
triggering means 20 embodied as an emergency switching track 21. A warning
switching element 12
and an emergency switching element 22 are operatively connected to the warning
switching track 11
and the emergency switching track 21 respectively. A coupling element 31 for
accommodating a cable
32 is directly connected to the cylinder 30. The cylinder 30 and the coupling
element 31 are movable
about a rotational axis 34. Also provided
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in the housing 29 is a latching element 35 with a return element 36 coupled
thereto.
Figs. 3 and 4 show a cross-sectional view of the cable-operated emergency
switch 100 in a central
position M. In this, a roller 37 of a switching lever 38 of the emergency
switching element 22 is
arranged centrally in the emergency switching track 21 and the warning
switching track 11. Originating
from the center position M, the switching path is the distance between the
roller 37 and the warning
switching point 43 or a distance between the roller 37 and the emergency
switching point 44,
respectively. A latching hook 39 of the latching element 35, which is
subjected to the spring load of a
latch spring 47, is in contact under load with a latching projection 40 of the
cylinder 30. During a
movement of the cable 32 along a movement path 41, the coupling element 31 and
the cylinder 30
rotate about the axis of rotation 34. As is shown in Fig. 4, the warning
switching element 12 with the
roller 37 and the switching lever 38 are arranged centrally in the warning
switching track 11. A
clockwise or anti-clockwise rotatory movement allows rotating the roller 37
with the switching lever 38
out of the warning switching track 11. Upon reaching the warning switching
position W (see Fig. 5d)
the roller 37 has reached a warning switching point 43 and the warning
switching element 12 initiates
a warning signal. In this, the latching hook 39 continues to rest upon the
latching projection 40, so that
no latching takes place and the cylinder 30 with the coupling element 31 can
return to the center
position M unimpededly. Consequently it is possible to detect a movement of
the cable 32 that might
indicate a maladjustment or a possible forthcoming emergency shutdown.
Measures can be
undertaken to prevent this emergency shutdown without having to interrupt
operations. A support 45
that is arranged on the housing holds the ends of the spring 33. The cylinder
30 and the coupling
element 31 are movable about the rotational axis 34, whereby the cylinder 30
as well as the coupling
element 31 are held in the center position M by means of the spring load of
the spring 33. In case of
a displacement of the coupling element 31
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and rotatory movement of the cylinder 30 away from the center position M, the
spring 33 will exert a
restoring force directed towards the center position M.
Fig. 5 shows a schematic representation of the cable-operated emergency switch
100 and the cable
32, which on two ends is connected to a cable tension spring 42 and
consequently is kept under
tension. In Fig. 5a the coupling element 31 is in the center position M. In
this, the force enacted by
the tension springs 42 upon the coupling element 31 is of equal magnitude in
opposing directions. A
warning switching position W according to Fig. 5d is reached as a result of a
short displacement of the
coupling element 31 caused by a movement of the cable 32. Also shown is the
cable-operated
emergency switch 100 in an emergency switching position N. In a first scenario
according to Fig. 5b
the cable 32 has broken on one side. As a result of the resulting one-sided
pull of the cable tension
spring 42 the coupling element 31 is pulled into the emergency switching
position N. In a second
scenario with an end-to-end intact cable 32 according to Fig. Sc, the
emergency switching position N
is effected either by a decrease in tension on the one side and/or an increase
in tension of the cable
32 of the cable-operated emergency switch 100. For example because of conveyed
goods dropped
onto the cable from a conveyor belt or due to temperature fluctuations and the
accompanying
expansion or contraction of the cable 32.
Figs. 6a and 6b show a portion of the cylinder 30 as viewed along the
rotational axis 34, with the
emergency switching track 21 in the center position M in Fig. 6a, and in the
emergency switching
position N in Fig. 6b. In this, the switching lever 38 with the roller 37 are
rotated out of the emergency
switching track 21 and are positioned at the emergency switching point 44 on
the cylinder 30. As a
result of the movement of the switching lever 38, the emergency switching
element 22 (not shown
here) is switched and an emergency switching signal is output. In this
position, the latching hook 39
has jumped and latched in front of or behind a projecting edge 46 of the
latching projection 40, which
prevents a return movement to the center position M. In this, the latching
hook 39 rests upon the
cylinder 30 under the applied spring load
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of the latch spring 47. The emergency switching position N described here is
reached by a clockwise
or anti-clockwise rotation. An advantage of this arrangement with an emergency
switching track 21
and a latching projection 40 is that even in the case of continued rotation or
over-rotation of the cylinder
30, the switching lever 38 remains in its position and the latching hook 39
will catch at the projecting
edge 46 when the cylinder 30 is rotated back. Consequently, no damage to
components can occur
and the emergency switching signal is output continuously.
Fig. 7 shows a cylinder 30 with the warning switching track 11 and emergency
switching track 21
arranged nested within each other therein. A clockwise or anti-clockwise
rotational movement causes
the switching lever 38 with the roller 37 to be swung out of the warning
switching track 11 into the
emergency switching track 21, which, upon reaching the warning switching point
43, outputs the
warning signal. Continued rotational movement to the emergency switching point
44 issues the
emergency switching signal.
Shown in Fig. 8 is a safety device 110 of a conveyor belt system 120,
comprising a conveyor belt 121,
conveyor belt rollers 122, and a conveyor belt drive 123. The safety device
110 comprises the cable-
operated emergency switch 100 with the cable 32 connected thereto as well as a
control module 111,
which is connected to the cable-operated emergency switch 100 via a signal
cable 112 to receive the
warning signal and the emergency switching signal. The control module 111
further is connected to
the drive 123 as well as to signal means 113. Upon receiving the emergency
switching signal, the
control module 111 effects a deactivation of the drive 123 as well as the
output of the emergency
switching signal by the signal means 113. Upon receiving a warning signal, the
control module 111
sends a warning message to a control center that is not shown here.
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List of reference labels:
Warning switching triggering means
11 Warning switching track
12 Warning switching element
Emergency switching triggering means
21 Emergency switching track
22 Emergency switching element
29 Housing
Cylinder
31 Coupling element
32 Cable
33 Spring
34 Rotational axis
Latching element
36 Return element
37 Roller
38 Switching lever
39 Latching hook
Latching projection
41 Movement path
42 Cable tension spring
43 Warning switching point
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44 Emergency switching point
45 Support
46 Projection edge
47 Latch spring
M Center position
N Emergency switching position
W Warning switching position
100 Cable-operated emergency switch
110 Safety device
111 Control module
112 Signal cable
113 Signal means
120 Conveyor belt system
121 Conveyor belt
122 Conveyor belt rollers
123 Conveyor belt drive
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