Rocker arm assembly for an aerial tramway

A rocker arm assembly for support of the haul rope of an aerial tramway or the like is disclosed. The assembly includes rocker arms, rope supporting sheaves rotatably mounted to the rocker arms and cantilevered from an inwardly facing side of the rocker arms. The rocker arms are additionally formed with rope catching groove or recess positioned outwardly of the sheaves and having a configuration which will enable not only the rope, but a hanger arm and grip to pass over the rope catcher in the event that the haul rope derails from the sheaves. The rocker arm assembly also preferably includes a platform which acts as a mount for the rocker arms and can be used for maintainence and repair of the rocker arms and rope supporting sheaves. Additionally, the rocker arm assembly includes haul rope derailment responsive apparatus formed to shutdown the tramway operation upon derailment of the rope from the sheaves.

BACKGROUND OF THE INVENTION 
Aerial tramways are conventionally supported from towers on which sheaves 
or pulleys are mounted for guided support of the wire or fiber rope on 
which the personnel carriers, such as chairs, gondolas, etc., are secured. 
As used herein, the expression "aerial tramway" shall include chairlifts, 
gondolas, ski lifts, trams and other wire or fiber rope mounted personnel 
conveying devices which are moved in an endless loop or are shuttled or 
reciprocated between stations. Usually the aerial tramway tower includes a 
pair of rocker arm assemblies to which the rope supporting sheaves are 
rotatably mounted. A typical rocker arm design includes a pair of sheaves 
mounted proximate opposite ends of a rocker arm, with the middle of the 
arm being pivotally mounted to a support structure. In a large rocker arm 
assembly there may be four rocker arms on which eight sheaves are mounted. 
The four rocker arms will be supported from pairs of intermediate rocker 
arms, and the pairs of intermediate rocker arms supported from opposite 
ends of a common even larger base or support rocker arm. The base or 
support rocker arm is, in turn, pivotally mounted to a transversely 
extending tower arm. 
This rocker arm assembly construction allows the various rocker arms to 
pivot so as to accommodate and evenly support the haul rope, even when a 
carrier grip passes over the sheaves. The various pivotally mounted rocker 
arms can rock, walk or pivot to accommodate irregularities along the 
length of the wire rope and dynamic load changes on the rope. 
One of the most important aspects of any aerial tramway rocker arm assembly 
is that the assembly be constructed in a manner which allows the 
incorporation of haul rope catching devices into the assembly. Thus, 
should the haul rope jump or derail from the sheaves, the rocker arm 
assembly should include means for catching the rope to prevent the 
personnel carrier from falling to the ground. Where possible, the rope 
catching device should redirect the rope back onto the sheaves. 
Providing a rope catching structure on the inward or tower side of a rocker 
arm assembly is relatively easy. As used herein, the "inward" side of the 
rocker arm assembly shall mean the side of the assembly on which the 
hanger arm for the personnel carrier does not pass. When a central tower 
is employed having transversely extending arms on which the rocker arm 
assemblies are mounted, the inward side is the side closest to the central 
tower. The "outward" side of the rocker arm assembly is the side on which 
the hanger arm does pass. 
Since the hanger arm does not pass over the inward side of the assembly, it 
is a relatively simple matter to provide a deflector arm or post which 
extends alongside and up above the rope proximate the lead and trailing 
sheaves of the rocker arm assembly. This deflector or rope catcher will 
prevent the haul rope from crawling up over the inside of the lead and 
trailing sheaves and will deflect the rope back down onto the sheave 
assembly. 
On the outwardly facing side of the rocker arm assembly, however, the 
problem of catching or preventing the rope from jumping from the sheaves 
is much more substantial. Any rope catching structure must not interfere 
with passage of the hanger arm over the rocker arm assembly and the 
support sheaves. In prior aerial tramways, the rope catcher on the outward 
side of the rocker arm assembly has been provided by an arm or post which 
is mounted outwardly of the sheaves or rockers so as to catch the rope in 
the event that it should jump off of the sheaves. For most towers there 
will be considerable downward force on the rope as a result of the load, 
and the haul rope will drop downwardly immediately upon derailing from the 
sheaves. As it is downwardly displaced, the rope will become hooked or 
caught on the outside rope catcher. As will be understood, some towers 
will have rocker arm assemblies which hold the rope down. In those 
instances the rope catcher on the outside of the assemble presents little 
problem since the hanger arm need not pass over the outside rope catcher. 
Various devices have been provided on rocker arm assemblies to shut down an 
aerial tramway as soon after the haul rope leaves the sheaves as possible. 
Typical of such prior art derailment actuated shutdown devices are the 
apparatus set forth in my U.S. Pat. Nos. 4,019,002 and 3,822,369 and my 
pending U.S. patent application Ser. No. 207,259, filed Nov. 17, 1980 now 
U.S. Pat. No. 4,363,945 and entitled "Cable Derailment Responsive 
Apparatus." One serious problem that has been encountered with prior 
rocker arm assemblies and rope catchers, however, has been that while the 
haul rope will be caught by the rope catcher upon jumping from the 
sheaves, the hanger arm on the next carrier will be pulled into the rope 
catcher before the lift can be stopped by the derailment responsive 
shutdown device. If the haul rope jumps the sheaves just after the hanger 
arm passes the sheave assembly, the aerial tramway will normally be 
shutdown before the next hanger arm reaches the rope catcher. 
Statistically, however, it is almost certain that situations will occur in 
which the rope will jump from the sheaves just as a hanger arm approaches 
the rocker arm assembly. The result will be that the hanger arm hits the 
rope catcher before the lift can be stopped, which can result in a violent 
decelleration of the rope, jumping of the haul rope over the rope catcher, 
or breaking of the rope catcher free of the rocker arm assembly, all with 
potentially dangerous consequences. 
Rocker arm assemblies have typically heretofore been constructed in one of 
four manners. In the first case, the sheaves are cantilevered from an 
outward side of the rocker arms. The rocker arms in turn are cantilevered 
from an outward side of intermediate rocker arms, which in turn are 
cantilevered from the outward side of the base or assembly rocker arm. 
Rope catchers are provided as post or hooked shaped catchers proximate the 
lead and trailing sheaves and are secured to the lead and trailing rocker 
arms. This structure has the advantage of positioning all of the sheaves 
on the outward facing side of the assembly, which enables their easy 
replacement. A second type of prior rocker arm assembly construction is 
shown in my U.S. Pat. No. 4,019,002. In this patent, the sheaves are 
mounted in yoke-like rocker arms, which in turn are mounted in 
successively larger yokes, with the base or largest yoke being 
cantilevered from the tower arm. This structure affords certain advantages 
in enabling placement of rope catching posts, but it has the disadvantage 
of requiring pivoting of the yokes and holding of the same in a pivoted 
position for replacement of all but the lead and trailing sheaves. 
A third prior rocker arm construction has included rocker arms in which the 
sheaves are supported above the various rocker arms so that the center 
line of the sheave axles is above the center line of the rocker arm pivot 
pins. This has the advantage of making the sheaves accessible for 
replacement, however, the mounting of rope catchers is more difficult. 
In a fourth type of prior rocker arm assemblies, the sheaves are 
cantilevered on the outside of the rocker arm, but the rocker arm has a 
C-shaped cross section so that the sheaves and haul rope are suspended 
below the pivot points of the rocker arms. While the sheaves are 
self-aligning to some degree, this construction makes the outward rope 
catchers less able to support the haul rope due to the tendency of the 
sheaves to swing inwardly when loaded. 
In all prior rocker arm assemblies, considerable care must be taken so that 
the rockers allow clearance for the hanger arm and chair parts at all 
possible angles of swing. The aerial tramway codes require that the rocker 
arm assembly be constructed so that it will allow for clearance of the 
hanger arm for carriers which are swung inwardly by 10 to 15 degrees. 
Maintenance of prior rocker arm assemblies has been largely accomplished by 
means of clambering over the tramway tower arms out to the rocker arm 
assemblies using a platform mounted on one of the carriers and climbing 
onto the tower if necessary, or using a vehicle having a cherry picker, 
personnel carrying platform. Since many tramway towers are inaccessible to 
vehicles, the cherry picker approach is not suitable in many instances. 
Climbing over the tower arms from the ground or from a platform on a 
carrier, particularly when the towers are sloped and the terrain is steep, 
can pose a safety problem. Accordingly, in recent years aerial tramway 
code requirements have tended to move toward requiring a platform on the 
aerial tramway tower which can be used by repair and maintenance personnel 
to service the sheaves and the derailment shutdown apparatus of the rocker 
arm assemblies for the aerial tramway. 
Prior rocker arm service platforms, however, have been added largely as an 
afterthought, and their design has not been integrated or coordinated to 
any significant degree with the rocker arm assemblies. Essentially, 
walkways or platforms have merely been mounted to the transverse tower 
arms, with the result that the platforms are awkward to use, unsightly, 
cause snow build-up, and often do not afford good access to the rocker 
arms. The rocker arms, moreover, were not designed, in many cases, for 
servicing from the inside or tower side of the rope, making tower mounted 
platforms of little assistance during maintenance and repair. 
The rocker arm assembly mounted derailment responsive apparatus previously 
employed, including my above referenced inventions, have tended to employ 
one of two operating principles. Either a frangible element is impacted or 
struck by the derailing haul rope or derailment of the rope results in 
movement of the sheaves which is sensed and used to shutdown the tramway. 
There can occur, however, situations in which the haul rope does not hit 
the frangible element or the sheaves do not move significantly upon 
derailment. 
OBJECTS OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a rocker 
arm assembly for an aerial tramway or the like which has enhanced safety 
and simplicity of construction. 
Another object of the present invention is to provide a rocker arm assembly 
for support of a haul rope for an aerial tramway which includes an 
improved rope catching structure. 
A further object of the present invention is to provide a rocker arm 
assembly for support of a haul rope for an aerial tramway in which the 
rocker arm components are constructed and supported to minimize wear and 
fatigue. 
Still a further object of the present invention is to provide a rocker arm 
assembly for an aerial tramway or the like in which the rope supporting 
sheaves of the assembly are all mounted for easy and independent 
maintenance and removal. 
A further object of the present invention is to provide a rocker arm 
assembly for an aerial tramway or the like which is simple to construct, 
durable, adaptable to mounting on a wide range of support structures, and 
serviceable with relatively simple tools and equipment. 
It is a further object of the present invention to provide a service 
platform for aerial tramway rocker arm assembly which provides increased 
safety for repair and maintenance personnel. 
Another object of the present invention is to provide a rocker arm assembly 
and service platform which are integrally formed and coordinated for ease 
of repair and maintenance of the rocker arm assembly. 
Still another object of the present invention is to provide an aerial 
tramway repair and maintenance platform which can be used to install and 
maintain rocker arm assemblies and sheaves and provides greatly enchanced 
access to sheaves on both sides of the aerial tramway tower. 
Still another object of the present invention is to provide a maintenance 
and repair platform for rocker arm assemblies on an aerial tramway which 
is inexpensive to construct, may be easily added to existing towers, is 
highly durable, will not cause snow build-up, and will not interfere or 
inhibit tramway operation. 
A further object of the present invention is to provide a rocker arm 
assembly having an improved rope derailment responsive tramway shutdown 
apparatus. 
Another object of the present invention is to provide a rope derailment 
responsive apparatus which has improved reliability of operation. 
Still a further object of the present invention is to provide a rope 
derailment responsive apparatus which is actuated by either haul rope 
impact or rope derailment from the rocker arm assembly. 
The rocker arm assembly of the present invention has other objects and 
features of advantage which will become apparent from the following 
description of the preferred embodiment and the accompanying drawing. 
SUMMARY OF THE INVENTION 
The rocker arm assembly of the present invention includes rocker arm means, 
haul rope supporting sheaves rotatably mounted to the rocker arm means, 
and rocker arm mounting means formed for pivotal mounting of the rocker 
arm means outwardly from a support structure. The assembly further 
preferably includes haul rope derailment responsive apparatus formed to 
shutdown the tramway and a maintenance and repair platform. 
The improvement in the rocker arm assembly comprises, briefly, the sheaves 
being cantilevered inwardly from the rocker arm means for support of the 
haul rope inwardly of the rocker arm means. Additionally, it is preferable 
that the rocker arm means are formed with rope catching means, such as a 
groove or recess, on an upwardly facing surface thereof and that the 
rocker arm means are formed for passage of the hanger arm of a personnel 
carrier over the rocker arm when the haul rope is caught by the groove or 
recess in the rocker arm. 
In another aspect of the present invention, a tower mounted maintenance and 
repair platform for an aerial tramway is provided which includes platform 
mounting means formed for securement to the tramway tower, platform means 
formed for support of personnel thereon and secured to said platform 
mounting means, and rocker arm assembly mounting means carried by said 
platform means and formed for receipt and support of a rocker arm assembly 
thereon. 
Finally, the improved rocker arm assembly includes haul rope derailment 
responsive apparatus mounted to the rocker arm means and formed with an 
electrical circuit coupled to terminate tramway operation. The improved 
rope derailment responsive apparatus has a frangible element positioned on 
the rocker arm for impact by the rope and circuit breaker means formed to 
break said frangible element upon movement of the rocker arm means when 
the rope derails and fails to be caught by the rocker arm.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The rocker arm assembly as shown in FIGS. 1 and 2 of the drawing is an 
eight sheave rocker arm assembly, which is particularly useful in 
illustrating the improvements of the present invention. It will be 
understood, however, that the rocker arm assembly construction of the 
present invention is suitable for use with four sheave assemblies (FIG. 
8), three sheave assemblies (FIGS. 11 and 12), two sheave assemblies, 
sixteen sheave assemblies, and various other numbers of sheaves. 
In FIGS. 1 and 2, the rocker arm assembly, generally designated 21, 
includes eight sheaves 22 mounted to a plurality of sheave carrying rocker 
arm means 23. Each of the sheave carrying rocker arms 23 in turn is 
mounted to an intermediate rocker arm 24, and the two intermediate rocker 
arms 24 are pivotally mounted to an assembly rocker arm 26, which is 
pivotally mounted to a support structure, such as the transverse arm 27 of 
tramway tower 28. 
As will be described in more detail hereinafter, each of sheaves 22 is 
rotatably mounted to the sheave carrying rocker arms 23 for movable 
support of the aerial tramway wire or fiber haul rope. In the assembly 
shown in the drawing, each of the sheave carrying rocker arms 23 has a 
sheave mounted proximate the end thereof, and they are accordingly 
referred to in the industry as "two-sheave rockers." Since the two-sheave 
rockers are pivotally mounted at 31 to intermediate rocker arm 24, the 
intermediate rocker arm 24 carries a total of four sheaves and is referred 
to as a "four-sheave rocker." The assembly rocker arm 26, which has two 
four-sheave rockers pivotally mounted thereto at pivot points 32, is also 
known as an "eight-sheave rocker." 
As is true with conventional rocker arm assemblies, the purpose of 
pivotally mounting the various rocker arms to each other and to the 
support arm 27 on the tower is to cause the sheaves to automatically 
adjust to the load on haul rope 29. The pivoting or rocking of the various 
rocker arms allows the sheaves to in effect walk or be rocked 
progressively as irregularities in the rope, the carrier grips and load on 
the rope are transmitted to the assembly. This dynamic action of the 
rocker arm assembly enhances the even support of the haul rope and tends 
to prevent the rope from climbing up and falling off the sheaves. 
Rocker arm assemblies are used in various types of aerial tramways. As 
shown in FIG. 3, triple chair 33 is supported by frame 34, which is 
coupled to hanger arm 36 by a mounting assembly 37, preferably constructed 
as set forth in my U.S. Pat. No. 4,179,994. As will be understood, 
however, other personnel carriers, such as a gondola, tram body, or even a 
ski lift support seat, can be coupled to hanger arm 36. The upper end of 
hanger arm 36 will be provided with a rope grip, generally designated 38, 
which can take a number of different forms. Grip 38, for example, can be 
permanently or removably attached to rope 29. Moreover, the grip 38 can be 
buried inside a wire rope or formed with rope clamping jaws that grip the 
outside of the rope. Usually the grip is provided with motion damping 
means to minimize the swing of the hanger arm, such as is described in my 
co-pending U.S. Application Ser. No. 249,003, now U.S. Pat. No. 4,401,198 
entitled "Friction-Based Motion Damping Assembly for Chairlift or the 
Like." 
The rocker arm assembly of the present invention as thus far described 
includes structure which is found in prior aerial tramway rocker arm 
assemblies. Thus, rope supporting sheaves 22 have conventionally been 
rotatably mounted to rocker arm means, such as rocker arms 23, and 
mounting means have been provided for pivotal cantilevered mounting of the 
rocker arm means 23 to a support structure, in this case intermediate 
rocker arms 24, assembly rocker arm 26, transverse tower arm 27 and 
support tower 28. 
In the improved assembly of the present invention, however, while rocker 
arms 23 are outwardly cantilevered from support rocker arms 24, sheave 
means 22 are cantilevered inwardly toward the support structure from 
rocker arm means 23. This results in a positioning of haul rope 29 
inwardly of the rocker arm means 23, which can best be seen in FIGS. 3, 5 
and 6. More particularly, the two-sheave rocker arm 23 can be seen to be 
cantilevered outwardly on pivot member or shaft 31 from four-sheave rocker 
arm member 24. Instead of cantilevering sheave 22 outwardly from the 
two-sheave rocker 23, as is common in the industry, and inwardly 
cantilevered shaft or pipe 39 is provided for rotatable support of sheaves 
22. Thus, rope 29 is between the tower and the two-sheave rocker 23. 
The inward cantilevering of the sheaves off of the two-sheave rockers 23 
has several important advantages. First, all of the sheaves can be 
independently reached and removed from the assembly by simply removing the 
end cap 41 which is bolted by means of a bolt 42 to a nut 43 welded inside 
the tubular shaft 39 on which the sheaves are rotatably mounted. The 
sheave is then removed from the inward side of the assembly, instead of 
the outward side of the assembly. 
A second important advantage of the inward cantilevering of sheaves 22 is 
that rocker arm 23 can be readily formed with rope catching means, 
generally designated 46, on the outward side of sheave 22. In the 
preferred form, rope catching means 46 is provided as a groove or recess 
47 extending parallel to the haul rope in an upwardly facing side of 
rocker arm 23. Groove 47 can be defined on the inner and outer sides by 
ridges 48 and 49 which extend longitudinally so as to assist in retaining 
the rope should it jump or derail from the sheaves. As will be seen in 
FIGS. 4 and 5 in phantom, rope 29 will be supported and rest in groove 47 
along the two-sheave rockers of the assembly in the event that it should 
climb up over the outer rim of 51 (FIG. 5) of sheave 22. 
It is a further important feature of the present invention that the rocker 
arm and rope catching groove 47 be formed for passage of the rope and 
hanger arm 36 and grip assembly 38 over the rocker arms or along the rope 
catching grooves when the rope is supported in the grooves. Thus, rocker 
arms 23 can be seen to be formed with rounded leading and trailing 
surfaces 52 and 53 which are faired into rope catching groove 47 so that 
there are no discontinuities or interruptions which would cause a hanger 
arm or grip to bounce out of the groove or stop suddenly. The rocker arm 
assembly of the present invention, therefore, will allow a haul rope which 
has derailed or jumped from the sheaves onto the groove to still advance, 
even when the hanger arm reaches the rope catcher, until the lift is shut 
down. Since it is predictable that hanger arms will be advanced to the 
rocker arm assembly before the lift can be shut down in at least some 
instances of the rope jumping from the sheaves, the rocker arm 
construction of the present invention greatly enhances safety as compared 
to previous apparatus designed to catch the haul rope on the outwardly 
facing side of the rocker arm assembly. 
Proximate the inward rim 54 of the lead and trailing sheaves of the rocker 
arm assembly is a haul rope deflector or catcher 56. As will be seen from 
FIGS. 3 and 5, the inward rope catcher-deflector 56 can be very closely 
mounted to the inward rim of the sheave because the grip assembly and 
hanger arm do not have to pass over rim 54. Accordingly, deflectors 56 
will simply re-direct a rope which tends to climb over rim 54 back down 
onto the sheaves. As best may be seen in FIG. 4, deflector 56 includes an 
arm portion 57 which extends upwardly from end cap portion 41 and can be 
bolted on the lead and trailing sheaves at shafts 39 instead of a 
cylindrical end cap 41. In order to resist any torque which the deflector 
may experience about shaft 39, it will be noted from FIG. 4 that bolt 42 
is bolted to a nut welded to the side wall of the inside of tubular shaft 
39, which results in the bolt 42 being off center and in a position to 
resist rotation. To further resist rotation, it is preferable to pin the 
deflector collar portion 41 at 58 to tubular shaft 39. 
A third important aspect of the rocker arm assembly construction of the 
present invention is the ability to position the pivotal and rotatable 
bearings in substantial alignment with haul rope 29. As may be seen in 
FIG. 6, it would be possible to fixedly mount sheaves 22 to shaft 39 and 
pivot shaft 39 with respect to rocker arm means 23. In the preferred form, 
however, the pivotal mounting shaft 39 is integrally cast in a boss or 
socket 59 of rocker arm 23. Mounted on the inwardly cantilevered end of 
the shaft 39 is the bearing assembly, schematically shown at 61, for 
sheaves 22. Thus, sheave bearing assembly 61 is positioned in substantial 
alignment with, and in this case beneath, rope 29. While the rocker arm 
assembly of the present invention is shown with the rope mounted on top of 
the sheaves, it will be readily apparent to those in the industry that in 
some assemblies, the sheaves hold the haul rope down and the assembly 
would essentially be inverted. This would position the rope below the 
various bearings, but whether below or above, the rope will be in general 
alignment with bearings 61 and the pivotal mounts for the various rocker 
arms in the assembly. 
In the preferred form of the assembly of the present invention the pivotal 
shaft 31 between the two-sheave rocker arms 23 and the support rocker arms 
24 is also cast in a boss or socket 62 and extends inwardly from the 
two-sheave rocker arm. Mounted on the inwardly extending end of pivotal 
shaft 31 is a rocker arm bearing 63 (preferably a low-friction sleeve such 
as a TEFLON sleeve) on which is carried by the four-sheave rocker arm 24. 
Bearing 63 will be seen to be aligned with rope 21 so that wear and 
loading of rocker arm bearing 63 will be even. Moreover, as best may be 
seen in FIG. 5, a pivot shaft or pin 64 between eight-sheave rocker arm 26 
and four-sheave rocker arm 24 can be rigidly secured in the eight-sheave 
or assembly rocker arm 26 and mounted for pivotal movement by another 
rocker arm bearing 66 (e.g., a TEFLON sleeve) in a socket 67 provided in 
the central portion 68 of the four-sheave rocker arm 24. As will be seen, 
rocker arm bearing 66 is again positioned in substantial alignment with 
rope 29 for even loading of this bearing. 
The final pivotal mount for the rocker arm assembly is provided by a pivot 
shaft 71 which is journaled inside a bearing (not shown) mounted in 
transverse tower arm 27 and is fixedly secured to eight-sheave rocker arm 
26. Pivotal shaft 71 cannot be provided with bearings mounted underneath 
or in alignment with rope 29, but is possible to provide very large 
bearings in arm 27 so that the cantilevering of shaft 71 with respect to 
the load on rope 29 can be readily supported. The size of the bearing for 
shaft 71, therefore, can be selected so that wear and maintenance are not 
a substantial problem. 
The inward cantilevering of sheaves 22 plus selection of which elements 
pivot with respect to the remaining elements, therefore, results in 
alignment of sheave bearings 61 and rocker arm bearings 63 and 66 directly 
under the rope load for even wear. This is a substantial benefit as 
compared to pivotal mounting arrangements in which the bearings must 
support a cantilevered load. 
As best may be seen in FIG. 5, one manner of securing two-sheave rocker 23 
to four-sheave rockers 24 is to form a slot 72 in tubular member 31 into 
which bolt 73 can extend. Boss or socket 62 is threaded to receive bolt 
73, and slot 72 extends circumferentially a sufficient distance to 
accommodate rocking or pivoting of rocker 23. 
A similar structure is used to secure pivot pin or axle 64 to the middle of 
four-sheave rocker 24. Thus, bolt 74 is threaded through boss 68 and 
projects into a notch or groove 76 in pin 64. Other securement structures 
are possible, but an advantage of the above structure is its universal 
nature. If, for example, an assembly is to include only two sheaves, the 
pin 64 can be mounted inside tube 31 and a bolt 73 will protrude into 
notch 76. It is a further feature of the present invention that the pin 64 
and tube 31 be formed for telescopic mounting together and that notch 76 
and slot 72 can be superimposed. 
In recent years tramway codes have begun to require that the aerial tramway 
towers include a personnel support platform for maintenance and repair of 
sheaves and rocker arm assemblies. FIG. 7, 8, 11 and 12, illustrate 
platform means which have been incorporated into and form a part of the 
tower structure and rocker arm assembly of the present invention. Thus, 
the rocker arm assemblies 21, 21a and 21b are shown mounted to platform 
means, which in turn are secured to towers. In FIGS. 7 and 8, platform 
means 81, therefore, acts as mounting means for the rocker arm assemblies 
21 and 21a, the latter of which is a four-sheave assembly on the return 
side of the tramway haul rope. In FIG. 12 platform means 141 is 
incorporated into what is essentially the seven-sheave rocker (an assembly 
of a four-sheave rocker and a three-sheave rocker) as is described in more 
detail hereinafter. 
In FIGS. 7 and 8, platform means 81 is constructed out of side frame 
members 83 and 84 to which a preferably open platform surface, such as 
expanded metal member 86, is secured. The side frames are held in rigid 
spaced apart relation by three cross bracing tubular members 87, 88 and 
89, with the expanded metal platform 86 being supported on frame elements 
91 to provide a rigid surface which will support several maintenance and 
repair workers. The use of an expanded metal for the platform surface 
tends to reduce snow and ice build up on the tower. 
As best may be seen in FIG. 7, the platform 86 is positioned proximate 
rocker arm assemblies 21 and 21a so that the sheaves 22, two-sheave 
rockers 23, and four-sheave rockers 24 are easily accessible to personnel 
on the maintenance platform. Moreover, the inward cantilevering of sheaves 
22 from two-sheave rockers 23 affords workers ready access to remove the 
sheaves anywhere along the rocker arm assembly by pulling them inwardly 
toward the platform. 
Rocker arm assembly 21 is an eight-sheave assembly in which the 
eight-sheave rocker 26 of FIGS. 1 and 2 has been replaced by beam or frame 
member 83. Each of the four-sheave rockers 24 is mounted to a laterally 
extending rocker arm mount 92, which is rigidly secured to frame member 
83. Frame member 83 inturn is rigidly secured to transverse pipe 88 that 
is clamped by means of mounting clamps or brackets 93 proximate the top or 
upper end 94 of tower 82. 
As shown in FIG. 7, rocker arm assemblies are usually secured to the tower 
on which they are mounted at an angular orientation other than 
perpendicular. This angle can vary considerably, and the tower 82 can be 
oriented in a vertical direction as shown in FIG. 7 or angularly displaced 
from the vertical, depending upon the tower design and the terrain. 
The platform mounting means or clamp structure 93 allows platform 82 to be 
angularly adjusted with respect to tower 82. Once the platform and 
accordingly the rocker arm assemblies are properly oriented in accordance 
with the tramway design, fasteners 96 can be tighted to lock the angular 
orientation of the platform in place. If necessary or desirable, the cross 
beam 88 can even be welded to clamp members 93 or the fasteners can be 
welded against backing out of the mounts. 
Such a rigid securement of the angular orientation of side beams 83 and 84 
takes the pivotal mounting out of what was the eight-sheave rocker 26. It 
has been found, however, that eight-sheave rockers, under maximum load 
variation, will undergo an angular displacement at the pivot mount 71 of 
only about 1 to 11/2 degrees. The displacement of the two-sheave and 
four-sheave rockers, therefore, will accommodate a wide range of loading 
conditions, and fixing the eight-sheave rocker such as by clamps 93 (or 
four-sheave rocker on the return side) will not induce unacceptable stress 
variations in the tower or haul rope. 
On the return side of the tower, four-sheave rocker arm assembly 21a is 
mounted to a transversely extending amount 92a and is preferably 
constructed with rocker arms 23a from which sheaves 22a are inwardly 
cantilevered. Additionally, the two-sheave rockers 23a are preferably 
formed with a groove or recess 47a which extends parallel to rope 29a on 
the outward side of the rope to act as rope catching means. 
The lateral extending mounts 92 and 92a position the rope outwardly of 
platform 86 at a distance which ensures that the platform will not 
obstruct tramway operation and yet the platform is close enough to make 
working on the sheaves relatively easy. Typically, the lateral mounts 92 
and 92a will extend about 1 to 2 feet outwardly from platform side frame 
members 83 and 84. 
It is a further important advantage of the platform and rocker arm assembly 
of the present invention that the platform means be provided with hoist 
support means positioned in superimposed relation over haul rope 29 and 
29a. Thus, the platform includes posts 97 on which laterally extending 
cross beams 98 are mounted. Beams 98 extend to a position superimposed 
above rope 29 and 29a, as best may be seen in FIG. 8. The extension of 
transverse beams 98 beyond side frames 83 and 84 affords a member to which 
a hoist or the like can be secured to enable raising and lowering of a 
variety of components during construction and maintenance of the towers. 
Thus, the rocker arm assemblies, sheaves and rope can all be hoisted off 
of transverse beams 98 and held in position until the construction or 
repair is completed. 
Finally, it is an important feature of the platform and rocker arm assembly 
of the present invention to provide rail means 99 which extends 
substantially around the periphery of platform 81. Rail means 99 acts as a 
restraining device so that the personnel will not inadvertently fall from 
the platform. The transverse members 98 further function as rails along 
the ends of the platform, as do cross bracing members 101 between the 
posts 97. It is preferable to mount the longitudinally extending rail 
members 99 to cross beams 98 and to mount posts 97 to cross members 87 and 
89 in a manner which allows angular displacement of the posts and rails as 
a parallelogram in order to accommodate the angular displacement of side 
frames 83 and 84 during set up and clamping of the platform to tower 82. 
Once the platform is positioned, the rails and posts can be locked in 
their angular orientation by clamps, fasteners or even welding. 
As will be understood, the rocker arm assembly of the present invention can 
be pivotally mounted on an eight-arm rocker to a transversely extending 
member, such as member 88 so that the assembly will pivot or rock 
independently of the platform means 81. The platform would, in that 
instance, still provide the advantages of access and safety without acting 
as mounting means for the rocker arm assembly. 
FIGS. 11 and 12 illustrate an alternative embodiment of a rocker arm 
assembly 21b which includes platform means 141. Instead of providing eight 
sheaves, assembly 21b includes seven sheaves 22b which support haul rope 
29b. The left sub-assembly in FIGS. 11 and 12 is a four-sheave rocker 
including a pair of two-sheave rockers 23b and four-sheave rocker 24b, 
constructed as above described for the assembly of FIGS. 1 through 6. The 
right sub-assembly in FIGS. 11 and 12 is a three-sheave rocker 142 
including a two-sheave rocker 23b mounted on arm 143 and a single sheave 
mounted on arm 144. 
Three-sheave rocker 142 has arms 43 and 144 which have a length selected so 
that the moment about pivot pin 64b is zero. Thus, the arm 143 is shorter 
than arm 144 so that there is no imbalance in the moment about pivot 32b 
as a result of the presence of two sheaves on one arm and one sheave on 
the other. 
Arm 144 is preferably formed to extend outwardly from tower 28b as compared 
to arm 143 (best seen in FIG. 12) so that the sheave mounted on arm 144 
can be inwardly cantilevered and rope catching means 146 can be provided 
outwardly of rope 29b. Rope catcher 146 is formed in a manner similar to 
rope catcher 23b with faired lead end 147 and trailing end 148 and a rope 
catching groove 149. 
Instead of providing platform means 141 as a platform which extends across 
the tower (some towers have a haul rope on only one side), platform 141 is 
provided by forming the seven-sheave "rocker" as a pair of spaced-apart 
plate members 151 and 152 which are mounted to transverse tower arm 27b. 
The seven-sheave "rocker" is not a true rocker since it is not free to 
pivot, as will be set forth below. 
Extending between plates 151 and 152 are a pair of rectangular mounting 
housings 153 and 154 which include pivot post or pins 64b that can be 
angularly adjusted by adjustment screws 156 in a manner well known in the 
industry. 
A pair of auxiliary rods 157 project outwardly from housings 153 and 154 
and into hollows in the castings for arms 24b and 142 to limit to some 
degree the pivoting of the arms. These limit rods 157 hold the arms 24b 
and 142 in an upright position for assembly until rope 29b is supported on 
the sheaves. The openings or hollows in arms 24b and 142 into which the 
rods 15 project are of sufficient size that the rocking of the arms during 
dynamic loading is not inhibited by rods 157. 
Also extending between plates 151 and 152 are a plurality of bars 161 which 
form an open platform in immediate proximity to sheaves 23b. Bars 161 can 
advantageously be provided by ribbed reinforcing bars and they are secured 
proximate the bottom of plates 151 and 152 so that the sides of the plates 
aid the service personnel in maintaining their balance on the platform. 
The bar-type platform also acts as a slightly inclined ladder for arms 
which are sloped, as is most often the case. The openings between bars 161 
are sufficient to insert the heel or toe of a boot for good traction even 
though plates 151 and 152 are inclined. 
Securement of the rocker arm assembly of FIGS. 11 and 12 is preferably 
accomplished by forming plate 152 with an opening 162 sufficient to pass 
over square tubular tower arm 27b. Fixedly mounted to tower arm 27b, 
however is an inner annular collar or flange 163. Plate 152 will, 
therefore, abut against collar 163 when slipped over the end of arm 27b. 
The end 164 of tower arm 27b is closed with a plate in which an inwardly 
extending tube 166 is secured. Welded to the inside of plate 151 is a 
cylindrical member 167 which telescopes inside tube 166 as plate 152 is 
slid over the arm end and urged into engagement with collar 163. Before 
cylindrical projection 167 is inserted into tube 166, however, a second 
collar or flange 168 is slid down arm 27b until it is in abutment with the 
inside of plate 152. Bolts 169 are then passed through opening 162 and 
used to pull collar 168 toward collar 163 with plate 152 sandwiched 
between. Thus, a very substantial friction force is generated between 
collars 163 and 168 so as to enable locking of plate 152, and therefore 
the entire assembly, between at any desired angular orientation on arm 
27b. When tower 28b is erected, therefore, plates 151 and 152 can be 
mounted on arm end 164 and collars or flanges 163 and 168 used to lock the 
arm in the desired angular orientation. Other mounting structures for the 
open-bar rocker arm platform of FIGS. 11 and 12 are also feasible. 
Referring now to FIGS. 9 and 10, the rocker arm assembly of the present 
invention can further be seen to include haul rope derailment responsive 
apparatus formed to terminate opration of the tramway in the event of 
derailment or jumping of the rope from sheaves 22. Mounted to rocker arm 
means 23 is rope derailment responsive apparatus, generally designated 
111, which is formed with an electrical circuit coupled to terminate 
operation of the tramway. Thus, electrical wires 112 and 113 are coupled 
to frangible element 114, which has a weakened plane or notch 116 that 
ensures the frangible element will break or rupture at notch 116. The 
frangible element 114 is formed of an electrically conductive material and 
is coupled by connectors 117 to wires 112 and 113. Numerous materials are 
suitable for formation of the electrically conductive frangible element 
114, but a brittle cast zinc can be advantageously used as the frangible 
element of the present apparatus. Wires 112 and 113 are mounted in their 
own insulating coverings and in turn are mounted in common sheath 118 
which extends from the tram electrical control panel to each tower along 
the lift line. 
The electrical circuit in which frangible elements 114 at each tower are 
incorporated can take several different forms, but preferably the 
frangible elements act as normally closed switches connected in series. If 
any one of the frangible elements is broken, the switch will open, which 
actuates a solenoid to in turn shutdown the drive motor driving haul rope 
29. Such a circuit is described in more detail in my U.S. Pat. No. 
4,019,002 and will not be repeated herein. 
In order to cause breaking of frangible element 114 by rope impact, the 
upper end 119 of frangible element 114 protrudes above the bottom of 
two-sheave rocker arm groove 47. A rope which jumps or derails from the 
sheaves and is caught by the rope catching groove 47 will impact or strike 
and drive frangible element 114 downwardly. This will cause shattering of 
the frangible element at notch 116, with the result that there will be a 
gap at the apex 121 between the two conductive legs 122 of the frangible 
element. It is preferable to provide flexible shield means 123, such as a 
thin rubber cap, over the protruding end 119 of the frangible element. The 
shield will collapse under rope impact, and it is sealed with respect to 
the groove 47 so that ice and snow cannot go down inside the rocker arm 
axle and affect performance of the derailment responsive lift shutdown 
apparatus. 
While positioning of the frangible element 114 for impact by rope 29 will 
terminte lift operation if the haul rope is caught by rope catching groove 
47, there is the possibility that the rope will derail under dynamic 
conditions of which will cause the rope to jump free of the rocker arm and 
not be caught by rope catching means 46. If such a rope derailment should 
occur, it is a further important feature of the derailment responsive 
means 111 that it be formed to break frangible element 14 even upon 
failure of the rope to impact the frangible element. This can be 
accomplished by biasing the lead and trailing rocker arms for pivotal 
movement in the event that the rope is no longer supported on the sheaves 
or rocker arms. Such a biasing can be a gravity biasingby weighting of the 
rocker arms or a spring biasing, as is disclosed in my U.S. Pat. No. 
4,019,002 and my pending application Ser. No. 207,259. The weight of the 
inside rope catcher 56, for example, gravity biases rocker arms 23 to 
rotate upon derailment of the rope from the sheaves and rocker arm. A 
tension spring connected between rocker arm 23 and rocker arm 24, could 
also be employed. 
When the haul rope is supported on the rope catching grooves in rocker arm 
23, the rope load would prevent rotation of the rocker arm, just at it 
does when the rope is supported on the sheaves. When caught, however, the 
rope will impact the end 119 of the frangible element to thereby destroy 
the same. 
In the event that the haul rope derails and jumps the rocker arm, the 
biasing weight of rope catcher 56 will cause pivoting of the lead and 
trailing rocker arms 23. The rope derailment responsive apparatus of the 
present invention further includes a circuit breaker element 124 mounted 
rocker arm means 23 for movement of at least one of the frangible element 
114 and circuit breaker element 124 until the circuit breaker element 
impacts and breaks the frangible element during rotation of rocker arm 23. 
In the form of the apparatus shown in FIGS. 9 and 10, circuit breaker 
element 124 is fixidly mounted by the end 126 of nut 73 which passed 
through a circular opening 127 in the circuit breaker element. Thus, the 
circuit breaker element remains in the same angular orientation as the 
four-sheave rocker arm 24, while two-sheave rocker arm 23 pivots under the 
biasing weight when the rope derails from the sheaves and the rocker arm. 
This pivoting action can best be seen in FIG. 10 where the frangible 
element 114 can be seen in phantom to impact the edge 128 of a slot in the 
end of fork-shaped circuit breaker element 124. As rocker arm 23 rotates 
under the biasing, frangible element 114 is sheared or broken at notch 116 
when the frangible element impacts the side 128 of circuit breaking member 
124. 
Since rocker arm 23 will be constantly rocking under dynamic loading, 
circuit breaker element 124 should be formed with a fork in which slot 128 
at the upper edge and at lower edge 129 will accommodate rocking without 
breaking the frangible element. The size of slot or fork in element 124 
can vary depending upon the dynamics of each individual lift, but usually 
a slot which would accommodate rocking in either direction by about 15 
degrees will more than suffice for even the most dynamic rocker arms. 
Accordingly, the biasing means for rotation of rocker arm 23 on derailment 
should displace the rocker arm through a substantial angle, namely, an 
angle great enough to ensure that the edge 128 of the forked circuit 
breaker element 124 impacts and breaks the frangible element. 
It is further preferable that the circuit breaker element be mounted inside 
tubular axle 31 and below the rope supporting groove 47 so that it is not 
exposed to the adverse environment. In this regard, providing and end cap 
131 on the end of circuit breaker element 124 effectively closes the open 
end of tubular axle 31 and prevents the entry of snow and ice into the 
inside of the axle. 
Frangible element 114 is preferably mounted in electrically insulating 
mounting means, generally designated 132, for easy replacement. This can 
be accomplished by forming mounting means 132 with a first piece 133 which 
can be threaded into the base 134 of rocker 23 and extends through tubular 
axle 31. A second mount member 136, which carries frangible element 114 
can be slid upwardly inside the bore 137 in first member 133. Once the 
frangible element is positioned in place, thumb screw 138 can be used to 
lock the two-piece mount 132 together as a unit. Sheath 118 and wires 112 
and 113 extending from the mount should be long enough and flexible enough 
to accommodate rocking of the rocker arm during loading and even when the 
haul rope derails from the sheaves and is not caught by the rocker arm. 
It should be noted that in most rocker arm assemblies there will be a rope 
derailment responsive device 111 positioned proximate both the lead and 
trailing sheaves. Thus, when a haul rope derails breaking of the frangible 
element in either of devices 111 will terminate lift operation. 
It is preferable to form rocker arms 23 as cast aluminum members having 
steel tubular axles 31 cast integrally therewith. Similarly, rocker arm 24 
can be cast, and as best may be seen in FIGS. 4, 5 and 6, both rocker arms 
23 and 24 can be hollowed out with occasional reinforcing ribs so as to 
minimize the material in and the weight of the rocker arm castings. As was 
described in connection with FIGS. 11 and 12, a rod or retention device 
can be inserted into the hollows of the casting to prevent rotation of 
rocker arm 24 to an inverted position prior to loading or support of the 
haul rope on the sheaves. 
An additional important feature of the rocker arm assembly of the present 
invention can best be understood by reference to FIG. 6. In order to 
minimize any tendency for ice or snow to inhibit or affect rotation of 
sheaves 22, it is preferable to form sheaves 22 with a flexible 
non-metallic side panel 181 and to position the inner edge 182 of 
two-sheave rocker 23 in close proximity to panel 181. Edge 182 of the 
two-sheave rocker will shear off any snow or ice adhering to the side 
panels of the sheaves. Flexure of side panels 181, as shown in phantom, 
will further cause ice spanning between rocker arm 23 and sheave 22 to 
fall away. 
It is preferred to form panels 181 of a relatively ultraviolet radiation 
insensitive, flexible plastic such as polyethylene with a smooth, low 
coefficient of friction outer surface. Since rocker arms 23 are preferably 
cast aluminum, ice and snow do not permanently adhere to the dissimilar 
materials and will quickly be wiped off the flexible sheave side panel by 
edge 182. Just as flexure of plastic ice trays releases the ice cubes, 
flexure of plastic side panels 181 will cause ice to fall away from 
sheaves 22.