Note: Descriptions are shown in the official language in which they were submitted.
1~37~37
The electrical collectors that travel along trolley
wires or rails take the fonm of either rotating wheels or slid-
ing shoes. Por industrial use, such as the collectors used
with electric cranes, sliding shoes are practically always
usod. Such a shoe i8 provided with a groove that receives the
trolley wire 80 that the shoe will stay on the wire. The shoe
is made of copper or a similar good electrical conductor and,
a~ it slides back and forth along the wire, the metal of the
shoe is gradually worn away at the base of the groove.
The shoe olt by one manufacturer is made from a bar
of sintered powdered copper, with which graphite has been mixed
to provide lubrication and reduce we-r. The shoe i8 provided
in the side opposite its groove with a pair of longitudinally
spaced threaded holes, in which there are screws that are used
for attaching the shoe to a metal plate that i8 connected with
n l-ctric cable leading to a crane motor, electromagnet or
other device that requires electricity to operate Lt. In the
past, these screws have been steel. m e inner ends of the
screw holes in the shoe are spaced from the base of the groove.
When such a shoe is installed, the maintenance people
are told that as 800n as the shoe wears to the point where the
inner ends of the holes become vi~ible at the base of the
groove, the shoe should be replaced by a new one. In practice,
'1 however, wear of the shoe is often ignored, with the result
l that the inner ends of the steel screws eventually come in con-
;~ tact with the trolley wire. Since the screws are ~uch harder,
- 2 - ~ -
103713 7
i.e. wear resistant, than the shoe itself, they force the trol-
ley wire to one ~ide of the groove ~o that the wire cuts into
the side wall of the groove. This wear often is allowed to
continue until the worn side of the shoe becomes so thin that
it breaks away and releases the shoe from the wire. The moment
this occurs, the spring-pressed shoe support will extend and
may strike the trolley wire or some other ob~ect and become
bent or damaget, or it may swing to one side and cause a short
circuit with a parallel trolley wire. In any case, if the shoe
breaks away from the trolley wire, it is a very serious matter.
Besides causing damage, it shuts down the crane. This may put
several dozen men out of work until repairs can be made or, if
the shoe i8 electrically connected to an electromagnet holding
a load of scrap metal for exa ple, the scrap will be released
and could seriously in~ure or kill anyone on ~hom it might fall.
It i8 an ob~ect of this invention to provide a
trolley electrical conductor, in which any wear that occurs in
the ~hoe after the trolley wire reaches the inner ends of the
mounting screws will continue to be in a direction extending
~ially of those screws and not at an angle to them.
The preferred embodiment of the invention is illus-
trated in the accampanying drawings, in which
Fig. 1 is a fragmentary side view of a trolley
; conductor and guard, with part of the guard broken away to show
the trolley shoe;
1 ~3r71 37
Figo 2 is a vertical section taken on the line
II-II of Fig. l;
Fig. 3 is a reduced plan view of the shoe alone; and
Fig. 4 is a view similar to Fig~ 2~ but showing the
shoe after it has been worn to a considerable extent.
Referring to Figs. 1 and 2 of the drawings, an over-
head trolley conductor of any desired length ls fonmed of
metal that is a good conductor of electricity, such as copper.
Although the conductor shown resembles a rail to some extent,
it will be referred to herein as a trolley wire since the in-
vention discloset herein can also be used with a round wire.
The illustrated wire has a head 1 and a foot 2 extending through-
out its length and they are separated by a vertical web 3 that
i8 integral with them. The wire is suspended from hangers
(not shown) located at spaced intervals along its length, The
foot of the wire projects from opposite sides of the web above
it and has a transversely curved lower contact surface. The
web of the wire spaces the foot far enough from the head to
locate the foot a considerable distance beneath the upper por-
tion of a tubular guard 4 that extends along the wire, whichit encloses to protect the wire from snow and ice and from
accumulations of dirt. This guard is made of flexible rubber-
like material and is supported by the wire. The bottom of the
guard is split lengthwise throughout its length to provide it
with lower edges that normally engage each other or overlap,
whereby the wire ~s enclosed in a flexible tube.
- 4 -
~ 3~ ~3~7
Slidably mounted on the trolley wire inside the
tubular guard is a trolley shoe 6. The shoe is made from a bar
of electrical conducting material, preferably sintered powdered
copper, with which graphite has been mixed. The upper side of
the shoe is provided with a central longitudinal trough or
groove 7 that extends throughout the length of the shoe. The
lower portion of this groove i8 curved transversely to engage
and more or less fit the curved lower contact surface of the
trolley wire, with the sides of the groove initially extending
part way up the opposite ~ides of the wire. The groove guides
the shoe as it is moved along the rail so that it cannot slide
sldeways away from the wire. The bottom side of the shoe is
; 8eated upon a flat plate 8 rigidly mounted on the upper end of
a tubular plunger 9 that is urged upwardly at all tfmes by a
spring (not ~hown). Inside the plunger there is a copper rod
10, the upper end of which is ~oined to the plate and the
lower end of which is connected to an electric cable that leads
to the equipment that the current collected by the shoe is to
operate.
The shoe is rigidly mounted on supporting plate 8 by
means of a pair of screws 12 that extend up through openings
in the opposite ends of the plate and into threaded holes 13
extending upwardly into the shoe. The upper or inner ends of
these holes are spaced from the bottom of groove 7 in order to
provide a body of metal between the bottom of the groove and
the upper ends of the holes that can be worn away by the trolley
10371~7
wire before the holes and the upper ends of the screws wlll be
exposed. When the ~oles are exposed, the shoe ~hould be re- -
placed by a new one because it ha3 served its norm~l life, but
it is a ~eature of this invention that if replacement does not
occur at that time the shoe will continue to wear straight down
for a considerable additional period of time as shown in Fig.
4, until it i8 clearly apparent that there is not much left
of the shoe and that it will have to be replaced. Accordingly,
the mounting screws are made of a metal that is at least a~
soft a8 the shoe metal, by which is meant that the screws will
be worn away by the trolley wire as fast as, or at the same
rate as, the shoe itself. The preferred metal for the screws
is aluminum because it not only is ~ofter than the ~hoe but
it also is a good electrical conductor. Another screw
material coult be magnesium or zinc. Copper is not satisfac-
tory when the shoe i8 made of powtered copper and graphite,
because copper screws would be too hard and, like steel, would
urge the trolley wire to one side or the other of groove 7
since the screws would resist wear more than the side wall of
the groove.
If, for example, the original thickness of the shoe
between the base of its groove and the bottom of the shoe is
5/8 inch ant the screw holes are 3/8 inch long, the metal
between the bottam of the groove and the upper ends of the
holes will be 1/4 inch thick. After this metal has been worn
away, wear can continue straight down through the shoe for
~ Q371;~7
about another 1/4 of an inch, the upper ends of the screws
being worn away in the process at the same rate as the shoe.
Although this additional wear i8 not recommended, it reæults
in the shoe lasting about twice as long as intended. Of
course, the big advantage is that all of the wear is along the
central vertical longitudinal plane of the shoe and does not
extend off to one side, which would result in the side of the
shoe breaking away and releasing the shoe from the trolley
wire. m e shoe di~closed herein, therefore, can avoid the
damage to equipn nt that has occurred heretofore and can also
eliminate the town time that results when a shoe breaks away
from a trolley wire.
To prevent the top of the shoe at opposite side~ of
its groove from engaging the tubular guard above it when the
groove starts to become deep, abrasive dressing devices, such
A ~ shown in~patent No. 3,321,587, can be mounted on the trolley
wire to grind down the top of the shoe as it travels back and
forth across the dressing devices. The shoe in Fig. 4 has
been ground down in this manner.
