Note: Descriptions are shown in the official language in which they were submitted.
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SIGNAL MAST ASSEMBLY
The present invention relates to a signal mast assembly particularly for use
with railroad signal lights.
BACKGROUND OF THE INVENTION
Railroad signal lights located on masts often require replacement or
maintenance. A ladder is typically used to provide a worker to access the
signal light. Such ladders have conventionally been permanent installations
either attached to the mast with a cantilever mount, or positioned adjacent to
the signal mast and having a pier system or foundation separate from that of
the
mast.
It is well known within the art that present signal mast assemblies are
prone to premature failure, for example, as a result of wind storms and ice
loads. Attachment of a ladder to a mast using a cantilever mount has the
further disadvantage that extra stress is placed on the mast to support the
weight
of the ladder, which can lead to mast failure. If the mast and the ladder have
separate foundations, the shifting of the ground which occurs over time may
result in a change in the position of the ladder relative to the mast,
necessitating
replacement of either the ladder or the mast. When the mast and ladder are
mounted on separate foundations, wind and ice loads can easily stress and thus
damage the mast or the ladder.
In response to the problem of shifting ground, various foundations such
as those disclosed in U.S. Patents Nos. 5,257,489 (Anglette; Nov. 2, 1993) and
5,533,845 (Anglette, July 9, 1996) have been proposed for securing railroad
signal masts. However, support for an adjacent ladder is not addressed.
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U.S. Patent No. 3,952,978 (Reinitz; April 27, 1976) teaches a cantilever
arm signal assembly for use in suspending signal lights over a roadway.
Catwalk panels may be used along the cantilever arm, for a worker to access
the signal lights when maintenance or repair is needed. Such an assembly
causes stress on the mast to support the weight of the cantilever arm, and
thus
the mast must be formed of sturdy stress-resistant materials. A mast and
ladder
assembly providing access the catwalk is not addressed by Reinitz.
An increase the standard size of existing masts for railroad signals from
the standard 5.5 inch outer diameter to an 8 to 10 inch outer diameter would
contribute mast stability and strength. However, there is reluctance in the
industry to change from 5.5 inch outer diameter, since signal light fixtures
and
accessories are sized for the current standard, and considerable expense would
be incurred if this standard were to be changed. It is therefore desirable to
achieve increased mast stability without increasing mast diameter.
It is an object of the present invention to provide a mast and ladder
assembly which substantially obviates the above-noted deficiencies of the
prior
art.
SUMMARY OF THE INVENTION
According to the invention, there is provided a signal mast assembly
comprising a unified base, a mast mounted to the unified base, a ladder
mounted to the unified base, and a joining means for joining the mast and the
ladder at a location above the unified base.
The mast and ladder are coupled by the joining means, which acts as a
truss, thereby providing superior load carrying capability and deflection
resistance when compared to a mast alone.
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The unified base may comprise a foundation for placement on the
ground and a base plate attached to an upper portion of the foundation,
wherein
the mast and the ladder are mounted on the base plate. A fixture, such as a
signal light may be attached at an upper portion of the mast. The joining
means may comprises a platform positioned between the mast and the ladder,
and connecting rails may be positioned between the mast and the ladder. The
joining means may also include at least one support bracket or gusset.
The signal mast assembly of the present invention has the advantage that
the mast and the ladder share the unified base. Thus, shifting in the ground
below the assembly does not change the arrangement of the mast and ladder
relative to each other. Structurally joining the ladder to the mast also has
the
advantage of providing enhanced load carrying capability, and much lower
deflection than a mast not joined to a ladder structure. Thus, the assembly of
the present invention has an enhanced capacity to withstand wind and ice
loads.
A further advantage of the invention is that the weight of the ladder is
not supported by the mast since both the ladder and the mast attach to the
unified base, reducing the likelihood of mast failure due to weight stresses
induced by a cantilever mounted ladder.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the invention will become more apparent from the
following description in which reference is made to the appended drawings
wherein:
FIGURE la is a perspective view of an aspect of an embodiment of the
invention, having one signal light;
FIGURE lb is a front view of the embodiment of FIGURE 1 a;
FIGURE lc is a side view of the embodiment of FIGURE 1 a;
FIGURE ld is a top view of the embodiment of FIGURE la;
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FIGURE 2a is a perspective view of another aspect of an embodiment
of the invention, having two signal lights facing the same direction;
FIGURE 2b is a partial side view of the embodiment of FIGURE 2a;
FIGURE 3a is a perspective view of another aspect of an embodiment
of the invention, having two signal lights facing opposite directions;
FIGURE 3b is a front view of the embodiment of FIGURE 3a;
FIGURE 3c is a side view of the embodiment of FIGURE 3a;
FIGURE 4a is a perspective view of another aspect of an embodiment
of the invention, having two signal lights facing opposite directions and
gussets;
FIGURE 4b is a front view of the embodiment of FIGURE 4a; and
FIGURE 4c is a side view of the embodiment of FIGURE 4a.
DESCRIPTION OF PREFERRED EMBODIMENTS
Having regard to FIGURES 1 to 4, the invention is described for use
with masts which support railroad signal lights. However, it is to be
understood
that the invention is not limited thereto. The invention may be used for any
mast requiring an adjacent ladder.
The invention provides a unified base for connection of the ladder and
mast to a generally horizontal and fixed surface. According to embodiments of
the invention relating to masts for support of railroad signals, the unified
base
may be any which is known in the art and which is adapted to have the mast
and the ladder attached thereto. Preferably, the unified base consists of a
foundation and optionally a base plate affixed to the foundation. The
foundation may be made of any appropriate rigid material such as cement or
metal. A pier type foundation may be used, having a plurality of vertical pier
supports for placement above or below the ground surface, such as depicted in
FIGS. 1 to 3, having 6 pier supports, and FIG. 4, having 4 pier supports.
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The base plate located on the foundation is a rigid horizontal surface
capable of having the lower portion of both the mast and the ladder affixed
thereto. For example, but not intending to limit the present invention in any
manner, according to the embodiments depicted in FIGS. 1 to 4, the
foundations comprise reinforced concrete legs to which a base plate, such as a
metal plate, is bolted. The mast and the ladder are bolted to the upper
surface
of the base plate. However, it is to be understood that other variations of
the
unified base are within the scope of the present invention. For example, the
mast and ladder may be set into the foundation directly or attached to the
foundation in an appropriate manner without the use of a base plate, provided
that the foundation to which the mast and ladder are attached is unified in
some
manner.
The mast may be any rigid pole or pillar extending upwardly from the
unified base. The mast may be affixed to the unified base through a permanent
or semi-permanent connection such as bolts, mechanical fasteners, welding,
etc.
Preferably, the mast is capable of supporting a fixture at the upper end
thereof.
When referring to the embodiment wherein the mast is used to support a
railroad signal, the mast may be of from 5 inches in outer diameter to over 10
inches in outer diameter, depending on the standards and requirements.
The ladder may be of any type which allows a worker to climb up and
access upper regions of the mast. The lower end of the ladder is affixed to
the
unified base through any appropriate means and may be set directly in the
foundation, or attached to the foundation or a platform using any suitable
means such as bolts, mechanical fasteners, welding, etc. As shown in FIGS 1
to 4, the ladder has a plurality of horizontal rungs.
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In order to further provide strength and rigidity to the signal mast of the
present invention, the mast and associated ladder may be interconnected
together by any suitable joining means which structurally joins the mast and
the
ladder at a position above the unified base, ensuring the formation of a truss-
like structure. According to one embodiment, the joining means may comprise
a platform, which may be a solid horizontal surface appropriate for a worker
to
stand on when manipulating a fixture positioned on the mast. The platform
may be a planar rectangular surface, and one of the edges of the rectangle may
be aligned with the mast and a side of the ladder.
A connecting rail may be positioned between the mast and the ladder at
a location above the unified base, to stabilize the position of ladder
relative to
the mast. The connecting rail may be any rigid and generally horizontal
attachment. In an embodiment of the invention wherein the joining means
comprises both a platform and a connecting rail, the connecting rail may be
positioned above the platform, so that a worker standing on the platform may
be able to grasp or lean on a connecting rail for stability. According to a
preferred embodiment, a plurality of connecting rails are located around all
four
sides of the platform, so as to surround a worker standing on the stage. In
this
embodiment, the connecting rails are supported by posts extending upwardly
from the four respective corners of the platform.
A support bracket such as that shown in FIGS. 3a and 3b may also be
provided to connect the ladder to the mast. The support bracket may be
positioned below the platform in a configuration which is not perpendicular to
the mast, to thereby further stabilize and support the assembly.
Further, a series of gussets, such as those shown in FIGS. 4a and 4b may
be used as trusses to structurally join the ladder or the mast to the platform
and
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thereby increase strength and reduce deflection as herein before described.
Such gussets may also be placed between the ladder and the base plate (as
shown in FIGS. 4a) and 4b), or between the mast and the base plate.
The joining means may be a full assembly unit comprising a planar
rectangular platform, connecting rails supported on posts extending upwardly
from the four corners of the platform, and a gusset or support bracket. A
plurality of such full assembly units may be used in vertical alignment.
FIGURE 2 illustrates an embodiment of the invention having two full assembly
units mounted in vertical alignment on the mast.
The fixture may be any structure capable of being supported by the mast.
Any fixture which requires regular maintenance, replacement or access could
be incorporated with the assembly of the invention. The fixture is preferably
located at the upper end of the mast, but may be located anywhere along the
mast in a region accessible to a person standing on the ladder or on the
platform. The signal light may be of any type, for example, but not wishing to
limit the invention in any manner, the signal light may be of the type used
along the railroad to wam local traffic before or during the passage of a
train, as
depicted in FIG. 1. A plurality of fixtures may be located on the mast, such
as
two signal lights vertically aligned both facing the same direction (see FIG.
2)
or two signal lights facing opposite directions (see FIG. 3). The mast
assembly
of the invention may also be used with those masts supporting cantilever
mounted signal lights, such as described in U.S. Patent No. 3,952,978.
The foregoing embodiments illustrate the invention, but should not be
considered as limiting. Modifications and equivalents which readily occur to
those skilled in the art also fall within the scope of the invention.
