Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02806865 2013-02-12
BUMPER MOUNTED STEP ASSEMBLY
FIELD OF THE INVENTION
The present invention relates to a step assembly for mounting on a
bumper, for example the bumper of a truck or trailer, and more particularly
relates to a
step assembly in which a linkage pivotally supports the step assembly for
movement
relative to the bumper between respective stored and working positions.
BACKGROUND
Various vehicular frames for transporting cargo are known, for example
truck beds or transport trailers of various forms. To accommodate suitable
suspension for transporting goods, it is common for transport frames to have a
high
elevation from the ground. Accordingly, it is known to be desirable to assist
users in
accessing the high elevation of the load supporting plafform with various
forms of step
assemblies. Examples of step assemblies are found in United States Patents
4,079,815 by Cormier, 3,887,217 by Thomas, 3,627,350 by Cross and 2,678,832 by
Wright.
One particularly desirable location to assist access of users is at the rear
doors of a highway transport trailer frame suited for being towed by a highway
tractor.
Such trailer frames are commonly provided with a rear bumper assembly
including a
standard sized square tubing member spanning in a longitudinal direction
horizontally
across the width of the vehicle perpendicularly to the forward rolling
direction. The
tubing member is supported spaced below the platform upon which cargo is
supported such that users are known to step on the bumper. The bumper however
is
recessed below the plafform so as to be awkwardly located for use as a step
such
that an additional step would be desirable.
Prior art step assemblies are generally not well suited for mounting in
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the location of a rear bumper on a highway transport trailer frame as typical
step
assemblies extend below the mounting location which would reduce the ground
clearance between the bumper and the ground in an undesirable manner.
Furthermore, prior art step frames generally protrude rearwardly of the
vehicle in an
operating position in a manner which can be readily damaged if backing into a
loading
dock for example.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a step
assembly for mounting on a bumper which spans in a longitudinal direction, the
step
assembly comprising:
a mount arranged for attachment to the bumper;
a step frame including at least one step member extending in a
respective lateral direction; and
a linkage coupling the step frame to the mount such that the lateral
direction of said at least one step member is substantially parallel to the
longitudinal
direction and such that the step frame is movable relative to the mount
between a
stored position in which the step frame is supported in proximity to the mount
and a
working position in which the step frame is farther from the mount than in the
stored
position and said at least one step member is arranged to support a user
stepping
thereon;
the linkage comprising:
a first link extending between a first end pivotally coupled to the
mount for relative pivotal movement about a first axis of the first link and a
second end
pivotally coupled to the step frame for relative pivotal movement about a
second axis
of the first link; and
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a second link extending between a first end pivotally coupled to
the mount for relative pivotal movement about a first axis of the second link
at a
location spaced from the first axis of the first link and a second end
pivotally coupled
to the step frame for relative pivotal movement about a second axis of the
second link
at a location spaced from the second axis of the first link;
wherein the first link, the second link, a portion of the mount between the
first axes of the first and second links, and a portion of the step frame
between the
second axes of the first and second links collectively define a four bar
linkage.
The configuration of a four bar linkage to support the step frame
between stored and working positions permits the step frame to be readily
returned to
a stored position if impacted from the rear while in the working position for
safely self-
storing without causing any unnecessary damage, for example when backing into
a
loading dock.
The four bar linkage is also particularly well suited for supporting the
step frame for movement between stored and working positions at a location
above
the bumper for storing between the bumper therebelow and the platform
supporting
cargo thereon thereabove without affecting ground clearance of the vehicle.
The four bar linkage is further readily arranged in an over-centre
configuration such that rotating the linkage through a top centre position
between the
stored and working positions allows the step frame to be self retained in
either
position without any additional structures being required.
Preferably the first and second links are parallel to one another
throughout pivotal movement between the stored position and the working
position.
Preferably the first and second links extend upwardly and forwardly from
the mount in the stored position, for example at an orientation of less than
45 degrees
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from vertical in the stored position.
Preferably the first and second links extend upwardly and rearwardly
from the mount in the working position, for example at an orientation of less
than 45
degrees from vertical in the working position.
Preferably a bottom end of the step frame is adjacent to the mount in the
stored position and is spaced rearwardly in the working position in relation
to the
stored position.
The step members of the step frame are preferably at substantially the
same elevation in the stored position and the working position.
Preferably a first stop member is fixed on the mount which engages at
least one of the links to prevent pivotal movement of the links beyond the
working
position when pivoting the links from the stored position to the working
position and a
second stop member is fixed on the mount which engages at least one of the
links to
prevent pivotal movement of the links beyond the stored position when pivoting
the
links from the working position to the stored position.
Preferably the step frame is fully forward in relation to a rearmost end of
the mount in the stored position and is fully rearward in relation to a
rearmost end of
the mount in the working position.
Preferably the step frame comprises two step members at a fixed
spacing from one another on the step frame.
The step frame may further comprise two parallel and spaced apart
uprights and two step members fixed between the uprights at vertically spaced
apart
locations in which the linkage is laterally offset to one side of the step
frame so as to
be directly coupled to only one of the uprights.
The step assembly is particularly suited for use with a rear bumper of a
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highway transport trailer in which the bumper comprises a tubular member of
square
cross section in which the mount comprises a C-shaped channel arranged to be
clamped about the tubular member.
More particularly, the mount may comprise an intermediate flange
5 spanning between two side flanges which are generally parallel to one
another in
which the side flanges are spaced apart by a prescribed spacing which is
substantially
equal to a corresponding dimension of the tubular member received
therebetween.
Preferably at least one fastener is arranged to be coupled between the two
side
flanges opposite from the intermediate flange so as to be arranged to clamp
the
tubular member between the two side flanges when the at least one fastener is
tightened.
One embodiment of the invention will now be described in conjunction
with the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of the step assembly in a working
position;
Figure 2 is a side elevational view of the step assembly in the working
position;
Figure 3 is a side elevational view of the step assembly in the stored
position; and
Figure 4 is a rear elevational view of the step assembly in the stored
position.
In the drawings like characters of reference indicate corresponding parts
in the different figures.
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DETAILED DESCRIPTION
Referring to the accompanying figures, there is illustrated a step
assembly for use in assisting user access to the cargo supporting area of a
transport
frame. The assembly is particularly suited for coupling to a vehicular bumper,
for
example, bumpers on any transport frame including a transport truck frame or a
trailer
frame.
The step assembly is best suited for use on the rear bumper of a
highway transport trailer of the type being arranged for towing by a highway
tractor.
The rear bumper 12 in this instance generally comprises a tubular member of
square
cross section which is elongate in a longitudinal direction spanning
horizontally across
the width of the trailer frame at the rear end thereof perpendicularly to the
forward
rolling direction.
The step assembly 10 generally includes a mount 14 for securement to
the bumper 12, a step frame 16 including two laterally extending step members
18 to
support a user stepping thereon, and a linkage 20 which supports the step
frame on
the mount such that a lateral direction of each step member is parallel to the
longitudinal direction of the bumper and such that the step frame is moveable
relative
to the mount between a stored position and a working position. In the stored
position
the step frame is supported in proximity to the mount above the bumper. In the
working position the step frame is spaced farther rearward from the mount than
in the
stored position at a similar elevation above the bumper. The linkage is
generally
rotated from the stored position upwardly and rearwardly to an intermediate
top centre
position and then rotated downwardly and rearwardly from the top centre
position to
the working position.
The mount 14 includes a channel 22 which is generally C-shaped in
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cross section to include an intermediate flange 24 spanning between two
opposing
side flanges 26. The intermediate flange is oriented vertically to span the
height of a
rear side of the bumper between the top and bottom surfaces thereof. The two
opposing side flanges 26 extend forwardly from the top and bottom ends of the
intermediate flange respectively to extend forwardly over the respective top
and
bottom surfaces of the bumper in a mounted position. The two side flanges are
spaced approximately by the vertical height of the bumper received
therebetween
such that the bumper is readily slidable into the space between the two side
flanges
within the channel while allowing the two side flanges to be clamped against
the top
and bottom sides of the bumper as described in the following.
The two side flanges project forwardly from the intermediate flange 24 to
respective forward free edges 28 by a distance which is greater than the
thickness of
the bumper in the forward direction such that the two free edges 28 protrude
forwardly
beyond the front side of the bumper in the mounted position. Suitable fastener
apertures 30 are located adjacent the free edges 28 in alignment with one
another to
receive suitable threaded fasteners 22 connected between the free edges of the
two
side flanges in the mounted position. Tightening the fasteners 32 permits the
top and
bottom side flanges 26 to be suitably clamped onto top and bottom surfaces of
the
bumper retained in fixed relation within the channel.
The mount 14 further includes a fixed leg 34 which is mounted on the
uppermost side flange on the top side of the channel towards one end thereof
to
extend upwardly at a forward inclination of less than 45 degrees vertical.
The step frame 16 generally includes two uprights 36 which are laterally
opposed from one another by the full width of the step frame such that each
upright
spans the full height of the frame between opposing top and bottom ends. Two
step
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members 18 extend in the lateral direction between the two uprights at
respective
opposing top and bottom ends of the uprights. The two uprights extend at an
upward
and forward inclination so as to be parallel to the fixed leg 34 throughout
the full range
of movement of the step frame relative to the mount.
The two step members each include an upper surface 38, which is
generally horizontal to define a tread for stepping thereon while the two
uprights are
supported at an upward and forward inclination throughout the range of motion
thereof. The uppermost step member is thus positioned upwardly and forwardly
in
relation to the lowermost step member.
In the stored position, the lowermost step member is positioned directly
adjacent the top side of the channel while the uppermost step member is
positioned
upwardly and forwardly from the channel in proximity to the top end of the
fixed leg.
In the working position, the lowermost step member 18 is spaced rearwardly
from the
channel near in elevation to the top side of the channel while the uppermost
step
member is in line with the rear edge of the mount at a location spaced
vertically
thereabove.
The step frame further includes a handle 40 in the form of an elongate
bar extending parallel to the uprights at a location spaced rearwardly from a
plane of
the uprights. The elongate bar of the handle 40 is suitably sized for gripping
in the
hand of a user and is aligned in a common vertical plane with one of the
uprights
nearest to the fixed leg 34 in which the common plane is perpendicular to the
lateral
direction of the step members.
The linkage 20 includes a first link 42 and a second link 44. Each of the
links spans between a first pivot coupling 46 and a second pivot coupling 48.
The first
pivot coupling 46 is located at a first bottom end of the link which is
coupled to the
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fixed leg of the mount for relative pivotal movement therebetween about a
respective
first axis oriented parallel to the lateral direction of the step members. The
second
pivot coupling 48 is located at the second end of the link which is coupled to
the step
frame for relative pivotal movement about a second axis also oriented parallel
to the
lateral direction of the step members.
The first axis of the first link is located spaced upwardly and forwardly in
relation to the first axis of the second link corresponding to the upward and
forward
inclination of the fixed leg. Similarly, the second axis of the first link is
also positioned
upwardly and forwardly in relation to the second axis of the second link by
the same
distance and inclination along an innermost one of the uprights of the step
frame
nearest to the fixed leg.
In this manner, the first and second links 42 and 44 are parallel to one
another throughout the range of movement of the step frame between stored and
working positions. Similarly, the portion of the fixed leg between the first
axis of the
first and second links and the corresponding portion of the upright between
the
second axes of the first and second link also remain parallel to one another
throughout the pivotal movement of the step frame between the stored and
working
positions.
The step frame is positioned to be laterally offset to one side of the
linkage such that the linkage is only coupled between the fixed leg and one of
the
uprights of the step frame. In the stored position, both links, the fixed leg,
and both
uprights of the step frame all lie generally in a common plane. This is
permitted by
the lateral offset of the links, the fixed leg and the step frame relative to
one another.
In the stored position, the two links are received between the fixed leg
and the nearest upright of the step frame by use of pivot shafts coupling the
links to
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the fixed leg and step frame respectively. More particularly, a first pivot
shaft 50 is
coupled along the first axis of the second link to span laterally between the
fixed leg
and the second link spaced therefrom by a sufficient lateral distance to
receive the
first link between the fixed leg and the second leg in the lateral direction.
Similarly, a
5 second pivot shaft 52 is coupled along the second axis of the first link to
span
between the laterally spaced apart first link and inner most upright of the
step frame
by a sufficient lateral distance to receive the second link laterally between
the first link
and the step frame.
Stop members are used to support the step member in the stored and
10 working positions. These include a first stop member 54 in the form of a
plate
supported on the fixed leg parallel to the plane of the links in the stored
position. The
plate is secured along the forward edge of the fixed link to be spaced
forwardly of the
first pivot couplings 46. The plate extends in the lateral direction from the
fixed leg by
a suitable width to overlap and abut the forward edges of both links and the
inner
most one of the uprights of the step frame in the stored position. The first
stop
member 54 thus prevents further rotation of the step frame from the working
position
to the stored position beyond the stored position.
Similarly, a second stop member 56 is also supported on the fixed leg
but for the function of stopping further rotation of the step frame from the
stored
position towards the working position and beyond the working position. The
second
stop member is also provided in the form of a plate which is fixed onto the
rear side of
the fixed leg adjacent the bottom end thereof so as to be positioned
rearwardly of the
first axis of the first link while the forwardmost edge is located spaced
directly
vertically above the first axis of the second link. The second stop member
spans in
the lateral direction by a prescribed distance so as to only overlap into the
plane of
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movement of the first link so that the second link is not affected by the
second stop
member. The forward edge of the second stop member is arranged to be engaged
by
the rear edge of the first link in the working position to prevent further
rotation of the
entire linkage and step frame.
In use, the mount is secured about the rear bumper of a transport trailer
frame such that the step frame is supported fully above the channel of the
mount and
the bumper received therein between the bumper therebelow and the platform for
supporting cargo thereon thereabove.
In the stored position, the linkage and the step frame is substantially
fully forward of a rearmost edge of the mount secured about the bumper.
Rotation of
the step frame to the working position involves rotating the step frame upward
and
rearward over the top centre position with continued rotation downward and
rearward
to the working position.
In the working position the step members are near in elevation but
spaced rearvvardly from their respective location in the stored position of
the step
frame. Engagement of the first link with the second stop member 56 permits
weight to
be carried on the step members to allow stepping thereon by a user accessing
the
cargo platform of the trailer in the working position.
Subsequent storing of the step assembly simply involves pushing the
step frame forwardly over the top centre position so that the step frame is
effectively
self retained in the stored position. If reversing the trailer frame into an
obstruction
while the step assembly is in the working position, the assembly will self-
fold to return
to the stored position without causing any undesirable damage.
Since various modifications can be made in my invention as herein
above described, and many apparently widely different embodiments of same made
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within the spirit and scope of the claims without department from such spirit
and
scope, it is intended that all matter contained in the accompanying
specification shall
be interpreted as illustrative only and not in a limiting sense.
