Note: Descriptions are shown in the official language in which they were submitted.
CA 02385481 2002-05-08
PORTABLE LOAD CARRYING DEVICE
BACKGROUND OF THE INVENTION
l . FIELD OF THE INVENTION
~f'Ihis invention relates in general to portable load carrying devices and
more particularly, but not
necessarily exclusively, to personal load carrying devices.
a!. DESCRIPTION OF THE RELATED ART
Personal Load Carriage Systems come in many different styles but all have two
basic
components a harness and a load. The harness i=ncludes shoulder straps and
waist straps. The
Load is typically supported by a "frame-sheet" and the harness is rigidly
attached to a bag that
~ s 1-~olds the load.
>_iackpacks have traditionally been designed with padding and wide straps to
distribute force over
tlhe body during locomotion. Padding works to make wide straps more compliant
to body
contours, and this arrangement distributes load more evenly over the body,
thereby reducing
2o contact pressures. Although this approach is effective, it does not reduce
the contact pressures to
an acceptable level under severe loading conditions. Discomfort, soreness and
bruising are all
common symptoms when using a backpack over an extended period of time. These
symptoms
CA 02385481 2002-05-08
are particularly noticeable when the backpack is heavy, and is being carried
over rough terrain.
'JValking causes vertical oscillations as a person moves through the phases of
gait. The body, and
arty load it is carrying, must continuously rise and fall in order to move
forward. Conventional
personal load carriage systems keep the load tight to the body so that the
load and the body are
f;ssentially one mass. As the load accelerates up and down, oscillatory force
is applied to the
body that can be several times the magnitude of the static load'.
It is therefore an object of the present invention to mitigate the above
mentioned disadvantages.
1O SUMMARY OF THE INVENTION
Briefly stated, the invention involves a portable load carrying device
comprising a harness frame
portion for carriage by a user, a load frame portion and a suspension portion
joining the harness
frame portion with the load frame portion, the suspension portion being
operable to reduce
t 5 dynamic forces exerted on the harness frame portion by the load frame
portion during the user's
gait.
Preferably, the suspension portion includes a pair of suspension members
movable relative to one
another, a first of the members being attached to the load frame portion and a
second of the
20 members being attached to the harness frame portion, the suspension portion
further including a
1 Kram, R. ( 1991 ) "Carrying loads with springy poles". .lournal q~ Applied
Pf~ysiolo~ 72: I 119 - 1122.
7
CA 02385481 2002-05-08
dynamic force absorbing or reducing arrangement to control relative movement
of the suspension
members between a first position and a second position. In this case, the
dynamic force
absorbing arrangement includes at least one spring-like element operable to
deliver the
~~uspension members to an intermediate: position between the first and second
positions. In this
case, the spring-like element may include spring-like elements such as
compressed gases, fluids,
resilient materials, and other energy storage media and the like, as well as
springs such as coil
springs.
Beneficially, in one embodiment, the spring-like element has characteristics
defined by a force
deflection curve having a first region in which the spring-like element has
minimal deflection
with increased force, a second transition region and a third region wherein
the spring has
minimal force increase with increased deflection. In this case, the force
exerted in the first
region corresponds generally to a rated maximum weight of a load to be
supported by the load
fame portion. Alternatively, means may be provided for adjusting the force at
which the spring
~ 5 enters the second transition region. In other words, the dynamic force
absorbing arrangement
nnay be provided with an adjustable spring mechanism in order that the
transitional force (namely
tlhe force corresponding to the second region of t:he force deflection curve)
may be adjusted
according to the weight being carried, for example.
2o Preferably, the spring-like element includes a pair of coiled springs, each
having an inner end and
an outer end which are anchored to either the harness frame portion or the
load frame portion.
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1?referably, the harness frame portion further comprises a pair of stays
positioned on opposite
sides of a central axis, the stays being attached to a shoulder attachment and
a waist attachment,
the load frame portion further comprising a load support panel.
In one embodiment, the suspension members are provided in the form of a slide
block member
and a track member to receive the slide block member. One example provides two
sets of slide
block members and two corresponding sets of track members. The slide block
members include
an outer flanged portion to engage the track member and an anchor portion for
attachment to the
load support panel.
Preferably, an enclosure is attached to the load support panel to contain a
load. The enclosure
rnay be semi-rigid, such as a thin walled plastic container, or a bag-like
structure formed from
synthetic fabrics, cottons or other materials.
~ 5 In another of its aspects, there is provided a method for reducing dynamic
forces in a back pack,
comprising the steps of:
a) providing a harness frame portion for carriage by a user
20 b) providing a load frame portion;
CA 02385481 2002-05-08
c) providing a suspension portion between the harness frame portion and the
load
frame portion; and
d) arranging the suspension portion to provide relative movement of the
harness
frame portion and the load frame portion between a first position and a second
position along a central axis, and to reduce the transmission of dynamic
forces
between the load carrying portion and the harness frame portion during the
user's
gait.
Preferably, step c) includes the step of:
e) providing a plurality of displacement elements between the harness frame
portion and the load frame portion.
~s Preferably, step e) includes the step of:
f) providing a number of sliding Mock elements, each of which travel along a
corresponding track element between the first and second positions.
2o Preferably, step d) includes the steps of:
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g) selecting a spring element whose characteristics are defined by a force
deflection curve having a first region in which the spring element has
minimal deflection with increased force, a second transition region and a
third region wherein the spring requires minimal force increase with
increased deflection; and
h) locating the spring element between the load frame portion and the harness
portion.
I o In a preferred embodiment, the force exerted in the first region of step
g) corresponds generally
to a rated maximum weight of a load to be supported by the load frame portion.
Alternatively,
the method may include the step of:
i) adjusting the force at which the spring enters the second transition
region.
In another of its aspects, there is provided a portable load carrying device
comprising a harness
and a load support frame and a suspension arrangement therebetween, the
suspension
arrangement providing relative movement between the harness and the load
support frame
~~etween a first position and a second position in a manner to control dynamic
forces on the
2o harness from load oscillations during gait.
~Ci
CA 02385481 2002-05-08
In still another of its aspects, there is provided a personal load carrying
device comprising a
harness and a load support frame and a suspension arrangement there between,
the suspension
~~rrangement providing relative independent movement between the harness and
the load support
iFrame on either side of a central position between a first limit position and
a second limit
position, wherein the load support frame is operable to adopt a transient
elevation at the central
position while the harness moves in an undulating motion between the first and
second limit
positions during gait.
In yet another of its aspects, there is provided a back pack comprising a load
support portion and
a harness portion and control means for controlling displacement of the load
support portion
relative to the harness portion, the control means providing a path of travel
of the load support
portion relative to the harness portion, the load support portion being
positionable at a central
transient position along said path, the control means further controlling the
displacement of the
load support portion from the central transient position along said path in
response to dynamic
~ 5 loads exerted thereon by the harness portion.
't'he teen 'dynamic forces' is intended to include those that can anise during
the carrying of the
device. These forces may be regular undulating forces exerted on the device by
the user when he
is walking at a steady pace or irregular undulating forces exerted on the
device when the user
2o changes direction or speed. These forces may also include sudden impulse
loads which can
occur, for example, when the user steps or jumps to another ground elevation.
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CA 02385481 2002-05-08
'Thus, the present invention is concerned with the control of dynamic forces
generated during the
~;,arriage of a load. These dynamic f«rc:es may be exerted on the suspension
portion by the user
through the harness portion. Alternatively, these dynamic forces may be
exerted on the
>uspension portion by the load through the load frame portion. In effect,
then, the forces are
~~ppearing at the suspension portion from either source and the suspension
portion is capable of
controlling those forces, more preferably reducing them, still more preferably
minimizing them.
BRIEF DESCRIPTION OF THE DRAWINGS
~>everal preferred embodiments of the present invention will be provided, by
way of examples only,
with reference to the appended drawings, wherein,
Figure 1 is a perspective view of a portable load carrying device;
t 5 Figure 2 is a fragmentary side view of a portion of the device shown in
figure 1;
Figure 2a is a plot of force versus deflection for a portion of the device
shown in figure l;
Figure 2b is a schematic view of a portion of an alternative load carrying
device;
Figure 2c are two force displacement plots of the elements of the device shown
in figure 2b;
CA 02385481 2002-05-08
Figure 3 is a fragmentary perspective view of another portion of the device
shown in figure 1;
:Figure 4 is a sectional view taken one line 4-4 of figure 3;
lFigure 5 is a view of another portion of the device shown in figure 1;
1~igures 6a and 6b are schematic views of the device of figure I in two
operative positions;
1~ figure 7 is a schematic view of a porti<»i of another load carrying device;
and
1i figure 8 is a schematic view of still another load carrying device.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
~s
Referring to the figures, there is provided a portable load carrying device
10, in the form of a
backpack, having a harness frame portion 12 for carriage by a user, a load
frame portion 14 and a
suspension portion 16 joining the harness frame portion with the load frame
portion. As will be
dlescribed, the suspension portion 16 is operable to reduce dynamic forces
exerted on the harness
2o frame portion by the load carrying portion during the user's gait.
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'The harness frame portion 12 further comprises a pair of stays 18 positioned
on opposite sides of
.a central axis "c". The stays are semi-rigid and may typically be made of
aluminum or molded
;plastics or the like. In this case, the stays are shaped to accommodate the
contours of the back of
nhe user and are attached to a shoulder attachment 20 and a waist attachment
22.
'rhe load frame portion 14 has a load support panel 24 which supports an
enclosure 26. The
latter is a bag-like structure formed from synthetic fabrics, cottons or other
materials.
Preferably, the load support panel is fovned from semi rigid materials, for
example polymer
materials including polyethylenes, polyurethanes, or polypropylenes, although
other materials
may also be used.
rfhe suspension portion 16 includes a number of complementary displacement
elements 40,
which are coupled between the stays 18 and the load support panel 24, for
providing relative
movement therebetween along the central axis. The displacement elements 40
are, in this case,
v 5 in the form of slide block members 42 which slide along track members 44.
The displacement
elements 40 are divided into two groups, each on opposite sides of the central
axis "c". As
shown in figures 4 and 5, the slide bli>ck members 42 are mounted on the stays
at regular
locations and include an outer flanged portion 42a to engage the track member
and an anchor
portion 42b for attachment to the corresponding stay by way of threaded
fasteners 42c.
>=ieneficially, the stays 18 are shaped to accommodate the contour of the back
of the user. The
slide block members are thus arranged, also, to accommodate the shape of the
stays by adjusting
CA 02385481 2002-05-08
the length of each anchor portion 42b according to the location of the slide
block member. For
example, the slide block member at the upper end of the stay has a relatively
long anchor portion
~I2b, while the slide block member in the. central region of the stay has an
anchor portion of
essentially little or no extended length from the stay. The adjustment of the
length of the anchor
portions thus provides the outer flanged portions to lie in a substantially
common suspension
plane "D"
The suspension portion 16 further includes a dynamic force absorbing or
reducing arrangement
'.>0 which is operable between the stays 18 and the load support panel 24 for
controlling
movement of the slide block members relative to the corresponding track
members between a
first position (shown in solid lines in figure 2) and a second position (shown
in dashed lines in
figure 2). The dynamic force absorbing arrangement 50 includes a pair of
spring elements 52
which biases, under a no load condition, the slide block members to the first
position. In this
ease, the spring elements 52 are constant force coiled springs, each spring 52
having an inner end
~ 5 '~2a and an outer end 52b. As shown in figure 5, each outer end 52b is
anchored to a
corresponding stay by way of a fastener 52c. Each inner end 52a is mounted to
a transverse
anchor bar 54 extending across the axis "C" and is mounted to the load support
panel by way of
a pair of split anchor blocks 56, although one split anchor block may be used
if desired.
2o F;eferring to figure 2a, each of the spring elements 52 has a force
deflection curve which includes
a first region in which the spring element has minimal deflection with
increased force, a second
transition region and a third region wherein the spring has minimal force
increase with increased
CA 02385481 2002-05-08
.deflection. In this case, the force exerted in the first region corresponds
generally to a rated
:maximum weight of a load to be supported by the load frame portion. If
desired, however, the
~~ynamic force absorbing arrangement 'may be provided with an adjustable
spring mechanism in
birder that the transitional force (namely the force corresponding to the
second region of the force
~~eflection curve) may be adjusted according to the weight being carried, for
example.
;Figure 2b illustrates, schematically, a "linkage with spring" arrangement 60
which includes a
rigid ann 62, a spring 64 and coaxial springs 66. The rigid ann 62 and spring
64 are provided
~,vith pivot points 68, 70 for attachment to the load support panel 24 or the
stays 18. The coaxial
1 o springs include a number of springs of different length and in parallel.
As the coaxial springs are
compressed initially, only one spring in the set is compressed. After a set
amount of
compression, a second spring begins to compress increasing the stiffness of
the coaxial spring.
The spring rate of the coaxial spring, then, is determined by the number of
springs placed in the
coaxial spring. The force deflection curves for the linkage and a three spring
coaxial spring
I S arrangement is shown in figure 2c.
'the curve summing the curves a) and b) of figure 2c is the desired force-
deflection curve of the
embodiment shown in figure 2a. These characteristics are achievable using
defonnable plastic
elements or mechanical spring elements. The system may be tuned to the load
being carried by
2o changing the distance between the two pin joints shown at 68 and 70,
adjusting the position of
the coaxial spring in the "y" direction {as shown in figure 2b), adjusting the
length of the linage
>2 or by adjusting the point along th-a link that the load is applied.
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'The device 10 may be used as follows. First, load is installed in the
enclosure. For this
particular example, it will be assumed that the installed load has a weight
which approximates
the transitional force f«r the springs. T'he user then mounts the backpack on
his back. Once the
device is in its operative position, the load will exert the transitional
force on the spring elements
pausing them to move to their second transitional region. As a result, further
forces exerted on
~:he springs, either from the harness portion or the load carrying portion,
should cause the spring
~:o deflect. This will then have the effect of cau sing relative movement of
the harness portion
relative to the load car-r-ying portion.
1o
Therefore, as the user walks, his gait will induce. a slight oscillatory or
undulating motion on the
harness portion, as shown in figure 6a in exaggerated fashion for illustrated
purposes.
Beneficially, this undulating motion can then be seen in the slide block
members traveling in an
oscillatory motion in their associated track merrrbers. On the other hand, the
track members can
~ 5 gravel relative to the slide block members depending on the changing
orientation or forces that
are exerted on the load as shown in figure 6b. This would occur, for instance,
in a situation
~Nhere the user steps from an upper position to a lower position, causing the
load to be exposed to
a downward force. In this case, the load may then displace in an oscillatory
fashion to
accommodate the downward force and then return to its normal position.
l3
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'Thus, the suspension an-angement of the device 10 is capable of providing
relative movement
between the harness and load support frame between a first and a second
position in a manner to
control dynamic forces on the harness from load oscillations during gait.
If desired, the suspension arrangement may be arranged to provide relative
independent
onovement between the harness portion and load support frame on either side of
a central position
between a first limit position and a second limit position, wherein the load
support frame is
operable to adopt a transient elevation at the central position while the
harness moves an
undulating motion between the first and second limit positions during gait. In
this case, figure 6a
illustrates the central position in solid lines and the first and second limit
positions in dashed
1 fines.
l n some applications, the dynamic force control may alternatively be provided
by a shock
absorber (shown in dashed lines at 69 in figure l ), such as a gas charged
shock absorber, which
~ 5 would dampen motion between the harness fi-ame portion and the load frame
portion.
Figure 7 shows a portion of an alternative device. A harness frame panel 80 is
attached to an
outer sleeve portion 82 at its peripheries 82a to form a passage 84 to receive
an inner load
~~upport panel 86. In this case, the panel 80 is attached to a foam panel 88
and is shaped to
20 accommodate the shape of the user"s back by way of an appropriate foam
material. The load is
shown schematically at 90 and is attached to the inner load support panel 86
by way of passages
through the outer sleeve portion 82 (not shown).
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CA 02385481 2002-05-08
While the device 10 makes use of stays, they may instead be replaced by a
single panel to which
nhe shoulder and waste straps are attached. In this case, the single panel may
be provided with a
foam pad or similar padding which is shaped to conform to the user's back.
Similarly, while the
stays in the device 10 are described as being adjustable to accommodate the
shape of the user's
hack, it will be understood that the stays may be made standard and padding
may be provided on
them to allow the device to be custom tailored to the user's back. While the
suspension
arrangement provided in the device 10 makes use of sliding blocks and tracks
elements, other
means may be used to achieve motion between harness frame portion and the load
frame portion,
such as by the use of wheels and bearings, lubricated sliding surfaces and two
surfaces separated
by a gas. In this case, the wheels could be added to the inner load support
panel and run against
the harness frame panel 80. Alternatively, the two could slide relative to one
another.
'JVhile the device 10 makes use of a suspension having a track for sliding
movement along a path,
~ 5 it is also contemplated that the suspension may be provided with a
parallel link arrangement as
~,hown in figure 8. In this case, a harness portion shown at 90 and a load
frame portion 92 are
joined by a dynamic force control portion 94 which has a pair of anchor panels
96a, 96b to which
a number of parallel links 98 are pivotally attached. In this case,
displacement controllers, such
avs a spring arrangement shown at I 00, control the motion of the parallel
links allowing the
2o suspension to control dynamic forces and to permit the load to travel
through an arcuate travel
path F. The link arrangement may then establish a central transient position
(denoted for
CA 02385481 2002-05-08
.example, by the levers being in a "3 o'clock" position) between an upper
limit position (for
~°xample, a "I o'clock" position) and a lower limit (for example, a "4-
o'clock" position).
While the devices illustrated herein are intended to be used by a single user,
the dynamic force
controlling characteristics provided by the present invention may also be
applied to portable
carrying devices which involve two or more people, such as, for example,
device having a back
pack unit for each of two users where the back pack units include a support
portion for carrying
one end of a stretcher, a canoe, or multiple stretchers or canoes in tandem.
to 'While the load frame portion used herein is described in association with
an enclosure 26 to
contain a load, it will be understood th<zt the load frame portion may be
provided in a number of
different forms including a frame sheet, for example an L-shaped sheet for
example, which
together with straps or other restrains, anchors the load firmly thereto, as
shown schematically in
cashed lines in figure 6a.
'JVhile the devices disclosed herein are described as having dynamic force
absorbing
arrangements, such as that illustrated at 50 in figure 5, it will be
understood that the force
absorbing arrangement may be one which, in effect, reduces the transmission of
dynamic forces
from the harness portion to the load frame portion and vice versa while not
completely absorbing
2o such forces.
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CA 02385481 2002-05-08
While the present invention has been described for what are presently
considered the preferred
embodiments, the invention is not so limited. Tu the contrary, the invention
is intended to cover
~~arious modifications and equivalent arrangements included within the spirit
and scope of the
appended claims. The scope of the following claims is to be accorded the
broadest interpretation
so as to encompass all such modifications and equivalent structures and
functions.
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