Note: Descriptions are shown in the official language in which they were submitted.
CA 02851900 2014-05-09
TITLE: FAIL-SAFE LATCH MECHANISM
FIELD OF THE INVENTION
[0001] The present invention relates to industrial carts and the like, and
more
particularly to a fail-safe latch mechanism for coupling together one or more
industrial
carts.
BACKGROUND OF THE INVENTION
[0002] In the art, industrial carts are widely known and used for material
and parts
handling. In the automotive industry, for example, industrial carts are
utilized to deliver
parts and other materials to automated assembly lines and other areas of the
physical
plant. The industrial carts are typically coupled together to form a train of
two or more
carts for material delivery and handling.
[0003] The industrial carts are coupled together with a latch mechanism. In
order to
facilitate material delivery and handling efficiency, the latch or coupling
mechanism is
configured to be releasable without the need for special tools and the like.
Typical latch
mechanisms include a spring mechanism that is configured to bias the latch
mechanism
into a closed or engaged position.
[0004] It will, however, be appreciated that over time the spring will
weaken and as
result the latch mechanism will be more susceptible to accidental opening or
complete
failure. The accidental opening or failure of the latch mechanism can, in
turn, lead to a
runaway cart or other unintended movement or displacement. Since the
industrial cart can
be carrying heavy loads, a runaway condition presents a serious safety concern
or
industrial hazard.
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[0005] Accordingly, there remains a need for improvements in the art.
BRIEF SUMMARY OF THE INVENTION
[0006] The present invention is directed to a latch with a fail-safe
mechanism and is
suitable for use with industrial carts, dollies and other types of industrial
vehicles or other
mobile material delivery and handling systems.
[0007] According to one embodiment, the present invention comprises a latch
suitable for use with an industrial cart, the latch comprises, a support
structure configured
to be connected to the industrial cart; a hitch hook operatively coupled to
the support
structure and configured to move between a closed position and an open
position; a latch
mechanism coupled to the hitch hook and configured to bias the hitch hook to
said closed
position; and a fail-safe mechanism coupled to the hitch hook and configured
to bias the
hitch hook in the closed position and maintain the hitch hook in the closed
position
during a failure of the latch mechanism.
10008] According to another embodiment, the present invention comprises a
fail-safe
latch for use with an industrial cart, the fail-safe latch comprises; a
housing and including
a back plate configured to be connected to the industrial cart; a latch
mechanism
including a shaft and first and second spring positioning plates, the first
and second
spring positioning plates being attached to the back plate in a spaced
arrangement, and
further including first and second hitch hook side plates, the first and
second hitch hook
side plates being attached to the back plate between the first and the second
spring
positioning plates and configured to form a hitch hook channel, and each of
the first and
the second spring positioning plates including a spring plate positioning
hole, and each of
the first and the second hitch hook plates including a hitch hook plate hole,
and the spring
positioning plate holes being on center with the hitch hook side plates and
configured to
support the shaft; a hitch hook having a hole for receiving the shaft, and the
hitch hook
being pivotally mounted on the shaft and in the hitch hook channel, and
including a hook
end configured to engage a latch ring, and a pivot end; the latch mechanism
further
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including a foot plate, and the foot plate being connected to the hitch hook,
and the foot
plate including first and second spring retainer; the latch mechanism further
including
first and second springs, and each of the spring positioning plates including
a spring tab,
the first spring being mounted on a section of the shaft between the first
spring
positioning plate and the first hitch side plate and having one end secured by
the spring
tab, and the second spring being mounted on a section of the shaft between the
second
spring positioning plate and the second hitch side plate and having one end
secured by
the spring tab, and the first spring having another end secured by the first
spring retainer
on the foot plate and the spring being mounted on the shaft under tension to
bias the foot
plate and the hitch hook into a latch closed position, and the second spring
having another
end secured by the second spring retainer on the foot plate and the second
spring being
mounted on the shaft under tension to bias the foot plate and the hitch hook
into the latch
closed position; and a counter weight, the counter weight being attached to
the pivot end
of the hitch hook, and configured to generate a force to bias the hitch hook
and the foot
plate into the latch closed position.
[0009]
According to a further embodiment, the present invention comprises an
industrial cart comprising, a frame; a carrier coupled to the frame and
configured to carry
a load; a plurality of wheels operatively coupled to the frame; the frame
including a
mounting plate; and a fail-safe latch comprising, a housing and including a
back plate
configured to be connected to the mounting plate; a latch mechanism including
a shaft
and first and second spring positioning plates, the first and second spring
positioning
plates being attached to the back plate in a spaced arrangement, and further
including first
and second hitch hook side plates, the first and second hitch hook side plates
being
attached to the back plate between the first and the second spring positioning
plates and
configured to form a hitch hook channel, and each of the first and the second
spring
positioning plates including a spring plate positioning hole, and each of the
first and the
second hitch hook plates including a hitch hook plate hole, and the spring
positioning
plate holes being on center with the hitch hook side plates and configured to
support the
shaft; a hitch hook having a hole for receiving the shaft, and the hitch hook
being
pivotally mounted on the shaft and in the hitch hook channel, and including a
hook end
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configured to engage a latch ring, and a pivot end; the latch mechanism
further including
a foot plate, and the foot plate being connected to the hitch hook, and the
foot plate
including first and second spring retainer; the latch mechanism further
including first and
second springs, and each of the spring positioning plates including a spring
tab, the first
spring being mounted on a section of the shaft between the first spring
positioning plate
and the first hitch side plate and having one end secured by the spring tab,
and the second
spring being mounted on a section of the shaft between the second spring
positioning
plate and the second hitch side plate and having one end secured by the spring
tab, and
the first spring having another end secured by the first spring retainer on
the foot plate
and the spring being mounted on the shaft under tension to bias the foot plate
and the
hitch hook into a latch closed position, and the second spring having another
end secured
by the second spring retainer on the foot plate and the second spring being
mounted on
the shaft under tension to bias the foot plate and the hitch hook into the
latch closed
position; and a counter weight, the counter weight being attached to the pivot
end of the
hitch hook, and configured to generate a force to bias the hitch hook and the
foot plate
into the latch closed position.
[00010] Other aspects and features of the present invention will become
apparent to
those ordinarily skilled in the art upon review of the following description
of
embodiments of the invention in conjunction with the accompanying figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[00011] Reference will now be made to the accompanying drawings which show, by
way of example, embodiments of the present invention, and in which:
[00012] Fig. IA shows in diagrammatic form a plurality of industrial carts
each
configured with a latch and fail-safe mechanism according to an embodiment of
the
present invention and coupled together to form an industrial material delivery
train;
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[00013] Fig 1B is a bottom plan view of the industrial carts of Fig. 1A
showing the
underbody or under carriage configuration of the carts;
[00014] Fig. 1C shows in diagrammatic form two of the carts of Fig. 1A coupled
together with the latch and fail-safe mechanism according to an embodiment of
the
present invention;
[00015] Fig. 1D shows in diagrammatic form another view of the latch and fail-
safe
mechanism according to an embodiment of the present invention for coupling
together
two carts as depicted in Fig. 1A;
[00016] Fig. 2 is an isometric view of a latch and fail-safe mechanism
according to an
embodiment of the present invention;
[00017] Fig. 3 is an isometric view of the latch and fail-safe mechanism of
Fig. 2 with the housing depicted in dotted-chain outline;
[00018] Fig. 4 is a front isometric view of the latch and fail-safe
mechanism of Fig. 2;
[00019] Fig. 5 is an isometric view of the hitch hook member of the fail-
safe latch
mechanism shown in isolation;
[00020] Fig. 6 is an isometric of the hitch hook member together with the
counter
weight;
[00021] Fig. 7 is a side view of the hitch hook member together with the
counter
weight; and
[00022] Fig. 8 is a side view of the fail-safe latch mechanism moving between
a closed
(i.e. engaged) position to an open (i.e. disengaged) position.
[00023] Like reference numerals indicate like or corresponding elements or
components in the drawings.
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DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION
[00024] Reference is made to Fig. 1A, which shows in diagrammatic form an
exemplary operating environment and configuration for implementing and
practising a
latch and fail-safe mechanism according to embodiments of the present
invention. The
operating environment according to an embodiment and indicated generally by
reference
100 comprises a plurality of industrial carts 110, indicated individually by
references
110a, 110b,....110n with each of the carts 110 being configured with a latch
and fail-safe
mechanism according to the present invention and indicated generally by
reference 200.
The industrial carts 110 may comprise a conventional or known cart, dolly,
trailer or the
like, and will typically comprise a base frame or support structure 112 (as
also shown in
Figs. 113 and 1C), and a platform or cargo bed or carrier surface 114, a wheel
structure or
assembly, indicated generally by reference 116. The wheel assembly 116 is
coupled to
the frame 112 and according to an exemplary implementation comprises a four
wheel
configuration, with the wheels indicated individually by references 116a,
116b, 116c and
116d. According an exemplary implementation, two of the wheels 116a and 116d
(e.g.
the front wheels) are configured to be rotatable, for example, for steering or
turning the
cart(s) 110. The platform 114 is configured to carry the load or material,
e.g. automotive
parts and components, or palletized loads. As shown in Fig. 1, the fail-safe
latch 200 is
connected or installed on one end of the cart 110. According to an exemplary
implementation, the cart 110 includes a mounting bracket 130 as shown in Fig.
1C and
Fig. 1D for mounting or attaching the fail-safe latch 200 to the cart 110, for
example, the
rear end of the cart 110. The fail-safe latch 200 may also be connected
directly to the
frame 112 of the cart 110. The other end of the cart 110, for example, the
front end of the
cart 110, includes an arm 120 (e.g. a pintel arm) with a latch ring or ring
122 (e.g. a pintel
ring) which is compatible with and configured for engaging a hitch hook in the
fail-safe
latch 200, as shown in Fig. 1C and Fig. 1D, and described in detail below.
According to
an exemplary implementation, the cart 110 includes a hinge mechanism 124 (as
shown in
Fig. 1A) for connecting the pintel arm 120 (and latch ring 122) to the cart
110 and
allowing the arm 120 to pivot or swing up and down via the hinge mechanism
124.
According to another as aspect, the carts 110 may include a stop mechanism
indicated
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generally by reference 140. The stop mechanism 140 is configured when actuated
to
maintain or hold the cart 110 in a stationary position.
[00025] In the following description, the terms latch and fail-safe
mechanism and fail-
safe latch are used interchangeably. While embodiments according to the
present
invention are described in the context of industrial and manufacturing
applications, it will
be appreciated that the embodiments have wider application to other fields,
for example,
baggage and freight delivery trailers or carts or trains typically utilized,
for example, at
airports, for the loading and unloading of airline luggage and/or freight.
[00026] Reference is next made to Figs. 2 to 4, which show a latch with a
fail-safe
mechanism according to an embodiment of the present invention and indicated
generally
by reference 200. The latch with a fail-safe mechanism 200 comprises a housing
or
enclosure indicated generally by reference 210, a hook foot plate or pedal
220, a hitch
hook 230, a latch mechanism indicated generally by reference 240 in Figs. 3
and 4, and a
fail-safe mechanism indicated generally by reference 260.
[00027] As shown in Fig. 2, the latch housing 210 forms a support structure
for the
hook hitch 230 and the latch mechanism 240. The latch housing 210 is also
configured to
attach or connect to the cart or dolly, for example, bolted to the frame 112
and/or a
mounting plate or bracket 130 on the cart 110 (for example, as shown in Figs.
1C and
1D). According to an embodiment, the latch housing 210 comprises a back or
rear plate
212, a top plate 214 and respective side plates indicated by references 216
and 217.
According to an exemplary implementation, the latch housing 210 is fabricated
using
individual steel plates that are welded together to form the housing utilizing
known
techniques.
[00028] The hook foot plate or pedal 220 is configured to be responsive to a
downward applied force and actuate the latch mechanism 240 and move the hitch
hook
230 into an open or disengaging position (for example, as indicated by
reference 810 in
Fig. 8). The downward force can be foot pressure applied by an operator or
technician.
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[00029] The latch mechanism 240 is configured to maintain or hold the hitch
hook 230
(and the hook foot plate 220) in a closed or engaging position, for example,
as indicated
by reference 820 in Fig. 8 and also illustrated in Figs. 1C and 1D. As shown
in Fig. 3, the
latch mechanism 240 comprises a bias mechanism indicated generally by
reference 242,
which is configured to bias or retain the hitch hook 230 in the closed
position, for
example, as depicted in Fig. 3, and also in Fig. 8 (i.e. indicated by
reference 820) and
Figs. IC and 1D. According to an embodiment, the bias mechanism 242 comprises
a
spring 244, which is mounted on a shaft 246. Each end of the shaft 246 is held
in place or
supported by respective spring positioning plates 248a and 248b as shown in
Fig. 3. The
spring positioning plates 248a and 248b are affixed or connected to the inside
of the back
plate 212 for the latch housing 210, for example, using welding or other known
assembly
or connection techniques. As shown in Fig. 4, the shaft 246 is secured in
place using a
suitable fastener, for example, a hex slotted nut 247a and a slotted pin 247b
at one end of
the shaft, and another hex nut 247c, which is welded or otherwise securely
affixed to the
other end of the shaft 246. Referring back to Fig. 3, the spring positioning
plate 248a
includes a spring tab 249a for engaging one end of the spring 244. The other
end of the
spring 244 is engaged or secured by a spring retainer 250a which is affixed or
formed on
the hook foot plate 220 as shown in Figs. ID, 3 and 6. The spring 244 is
secured in
tension to provide a force that acts to bias or force the hook foot plate 220
upward, i.e.
into the closed position 820 as shown in Fig. 8 and also in Figs. 1C, 1D and
Fig. 3.
[00030] According to another embodiment and as shown in Fig. 3, the latch
mechanism 240 comprises a second spring 245. The configuration of two springs
244 and
245 provides a degree of redundancy should the first spring 244 (or the second
spring
245) fail. As shown in Fig. 3, the spring positioning plate 248b includes a
spring tab 249b
for engaging one end of the second spring 245, and the other end of the spring
245 is
secured by a spring retainer 250b on the hook foot plate 220 as shown in Fig.
3 and also
in Fig. 6. Each of the springs 244 and 246 will be specified to produce a
force (e.g.
retention force) sufficient to maintain the hitch hook 230 and the hook foot
plate 220 in
the closed or engaged position 820 (Fig. 8) and also depicted in Fig. 1C. The
particular
selection of suitable components for the spring 244, and the second spring 246
in a two-
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spring configuration, will be based in part on the spring K factor as will be
readily within
the understanding of one skilled in the art.
1000311 Reference is next made to Fig. 5, which shows the hitch hook 230
according
to an embodiment of the present invention. According to an exemplary
implementation,
the hitch hook 230 is configured as a pintel type hook for engaging a latch
ring (e.g. a
pintel ring) on another or adjacent cart in order to couple the two carts 110a
and 110b
together (for example, as described above with reference to Figs. lA to 1C).
According to
an embodiment, the hitch hook 230 is affixed or connected to the hook foot
plate 220, for
example, welded or bolted from the underside. In this configuration,
depressing the hook
foot plate 220 moves the hitch hook 230 downwards, i.e. the open or disengaged
position
810 as shown in Fig. 8, and described in more detail below.
[00032] As shown in Fig. 5, the hitch hook 230 comprises a hook 232, a hook
arm 234
and a hook pivot 236. The hook 232 comprises a shape or profile that is
configured to
securely engage a latch ring (for example, as indicated by reference 122 in
Figs. 1A, 1B
and IC) on another cart for coupling two carts together. The hook atm 234 is
configured
to provide a clearance or span for engaging (and disengaging) the latch ring
to and from
the hook 232. The hook pivot 236 is configured to provide a pivot point for
moving or
swinging the hitch hook 230 between the open 810 and the closed 820 positions,
for
example, as depicted in Fig. 8. According to an exemplary implementation, the
hook
pivot 236 includes a hole or bore 237 which allows the hitch hook 230 to be
mounted on
and supported at the pivot point by the shaft 246, and pivot or swing between
the open
810 and closed 820 positions as shown in Fig. 8.
[00033] According to an embodiment, the latch mechanism 240 further includes
hitch
hook side plates 252a and 252b as shown in Fig. 3. The hitch hook side plates
252a, 252b
are connected, e.g. welded, to the hitch back plate 210, and are configured to
define a
recess or channel for the hitch hook 230. The hitch hook side plates 252a,
252b are also
configured to provide a stop for the hook foot plate 220, when the hitch hook
230 is in
the closed position. As shown in Figs. 3 and 8, the top surface of hook foot
plate 220
abuts or rests against the lower edge or underside of the hitch hook side
plates 252a, 252b
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in the closed or engaged position 820 (and also shown in Fig. 1D). According
to another
aspect, each of the hitch hook side plates 252a, 252b includes a hitch hook
arm indicated
by references 253a and 253b, respectively, for instance as depicted in Figs. 3
and 8. The
hitch hook arm 253 is configured to guide the latch or pintel ring 122 (Fig.
1C) into
engagement with the hitch hook 230, i.e. the hook 232. The hitch hook arm 253
also
facilitates disengaging the latch ring from the hitch hook 230 when the hook
foot plate
220 is depressed to the open position 810 (Fig. 8) and the hitch hook 230
pivots
downwards. According to another aspect, the hitch hook side plates 252a and
252b each
include a hole or bore, indicated by respective references 255a (Fig. 3) and
255b (Fig. 8),
for the shaft 246. According to an exemplary implementation, a thrust washer,
indicated
generally by reference 254 in Fig. 4, is mounted between each hitch hook side
plate 252a,
252b and the hitch hook 230. The thrust washer 254 is formed from a softer
metal, for
example, bronze, and comprises a replacement part that limits the wear which
would
otherwise occur between the hitch hook side plates 252a, 252b and the hitch
hook 230
through the operation of the latch 200.
[00034]
Reference is made to Fig. 8, which further illustrates operation of the fail-
safe
latch 200 according to an embodiment of the present invention. The latch
mechanism 240
as described above with reference to Fig. 3 holds the hitch hook 230 in the
closed or
engaged position indicated by reference 820. The closed position 820 is
maintained by
the force exerted by the spring 244 and/or the spring 245 (e.g. both springs
in a two
spring configuration). To disengage the hitch hook 230, i.e. move the hitch
hook 230
downwards to the open or disengaged position 810, an operator applies a
downward force
on the hook foot plate 220, e.g. steps down on the plate 220 with his foot.
This downward
force counteracts the force being exerted by the spring(s) 244, 245, and
allows the hitch
hook 230 to pivot or swing down to the open or disengaged position 810. Once
the
operator removes her foot from the hook foot plate 220, the force of the
spring(s) 244,
245 pulls the hook foot plate 220 and the hitch hook 230 upwards to the closed
or
engaged position 820 as shown in Fig. 8 and also in Figs. 1C, 1D and Fig. 3.
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[00035] According to a further embodiment, the latch mechanism is configured
with a
counterweight indicated generally by reference 260. The counterweight 260 is
configured
to provide a fail-safe mechanism, and functions to bias and maintain the hitch
hook 230
in a closed or engaged position, i.e. engaging the latch ring of an adjoining
cart (Figs. lA
to 1D), should the first spring 244 and/or the second spring 245 fail or
experience fatigue
to the point that the spring force is insufficient to hold the hitch hook 230
in the closed or
engaged position 810 (Fig. 8). According to an exemplary implementation, the
counterweight 260 comprises a mass that is affixed or connected to the hook
pivot section
236 of the hitch hook 230, as shown in Figs. 6 and 7. The counterweight 260 is
configured to exert a force that is sufficient to keep the hitch hook 230 (and
the hook foot
plate 220) in the closed position, for example, as indicated by reference 820
in Fig. 8, in
the event that the spring(s) 244 and/or 245 fail. It will be appreciated that
a moment arm
or lever, indicated generally by reference 262 in Fig. 7, is formed between
the pivot point
of the shaft 246, i.e. the center of the hole 237, and the center of mass of
the
counterweight 260. Accordingly, the moment arm 262 may be factored into
determining
an appropriate weight for the counterweight 260, as will be readily within the
understanding of one skilled in the art. According to an exemplary
implementation, the
springs 244 and 245 are configured to exert a force of approximately 35 pounds
and the
counterweight 260 is configured to exert a force of approximately 5 pounds in
the event
of spring failure.
[00036] In
operation, if the spring 244 (or both springs 244 and 245 in a two spring
configuration) no longer exerts sufficient force to hold the hook foot plate
220 and the
hitch hook 230 in the closed position, for example, as a result of spring
fatigue or total
spring failure, the counterweight 260 functions to exert a downward force,
indicated
generally by reference 264 in Fig. 7, that holds or maintains the hook foot
plate 220 and
the hitch hook 230 in the engaged or closed position (as shown in Figs. 1C, 1D
and Fig.
3, and indicated by reference 820 in Fig. 8). This, in turn, prevents the
accidental or
inadvertent release or disengagement of the hitch hook 230 from the latch or
pintel ring
of a coupled cart resulting in a runaway or uncontrolled cart in the plant.
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[00037] The present invention may be embodied in other specific forms without
departing from the spirit or essential characteristics thereof Certain
adaptations and
modifications of the invention will be obvious to those skilled in the art.
Therefore, the
presently discussed embodiments are considered to be illustrative and not
restrictive, the
scope of the invention being indicated by the appended claims rather than the
foregoing
description, and all changes which come within the meaning and range of
equivalency of
the claims are therefore intended to be embraced therein.
