Note: Descriptions are shown in the official language in which they were submitted.
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UPPER BLOCK
Related Application
This application is a divisional of Canadian Patent Application No. 2,503,744.
Background of the Invention
The present invention relates to overhead cranes and particularly to upper
blocks of
overhead cranes. More particularly, the present invention relates to failure
proof
mechanisms for upper blocks of overhead cranes.
Conventional overhead cranes include an upper block that, in combination with
a
lower block and a drum, is used to raise or lower a hook or other lifting
mechanism
attached to the lower block. Often, conventional overhead cranes include
failure proof
mechanisms within the upper block to shut down the crane if an overload or
uneven-load
condition is present.
Summary of the Invention
The present invention provides a crane having a drum, an upper block, a lower
block, and at least two rope ends. The upper block includes an equalizer yoke
pivotally
mounted to a support wall of the upper block and having two load pins. Each
rope end is
coupled to one of the load pins, and the rope ends,are substantially parallel
to one another
in a direction substantially perpendicular to a line running through the two
load pins.
In another embodiment of the present invention, an equalizer is provided for a
crane having a drum, a lower block, an upper block, and at least two rope
ends. The
equalizer comprises a support wall and an equalizer yoke pivotally coupled to
the support
wall. The equalizer yoke includes two load pins, each rope end being coupled
to one of
the load pins through a connection bracket. The connection bracket includes a
frame
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substantially surrounding and movable relative to the load pin and an
adjustment
screw threaded through a top wall of the frame, the adjustment screw having an
end
in engagement with the load pin, wherein rotation of the adjustment screw
moves the
frame relative to the load pin.
Still another embodiment of the present invention provides an equalizer
for a crane having a drum, a lower block, an upper block, and at least two
rope ends.
The equalizer comprises a support wall, an equalizer yoke, and a third pin.
The
equalizer yoke is pivotally coupled to the support wall and includes two load
pins,
each rope end being coupled to one of the load pins. The third pin is mounted
to the
equalizer yoke and extends through a tapered slot in the support wall, the
third pin
being wedged in a tapered end of the tapered slot when the yoke pivots.
In yet another embodiment of the present invention, an upper block for
an overhead crane comprises a guide frame and a support wall movably
positioned
within the guide frame. A hydraulic cylinder is positioned between the guide
frame
and support wall. And, a pressure relief valve is connected to the hydraulic
cylinder,
the pressure relief valve opening if the fluid in the hydraulic cylinder
exceeds a
predetermined pressure value.
A further embodiment of the present invention provides an overhead
crane comprising: a rotatable drum; a lower block; an upper block having a
support
wall; two wire ropes having ends secured to the upper block and extending from
the
upper block to the lower block and from the lower block to the upper block so
that the
lower block is lifted when the drum rotates to wind the wire ropes around the
drum
and so that the lower block is lowered when the drum rotates to unwind the
wire
ropes from the drum; a guide frame; wherein the support wall is movably
positioned
within the guide frame and restricted to only vertical movement within the
guide
frame; at least one hydraulic cylinder vertically positioned between the guide
frame
and support wall so that the support wall is supported on the guide frame by
the at
least one hydraulic cylinder and any load carried by the crane translates into
fluid
pressure within the at least one hydraulic cylinder; and a pressure relief
valve
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connected to the hydraulic cylinder, the pressure relief valve opening if the
fluid in the
hydraulic cylinder exceeds a predetermined pressure value to relieve pressure
within
the hydraulic cylinder and cause the support wall to move down within the
guide
frame.
A still further embodiment of the present invention provides an
overhead crane comprising: a rotatable drum; a lower block; an upper block
having a
support wall; two wire ropes having ends secured to the upper block and
extending
from the upper block to the lower block and from the lower block to the upper
block
so that the lower block is lifted when the drum rotates to wind the wire ropes
around
the drum and so that the lower block is lowered when the drum rotates to
unwind the
wire ropes from the drum; a guide frame; wherein the support wall is movably
positioned within the guide frame and restricted to only vertical movement
within the
guide frame; a movable trolley which carries the drum and the guide frame;
wherein
the drum is located adjacent the guide frame on the trolley and above the
lower
block; a plurality of hydraulic cylinders vertically positioned between the
guide frame
and the support wall so that the support wall is supported by the plurality of
hydraulic
cylinders and any load carried by the crane translates into fluid pressure
within the
plurality of hydraulic cylinders; a pressure relief valve connected to the
plurality of
hydraulic cylinders; and wherein the pressure relief valve opens if fluid in
the
hydraulic cylinders exceeds a predetermined pressure value to relieve pressure
within the hydraulic cylinders and cause the support wall to move down within
the
guide frame.
Brief Description of the Drawings
The detailed description particularly refers to the accompanying figures
in which:
Fig. 1 is a perspective view of a crane including a trolley having an
upper block according to the present invention;
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Fig. 2 is a front view of an equalizer, within the upper block of Fig. 1,
having two wire ropes connected to connection brackets of the equalizer;
Fig. 3 is a side view of the equalizer of Fig. 2;
Fig. 4 is an alternative embodiment of the equalizer of Fig. 2;
Fig. 5 is a side view of a schematic representation of the upper block of
Fig. 1; and
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Fig. 6 is a top view of the trolley of Fig. 1, illustrating a schematic
representation
of the upper block.
Detailed Description of the Drawings
Referring to Fig. 1, a crane 10 includes a trolley 16 that moves along girder
rails 20
that sit atop a first girder 12 and a second girder 14. The first girder 12
and second girder
14 translate along a main support beam 18 on one end and an additional support
beam (not
shown) parallel to beam 18 on the other end. The trolley 16 includes a drum 26
around
which is wrapped two wire ropes 54, 56. As the drum 26 rotates and winds up
the wire
ropes 54, 56, a lower block 30 is lifted, as will be readily apparent to those
of skill in the
art. As illustrated in Fig. 1, the lower block 30 includes a hook that can be
used for lifting.
However, the lower block 30 could include other configurations for lifting, as
will also be
readily apparent to those of skill in the art.
The translation of the trolley 16 along the first and second girders 12, 14
and the
translation of the first and second girders 12, 14 along the main support
beams 18 (only
one of which is shown), allows the crane 10 to position the lower block 30 in
virtually any
location in a space in which the crane 10 is installed. The main support beam
18 is shown
as a straight beam. As will be readily known to those of skill in the art, the
main support
beam 18 may alternatively be curved to match the inside wall contours of a
round
building. For example, a polar crane similar to crane 10, shown in Fig. 1, may
be used in a
nuclear containment building that is built in a round configuration, in which
case the main
support beam 18 will be shaped in a circle instead of a straight line.
As shown in Fig. 1, the wire ropes 54, 56 extend from the drum 26 to the lower
block 30, which contains a plurality of sheaves (not shown) around which the
wire ropes
54, 56 pass. From the lower block 30, the wire ropes 54, 56 extend to an upper
block 28
that also contains a plurality of sheaves (not shown). After reeving back and
forth
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between the lower block 30 and upper block 28, as will be readily understood
by those of
ordinary skill in the art, the wire ropes 54, 56 end at an equalizer 32, as
best seen in Fig. 2,
within the upper block 28.
According to the present invention, as shown in Fig. 2, the first and second
wire
ropes 54, 56 are coupled to an equalizer yoke or sheave 76 that is pivotally
supported in a
saddle 52 by a main pin 62. The saddle 52 is pivotally supported within the
upper block
28 through a sleeve support 34 that allows the entire equalizer 32 to swing
within the
upper block 28. The saddle 52 includes two support walls 51 between which the
equalizer
yoke 76 is sandwiched (see Fig. 3). The equalizer yoke 76 is illustrated as a
round sheave,
or wheel, in Fig. 2, but could be formed in any other shape (e.g., the
hexagonal-shaped
yoke 276, shown in Fig. 4 and discussed below) and pivotally supported by the
saddle 52.
The first and second wire ropes 54, 56 are coupled to the equalizer sheave 76
with
first and second connection brackets 68 and 70. The connection brackets 68, 70
are
adjustable to correct for minor variations in the lengths of first and second
wire ropes 54,
56 and to thereby even out the forces placed on the wire ropes 54, 56 by the
bottom block
30. The connection brackets 68, 70 couple the wire ropes 54, 56 to first and
second load
.cell bushings 57, 59 that include first and second load cells or load pins
58, 60,
respectively, mounted to the equalizer sheave 76. The connection brackets 68,
70 are
supported on the load cell bushings 57, 59 by first and second adjustment
screws 72, 74.
The adjustment screws 72, 74 are threaded through the top walls of the
connection
brackets 68, 70 and their ends engage the load cells or load pins 58, 60
through their
respective load cell bushings 57, 59. Rotation of the adjustment screws 72, 74
causes the
screws 72, 74 to push against the load cell bushings 57, 59 and respective
load cells 58, 60.
In this way, the adjustment brackets 68 and 70 move up and down relative to
the load cell
bushings 57, 59 as the adjustment screws 72, 74 are turned.
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As mentioned, the first and second load cell bushings 57, 59 include first and
second load cells or load pins 58, 60 that measure the load carried by the
load cell
bushings 57, 59. Before a load is lifted by the lower block 30 of the crane
10, the
adjustment screws 72, 74 may be adjusted until the load cells 58, 60 register
the same load
reading, indicating that the load of the lower block 30 is equally shared by
the first and
second wire ropes 54, 56. Initially, when the only load carried by the wire
ropes 54, 56 is
the lower block 30 itself (i.e., the hook of the lower block 30 is not
attached to any
additional load), the adjustment screws 72, 74 are adjusted to take up minor
discrepancies
in the lengths of the wire ropes 54, 56 and to equalize the forces carried by
the ropes 54,
56. When an additional load is attached to the lower block 30 the load cells
58, 60
indicate the additional load being lifted by the crane 10 and all of the load-
bearing
components of crane 10. As the drum 26 lifts the lower block 30 and any load
attached
thereto, the load cells 58, 60, in combination, measure the total load being
lifted by the
lower block 30 and, individually, the respective loads carried by each of the
first and
second wire ropes 54, 56.
By monitoring the readings of the load cells 58, 60, various load conditions
can be
monitored. For example, an overload condition on the entire crane system can
be
monitored, as well as a failure or overload of one of the first and second
wire ropes 54, 56
(i.e., an uneven-load condition). If the crane 10 attempts to lift a load
beyond its capacity,
the total load registered by first and second load cells 58, 60 will register
the excessively
large load. A human or computer system can monitor the readings of the load
cells 58, 60
and shut down the crane 10 if such an overload condition occurs.
Similarly, if, when lifting a load, one of the first and second wire ropes 54,
56 fails
(i.e., breaks), the load cell 60 or 58 associated with the other (non-broken)
wire rope 56, 54
will register all of the load carried by the lower block 30. The load cell 58
or 60
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associated with the failed wire rope 54, 56 will register relatively no load.
Again, a human
or computer system monitoring the load cells 58, 60 can shut down the crane 10
if such a
condition occurs. If one of the first and second wire ropes 54, 56 does not
fail, but
registers an excessively high reading relative to the other wire rope 56, 54
because of a
misaligned or uneven load on the lower block 30 or other such condition, the
crane 10 can
similarly be shut down.
As mentioned, the wire ropes 54, 56 are coupled to the equalizer sheave 76
through
connection brackets 68, 70. As also mentioned, the load is carried by first
and second
adjustment screws 72, 74 that engage the load cell bushings 57, 59. Therefore,
the load is
also carried by the threads of the adjustment screws 72, 74 and their threaded
engagement
with the top, walls of the connection brackets 68, 70. If the threads of
either adjustment
screw 72, 74 fail, the corresponding connection bracket 68, 70 will fall until
the top wall of
the connection bracket 68, 70 hits the load cell bushing 57, 59. In this way,
a failure of the
threaded connection between either or both adjustment screws 72, 74 and their
respective
connection brackets 68, 70, will not result in one or both of the wire ropes
54, 56
disconnecting from the equalizer sheave 76. The bracket 68, 70 will fall a few
inches and
directly engage the load cell bushing 57, 59.
Relatively small variations in the loads carried by the first and second wire
ropes
54, 56 will cause the equalizer sheave 76 to rotate, thereby equalizing the
loads in the wire
ropes 54, 56. If one of the first or second wire ropes 54, 56 breaks, the
other wire rope 56,
54 will suddenly "feel" all of the load carried by the lower block 30. This
will cause the
equalizer sheave 76 to rotate more drastically about the main pin 62 that
couples the
equalizer sheave 76 to the saddle 52. The equalizer sheave 76 also includes
upper and
lower pins, 48 and 50 respectively, that move within respective saddle slots
46 in the
saddle 52 when the equalizer sheave 76 rotates.
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For example, if the second wire rope 56 were to break, all of the load on the
lower
block 30 will suddenly be carried by the first wire rope 54. This will cause
the equalizer
sheave 76 to rotate counter-clockwise within the saddle 52, thereby causing
the upper pin
48 to move to the left in its tapered saddle slot 46 and the lower pin 50 to
move to the right
in its tapered saddle slot 46. Upon such rotation of the equalizer sheave 76,
the upper and
lower pins 48 and 50 move into tapered ends of the saddle slots 46 and prevent
further
rotation of the equalizer sheave 76. As the upper and lower pins 48 and 50
move into the
tapered ends of the saddle slots 46, they progressively wedge themselves into
the tapers of
the saddle slots 46, thereby dampening the impulsive load placed on the first
wire rope 54
when the second wire rope 56 breaks.
To help dampen this impulsive force and prevent the first wire rope 54 from
breaking under the nearly instantaneous additional force placed on it, the
upper and lower
pins 48 and 50 are surrounded by upper and lower rubber bumpers 64 and 66,
respectively.
The rubber bumpers 64 and 66 bump up against stop plates 38 and 44,
respectively, which
are connected to the saddle 54. By bumping up against the stop plates 38, 44,
the rubber
bumpers 64, 66 help absorb some of the impulsive force felt by the first wire
rope 54 when
the second wire rope 56 breaks. If the first wire rope 54 breaks instead of
the second wire
rope 56, as presented by way of example above, the equalizer sheave 76 will
rotate
clockwise within the saddle 52 and cause upper and lower rubber bumpers 64, 66
to
respectively engage stop plates 40 and 42, both connected to the saddle 52.
Mechanisms
other than the rubber bumpers 64, 66 could be used to dampen the forces felt
by the
remaining rope 54, 56, when the other rope 56, 54 breaks. For example, and as
will be
discussed in further detail below, pneumatic cylinders, as shown in Fig. 4
could be used.
Further, springs or other similar devices connected between the upper and
lower pins 48,
50 and the saddle 52 could be used to dampen such forces.
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In addition to dampening the forces felt by one rope 54, 56, if the other rope
56, 54
breaks, the upper and lower pins 48, 50 serve to secure the equalizer sheave
76 to the
saddle 52 if the main pin 62 fails. If the main pin 62 breaks, the upper and
lower pins 48,
50, will engage their respective tapered saddle slots 46 and hold the
equalizer sheave 76
and the load carried by the crane 10, preventing them from falling.
Referring to Fig. 4, a second embodiment of an equalizer 232 is shown. The
equalizer 232 includes a sleeve support 234, similar to the sleeve support 34
of Figs. 2 and
3, which pivotally supports the equalizer 232 within the upper block 28 of the
crane 10.
The equalizer 232 includes an equalizer yoke 276 that is pivotally coupled to
a saddle 252
that pivots with the sleeve support 234. The equalizer yoke 276 supports the
first and
second wire ropes 54, 56 and equalizes the forces carried by them by pivoting
about a
main pin 262 that connects the equalizer yoke 276 to the saddle 252.
The first and second wire ropes 54, 56 are coupled to the equalizer 276 by two
load
pins 257 and 259, respectively. The load pins 257 and 259 include load cells
that measure
the forces carried by each of the wire ropes 54 and 56. In this way, the load
cells 257 and
259 function much the same way as the load cell bushings 57 and 59, and their
associated
load cells or load pins 58 and 60, of the equalizer 32 shown in Figs. 2 and 3
and can be
utilized to perform the same functionalities discussed with respect to the
equalizer 32
above. The wire ropes 54, 56 are attached to the load pins 257, 259 by sheaves
268 and
270 that surround the load pins 257 and 259, respectively. Rope clamps 258
secure the
wire ropes 54, 56 around the sheaves 268, 270. The sheaves 268, 270 rotate
about the load
pins 257, 259. In this way, regardless of the exact direction the wire ropes
54, 56 are
pulling, the sheaves 268, 270 will rotate to keep the forces aligned with the
load pins 257,
259. Similarly, the connection brackets 68, 70, shown in Figs. 2 and 3, rotate
about the
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load cells 58, 60 to keep the forces carried by the ropes 54, 56 aligned with
the load cells
58, 60.
Like the equalizer 32, the equalizer 232 includes dampers 280 that serve to
dampen
an impulsive force felt by one of the wire ropes 54, 56 in the event the other
of the wire
ropes 56, 54 breaks. Unlike the equalizer 32, however, the equalizer 232
utilizes
pneumatic cylinders 201, 202, 203, and 204 to dampen the impulsive force.
Upper pin 248
and lower pin 250 are coupled to the equalizer yoke 276 and extend through
upper slot 249
and lower slot 251, respectively, in the saddle 252. If one of the wire ropes
54, 56 breaks,
the equalizer yoke 276 will quickly rotate, thereby moving the upper and lower
pins 248,
250 within the upper and lower slots 249, 251. The pneumatic cylinders 201,
202, 203,
and 204 will dampen this motion by providing resistance on the upper and lower
pins 248,
250. All four pneumatic cylinders 201, 202, 203, and 204 work together to
provide
resistance on the upper and lower pins 248, 250 when the equalizer yoke 276
rotates.
As discussed above, both the equalizer 32 and the equalizer 232 include
provisions
for proofing against a failure of either or both of the wire ropes 54, 56
connected to the
equalizer yokes 76, 276. The system shown in Figs. 5 and 6 has an additional
level of
protection against overload of a crane, such as crane 10. Particularly,
exceedingly high
stresses placed on the saddles 52, 252 and sleeve supports 34, 234, shown in
Figs. 2, 3, and
4, will be prevented. If an excessively large load is placed on the lower
block 30 of the
crane 10 or the lower block 30 comes in contact with the upper block 28, the
system
shown in Figs. 5 and 6 will relieve the general overall load condition placed
on the upper
block 28.
Any equalizer, including either of equalizers 32, 232, can be connected to a
block
plate or support wall 99 of the upper block 28. The block plate 99 could be
used as the
saddle 52 or 152 for the equalizers 32, 232, respectively. Or, the sleeve
supports 34, 234
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of the equalizers 32, 232 could be coupled to the block plate 99 of the upper
block 28. In
any case, whatever component of an equalizer is coupled to the block plate 99
of Fig. 5,
the system illustrated in Fig. 5 serves to prevent a failure of the upper
block 28 in the event
the upper block 28 is placed under extreme or overload conditions.
Referring to Figs. 5 and 6, the block plate 99 is movably supported within a
guide
frame 88. Guide rollers 78 positioned between block plate 99 and the guide
frame 88
restrict the block plate 99 to only vertical movement within the guide frame
88. The block
plate 99 and its cap 98 are supported on the guide frame 88 by hydraulic
cylinders 100.
Any load carried by the crane 10, and thereby the block plate 99, translates
into a
fluid pressure within the hydraulic cylinders 100. Each of the hydraulic
cylinders 100 is
connected in parallel through hydraulic lines 94. In this way, the pressure in
each of the
hydraulic cylinders 100 is always the same. The hydraulic lines 94 all run to
a pressure
relief valve 80. The pressure relief valve 80 is preset to hold up to a
particular pressure
value and to release only when that pressure value is exceeded. If loads
placed on the
block plate 99 are within an acceptable range, the pressure relief valve 80
remains closed.
Because the pressure relief valve 80 remains closed, the fluid pressure within
the hydraulic
cylinders 100 is maintained. Therefore, the force exerted by the hydraulic
cylinders 100
on the block plate 99 is maintained. The hydraulic cylinders 100 include
linkages 95 that
connect the hydraulic cylinders 100 to the cap 98 of the block plate 99.
If the load on the upper block 28, and particularly the load on the block
plate 99,
exceeds a predetermined value, the fluid pressure in the hydraulic cylinders
100 and the
hydraulic lines 94 will correspondingly exceed a preset pressure value and
cause the
pressure relief valve 80 to open. Opening of the pressure relief valve 80 will
cause fluid
from the cylinders 100 to drain into an accumulator cylinder 84. This allows
the system to
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slowly relieve the overload force placed on the upper block 28 before a
component such as
the block plate 99 fails.
Relieving the fluid pressure in the hydraulic cylinders 100 by draining
hydraulic
fluid into the accumulator cylinder 84 causes the cap 98 of the block plate 99
to move
down within the guide frame 88. When the block plate 99 has moved down a
certain
extent, contact switches 90 coupled to the guide frame 88 are tripped by the
cap 98 of the
block plate 99. The tripping of switches 90 causes the crane control system to
shut down
the drum 26 and stop the function of the crane 10 until the overload condition
can be
relieved. Once the overload condition is relieved, a lever 82 coupled to the
accumulator
cylinder 84 is depressed to force the accumulated fluid in the accumulator
cylinder 84
through a one-way check valve 86, through the. hydraulic lines 94, and back
into the
hydraulic cylinders 100, thereby resetting the system.
The foregoing description of the present invention has been presented for
purposes
of illustration and description. Furthermore, the description is not intended
to limit the
invention to the form disclosed herein. Consequently, variations and
modifications
commensurate with the above teachings, and the skill or knowledge of the
relevant art, are
within the scope of the present invention. The embodiments described herein
are further
intended to explain best modes known for practicing the invention and to
enable others
skilled in the art to utilize the invention in such, or other, embodiments and
with various
modifications required by the particular applications or uses of the present
invention. It is
intended that the appended claims be construed to include alternative
embodiments to the
extent permitted by the prior art.
