Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ ~33~j~
MEANS TO R~DUCE OSCILI~TOR~' DEFLECTIO~
OF VEHICLE
Background of the Invention
Pield of ~se
This invention relates generally to means to reduce
oscillatory deflection of a vehicle, such as a rough-terrain
type mobile crane, in which the vehicle chassis tends to
oscillate angularly and vertically or "porpoise" and bounce
relative to the terrain over which the vehicle travels
because of terrain roughness or because of rapid acceleration
or deceleration of the vehicle. - -
Description o~ the Prior Art
Some prior art vehicles used in construction work, such
as rough-terrain type mobile cranes, for example, comprise a
chassis having ground-engaging tires and a large heavy
component~ such as a pivotable telescopic crane boom mounted
thereon. The tires typically take the form of large
resiliently compressible inflated balloon tires, which may
or may not be provided with additional resilient suspension
springs between the wheel axles and the chassis. These tires
(and axle springs, if any) serve as a resilient support means
which enable the chassis to move vertically (bounce or porpoise)
relative to the terrain. When driven from one job site to
another, the crane boom is lowered into a road transport
position and is usually secured to the chassis. Character-
istically, when such a vehicle is driven over rough terrain
or is accelerating or decelerating rapidly, the heavy chassis
with the heavy boom thereon tends to oscillate angularly or
"porpoise" relative to the terrain over which the vehicle travels.
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Such deflection, which ~ccurs at some uncontrolle~ natura~
mode and frequency of vibration, is possible because of the
resilient support provided by the tires and/or suspension
springs. Such deflection is undesirable for several reasons.
It can cause dangerous lack of driver control at road speeds
and can even cause the vehicle wheels to momentarily leave
the ground. Furthermorel it is uncomfortable and dangerous
for the vehicle driver within the cab. It also imposes undesir-
able stressful vertical and torsional dynamic load on the
wheel axles and other vehicle components. Then, too, it can
cause the vehicle to damage the road surface.
Efforts have been made to solve the specific problem of
vehicle bouncing as it pertains to trucks, as is shown by
U.S. Patent 2,744,749. ~fforts have also been made to solve
the general problem of system vibration as shown by U.S. Patent
3,322,375. ~owever, none of the teachings of these patents
are applicable to overcome the above-described problems.
Summary of the Present Invention
In accordance with the present invention there is provided
means to reduce angular and translational deflection of a
vehicle, such as a rough-terrain type mobile crane, for example,
having a chassis resiliently supported on the terrain by
balloon tires and/or axle suspension springs and on which a
heavy component, such as a telescopic crane boom or the like,
is mounted. The invention contemplates a chassis which, because
of the resilient support of the chassis, tends to deflect
angularly or "porpoise" or oscillate relative to the terrain
over which the vehicle travels because of terrain roughness
_3~ 3~!~
or because of accelera-tion or deceleration of the moving vehicle.
The invention provides in a vehicle movable across
terrain: a chassis vertically deflectable relative to said
terrain; a load-handling boom pivotally mounted on said chassis
and vertically deflectable relative to said chassis; a boom-hoist
cylinder for raising and lowering said boom; a source of hydraulic
fluid for operating said hoist cyli,nder boorn; deflection reduction
means, including a spring, and a volume of compressible gas and a
gas piston, connected between said boom and said chassis and oper-
able to reduce deflection of said chassis relative to said terrainas said vehicle moves thereacross; and a control system including
valve means operable to connect said boom-hoist cylinder to said
source in order to effect boom-hoist operations of said boom, said
valve means being further operable to connect said boom-hoist
cylinder to said deflection reduction means so that deflection of
said boom causes said boom-hoist cylinder to operate to impose or
relieve forces acting on said spring and said volume of compress-
ible gas in said deflection reduction means.
The invention also provides a vehicle movable across
terrain and comprising: a first mass including a vehicle chassis;
resilient support means including terrain-engaging wheel assemblies
connected to said chassis and enabling reciprocable vertical and
angular deflection of said chassis relative to said terrain as
said vehicle moves thereacross; a second mass including a load-
handling boom component carried by said chassis and independently
movable relative to said resilient support means, said first mass
being greater than said second mass; means for movably connecting
said load-handling boom component to said chassis and enabling
-3a-
reciproeable vertical angular deflection of said component rela-
tive to said chassis as said vehicle moves across said terrain;
and deflection reduction means connected between said chassis and
said load-handling boom component to reduce vertical and angular
deflection of said chassis relative to said terrain tending to
occur in response to dynamic loads imposed on said vehicle by
movement across uneven terrain or by acceleration or deceleration
of said vehicle; said deflection reduction means including
resiliently compressible and expandable load-bearing spring means
connected between said chassis and said load-handli.ng boom compon-
ent and responsive to and tending to enable limited vertical
angular deflection of said load-handling boom component relative
to said chassis which would cause spring motion at a predetermined
rate of speed in response to said dynamic loads, and said deflec-
tion reduction means further comprising damping means connected
between said chassis and said load-handling boom component and to
said spring means to reduce the rate of speed of spring motion as
rapidly as possible to thereby dissipate said dynamic loads.
The deflection reduction means or stabilizer means con-
trols the velocity of eompression and deeompression of the spring
to thereby reduce or inhibit or prevent oscillatory deflections of
the chassis relative to the terrain. The deflection reduction
means operate to employ the angular movement of the boom relative
to the chassis to generate natural modes of oscillation in which
the oscil.lation of the boom is out of phase with the otherwise
uncontrolled oscillation of the chassis (and any load thereon)
relative to the terrain.
In an embodiment of the invention disclosed herein, the
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auxiliary spring and the damping means are preferably embodied in
the boom hoist cylinder. In accordance with the invention, the
boom, instead of being rigidly and immovably secured to the
vehicle chassis during road transport as heretofore, is allowed to
pivot to a limited degree about its horizontal axis. However,
this angular motion is resisted by the auxiliary spring, and
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the damping means control the velocity of compression or
decompression of the spring. The deflection reduction means
provides optimum results when the speed of spring travel as
it expands and contracts is controlled by the damping means,
so that a load or force input on the vehicle axles is dissi-
pated to heat at the fastest possible rate. The pivot axis
and auxiliary spriny location, as well as the characteristics
of the auxiliary spring system and the damping means, are
chosen or determin~d so that the previously uncontrolled
natural modes of oscillation of the component are replaced
with natural modes which are dynamically coupled to movement
of the suspended mass relative to the vehicle chassis. The
vibrational amplitude of the component and auxiliary system
in any of its natural modes can then be controlled by adding
damping of selected characteristics to the auxiliary spring
system.
With such an arrangement, it is possible to control,
reduce or eliminate the large oscillatory deflections and
accelerations of the chassis associated with the road travel
of a resiliently supported vehicle chassis. T~he invention is
of particular importance when it is not possible or economically
feasible, as in large mobile cranes, to provide damping by
employing a conventional shock absorber arrangement for the
axle springs of such vehicles.
A vehicle, such as a mobile crane, embodying a dynamic
stabilization means in accordance with the invention for a
telescopic boom mounted on the chassis thereof, offers
numerous advantages over the prior art. For example, the
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chassis with the b~om thereo~ does not vibrate or oscillate
or "porpoise" excessivQly when passing over uneven or bu~p~
terrain or when accelerating or decelerating, thereby enhancing
safety of vehicle operation, vehicle life, operator comfort
and safety and reducing road surface damage. The damping
means is embodied in existing vehicle components, such as the
boom hoist cylinder, thereby reducing vehicle costs. The
spring and damping means are easily adjustable to suit different
vehicles and load conditions. The hydraulic-electrical control
system is relatively uncomplicated, employs numerous conven-
tional components, is economical to fabricate and easy to
service. Other objects and advantages of the invention will
hereinafter appear.
Drawings
FIGURE 1 is a side elevation view of a mobile crane
embodying dynamic stabilization means in accordance with the
present invention;
FIGURE 2 is a rear end elevation view of the crane shown
in FIG. l;
FI~URE 3 is an elementary schematic diagram of certain
components of the crane of FIGS. 1 and 2,
FIGURE 4 is a more complex schematic diagram or mathematical
model of certain components and physical relationships embodied
in the crane of FIGS. 1 and 2;
FIGURE 5 is a simplified cross-section view of a boom
hoist cylinder for the crane boom shown in FIGS. 1 and 2 and
a schematic diagram of a hydraulic control circuit therefor,
which cylinder and circuit also ~mbody deflection damping means
in accordance with the invention;
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FIGURE 6 is an enlarged more complete cross-section view
of the cylinder shown in FIGS. 1, 2 and 5;
PIGURE 7 is an end view of the cylinder ta]cen on line
7-7 of FIG. 6;
FIGURE 8 is a side elevation view of a valve assembly
shown schematically in FIG. 5;
FIGURE 9 is a cross-section view of the valve assembly
taken on line 9-9 of FIG. 8;
FIGURE 10 is a schematic diagram of an electric control
circuit for use with the valve assembly shown in FIGS. 5, 8
and 9;
FIGURE 11 is an enlarged front elevation view of a
control panel on which certain of the electrical components
shown in FIG. 10 are mounted;
FIGURE 12 is a side elevation view of the panel shown
in FIG. 11;
FIGURE 13 is a rear elevation view of the panel shown
in FIGS. 11 and 12;
FIGURE 14 is a schematic diagram showing three contact
positions for an electric rocker switch shown in FIGS. 10-
through 13;
FIGURE 15 is a graph depicting the typical oscillation
or angular deflection of a chassis in a crane not employing
stabilization means; and
FIGURE 16 is a graph depicting the typical oscillation
effect of dynamic stabilization means in accordance with
the invention.
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Description of a Preferred Embodiment
Referring to Figs. 1 and 2, the numeral 10 designates a
self-propelled vehicle, such as a mobile crane, which carries
a large heavy component 12 in the form of a telescopic crane
boom exhibiting the characteristics of an integral mass
mounted on a chassis 18 of the vehicle. Vehicle 10 embodies
dynamic stabilizatiDnmeans in accordance with the present
invention to overcome any tendency for the chassis 18 (and
the heavy component 12 mounted thereon) to oscillate angularly
or "porpoise" or bounce relative to the terrain T over which
the vehicle travels in response to dynamic loads resulting
from terrain roughness or from rapid acceleration or decelera-
tion of the vehicle 10. Vehicle 10 generally comprises a
lower section 14 on which an upper section 15 is mounted by
means of a slew ring assembly 16 for rotation in either
direction to an unlimited degree about a vertical axis 17
during crane operation.
Lower section 14 comprises a chassis 18 on which are
mounted four wheel assemblies such as 20, a fixed ring 21 of
the aforesaid slew ring assembly 16, four extendible out-
riggers such as 22 for deployment during crane operation, a
source of power 23 such as an internal combustion engine for
pro~iding operating power to the crane and for providing
motive power for the wheel assemblies 20, an electric
battery 24 for starting the engine 23, and a hydraulic fluid
reservoir 25 for supplying operating fluid to certain
vehicle and crane components.
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Upper section 15 comprises a rotatable ring 28 of the
aforesaid slew ring assembly 16 and a support frame 30 which
is rigidly secured to ring 28. A b~om support assembly 32
is rigidly mounted on support frame 30 and telescopic boom
12 is mounted by means of a pivot assembly 34, including a
pivot pin 35, on support frame 30 for pivotal movement between
raised and lowered positions about a horizontal axis 36 during
crane operation. Telescopic boom 12 includes a base boom
section 40, an inner boom section 41 telescopable within the
base boom section, an outer boom section 42 telescopable
within the inner boom section, and at least one hydraulic ram
(not shown) for effecting extension and retraction of boom
sections 41 and 42. Support frame 30 also affords support
for two cable winches such as 37, a counterweight 38 and an
operator's cab 39.
A pair of boom hoist cylinders such as 45, hereinafter
described in detail, are each connected between boom support
assembly 30 and base boom section 40 to raise and lower the
telescopic boom 12 and each cylinder 45 also embodies dynar,lic
stabilization means in accordance with the invention, as here-
inafter explained.
Each wheel assembly 20 for chassis 18 of lower section
14 of Yehicle 10 includes an axle 48, a wheel 50 rotatably
mounted on the axle, and a resilient large inflated balloon
tire 52 mounted on the wheel and engageable with the terrain
T indicated i~ Figs. 1 through 4, which may be a road surface
or earth surface over which vehicle 10 is movable. In the
embodiment shown in the drawings, axle 48 is secured to
chassis 18 in such a manner that, while rotating and steering
movement of the axle 48 may be possible, relative vertical
motion between the axle 48 and the chassis 18 is not possible.
However, the large inflated balloon tire 52 is resiliently
compressible vertically downward to a certain extent in response
to vertical loads imposed downwardly by the upper and lower
sections 14 and 15, respectively, of vehicle 10. Tire 52 is
also resiliently decompressible vertically upward in response
to relieving of such a vertical load. As a result, the tire
52 serves as a resilient support means for chassis 18 and
chassis 18 is resiliently movable vertically and angularly,
both upwardly and downwardly in the direction of arrow A and
angularly in the direction of arrow B shown in Fig. 3 relative
to the terrain T as the vehicle 10 moves thereacross, as
hereinafter explained.
In the embodiment shown, vehicle 10 is self-propelled
and one or more axles 48 are adapted to be rotatably driven
by engine 23 by suitable drive and power transmission means
(not shown~ to propel the vehicle 10. Furthermore, either
two or four of the axles 48 are steerably movable by suitable
steering means (not shown) to enable vehicle 10 to be steered
while being driven. However, it is to be understood that the
present invention can be embodied in a type of mobile crane
which is mounted on a trailer type vehicle (not shown) which
is ~ot self-propelled but is adapted to be towed by another
vehicle such as a truck (not shown). Furthermore, instead of
relying solely on resilient tires 52 to enable relative
--10--
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vertical movement between c~assis 18 and the terrain T, each
axle 48 could be connected or secu:red to chassis 18 by a
conventional axle spring ~not shown) with or without conven-
tional axle sprlng shock absorber (not shown) associated
therewi.th to serve as another form of resilient support means
for chassis 18 and to ena~le relative vertical motion between
chassis 18 and the terrain T.
The pair of boom hoist cylinders such as 45 are operable
to pivotably raise and lower telescopic boom 12 vertically
about pivot pin 35. Each boom hoist cylinder 45 i5 connected
at its lower end by a lower pivot pin 54 to a point Pl (see
FigsO 1 and 4) on boom support assembly 32 (and thus on
chassis 18) and at its upper end by an upper pivot pin 55
to a point P2 (see Figs. 1 and 4) on boom base boom section
40. As hereinafter explained, each boom hoist cylinder 45 is
also constructed to embody portions of the dynamic stabiliza-
tion means in accordance with the invention.
Operator's cab 39 houses certain control levers and
switches, hereinafter identified, for actuating the stabiliza-
tion means, as well as conventional controls for driving andsteering the vehicle 10, for operating the crane upper section
15 and the crane boom 12 and for operating the outriggers 22.
As Figs. 3, 4, 5 and 6 show, the dynamic stabilization
means generally comprises a~ least one auxiliary spring 60
(a pair of which are shown) effectively connected between the
chassis 18 and the boom or component 12 to resist vertical
and angular deflections therebetween, and damping means 62,
including a cylinder housing 80, a piston assembly 112 therein
in parallel with each spring 60 and a hydraulic fluid orifice
to dampen the motion of the spring. In the embodiment of the
invention disclosed herein, Figs. 5 and 6 show a spring 60
and damping means 62 are economically and conveniently embodied
in a boom hoist cylinder such as 45 which is provided for
raising and lowering the boom 12.
Before providing a detailed explanation oE the construc-
tion of the dynamic stabilization means, its operation should
be generally understood. In accordance with the invention
the component, such as a boom 12~ instead of being rigidly
and immovably secured to the vehicle cnassis 18 during road
transport as the conventional practice, is allowed to swivel,
pivot or deflect angularly about the horizontal pivot axis
of pin 35 in the pivot assembly 34 as the ~ehicle 10 tends to
bounce or porpoise as it is propelled over the terrain T.
However, this angular motion of boom 12 is controlled by
the aforesaid spring 60 and damping means 62. The system is
found to provide optimum results when the rate of spring force
as spring 60 expands and contracts and the rate of damping
force of the damping means 62, as well as the relative
positions of the pivot axis of pin 35, spring 60, and other
components are chosen so that a load or force input on the
vehicle axles 48 is dissipated to heat at the fastest possible
rate~ The pivot axis of pin 35 and spring locations of
spring 60, as well as spring and damping characteristics,
are chosen or determined so that the previously uncontrolled
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natural modes of oscillation of chassis 1~ are replaced with
natural modes which are dynamically coupled to movement of
the suspended mass or boom 12. The ~ibrational amplitude of
the chassisin any of its natural modes can then be controlled
by adding damping to the auxiliary spring system.
Referring now to Figs. 5, 6 and 7, it is seen that a
boom hoist cylinder 45 with dynamic stabilization means embodied
therein is constructed as follows. Cylinder 45 comprises an
axially stationary cylinder housing assembly 63 and an axially
movable main piston 78 -slidably mounted thereon. Cylinder
housing assembly 63 comprises a hollow outer cylinder 66 having
an end cap 68 rigidly secured at one end and a piston rod
seal 70 at and within its other end. End cap 68 comprises a
fluid port 72 which communicates with one chamber 73 in outer
cylinder 66. Cylinder 66 comprises a fluid port 74 which
communicates with another chamber 75 in outer cylinder 66.
The chambers 73 and 75 are separated by main piston 78
which is slidably mounted in the bore of outer cylinder 66.
Main piston 78 is connected to a hollow piston rod 80 which
extends outwardly of the said other end of outer cylinder 66
through a hole 82 in piston rod seal 70.
When pressurized hydraulic fluid is supplied through
port 72 to chamber 73 in outer cylinder 66, piston 78 and
its attached rod 80 are shifted toward boom hoist cylinder
extend position, boom 12 is raised, and fluid is exhausted
from chamber 75 out through port 74. Conversely, when pres-
surized hydraulic fluid is supplied through port 74 to chamber
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75 in outer cylinder 66, piston 78 and its attached rod 80
are shifted toward boom hoist cylinder retract position, boom
12 is lowered, and fluid is exhausted from chamber 73 out
through port 72.
Boom hoist cylinder 45 as thus far described is operable
to raise and lower the boom 12 in response to operation of
a hydraulic control system shown in Fig. 5. This control
system comprises a manually operable, three-position (neutral,
raise, lower), boom hoist directional control valve 85 for
connecting the fluid ports 72 and 74 in main cylinder 66 to
the hydraulic reservoir 25. The control system also comprises
a valve assembly 86 (shown schematically in Fig. 5, in a top
view in Fig. 8 and in section in Fig. 9) which includes a
holding valve 92, an integral detented shuttle valve 94
including a shiftable spool 94A and detent assembly 94B~ a
solenoid-operated check valve 96, and necessary interconnecting
fluid lines or passages. When valve 85 is shifted from its
neutral position (shown in Fig. 5) to its raise position, a
pump 87 (driven from engine 23) receives hydraulic fluid from
reservoir 25 and supplies it under pressure through selector
valve 85, through a fluid line 89, through one-way check valve
90 portion of holding valve 92 and through a fluid line 91 to
port 72 of cylinder 66 to effect boom hoist cylinder extension.
At the same time exhaust fluid from port 74 of cylinder 66
flows through a fluid line 93, through a shuttle valve 94,
through a fluid line 95 and through a selector valve 85 to
reservoir 25.
`` '.~2133(~0
When selector valve 85 is shifted from neutral position
to its lower position, pump 87 receives hydraulic fluid from
reser~oir 27 and supplies it under pressure through control
valve 85, through shuttle valve 94, and through fluid line 93
to port 74 of cylinder 66 to effect boom hoist cylinder re-
traction. At the same time exhaust fluid from port 72 of
cylinder 66 flows through fluid line 91, through holding ~alve
92 (which is shifted to open position when fluid line 95 is
pressurized and supplies pilot pressure through a passage 100),
through line 89 and through control valve 85 to reservoir 25.
~ hen selector ~alve 85 is in neutral position as shown
in Fig. 5, the holding valve 92 remains in ~losed position as
shown in Fig. 5 and prevents hydraulic fluid from being ex-
hausted from boom hoist cylinder chamber 73 and thereby pre-
venting unintentional retraction of the boom hoist cylinder45 under _he weight of the boom 12 and any load thereon.
As Figs. 3, 4, 5 and 6 further show, the dynamic stabili-
zation means are embodied in boom hoist cylinder 45 and are
constructed as follows. Piston rod 80 is hollow and has a
cylindrical bore 102`therein which is closed at the outer end
of the rod by an end cap 104 rigidly secured to the rod. The
bore 102 is closed at the inner end of the rod 80 by a rigidly
secured end plate 106. A support ring 103 is rigidly mounted
within the cylindrical bore 102 in piston rod 80 and is located
between the end cap 104 and the end plate 106. Support ring
103 has a hole 109 therethrough for accommodating a solid
cylindrical spring guide 110 which is slidably mounted therein.
Ring 103 has gas passages 103A therein.
3~
An auxiliary piston 112 is rigidly secured to one end of
spring guide 110 by a set screw 114 and is slidable in bore
102 in piston rod 800 A hollow tube spacer 116 is mounted in
bore 102 and is rigidly connected at one end to support ring
103 and at its other end to end cap 104. Spacer 116 serves to
insert and position support ring 103 in bore 102, A plurality
of Bellville type spring washers 117 are mounted on spring
guide 100 and fill the space between support ring 103 and
auxiliary piston 112 and, in the position shown in Fig. 6,
are under slight compression.
The washers 117 ~aken
together correspond ~o the hereinbefore reerred to auxiliary
spring 60. Piston rod 80 is provided at its innermost end
with hydraulic fluid passage 120 (which also extends through
end plate 106) to afford communication between hydraulic fluid
chamber 75 in outer cylinder 66 and a chamher 122 within bore
102 between end wall 106 and auxiliary piston 112. Chamber
122 is shown in Fig. 5 but is shown completely occupied in
Fig. 6. Piston rod 80 also includes another chamber 124 which
occupies the remainder of bore 102. Chamber 124 is sealed off
from chambPr 122 by a T-seal 125 on auxiliary piston 112 and
is filled with pressurized gas, such as nitrogen, which is
initially introduced through a passage 130 in end cap 104 and
which is closed off by a threaded plug 131. The pressurized
gas, for example, is maintained at a pressure of about 800 psi
in a cylinder 45 which is on the order of twelve feet long
when unextended. The pressurized gas acts to force or bias
piston 112 leftward (in Fig. 6), as do the spring washers 117,
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and ti~us serves to enable the use of smaller (less forceful)
washers 117 whicn would otherwise be required by exerting a
nearly constant force on piston 112.
Referring again to Figs. 5, 8, 9 and 10, it is seen that
the solenoid-operated cneck valve 96 includes
valve ports 130, 131, a passage 132, a one-way cneck valve 133,
a biasing spring 134 which normally biases the check valve 133
between the ports 130 and 131, and a solenoid 135 energizable
to shift passage 132 between the valve ports 130 and 131.
Energization and deenergization of solenoid 135 is controlled
by the electrical control circuit shown in Fig. 14 and herein-
after described in detail. It is to be understood that solenoid
135 is energized to bring the deflection reducing or stabilizer
apparatus in cylinder 45 into play after boom 12 has been lowered
to a road transport position which is about 10~ above its lowest
possible substantially horizontal position by operation of the
boom hoist operating or control valve 85 and the latter is
returned to its neutral position (see Fig. 5). Energization of
soleniod 135 shifts passage 132 between the valve ports 130 and
131 and causes the spool94A in shuttle valve 94 to shift rightward
(with respect to Fig. 5) past detent 94B and establishes a closed
hydraulic circuit as follows: from chamber 73 of outer cylinder
66 of boom hoist cylinder 45, through port 72, through line 91,
through passage 132 in solenoid check valve 96, through
shuttle valve 94, through line 93, and through cylinder port
74 to chamber 75 in outer cylinder 66 of boom hoist cylinder 45.
As is apparent, outer cylinder chamber 75 is in communica-
tion tnrough port, passage or orifice 120 with chamber 122 in
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hollow cylinder rod 80. Consequently, if road or driving
conditions affecting vehicle 10 tend ~o cause angular
deflection (up or down) of boom 12 about pivot pin 35 and
relative to chassis 18, then hydraulic fluid in chamber
76, being trapped in il~e aforesaid closed
hydraulic system, is forc~d out of or in~o chamber 122,
depending on the direction of boom motion, and the spring 60
made up of the washers 117 is able to decompress or to
further compress, depending on the direction of boom motion.
The diameter of the orifices or passages 120 and 132, which are
designed to be the smallest in the system, operate to control
the rate of transfer or the rate of fluid flow in the system
and thereby assist in controlling the rate at which the spring
60 can compress or decompress. This has the effect of damping
or dissipating the motion of boom 12 relative to chassis 18.
Referring to Fig. 10, the electrical control system for
the solenoid 135 of stabilizer valve 96 is seen to comprise
a source of electrical power, such as a battery B, a normally
open single pole single throw boom Position res~onsi~e limit
switch 150, and a panel board 149 on which are mounted a
normally open single pole relay 152 comprising a normally
open relay contact 153 and a relay coil 154, a rocker switch
156 having "off", "on" and "engage" positions, a "ready"
light 15~, and an "on" light 160. As Figs. 10 and 14 show,
rocker swtich 156 comprises six terminals designated Tl, T2,
T3, T4, TS and T6 and two tiltable switch leaves Ll and L2
which are actuatable by a manually operable toggle button
166 to the "off", "on" and "engage" positions. In "off" position
33~
lea~ Ll connects termina~ T2 and T3 and leaf L2 connects
terminals T5 and 16. In 'lon" position leaf Ll connects terminals
T2 and T3 and leaf L2 connects terminals T4 and T5. In "engage"
position leaf Ll connects terminals Tl and T2 and leaf L2
connects terminals T4 and T5. Battery B hasone terminal grounded
and the other terminal connected to one side of limit switch
150 which is located in association with boom 12 and adapted
to close when the boom is lowered to 10 degrees or less. The
other side of limit switch 150 is connected hy an electrical
conductor or wire 162 to one side of relay contact 154. The
other side of relay contact 154 is connected by an electri~al
conductor or wire 164 to switcn terminal T5. Conductor 162
is connected by a conductor or wire 170 to switch terminal T2.
Relay coil 164 has one side connected to ground and nas its
other side connected by conductors or wires 172 and 173 to
switch terminals Tl and T4, respectively. One side of solenoid
coil 153 is connected by a conductor or wire 174 to switch
terminal T4 and has its other side connected to ground. The
"on" light 160 is connected between conductor 174 and groun~
and turns on when rocker switch 156 is turned to "engage"---
and the relay contacts 154 are closed and solenoid 135 is
energized. q7he "ready" light 158 is connected between
conductor 162 and ground and turns on when limit switch 150
closes.
In operation, closure of limit switcn 150 by proper
placement of boom 12 (i.e., 10 from its lowermost position)
turns on "ready" light 15Y7. If toggle switch 156 is "off'7 or
"on", relay coil 154 and solenoid 135 remain deenergized. If
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toggle switch 156 is in "engage", relay coil 15~ is energized,
and relay contact 153 closes to cnergize solenoid 135 and
enable operation of the stabilizex system as hereinbefore
described.
Turning now to Fig. 4, there are depicted significant
points, relationships and distances which enable the stabi-
lization means to function at is optimum in accordance with
the following mathematical model using formulae of motion
wherein distances are in feet and masses are in slugs, i.e.,
Pounds
g Gravitational Acceleration (32.2)
In the formulae:
- Ll is the horizontal distance between the front wheel
axle 48 and the boom pivot 35;
- L2 is the horizontal distance between pin 35 and rear
axle;
- L3 is the distance between the axis of pivot pin 35
and the axial centerline of cylinder 45;
- L4 is the horizontal distance between the axis of pivot
pin 35 and the center of mass of chassis 18 and its
appurtenances;
- M1 is the mass of chassis 18 and its appurtenances;
- Jl is the principal mass moment of inertia about an
axis through the center of mass Ml;
- M2 is the mass of boom 12 and its appurtenances;
- J2 is the principal mass moment of inertia about an
axis through the center of mass M2;
- e 1 is the deflection angle of the chassis 18;
- e 2 is the deflection angle of boom 12;
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- Kl, K2 and K3 are respective spring rates in pounds per
foot;
- Cl, C2 and C3 are damping ratesin pounds x seconds/per
foot;
- X, Y and ~ represent vertical deflections and the
associated arrows show the direction.
In the following mathematical model or forumlae for
equations of motion:
~F is tne su~,lation of forces;
~1 is the summation of moments about the center of mass
Pll; and
M2 is the summation of moments about the center of mass
M2.
Thus:
f(Ml+M2) x -(Ml*L4)ël - (M2*L5)ë2 ~ (Cl+C2)x - (Cl*Ll+C2*L2)el
~+ (K1+K2)X (K1*L1+K2*L2 ) ël + For ~ A~l * Y + A~2 * ~ = 0 0
((-M1*L4)X + (J1~M1*L4 )e1 (C1XL1+C2*L2)X + (C1*L1 +C2*L22+
C3*L3 )e1 (C3*L3 )e2 (K1*L1+K2*L2)X + (K1*L1 +~2*L2 +~3*L3 )e1
~ (K3*L3 )e2 + TOR (K1*Y*L1~K2*Z*L2~ = 0 0
(-M2*L5)X + (J2+M2*L52)ë2 (C3*L32)e1 ~ (C3*L3 )e2
~ (-~3*L3 )e1 + (K3*L3 ) e2 = 0.0
In a typical case involving a mobile crane of specific
size and weight and having the input variables listed below,
solution of the equations by the Jacobi method resulted in
derivation of Eigen values representing three frequencies of
vibration and Eigen vectors defining three modes of vibration.
The three frequencies Nos. 1, 2 and 3 shown below pertain to
the vertical deflection X, an~ angular deflections ~l and e2
~L~133f~
-21-
Fig. 4. The matrixes A and B specified below are to be
understood to be intermediate steps in deriving the Eigen
values and vectors~ The node locations specified below
signify a point at that distance from the
boom pivot at which rotation about the point but no
vertical translation would occur.
The input variables A~l, A~2, AK3, ALl, AL2, AL3, AL4,
AL5, AMl, AJ1, AM2, AJ2, respectively, are:
132000.00 132000.00 200000.00 11.5000 1.0800 4.6000 3.6300
14,5800 1240.90 74543.00 388.90 34481.00
The following is the defined Matrix A:
264000.0000 -1660560.0000 0.0
-1660560.0000 21842964.8000 -4232000.0000
0.0 -4232000.0000 4232000.0000
-
The following is the defined Matrix B:
1629.8000 -4504.4670 -5670.1620
-4504.4670 9~894.2152 0.0
-5670.1620 0.0 117151.9620
Frequency No. 1 is 1,5322 HZ
The Eigen Vector is 0.9768 0.0957 0.0164 -
The Machine Node Location is 10.211
The Boom Mode Location is 59~618
The Amplitude Ratio Thetal/Theta2 is 5.839
.
Frequency No. 2 is 2.6845 ~Z
The Eigen Vector is -4.7572 0.8560 -0.3~82
The Machine Node Location is -5.557
The Boom Node Location is 12.255
The Amplitude Ratio Thetal/Theta2 is -2.205
~13~
-22-
Frequency No. 3 is 0.7984 ~Z
The Eigen Vector is 1.3159 0.3686 1.0030
The Machine Node Location is 5.197
The Boom Node Location is 1.910
The Amplitude Ratio Thetal/Theta2 is 0.368
Referring to Figsy 15 and 16, there are shown graphs
which exemplify, in Fig. 15, a mode or oscillation that
occurs in a mobile crane not embodying the present invention
and, in Fig. 16, a highly attenuated oscillation that results
in a mobile crane which does embody the present invention.
In applicant's system, generated modes of oscillation employ
the phase difference between chassis and boom rotation
effect reduction of bounce and porpoising.
