Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a multi-section
lifting boom, useful in such apparatus as cranes and aerial
lift platforms.
The present invention has as an object the provision
of a multi-section lifting boom in which a rotary member
serves both as a support for a hydraulic ram and as a
sprocket for a chain or cable which extends and retracts a
boom section. Another object is the provision of a
multi-section load lifting boom which permits limited
buckling of the piston rod of the hydraulic ram or motor
which extends and retracts the boom section. Another object
is to provide such a boom in which the cocking of an outer
section relieves strain on the piston rod of the hydraulic
ram or motor.
I,ifting booms for cranes and aexial lift plat~orms
typically are made;of multiple, extensible telescopic
section6. Extention and retraction is effected by one or
more hydraulic cylinders, or a combination of hydraulic
cylinders and cable or chains trained over pulleys or
sprockets.
When the booms are extended, and are under load, they
tend to depart from a theoretical arrangement in which the
boom sections are in alignment with each other. This is
known as arching or cocking, and steps have been taken in
the art to avoid harmful effects thereof.
Another problem which has been recognized is that if
the boom sections cock relative to each other, there is a
strain placed upon the hydraulic ram which extends and
retracts the boom sections, leading to damage to the ram,
such as occurs when the piston rod buckles under compressive
loads, since it acts as a lony column, and also has the
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harmful effect of deteriorating the seals of t~e hydraulic
ram. In addition, there have been proposals for providing
great strength, with minimum utilization of metal.
Various relavent disclosures are present in the prior
art. Thus, Sterner, U.S. Patent #3,736,710 discloses a four
section telescopic crane boom which utilizes three single
piston rams, one of which has the cylinder pin-connected at
its rear end to a boom mid-section, and e~tending forwardly,
the forward end of the cylinder resting on a slide-bearing
arrangement, the piston rod extending rearwardly, and having
its free end connected to the boom base section by a
floating arrangement allowing the end of the piston rod to
move transversely of the boom longitudinal axis.
Sakamoto, U.S.A. Patent #3,722,15~ discloses a
construction in which the piston rod of the hydraullc ram of
a multi-section telescopic boom has a buckle-preventing
device slidable thereon, and comprising outwardly extending
portions which movably engage with the inside sur~aces of
the relavent boom section, such as with the bottom of the
base section upper plate and the top of the base se~tion
bottom plate. The piston rod is pin-connected to one
section of the boom, and the cylinder is pin-connected to
another section of the boom. This construction severely
limits the amount of cocking of the boom sections which can
be tolerated without damage to the hydraulic ram, and
appears to actually increase the load of the hydraulic ram
when the boom sections are in the cocked attitude, by virtue
of the engagement o~ the buckle-preventing device
continuously with the boom section.
Kollmann et al, U.S.A. Patent #3,715,039 discloses a
telescopic boom having a plurality of boom sections, and a
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plurality of hydraulic rams in line, with the piston rod of
one ram being pin-connected to ~he cylinder of an adjacent
ram, and with a wheel structure mounted on the connecting
pin, the wheel structure being supported by the boom section
to thereby support the pin connection.
Hornagold, U.S.A. Patent # 3,837,502 discloses a
lifting boom in which fixed detents are engaged by the
piston rod of a hydraulic ram after some bending thereof.
There is provided herein a lifting boom which
comprises three telescopic sections, which are linearly
extensible and retractable. A single hydraulic ram is
utili7ed, having a piston rod free end which is connected by
a horizontal pin to the rear of the base section of the
boom, the connection being a "floating" connection, since
the horizontal pin is movable in generally vertical
extending guide slots provided at the rear of the boom base
section. A deflection limiting device is slidable alony the
piston rod, and i8 l~ss high than the base section, the top
of the deflec~ion limiter being spaced from the bottom of
the boom top plate when the boom is not under load, but
being in enga~ement therewith when the boom is extended and
is under load~ The rear of the ram cylinder has a ram
cylinder plate welded to it, and extending transversely of
its axis, the plate comprising horizontal pins which
pin-connect the plate and therefore the ram cylinder to the
mid-section. Pull rods are provided for moving the
deflection limiter, the rear ends of the pull rods extending
through a transverse plate of the deflection limiter, having
nuts on their rear end~, the pull rods passing forwardly
through the transverse plate o~ the deflection limiter and
through the ram cylinder plate. I'he forward ends of the
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pull rods have nuts or other detents thereon, so that when
the hydraulic ram has been extended, the front face of the
ram cylinder plate will engage the nuts or detents on the
forward ends of the pull rods, and pull the deflection
limiter along the piston rod of the hydraulic ram. A pair
of chains extends from the forward end of the base section
of the bottom plate thereof, rearwardly, passing around
sprockets carried at the rear end of the mid-section, and is Y
attached to the rear of the fly section a second chain
extends forwardly, passing around the forward end of the
hydraulic ram. A combined sprocket and roller is carried by
the forward end of the hydraulic ram, and the chain pas~es :~
on this sprocke~ and thence rearwardly to an anchor at the
rear of the base section. The combined sprocket and roller
rolls on the bottom plate of the fly section, to support the
forward end of the ram cylinder, during the boom extension,
and when ~ully extended the heel of the fly section engages
the ram cylinder at the bottom of the forward end, rotating
it on its pivots, rotation being limited by engagement of
the roller with the top of the fly section, that is, the
upper plate thereof. m is also serves to reduce buckling
stresses on the piston rod.
The invention therefore contemplates a multi~section `~
lifting boom having at least two sections in telescopic
relation and a hydraulic motor having a cylinder and piston
rod each connected to one said section for extension and
retraction of one said sect.ion relative to the other, and
wherein said piston rod is subject to deflection when said
hydraulic motor is extended and said boom is under load,
~0 means for limiting the deflection of said piston rod to a
predetermined amount after initial deflection thereof when
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said motor is extended and said boom is under load, said
deflection limiting means comprising means movable along
said piston rod, and means actuated by said motor cylinder
for moving said deflection limiting means along said piston
rod.
IN THE DRAWINGS
Figure 1 is a vertical cross sectional view of a
lifting boom in accordance with the present invention.
Figure 2 is a cross sectional view taken on the line
2-2 of Figure 1.
Figure 3 is a cross sectional view taken the line 3-3
of Figure 1.
Figure 4 is a view of the boom of Figure 1 in arched
condition.
Referring now to the drawings, wherein like or
corresponding reference numerals are used to designate like
or corresponding parts through out the several views, there
is shown in Figure 1 a multi-section lifting boomlsuitable
for cranes and aerial lift platfo~ms, designated 10, and ~ -
comprising a base section 11, a mid-section 12 and a fly
section 13. These sections may take various cross sectional
shapes, but in the herein disclosed preferred embodiment,
each section is a generally hollow rectangle in transverse
cross section, as is apparent ~rom Figures 2 and 3.
A hydraulic ram 20 is provided, ram 20 being in a
position which is inverted from that which is normal; thus,
the ram 20 includes the hydraulic cylinder 21 which extends
forwardly, and the piston rod 22, which extends rearwardly.
At its rear end, piston rod 22 has a transverse pin 23,
which is in a horizontal plane, and the ends of which are
positioned in a guide 24 which permit the pin 23 and
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therefore the end of the piston rod 22 to have limited
movement in a vertical plane transverse to the boom
longltudinal axis.
A ram cylinder plate 26 is welded at the rear end of
the cylinder 21 of`hydraulic ram 20, the hydraulic ram plate
26 including transversely extending pins 27, which are
horizontal, and which are journalled in suitable openings in
the mid-section 12.
A device 30 is provided for permitting limited
movement or buckling of piston rod 22, and comprises, as
shown in Figure 2, a transverse limiter plate 31 having an
aperture therein through which the piston rod 22 passes,
there being sliding engagement between transverse limiter
plate 31 and the exterior of piston rod 22. A pair o~
vertical limiter plates 32 and 33 are connected to the
transverse limiter plate 31, and as is clearly shown in
Figure 2, these vertical limiter plates 32 and 33 stop short
o~ engagement with the bottom of the top plate o~ boom base
section 11 in the condition in which the boom is not loaded.
Pull rod~ 34 and 35 extend generally axially, there being
provided at the forward ends of pull rods 34 and 35 detents
34a and 35b, which may take the form of nuts.` At their rear
ends, the rods 34 and 35 pass through apertures in the
transverse limiter plate 31, where enlargements, such as the
nuts 34b and 35b are provided. When the hydraulic ram 20 is
extended to the right, the ram cylinder plate 26 moves with
it, moving the mid-section 12, and the ram cylinder plate 26
passes along the pull rods 34 and 35 until the front thereo~
engages the rear of the nuts or detents 34a and 35a, after
which the piston ~od buckle limiter 30 i8 pulled along the
piston rod 22. The dimensional relationships are such that
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in the fully extended position of the hydraulic ram 20, the
piston rod buckle limiter 30 is approximately at the
mid-point of the piston rod 22.
A combination roller-sprocket 40 is provided,
supported on a support 41 which extends forwardly from the
forward end of a cylinder 21, and carries an axle 42.
Preferably, the support 41 is bifurcated. The outer surface
of the combination xollex-sprocket 40 has paralle] wheels
which serve as a roller, being in engagement with the upper
surface of the bottom plate of the fly section 13 during
initial extension o~ the boom. The combination
roller-sprocket 40 has the sprocket part thereof slightly
lesser effective diameter than the parallel wheels forming
the roller, as indicated by dashed lines, to accommodate the
thickness of a chain.
A pair of chains 43 extend rearwardly from an anchor
44 which is positioned at the front end of the bottom plate
of the base section 11. The chains 43 pass around sprockets
45 carried at the rear of the mid-section 12, and thence to
an anchor 46 on the rear of the fly section 13. A chain 47
passes from the anchor 46 fcrwardly, and around the
combirlation roller-sprocket 40, and thence extends
rearwardly to the anchor 48 which is located on the upper
plate of the boom base section 11.
When the boom 10 is extended and is under load as
shown in Figure 4, arching ox cocking of the boom sections
relative to each other will not result in harmful effect to
the hydraulic ram 20, due to the floating connection of the
free end of the piston rod 22, and the pin connection of the
cylinder 21 to the boom mid~section 120 In addition, the
forward end of the cylinder 21 is supported by thé
combination roller-sprocket 40, which supports the forward
end of the hydraulic ram 20, and serves as a guide for the
chain 47. In addition, the arching or cocking of the
sections will not damage the hydraulic ram 20~ and
particularly the piston rod 22 thereof, because the piston
rod 22 will be permitted a limited, predetermined amount of
buckling, due to the spacing of the upper end of the
vertical limiter plates 32 and 33 from the bottom surface of
the top plate of the boom base section 11, this spacing
permitting arching or cocking without transmission to the
piston rod 22 of undesirable loads, and without providing a
harmful effect on the seals where the piston rod 22 passes
through the left or inner end of the cylinder 21.
With further reference to the condition of the boom
as shown in Figure 4, in which the boom sections are fully
extended, and are under load, arching or cocking as
illustrated therein will occur. The heel of the boom fly
section 13, or more particularly the anchor ~6 which is at
the heel thereof will engage the cylinder 21 of the
hydraulic ram 20 at the bottom of the forward end ther~of.
The heel of the ~ly section is that portion which is at the
rear o~ the fly section. This will rotate the cylinder 21
about the axis provided by the pins 27, the rotation being
to a limited amount as determined by the engagement of the
combination roller-sprocket 40 with the bottom o~ the top
plate of the ~ly section 13. As will be understood, the
diameter of the roller-sprocket 40 is slightly less than the
vertical height of the space provided by the fly section 13,
and more particularly is slightly less than the space
between the top of the bottom plate of fly section 13. 'rhis
construction will thereby serve to enable the cylinder 21 to
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be rotated in a direction to reduce the stresses tending to
buckle the piston rod 22, and thereby further serves to
avoid harmful effects of arching or cocking of the boom
sections when extended and loaded on the ram 20, including
particularly the piston rod 22 thereof.
It will be obvious to those skilled in the art that
various changes may be made without departing from the
spirit of the invention, and therefore the invention is not
limited to what is shown in the drawings and described in
the specification but only as indicated in the appended
claims.
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