Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
9129
The present invention relates to a multi-section
- lifting boom, useful in such apparatus as cranes and aerial
lift platforms.
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The present invention has as an object the provision
;~ of a multi-section lifting boom in which a rotary member
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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
i8 to provide such a boom in which the cocking of an outer
section relieves strain on the piston rod of the hydraulic
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ram or motor.
Lifting booms for cranes and aerial lift platforms
typically are made of multiple, extensible telescopic
sections. 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 long column, and also has the
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harmful effect of deteriorating the seals of the hydraulic
ram. In addition, there have been proposals for providing
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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
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piston rams, one of which has the cylinder pin-connected at
its rear end to a boom mid-section, and extending forwardly,
the forward end of the cylinder resting on a slide-bearing
10 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 #3,722,154 discloses a
t, construction in which the piston rod of the hydraulic ram of
a multi-section teIescopic boom has a buckle-preventing
device slidable thereon, and comprising outwardly extending
portions which movably engage with the inside surfaces of
the relavent boom section, such as with the bottom of the
base section upper plate and the top of the base section
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 of the buckle-preventing device
continuously with the boom section.
Xollmann 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 the 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.
~ ornagold, ~.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
utilized, 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 thejboom base
section. A deflection limiting device is slidable along the
piston rod, and i8 less high than the base section, the top
of the deflection limiter being spaced from the bottom of
the boom ~op plate when the boom is not under load, but
being in engagement 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 ends, the pull rods passing forwardly
- 30 through the transverse plate of the deflection limiter and
through the ram cylinder plate. The 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 ~long 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
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 passes
on this sprocket 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 fully 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. This also serves to reduce buckling
stresses on the piston rod.
This invention therefore contemplates a telescopic
load lifting boom having a first, fixed section and two
movable sections, a linear fluid motor including a cylinder
and a piston rod, means connecting the cylinder to the
second section for movement of at least a part thereof in
the vertical median plane of said second section relative to
said second section, means connecting said piston rod to
said first section, means for extending and retracting said
third section upon extention and retraction movement of said
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second section, and means for relieving buckling stresses in
said piston rod upon extension of said boom and cocking of
said second and third sections comprising means for raising
the forward end of said linear motor relative to said second
section.
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 boom suitable
for cranes and aerial lift platforms, 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 from Figures 2 and 3.
A hydraulic ram 20 is provided, ram 20 being in a
position which iB 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
longitudinal 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 of
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
of engagement with the bottom of the top plate of boom base
section 11 in the condition in which the boom is not loaded.
Pull rods 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
transver~e 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 thereof
engages the rear of the nuts or detents 34a and 35a, after
which the piston rod buckle limiter 30 is pulled along the
piston rod 22. ~he 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 roller-sprocket 40 has parallel wheels
which serve as a roller, being in engagement with the upper
~urface of the bottom plate of the fly section 13 during
initial extension of the boom. The combination
roller-sprocket 40 has the sprocket part thereof sli~ghtly
lesser effect~ve 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 sprocXets
45 carrled 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 forwardly, and around the
combinatlon 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 or 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 12. In addition, the
forward end of the cylinder 21 i8 supported by the
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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 ~articularly the anchor 46 which is at
the heel thereof will engage the cylinder 21 of the
hydraulic ram 20 at the bottom of the forward end thereof.
The heel of the fly section is that portion which is at the
rear of 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 of the top
plate of the fly 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. This
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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