Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to excavating apparatus and, more
particularly, is concerned with a backhoe mechanism mounted on a trac-
tor or similar vehicle.
In the conventional prior art arrangements, the transport
position of the backhoe is characterized by a generally vertically
and slightly rearwardly extending boom carrying a folder dipper ass-
embly positioned as close as possible to the boom to hold the center
of gravity for the backhoe as near as possible to the rear of the
mounting vehicle. However, the center of gravity is still so far to
the rear of the vehicle that mechanical balance relationships are in-
sufficiently stable and handling is unduly difficult, even during nor-
mal use of the vehicle as a loader. On conventional backhoes, proper
weight distribution is accomplished by placing counterweights on the
front of the tractor. Counterweights have the disadvantage of increas-
ing total weight of the vehicle, and do not improve stability due to
the inertial moments caused by the length of conventional backhoes.
Commonly assigned U.S. Patent No. 3,376,984 to Long et al
solves these problems by providing a backhoe arrangement which is ar-
ranged to accommodate an overcenter movement of the boom cylinder as-
sembly when the boom is swung to the transport position. In the trans-
port position, the backhoe has a generally vertically and slightlyforwardly extending boom held locked in position by the boom cylinder
assembly which has gone overcenter.
These prior art arrangements comprise a unitary boom flanked
on both sides of boom cylinder assemblies, which limit the visibility
of the bucket by the operator.
In our co-pending Canadian application 240,254 we describe
and claim a backhoe boom which comprises a pair of transversely
spaced boom arms with a single boom cylinder and piston rod
assembly positioned therebetween. This arrangement overcomes the
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problem of poor visibility but it has been found in certain condi-
tions that increased torsional stiffness of the boom IS required.
According to the present invention there is provided a
backhoe comprising a vertically extending elongated support attach-
ment having a mounting portion thereon defining upper and lower
horizontal pivot axes, an elongated boom comprisingtw~transversely
spaced hollowboom sectionshaving a sleeve extending therebetweenat
one end, the sleeve defining a rigid interconnection ~etween the
hollow boom sections and providing a bearing member to pivotally
support the boom on the lower pivot axis so as to be swingable
through a neutral intermediate position wherein the boom sections
extend substantially vertically so that the said upper pivot axis
is located in a space between the sections, a double acting boom
cylinder assembly pivotally mounted on the upper pivot axis and
pivoted to the boom to extend in the space between the boom sections,
the boom cylinder assembly being extendable and retractable to ef-
fect pivotal movement of the boom and the lower pivot axis to either
side of the neutral intermediate position and interconnecting means
extending between the boom sections at the other end of the boom
to rigidly interconnecting the boom sections the interconnecting
means including a bearing member to pivotally support a material
handling unit on the other end.
Preferably the rigid interconnecting means comprise
sleeves extendingbetween the boomarms and beingaffixed theretoand
a pin extendingthrough one of said sleeves to pivotthe boom to the
mounting portion.
An embodimentof the inventionwill nowbe describedby way
of exampleonly with referenceto the accompanyingdrawings,in which:.
Fig. 1 is a side elevational view of the backhoe of this
invention representing in solid lines the parts in maximum trans-
port position wherein the boom cylinder is overcenter relative to
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the boom to effect a knee lock action, and in phantom represents
the parts in a rearward position which is assumed when digging;
Fig. 2 is a perspective view of the backhoe of Fig. 1
wherein the backhoe has a single cylinder and piston rod assembly;
Fig. 3 is a perspective view of an alternate embodiment
of this invention wherein the backhoe includes a pair of cylinder
and piston rod assemblies;
Fig, 4 is a perspective view similar to Fig. 3 and illustra-
ting another alternative embodiment of this invention;
Fig. 5 is a side elevational view similar to Fig. 1 showing
one specific construction for the boom;
Fig. 6 is an end view of the boom shown in Fig. 5, as view-
ed along line 6-6 of Fig. 5;
Fig. 7 is an enlarged sectional view of the upper end of
the boom shown in Fig. 6; and
Fig. 8 is a view similar to Fig, 7 showing a slightly modi-
fied construction of the bracket support means.
Referring now to the drawings, a backhoe arrangement or
assembly 10 is shown which is suitable for being pivotally mounted
zo upon the rear of a tractor.
Backhoe assembly 10 (Fig. 2) includes a support attachment
in the form of a swing tower 12 having upper and lower cylindrical
openings 14 and 16 which receive swivel pins (not shown in Fig. 2)
to pivotally mount the swing tower to a mounting bracket which
projects rearwardly from a tractor. The swing tower 12 is position-
ed by swing cylinder assemblies 18 and 20.
Swing tower 12 has a mounting portion having bottom horizon-
tal pivot shaft 22 mounting a boom 24 and an upper horizontal pivot
shaft 26 mounting a boom cylinder assembly 28. Boom 24 comprises
a pair of spaced apart hollow rectangular sections 30 and 32 which
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are rigidly interconnected by a sleeve 23. The shaft 22 passes
through the sleeve 23 to pivotally mount the boom 24 on the swing
tower 12. Boom cylinder assembly 28 is of a double-acting type
and has a cylinder 33 and a piston rod 34 which is pivotally con-
nected upon shaft 36 located adjacent to but spaced from the free
end of the boom sections, and is located within the space defined
between boom sections 30 and 32.
A dipper stick assembly 40 is mounted on a pivot shaft 42
extending between the free ends of the boom sections 30 and 32 to
define a pivot axis for the dipper at a location intermediate its
length, but substantially closer to the boom end than to the bucket
end of the dipper. The dipper stick assembly 40 includes a rigid
attachment plate 44 which receives pivot shaft 42 and constitutes
the boom end of the dipper stick assembly. A fluid ram means is
employed to effect swinging movement of the dipper stick assembly.
Referring to Figs. l and 2, brackets 48 and 50 are mounted on
intermediate portions of boom sections 30 and 32, respectively, or
may be integral therewith. The brackets are U-shaped in cross sec-
tion and have a space between the vertical walls. The brackets
have a pivot shaft 52 extending therebetween.
In the preferred embodiment illustrated in Figs. l and 2,
the fluid ram means comprises a single dipper cylinder assembly 54,
also of the double-acting type. Dipper cylinder assembly 54 has
a cylinder 55 and a piston rod 56 which is pivotally connected on
a pivot shaft 58 carried at the end corner of the attachment plate
44 and which is axially spaced from pivot shaft 42. Dipper cylin-
der 55 i5 pivotally mounted on pivot shaft 52 between brackets
48 and 50.
A bucket 70 is pivotally attached to the free end of the
dipper in the conventional way. A pair of drive links 72, 74 are
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pivoted to the dipper 40 and bucket 70 and are interconnected by
a floating knee shaft 76. A bucket cylinder assembly 78 of the
double-acting type has a cylinder 79 mounted on a pivot shaft 80
carried on an upstanding corner of the dipper attachment plate 44
and has a single-ended piston rod 82 pivotally connected to the
knee shaft 76.
The present backhoe arrangement has a normal transport posi-
tion as shown in solid lines in Fig. 1, wherein the boom extends
generally vertically and slightly forwardly, and the center of
gravity of the backhoe part is closer to the front end of the
tractor. The boom cylinder assembly 28 has a moment arm M, so
that any application of hydraulic pressure to the head end of the
boom cylinder tends to force boom 24 forward against swing tower
12 resulting in knee lock joint to hold the parts in the Fig. 1
position. If desired, boom 24 may be mechanically locked to swing
tower 12 by a bolt (not shown) extending holes 88 in boom sections
30 and 32 and swing tower 12. Balance and handling of the unit is
greatly improved as the effective center of gravity has been shift-
ed forward by more than 50% as compared to conventional prior art
structures.
The swing tower 12 includes a vertical wall 90 having hori-
zontal upper and lower forwardly projecting walls 91 and 92 having
openings 14 and 16 which receive mounting brackets 93 on the trac-
tor. Swing tower 12 further includes a pair of rearwardly project-
ing sidewalls 94 defining a channel space therebetween in which
boom sections 30 and 32 are nestable. Sleeve or elongated spacer
bearing 23 is secured to boom sections 30 and 32 and receives
horizontal pivot shaft 22 to maintain the boom sections in spaced
apart relation and rigidly interconnect the boom sections at the
lower end. Swing tower 12 also has a vertical wall 96 projecting
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rearwardly from a centrally located position on an upper portion of
swing tower 12. Vertical wall 96 has the upper horizontal pivot
shaft 26 to which boom cylinder 33 is mounted. There is clearance
between boom sections 30 and 32 and boom cylinder assembly 28.
This arrangement enables the boom to swing fully in a nested posi-
tion forwardly of vertical line A-A in Fig. 1, this being the trans-
port position, with boom cylinder assembly 28.~artially positioned
between boom sections 30 and 32.
In the operation of the backhoe, normal loading is perform-
ed in the usual way. However, the boom 24 may operate more nearlytowards a true vertical position to maintain the center of the
backhoe closer to the swing tower 12 and improve the balance and
handling characteristics. When the backhoe is swung from the phan-
tom position of Fig. 1 to the solid line position of Fig. 1, hy-
draulic pressure is applied to the rod end of the boom cylinder
assembly 28 to swing the boom to a true vertical position and then
slightly forwardly of vertical, wherein the line of action of
boom cylinder assembly 28 registers with the center line of the
boom sections 30 and 32. The forward momentum of the parts enables
the backhoe to continue through this position, wherein the center
lines are in registry, toward the solid lines position of Fig. 1.
Hydraulic pressure is applied at the piston end of the boom cylin-
der assembly 28 to assis, forward travel of the boom between the
position wherein the center lines are in registry to the transport
position illustrated in solid lines in Fig. 1. Thereafter, the
hydraulic pres ure effects a knee lock on the boom to hold the
backhoe in the transport position.
I~ may be noted that the swing tower 12 mounts the boom
cylinder pivot shaft 26 slightly rearward of the boom pivot shaft
22 so that in the neutral position indicated by line B-B in Fig. 1,
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wherein the center line of the boom sections 30 and 32 are in re-
gistry with the line of action of the boom cylinder assembly 28,
the boGm leans slightly forwardly of the true vertical position
defined by line A-A. ~his provides more positive control of assist-
ing the forward momentum in insuring that the backhoe swings over-
center to eanble hydraulic pressure to actuate the boom cylinder
assembly in a direction to assist the final forward increment of
travel.
To shift the backhoe from the solid line position of Fig.
1 towards the phantom position of Fig. 1, hydraulic pressure is
applied at the rod end of boom cylinder assembly 28 to initiate
rearward swinging movement of the boom. The bucket cylinder 78
is operated at the same time to curl the bucket 70 rearwardly,
thereby abruptly shifting the center of gravity to the rear and
assisting in the rearward launch of the boom. When the parts move
through the position indicated by line B-B in Fig. 1, wherein the
center line of the boom sections 30 and 32 is in registry with the
line of action with the boom cylinder assembly 28, the hydraulic
pressure is released from the rod end of the boom cylinder.
In the following portion of the description, two-digit num-
erals are used to refer to the embodiments in Figs. 1 and 2, three-
digit numerals 100-199 are used to refer to the embodiment illus-
trated in Fig. 3, and three-digit numerals 200-299 are used to
refer to the embodiment illustrated in Fig. 4. The same last two
digits in each numeral designate similar elements in the various
embodiments.
In the embodiments illustrated in Figs. 3 and 4, the fluid
ram comprises a pair of dipper cylinder assemblies 160, 162. Re-
ferring specifically to Fig. 3, dipper cylinder assemblies 160, 162
are of the double-acting type and each has cylinders 164 having
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one end pivotally mounted on pivot shaft 352 with each dipper cy-
linder located between the parallel lateral walls of an associat-
ed bracket. Dipper cylinder assemblies 160, 162 each has a sin~le-
ended piston rod 165 pivotally connected on pivot shaft 158 on
attachment plate 144. Backhoe 110 is otherwise identical to back-
hoe 10 of Figs. 1 and 2.
In the embodiment illustrated in Fig. 4, brackets 249 and
251 are solid, and the dipper cylinders 264 each has a mounting
member 266, 267 mounted on one end thereof to separately pivotally
mount the dipper cylinder on the brackets. Piston rods 265 are
pivotally connected to pivot shaft 258. Backhoe 210 is otherwise
identical to backhoe 10 illustrated in Figs. 1 and 2.
A further modified form of the invention is shown in Figs.
5, 6 and 7. Since many of the elements shown in the embodiment
of Figs. 5, 6, and 7 are identical, or very similar to the elements
described in connection with the embodiment of Figs. 1 and 2,
three-digit reference numerals 300-399 will be used in describing
this embodiment.
A boom 324 consists of a pair of transversely spaced hollow
20 rectangular boom sections 330 and 332 which are interconnected at
their lower end by a sleeve 323 that is pivotally supported on
shaft 322. As shown in Figs. 5 and 6, sleeve 323 extends through
both hollow boom sections 330 and 332 and is rigidly secured there-
to, as by welding. The hollow boom sections 330 and 332 are pivot-
ed about pivot pin or shaft 322 through fluid ram 328 that is pivot-
ed on shaft 326 at one end and pivoted on shaft 336 extending bet-
ween the two hollow boom sections at the opposite end. Shaft
336 extends through hollow sleeves 337 that are respectively fixed-
ly secured to boom sections 330 and 332, as by welding. Pivot
30 shaft 336 is preferably also welded to either sleeves 337 and/or
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to hollow boom sections 330 and 332, Thus, sleeves 337 and shaft
336 define a rigid interconnecting means betveen boom sections 330
and 332. With this arrangement, the sleeves 337 act as spacers
for maintaining piston rod 334 centered between the two boom
sections.
In the embodiment illustrated in Figs. 5, 6 and 7, the
interconnection means between boom sections 330 and 332 also in-
corporate bracket support means 341 consisting of a generally
hollow rectangular member 343 that has brackets 345 secured to
opposed walls thereof. The transverse dimension of hollow member
343 is substantially identical to the spacing between boom sections
330 and 332 and brackets 345, which are preferably welded to mem-
ber 343, have projections 347 extending from the lower ends there-
of. Projections 347 are received into the open ends of hollow
rectangular boom sections 330 and 332 to provide a further inter-
connecting means between the two boom sections so that the boom
sections essentially define a rigid integral unit that is capable
of withstanding substantial torsional stresses during normal opera-
tion of the dipper stick assembly. Hollow member 343 also has a
sleeve 349 on the outer free end thereof which receives pivot shaft
342 to pivotally support dipper stick assembly 340 on the outer
end of boom 324.
Thus, the embodiment of Figs. 5, 6, and 7, as the previous
embodiments, includes three rigid interconnecting means 323, 336,
and 341 between the two boom sections.
The lower ends of boom sections 330 and 332 are preferably
closed by plates 351 that may be welded thereto so that the hollow
boom sections are completely enclosed and are capable of being
used as a reservoir for hydraulic fluid if desired.
However, in the embodiment illustrated in Figs. 5, 6, and
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7, the conduits which supply hydraulic fluid to fluid ram 35 and
the bucket cylinder assembly (not shown) are located within hollow
boom sections 330 and 332. As more clearly shown in Figs. 5 and
7, particularly Fig. 7, a conduit or hose 361 extends through
hollow boom section 332 and hollow bracket 345 as well as hollow
member 343 and terminates in a connector 363 (Fig. 5) at the upper
end of bracket support means 341. Thus, a flexible hose 365 may
be connected to connector 363 and to the cylinder assembly Inot
shown). Of course, it will be appreciated that two such conduits
for one cylinder assembly will be located within either of the
boom sections 330 or 332.
Likewise, a conduit (not shown) could extend through a por-
tion of hollow boom sections 330 or 332 and through a portion of
hollow enclosed bracket 350 and terminate in a connector 351 with
a hose 353 extending from connector 351 to fluid ram 354. Again,
two such conduits would be used to supply fluid to opposite ends
of ram 354.
All of the conduits or hoses could either be flexible mem-
bers, or could alternatively be rigid members that terminate ~n
20 connectors 351 and 363.
A slightly further modified form of the invention is dis-
closed in Fig. 8 which is similar to the embodiment of Figs. 5,
6 and 7. The only difference is the interconnecting means at
the upper end of the boom. In this embodiment illustrated in Fig.
8, hollow rectangular boom sections 430 and 432 each have a sleeve
413 extending through an opening 415 and welded to the respective
boo~ sections 430 and 432. A~shaft 417 extends through the res-
pective sleeves, which are spaced from each other at the inner end
and pivotally support a dipper stick assembly 440. In this embodi-
ment, the upper interconnecting means includes sleeves 413 and
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shaft 417, which define ~irst sha~t means and sleeves 336 and shaft
337, which define second shaft means.
Dipper stick assembly 440 consists of a generally rectan-
gular hollow member 421 which has a bearing member 423 extending
therethrough and secured thereto as by welding. Bearing member
423 defines the pivotal connection of dipper stick assembly 440
on shaft 417, as well as sleeves 413. In order to rigidify the
entire unit, it is preferable that the area surrounding bearing
member 423 be reinforced by additional plates 425. Bearing member
~23 has an opening 427 for supplying lubricant to relatively mov-
able surfaces.
As can be appreciated, in the embodiment illustrated in
Fig. 8, the first shaft means including sleeves 413 and shaft 417
and the second shaft means including sleeves 336 and shaft 337 de-
fine the rigid interconnection between the two spaced boom sections
430 and 432 at one end thereof and this interconnection means also
includes a sleeve 323 at the lower end of the boom sections.
Summarizing the present invention, in all embodiments of
the invention disclosed herein, the transverse spaced boom sections
give the operator greater visibility for observing the operation
of the bucket at the outer end of the dipper stick assembly because
the operator can view the bucket directly from the operator's sta-
tion through the space between the boom sections and the single
boom cylinder assembly. This is particularly true when the boom
is in a lowered position since the only obstruction in that posi-
tion between the boom sections will be the piston rod of the bucket
cylinder assembly, which is normally less than one-half the spacing
between the boom sections. This will greatly increase the visibi-
lity the operator has for the material handling unit on the outer
end of the entire assembly.
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Also, the use of two hollow rectangular boom sections and
a single boom cylinder assembly greatly reduces the overall cost
as well as the overall weight of the backhoe unit. The overall
weight reduction not only is obtained from the use of only a single
cylinder while still retaining the overcenter feature discussed
above, but it also reduces the amount of hydraulic fluid that is
necessary to be in the reservoir since one of the fluid rams is
eliminated. Also, as explained above, the boom cylinder assembly,
particularly the piston rod thereof, is at all times protected
by the two boom section~ on opposite sides thereof to eliminate
exposure of the piston rod to damage.
In addition to the above advantages, the construction
illustrated, particularly in the embodiment of Fig. 5, allowsfor
the use of the present commercially available dipper stick assembly
that has been manufactured for several years by the assignee of
the present invention. Of course, the reduced overall weight of
the backhoe unit improves the balance of the entire vehicle dur-
ing transportation.
The use of twin boom sections and a simple boom cylinder
assembly has proven that the overall width of the boom assembly,
can be decreased by more than 35~ of a boom assembly, such as
known in the Long patent, without sacrificing overall strength.
In fact, the torsion resistance of the new boom is substantially
greater than previously known boom constructions.
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