CA1051831A - Overcenter backhoe - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A backhoe arrangement is disclosed wherein the boom comprises a pair of transversely spaced apart boom sections so that a single boom cylinder can be mounted therebetween and wherein overcenter forward movement of the boom sections and boom cylinder provide a transport configuration for the backhoe in which the center of gravity is substantially closer to the rear of the vehicle. The boom sections are rigidly interconnected at spaced points to increase the torsional stiffness of the boom.

Description

1051~31 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 ., - --1 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 , lOS1831 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 105183~
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, ~051831 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 ~05183~
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 ~OS183~
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 ~05~83i 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 105~831 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.

lOS1831 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.

Claims (12)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A backhoe comprising a vertically extending elongated support attachment having a mounting portion thereon defining up-per and lower horizontal pivot axes, an elongated boom comprising two transversely spaced hollow boom sections having a sleeve ex-tending therebetween at one end, said sleeve defining a rigid interconnection between said hollow boom sections and providing a bearing member to pivotally support said boom on said lower pivot axis so as to be swingable through a neutral intermediate position wherein said boom sections extend substantially vertically so that the said upper pivot axis is located in a space between said sections, a double acting boom cylinder assembly pivotally mounted on said upper pivot axis and pivoted to said boom to extend in said space between said boom sections, said boom cylinder assembly being extendable and retractable to effect pivotal movement of said boom and said lower pivot axis to either side of said neutral inter-mediate position and interconnecting means extending between said boom sections at the other end of said boom to rigidly intercon-necting said boom sections said interconnecting means including a bearing member to pivotally support a material handling unit on said other end.

2. A backhoe according to claim 1, in which said material handling unit includes a dipper stick assembly pivoted intermediate said other end of said boom sections, said backhoe further including bracket means mounted on an intermediate portion of each boom section and fluid ram means pivotally mounted at one end to said bracket means and at an opposite end to said dipper stick assembly to effect swinging movement of said dipper stick assembly on said boom sections.

3. A backhoe arrangement in accordance with claim 2, in which said fluid ram means includes a single cylinder and piston rod assembly which is pivotally mounted at one end between said bracket means.

4. A backhoe arrangement in accordance with claim 2, in which said fluid ram means includes a pair of cylinder and piston rod assemblies.

5. A backhoe arrangement in accordance with claim 4, in which the respective cylinder and piston rod assemblies have one end respectively mounted on said bracket means.

6. A backhoe according to claim 1 including a pair of aligned sleeves secured to respective boom sections intermediate opposite ends of said boom sections with a shaft extending through said sleeves, said boom cylinder being pivotally mounted on said shaft.

7. A backhoe arrangement in accordance with claim 1 or 6, in which said interconnecting means includes a shaft extending between said boom sections and secured thereto with said mater-ial handling unit pivoted on said shaft.

8. A backhoe arrangement in accordance with claim 1, in which said hollow boom sections are open at said opposite end and said interconnecting means includes a bracket having projections extending into said hollow open ends with said material handling unit pivotally mounted on a free end of said bracket.

9. A backhoe as defined in claim 8, in which said bracket support means includes a hollow member extending beyond said boom sections with a sleeve on said hollow member pivotally supporting said material handling unit.

10. In a backhoe having a vertically extending elongated support attachment having a mounting portion thereon defining upper and lower pivot axes; an elongated boom comprising two trans-versely spaced rectangular boom sections; a sleeve extending bet-ween said boom sections at one end and connected thereto to pro-vide a rigid connection between said boom sections with said sleeve pivoted on said lower pivot axis to pivotally support said boom on said attachment for vertical swinging movement through a neutral intermediate position wherein said boom sections extend substantially vertically so that the said upper pivot axis is located in a space between said sections, said boom sections hav-ing open opposite ends with interconnecting means including inte-gral bracket support means to rigidly interconnect the other ends of said boom section, said bracket support means having a pair of projections respectively received into the open ends of said boom sections and a sleeve on said bracket support means; a mat-erial handling unit pivoted on said sleeve, and a double-acting boom cylinder assembly having one end pivoted on said upper pivot axis and an opposite end pivotally supported between said boom sections said boom cylinder assembly being extendable and retrac-table to effect pivotal movement of said boom and said lower pivot axis to either side of said neutral intermediate position.

11. A backhoe as defined in claim 10, in which said mater-ial handling unit includes a unit fluid ram with conduit means ex-tending through at least one of said hollow boom sections to said unit fluid ram.

12. A backhoe as defined in claim 10, further including a hollow bracket extending from each hollow boom section and a further fluid ram having one end pivoted on said brackets and an opposite end pivoted on said material handling unit and further conduit means extending through at least a portion of one of said hollow boom sections and hollow brackets.