Implement stabilization method and apparatus
United States Patent 3901395

The fluid pressure supplied to the hydraulic cylinders which extend the stabilizing arms of a backhoe is replenished by pressure from the bucket-controlling cylinder whenever the arm-extending pressure falls below the bucket-controlling pressure, to offset the leak-down which eventually causes the arms to lose their original position.

Application Number:
Publication Date:
Filing Date:
Primary Class:
Other Classes:
60/484, 91/516, 91/519, 212/304, 414/699
International Classes:
E02F3/32; E02F9/08; (IPC1-7): E02F3/74
Field of Search:
212/145 214
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US Patent References:

Primary Examiner:
Spar, Robert J.
Assistant Examiner:
Weaver, Ross
Attorney, Agent or Firm:
Cullen, Settle, Sloman & Cantor
I now claim

1. In a land vehicle having a vehicle mounted extensible tool controlled by a double acting pressure cylinder having tool extending and retracting chambers and a pair of vehicle-stabilizing, ground-engaging arms, said arms each having a double acting fluid pressure cylinder including arm extending and retracting chambers and said arms extensible by said cylinders to support and stabilize said vehicle during extension and movement of said tool, and said cylinder chambers each selectively supplied with fluid pressure by a pump through a system of conduits, the improved control circuit for replenishing any loss of fluid pressure in either of said arm extending cylinder chambers, comprising:

2. The fluid supplementing circuit defined in claim 1, characterized in that said tool is a backhoe-mounted bucket, and wherein said fluid supplementing circuits interconnect the rod-extending chamber supply line for the bucket with the stabilizing arm-extending chamber supply line.


The present invention relates to stabilizing arrangements for vehicles, particularly for mobile machinery such as vehicle-mounted backhoes, cranes, shovels, or the like.

It is conventional to mount a variety of mobile machinery on a tractor-like vehicle, such machinery often including a mounting frame to which is pivoted a swing-frame or boom capable of swinging laterally about a vertical axis relative to the mounting frame of the vehicle. Material handling or holding means, such as buckets or other implements, are usually carried by the boom for movement therewith.

Generally, the wheelbase of the ground-engaging wheels of the tractor is insufficient to provide adequate stability for the machine during the operation of the swinging implement. This is particularly true in earth-moving machinery, such as shovels or backhoes, which are adapted to pick up a heavy load in an extended position of the boom and to raise the load and swing it, often to the opposite side of the tractor. This swinging movement of the heavily loaded and extended boom tends to unbalance the tractor, with the resulting danger of tipping if supplementary stabilizing means are not provided.

One well known form of stabilizing means are the outriggers or stabilizing arms adapted to be extended laterally from each side of the vehicle. An example of these stabilizing arms is shown in U.S. Pat. No. 3,630,544 to Grisham, et al, entitled "Stabilizer for Earth Moving Machinery". The arms are caused to extend downwardly or retract upwardly about horizontal axes by hydraulic cylinders pivotally mounted to the vehicle frame. During operation of the backhoe, the stabilizing arms are normally maintained in their extended position by constant hydraulic pressure.

A common problem in the use of these hydraulically operated stabilizing arms is hydraulic leakage past the cylinder piston seal or past the valve spool land. This constant leaking down of pressure prevents the cylinders from maintaining the preselected position of the stabilizing arms, and therefore requires the operator to interrupt his work to readjust or reposition the stabilizing arms. In the past, one method of minimizing this leakage has been to employ expensive pilot-operated check valves. However, the expense of these valves makes them an unsatisfactory solution.

Accordingly, it is the principal object of this invention to provide an improved means for preventing leak-down of hydraulic pressure in the hydraulic cylinders which control the position of the stabilizing arms of a piece of earth-moving equipment.


The present invention involves the provision of auxiliary conduits interconnecting the supply conduits for the implement-positioning cylinder with the arm-extending chambers of the stabilizing arm-positioning cylinders. These auxiliary conduits are provided with check valves which permit fluid flow only toward the stabilizing arm controlling cylinders. Thus, any leakage of fluid from the stabilizing cylinders will be replenished by fluid from the implement-positioning cylinder whenever the fluid pressure in the stabilizing cylinders falls below that in the implement-positioning cylinder.


FIG. 1 is a perspective view of a tractor vehicle having a conventional backhoe attached thereto, and provided with stabilizing arms.

FIG. 2 is a schematic diagram of the hydraulic cylinders and associated hydraulic control circuitry for the backhoe and stabilizing arms.

FIG. 3 is an enlarged view of a check valve forming a portion of the circuitry of FIG. 2.


Referring to FIG. 1, there is illustrated a tractor 10 having a conventional backhoe 12 pivotally mounted on a supporting frame 14 secured to the rear of the tractor. A control panel 16 controls the operation of the backhoe as well as that of the stabilizing arms 18 extending laterally from each side of tractor 10.

Backhoe 12 includes a bucket 20 pivotally mounted on the outer end of dipper arm 22, which is in turn pivotally mounted on boom 24 pivotally connected to supporting frame 14. Movement of bucket 20 relative to dipper arm 22 is controlled by bucket hydraulic cylinder 26, while movement of dipper arm 22 relative to boom 24 is controlled by dipper hydraulic cylinder 28. Boom 24 can be lifted or lowered under the control of boom hydraulic cylinder 30, while lateral swinging movement of boom 24 is effected by swing hydraulic cylinders 32.

As is conventional, each of the stabilizing arms 18 may be pivotally lowered into their extended ground-contacting positions, as illustrated, or raised to their retracted positions by hydraulic cylinders 34, 36.

As shown in FIG. 2, the various hydraulic cylinders disclosed herein are typically of the double-acting type. The circuitry includes a control valve, schematically shown at 38, which includes a series of manually operable valves for controlling each of the hydraulic cylinders associated with the stabilizing arms and backhoe. These valves distribute the fluid pressure supplied by pump 40 to the appropriate chambers of the desired cylinders. Supply lines 42 and 44 carry fluid to the arm-extending chambers of cylinders 34 and 36, while lines 46 and 48 carry fluid to the retracting chambers of those two cylinders. Similarly, lines 50 and 52 carry fluid to the respective chambers of bucket cylinder 26. The circuitry and elements described thusfar are conventional. For the sake of simplicity, hydraulic cylinders 28, 30 and 32, along with their supply lines, have been omitted from FIG. 2, since they are not essential to the operation of the present invention.

According to the present invention, a fluid distribution tap 54 is provided in line 50 leading to bucket cylinder 26. As will be seen from FIGS. 1 and 2, line 50 is pressurized whenever the cylinder rod of cylinder 26 is to be extended, as would be the case when the bucket is positioned to lift dirt. Auxiliary supply lines 56 and 58 lead from tap fitting 54 to the respective stabilizing arm extending chamber supply lines 42 and 44, joining with the supply lines at Tee fittings 60 and 62, respectively. Check valves 64 and 66 are provided in lines 56 and 58, for a purpose to be described below.

As shown in FIG. 3, check valves 66, which is typical of the construction of check valve 64 as well, includes an orifice 68 which is controlled by a ball type valve element 70. A pair of spring washers 72 within the check valve function to keep the ball from blocking flow at the right end of the valve. As is conventional, the ball will seat in orifice 68 whenever there is a tendency for fluid to flow from right to left in FIG. 3, but will permit free flow of fluid from left to right.

Stabilizing arms 18 are extended to their operative position as illustrated in FIG. 1 whenever fluid pressure is supplied through lines 42 and 44. In the event that some leakage from cylinders 34 and 36 or from control valve 38 occurs, replenishing pressure will be supplied to lines 42 and 44 from line 50 which supplies the bucket controlling cylinder 26. Thus, as shown in FIG. 2, replenishing fluid will be supplied through tap connection 54, line 56, check valve 64 and Tee 60, or through line 58, check valve 66 and Tee 62, whenever the pressure in line 50 exceeds that in either line 42 or 44.

The source of the replenishing fluid pressure has been described as being supply line 50 for the rod-extending chamber of bucket-controlling cylinder 26. This is the preferred embodiment of the present invention, because it has been discovered that this chamber normally has the highest fluid pressure of any of the backhoe-controlling cylinders, and therefore is most likely to have the necessary higher pressure to serve as a replenishing source for the stabilizing arm cylinders. However, it is to be understood that the supply lines (not illustrated) for the dipper cylinder 28 or boom cylinder 30 might alternatively be employed as replenishing sources if such lines had the necessary higher pressure at times when replenishment might be required.

This invention may be further developed within the scope of the following claims. Accordingly, the above specification is to be interpreted as illustrative of only a single operative embodiment of this invention, rather than in a strictly limited sense.