Title:
Hydraulic support for cylinder of piston cylinder motor
United States Patent 3912096


Abstract:
In a backhoe, a roughly horizontally extending piston-cylinder stick control motor, having a cylinder pivotally mounted to a boom and a piston rod pivotally mounted to a stick, is used to control the angular relationship of the stick with respect to the boom. The stick is mounted to the boom point in such a manner that when the motor is half retracted, the angular relationship between its longitudinal axis and the longitudinal axis of the boom is greater than the angular relationship of these parts when the motor is either fully extended or fully retracted. A piston-cylinder booster motor pivoted to the boom supports the rod end of the stick control motor cylinder against damaging deflection of axes the control motor cylinder and piston with respect to each other especially when subjected to the shock of a bucket on the stick striking the earth sharply. The booster motor is hydraulically connected to an accumulator, and provides more support for the control motor cylinder when the angular relation of the control motor axis to the boom is less, and provides less support when it is greater. A flow control block between the accumulator and the booster motor provides a restriction to flow of hydraulic fluid from the booster cylinder when excess gravitational forces are exerted tending to misalign the control motor cylinder and rod axes; and permits a free flow into the booster cylinder as the control motor causes the booster motor to tend to elongate.



Inventors:
CARPENTER EMERL R
Application Number:
05/483673
Publication Date:
10/14/1975
Filing Date:
06/27/1974
Assignee:
AMERICAN HOIST & DERRICK COMPANY
Primary Class:
Other Classes:
60/413, 92/8, 414/719
International Classes:
E02F3/32; E02F3/42; (IPC1-7): E02F3/32
Field of Search:
214/138R,138C,142,778 60
View Patent Images:
US Patent References:
3734320SUPPORT MEANS FOR BOOM RAM1973-05-22Redenbarger
3674162ROUGH TERRAIN VEHICLE1972-07-04Smith



Primary Examiner:
Spar, Robert J.
Assistant Examiner:
Weaver, Ross
Claims:
The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows

1. In combination with a hydraulic piston-cylinder work motor having a cylinder thereof pivotally mounted with respect to a relatively fixed base, and a piston, piston rod entity operably associated with a work load in such a manner that a piston-cylinder axis of said work motor changes its angular alignment with a longitudinal axis of said base as said work motor is elongated toward its maximum length, the improvement comprising:

2. The combination as specified in claim 1 wherein the booster motor cylinder entity is pivotally mounted with respect to said base and wherein said piston, piston rod entity is pivotally mounted to support the rod end of the work motor cylinder.

3. In combination with a hydraulic piston-cylinder work motor having a cylinder thereof pivotally mounted with respect to a relatively fixed base constituted as the boom of a backhoe excavator, there being a backhoe stick pivotally mounted to the boom point of the boom, and a piston, piston rod entity of the work motor being pivotally mounted to a portion of said backhoe stick spaced from the part of the stick to which the boom point is pivotally mounted so that a piston-cylinder axis of said work motor changes its angular alignment with a longitudinal axis of said boom as said work motor is elongated toward its maximum length, the improvement comprising:

4. The combination as specified in claim 3 wherein the booster motor cylinder entity is pivotally mounted with respect to said boom and wherein the piston, piston rod entity is pivotally mounted to support the rod end of the work motor cylinder.

5. The combination as specified in claim 3 wherein the compressible energy storage means in the first end of the accumulator includes a compression coil spring and a free floating piston situated in sealing relationship to the walls of the accumulator and between the hydraulic fluid filled portion thereof and the spring.

6. The combination as specified in claim 5 wherein the compressible energy storage means is constituted as a gas under pressure and filling the first end of the accumulator.

7. The combination as specified in claim 4 wherein said boom is provided with a cavity therein; and said booster motor cylinder is pivotally mounted with respect to said boom to lie in said cavity.

8. The combination as specified in claim 7 wherein said accumulator is mounted in said cavity.

Description:
BACKGROUND OF THE INVENTION

This invention has relation to providing support for the cylinder of relatively long piston-cylinder motors such that the damaging effects of gravity are resisted when such motors are subjected to transverse shock and other rigorous loading when substantially extended in a roughly horizontal configuration.

In order to achieve a maximum workable extension in a piston-cylinder motor without undo deflection of the axis of the piston rod with respect to the axis of the cylinder of the motor due to gravity, it has formerly been necessary to increase the diameter of the piston rod and/or to make the cylinder more massive. It has also been customary to provide an extensive, otherwise useless piston-cylinder overlap so that there will be enough distance between the rod end of the cylinder and the piston to keep the deflection between the rod and the cylinder within allowable limits. In the case of the use of such a motor to control the angular relationship of a backhoe stick with respect to a backhoe boom, for example, this use of excess mass or weight or overlap reduces the effective lifting capacity of the backhoe.

BRIEF SUMMARY OF THE INVENTION

In many installations, a piston-cylinder work motor includes a cylinder pivoted with respect to a base, while a piston rod is pivoted to a member which moves through an arc as the piston-cylinder work motor is activated. One such typical example is in the case of a backhoe excavator where the axis of a piston cylinder stick control motor moves closer in angular relationship to the longitudinal axis of a boom as the motor approaches full extension.

In order to prevent undo deflection of the axis of the piston rod with respect to the cylinder axis while the piston motor is extended, a piston-cylinder booster motor is pivotally mounted with respect to the boom and with respect to the rod end of the work motor cylinder. The relationship of the booster motor to the boom and the cylinder of the work motor will be such that the booster motor will be substantially fully extended when the work motor has maximum angular relationship with respect to the boom and will be substantially completely contracted when the angular relationship of the work motor axis to the boom axis is at a minimum.

A hydraulic line extends from a closed end chamber of the booster motor to an accumulator and this allows increasing hydraulic pressure against the booster piston as the piston is moved in direction toward the closed end of the booster motor cylinder. The accumulator can be in the nature of a spring loaded piston riding free in a cylinder, or can be a gas accumulator, or a combination of both.

To resist shock and other sudden loads transverse to the axes of the cylinder and rod of the work motor, and tending to shorten the length of the booster motor, a restriction is provided to the rate of fluid flow from the booster cylinder to the accumulator with no such restriction being present to impede flow from the accumulator to the booster cylinder.

While described in terms of resisting damage due to transverse gravity loading on extended and partially extended piston-cylinder motors, it is to be understood that the invention will work equally well to resist other kinds of sudden transverse one direction loading in approximate alignment with the axis of the booster motor.

IN THE DRAWINGS

FIG. 1 is a side elevational view of a backhoe excavator showing a piston-cylinder stick control work motor in its most extended position and in the closest angular relationship to a boom to which the cylinder of the motor is pivotally mounted, and showing a booster motor of the invention mounted in position relative to the rod end of the cylinder of that work motor and relative to the backhoe boom;

FIG. 2 is a side elevational view of the backhoe excavator of FIG. 1 but with the piston-cylinder stick control motor in its largest angular relationship to the boom;

FIG. 3 is an enlarged fragmentary elevational view with parts in section and parts broken away showing in full lines the relationship of the parts of the invention as seen in FIG. 1 and showing in dotted lines the relationship of parts of the stick control motor as seen in FIG. 2; and

FIG. 4 is an enlarged bottom plan view of a fragment of the boom and booster motor as seen in FIG. 3.

DESCRIPTION OF PREFERRED EMBODIMENTS

This invention, in a simple form, will find application wherever the weight of the parts of a piston-cylinder work motor tend to cause an undo deflection of the axis of the cylinder with respect to the axis of the piston rod when the motor is fully or even substantially extended, and where the extension of that motor changes the relationship of the rod end of the cylinder thereof with respect to the base to which the cylinder is mounted.

Typically, forces tending to move the axes of the cylinder and piston rod of such a work motor sufficiently out of alignment to cause damage are occasioned by transverse shock loading due to gravity.

The invention herein is illustrated with respect to a backhoe excavator 10 having a boom 12 pivotally mounted to a platform 14 which is rotatably mounted on a carbody 16 in any usual or preferred manner. The carbody is supported on side frames 18 of a pair of crawlers 20. The boom 12 is pivotally mounted to the platform as at 22; a backhoe stick 24 is pivotally connected as at 28 to the boom point; and a backhoe bucket 30 is pivotally mounted as at 32 to the outer end of the stick.

Movement of the boom 12 with respect to the rotating platform 14 is controlled by one or more piston-cylinder boom control motors 26 pivotally connected between the rotating platform and the boom, as shown in FIGS. 1 and 2. Suitable boom control lines extend to the cylinder of that motor.

The relative angular position of the stick 24 with respect to the boom 12 is controlled by a piston-cylinder stick control work motor 34, to which stick control lines 35 and 36 extend.

The angular positioning of the bucket 30 with respect to the stick 24 is controlled by a piston-cylinder bucket control motor 38, and suitable bucket control lines extend to the cylinder of this motor.

A cylinder 40 of the stick control motor 34 is pivotally supported on boom 12 as at 42, while a piston rod 44 of this motor is pivotally supported as at 46 to an end of stick 24 spaced from boom connection point 28. Piston rod 44 is integral with a piston 40 which is operably associated with an interior wall surface of cylinder 40 (see FIG. 3).

The boom 12 forms a base for the pivotal support of cylinder 40. It is to be noted that as stick control motor 34 is extended, that is, as the piston rod 44 extends outwardly from the cylinder 40 to move stick 24 toward and into position as seen in FIG. 1, the angular relationship between the axis of the rod 44 and cylinder 40 with respect to the longitudinal axis of the boom 12 approaches a minimum. See FIG. 1 and the full line representation of a portion of the stick control motor 34 and boom 12 in FIG. 3. Conversely, as the motor 34 is contracted by moving piston rod 44 back inside of cylinder 40, the angular relationship of the piston-cylinder axis with respect to the longitudinal axis of the boom 12 is increased. See FIG. 2 and the dotted representation of a portion of motor 34 in FIG. 3.

In order to provide increasing support for the rod end of cylinder 40 as piston-cylinder work motor 34 approaches full extension, a piston-cylinder booster motor 50 and a hydraulic accumulator 52 are provided. This motor 50 includes a piston rod 54 pivotally mounted as at 56 to the rod end of cylinder 40; a piston 58 is integral with and operably associated with the piston rod 54; and a cylinder 60 in which piston 58 and rod 54 move. This cylinder 60 is pivotally mounted as at 62 to an open boom sleeve 64 which provides a cavity through boom 12 in which the cylinder 60 of booster motor 50 and the accumulator 52 are mounted. Boom sleeve 64 is integral with the boom 12 and forms a part thereof.

In the form of the invention as shown, accumulator 52 includes a cylinder 66, a free floating piston 68 in sealing relation to the interior wall of cylinder 66, and an energy storage means such as compression spring 70. This spring, acting against the end of cylinder 66, tends to force piston 68 against the hydraulic fluid.

A hydraulic conduit 72 is open from a hydraulic accumulator chamber 74 located adjacent piston 68 in accumulator 52 to a closed end booster motor chamber 76 located between the piston 58 and the closed end of cylinder 60 of the booster motor 50. These chambers 74 and 76 and the conduit 72 are filled with a suitable hydraulic fluid.

OPERATION

When the piston-cylinder work motor or stick control motor 34 is retracted, and the rod end of cylinder 40 needs little support to prevent undo deflection of its parts, movement of the rod end of cylinder 40 toward position as seen in dotted lines in FIG. 3 has caused the piston rod 54 of the booster motor 50 to move piston 58 to draw most of the hydraulic fluid through conduit 72 and into the now enlarged booster motor chamber 76, causing piston 68 to allow spring 70 to be expanded to a point where it brings the hydraulic pressure to a minimum value, thus providing a minimum upward force against the rod end of cylinder 40 by piston 58 and piston rod 54.

When work motor 34 is elongated by the application of hydraulic pressure in stick control line 35, to move toward the position of the parts as seen in FIG. 1 and as seen in full lines in FIG. 3, considerably more support is needed on the rod end of cylinder 40 from the booster motor. At this point, the piston 58 in booster motor 50 has forced much of the hydraulic fluid from the now greatly shortened booster motor chamber 76, through hydraulic conduit 72, and into hydraulic accumulator chamber 74. This action necessarily greatly increases the size of the accumulator chamber 74 as the piston 68 is forced upwardly against compression spring 70. As this spring is compressed, energy is stored in the accumulator, and the pressure within the hydraulic system rises so that the support afforded by piston rod 54 on the rod end of cylinder 40 of the work motor 34 is very greatly increased. The tendency toward misalignment of the parts due to the weight of the parts and due to the lack of lateral support moment as the piston 48 of the work motor 34 approaches the rod end of the cylinder 40 is thus overcome. It is to be noted that the degree of support from the booster motor increases as the need for support due to the elongation motor 34 increases.

Located in hydraulic conduit 72 is a flow control block 80. The interior of the block 80 is shown schematically in FIG. 4, and includes a fixed flow resistance orifice 82 in the conduit 72 and a check valve 84 bypassing the fixed flow resistance orifice 82. As will be seen, this construction allows rapid passage of the hydraulic fluid from the accumulator chamber 74 to the booster motor chamber 76 as the booster motor is extended, but limits the rate of return flow as the booster motor is contracted. This, in effect, provides a stiff-legged lateral support for the work motor, during the digging operations of the backhoe. For example, as the backhoe goes into its digging operation as seen in FIG. 2, upon contraction of boom control motor 26, the bucket 30 may strike the earth sharply, thus causing a very great reaction on the stick control motor or work motor 34, tending to force the axis of the piston rod 44 out of alignment with the axis of the cylinder 40. This force is resisted by the piston rod 54 and the piston 58 of the booster motor 50 due to the presence of orifice 82 in control block 80, and the consequent relative firm resistance to downward movement of piston 58 and piston rod 54.

Elimination or reduction of the effect of such shocks on the stick control motor 34 allows that motor to be designed much lighter than would otherwise be the case. This weight reduction allows a proportional increase in the net load the machine can handle.

In FIG. 3 there is disclosed a fitting 78 on the end of accumulator cylinder 66. To operate the accumulator as a mechanical energy storage device, this fitting will be left open to allow atmospheric pressure to be present in the accumulator cylinder chamber above the piston 68. In another form of operation, this fitting 78 can be operated as a one way valve, and can be used to charge gas pressure into the accumulator cylinder, thus causing the energy storage to take place due both to the compression of gas and to the compression of the spring 70. In yet another form of operation, the spring 70 can be omitted, and the accumulator 52 can act as a gas accumulator, with the fitting 78 again being used to charge gas into the accumulator chamber.