Wheel substitutes for land vehicles – With means for tensioning track by moving at least one endwheel – Having hydraulic adjusting means
Reexamination Certificate
1999-12-16
2001-08-21
Morano, S. Joseph (Department: 3617)
Wheel substitutes for land vehicles
With means for tensioning track by moving at least one endwheel
Having hydraulic adjusting means
C305S144000
Reexamination Certificate
active
06276768
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to a drive track chain of a work machine, and more particularly to track tensioning assembly for adjusting tension on a drive track chain of a work machine having a slack adjuster device associated therewith.
BACKGROUND OF THE INVENTION
A work machine, such as a track-type tractor or excavator, is typically supported and propelled by a pair of undercarriage assemblies, each one of which includes an endless drive track chain having a plurality of interconnected articulating components or links. The undercarriage assembly typically also includes a drive sprocket and one or more idler wheels, around each of which the drive track chain is advanced.
During operation of the work machine, it is necessary to maintain tension on the drive track chain in order to keep the chain from derailing from the drive sprocket and/or the idler rollers. In order to maintain tension on the drive track chain, a tension adjustment mechanism such as a hydraulic cylinder or coiled spring is often included in heretofore designed undercarriages. In particular, the cylinder or coiled spring urges the front idler roller in a direction away from the rear idler roller (or rear drive sprocket in the case of an excavator) thereby creating tension on the track chain.
Over a period of time, a number of the components associated with the undercarriage assembly, such as the links and bushings of the drive track chain and even the idler rollers themselves, begin to wear thereby creating slack in the drive track chain. In order to remove the slack from the drive track chain, it is necessary to increase the tension of the track chain. Such an increase in the tension is generally accomplished by manually injecting or otherwise inserting a material, such as grease, into the tension adjustment mechanism associated with the undercarriage assembly.
The use of such tension adjustment mechanisms has a number of drawbacks associated therewith. For example, manual injection of grease into the slack adjustment mechanism is a labor intensive task which can often lead to a decrease in the efficiency associated with operation of the work machine. Moreover, the drive track chain may inadvertently be operated for a period of time with excessive slack therein. This is true since the drive track chain may be operated with excessive slack from the point in time in which slack is first introduced into the track chain until the point in time in which the tension is manually increased. Such excessive slack may cause irregular wear of a number of the components associated with the undercarriage assembly. Moreover, such excessive slack may also cause the drive track chain to derail during movement of the work machine thereby reducing the efficiency of the work machine due to the delays caused by repair of the undercarriage assembly.
In order to avoid the problems associated with excessive slack in the drive track chain, heretofore designed undercarriage assemblies have been operated with relatively large amounts of tension on the drive track chain. However, operation of the undercarriage assembly with a relatively taut track chain during advancement of the work machine increases the rate at which components associated with the undercarriage assembly wear thereby potentially reducing the useful life of the undercarriage assembly.
Moreover, with particular regard to excavators, it is generally desirable to have the drive track chain relatively taut during performance of a digging or other type of work function in order to prevent the excavator from rolling back and forth within the interior of the drive track chain as a result of recoil forces generated during performance of the digging operation. Hence, a relatively high tension level is typically maintained on the drive track chains of excavators at all times even though it is known that use of such a high tension level increases the rate at which components associated with the undercarriage assembly wear during advancement of the excavator.
What is needed therefore is a track tensioning assembly which overcomes one or more of the above-mentioned drawbacks.
DISCLOSURE OF THE INVENTION
In accordance with a first embodiment of the present invention, there is provided an undercarriage assembly of a work machine. The undercarriage assembly includes a first drive track chain and a second drive track chain. The undercarriage assembly also includes a first hydraulic actuator mechanically coupled to the first drive track chain so as to adjust tension on the first drive track chain and a second hydraulic actuator mechanically coupled to the second drive track chain so as to adjust tension on the second drive track chain. The undercarriage assembly further includes a slack adjuster assembly. The slack adjuster assembly has (i) an adjuster housing defining (a) a main chamber, (b) a fluid inlet, (c) a first fluid outlet which is fluidly coupled to the first hydraulic actuator, and (d) a second fluid outlet which is fluidly coupled to the second hydraulic actuator, (ii) a first piston positioned in the main chamber, the first piston (a) isolates the fluid inlet from the first fluid outlet when the first piston is positioned in a first decreased-tension position, and (b) places the fluid inlet in fluid communication with the first fluid outlet when the first piston is positioned in a first increased-tension position, and (iii) a second piston positioned in the main chamber, the second piston (a) isolates the fluid inlet from the second fluid outlet when the second piston is positioned in a second decreased-tension position, and (b) places the fluid inlet in fluid communication with the second fluid outlet when the second piston is positioned in a second increased-tension position. Movement of the first piston from the first decreased-tension position to the first increased-tension position causes actuation of the first actuator so as to increase tension on the first drive track chain. Movement of the second piston from the second decreased-tension position to the second increased-tension position causes actuation of the second actuator so as to increase tension on the second drive track chain.
In accordance with a second embodiment of the present invention, there is provided an undercarriage assembly of a work machine. The undercarriage assembly includes a first idler wheel and a second idler wheel. The undercarriage assembly also includes a first drive track chain which is advanced around the first idler wheel and a second drive track chain which is advance around the second idler wheel. The undercarriage assembly further includes a first hydraulic cylinder having a first cylinder housing with a first rod extending therefrom. The first rod being mechanically coupled to the first idler wheel. The undercarriage also includes a second hydraulic cylinder having a second cylinder housing with a second rod extending therefrom. The second rod being mechanically coupled to the second idler wheel. The undercarriage assembly also includes a slack adjuster assembly. The slack adjuster assembly has (i) an adjuster housing defining (a) a main chamber, (b) a fluid inlet, (c) a first fluid outlet which is fluidly coupled to the first hydraulic cylinder, and (d) a second fluid outlet which is fluidly coupled to the second hydraulic cylinder, (ii) a first piston positioned in the main chamber, the first piston (a) isolates the fluid inlet from the first fluid outlet when the first piston is positioned in a first decreased-tension position, and (b) places the fluid inlet in fluid communication with the first fluid outlet when the first piston is positioned in a first increased-tension position, and (iii) a second piston positioned in the main chamber, the second piston (a) isolates the fluid inlet from the second fluid outlet when the second piston is positioned in a second decreased-tension position, and (b) places the fluid inlet in fluid communication with the second fluid outlet when the second piston is positioned in a second increased-tension
Caterpillar Inc.
Maginot, Addison & Moor
Morano S. Joseph
Nguyen Long Bao
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