Telescoping drive shaft having lubricating passage

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is directed to a telescoping drive shaft having internal passages for directing lubricating grease to the engaging assemblies of the shaft elements.

2. Description of the Prior Art

Many large four-wheel drive work vehicles, such as agricultural tractors, industrial loaders, and logging skidders are articulated in the middle. That is, the front and rear wheel assemblies can pivot with respect to one another. Typically, the front wheels are provided with a differential mounted on a front housing portion whereas the rear wheels are provided with a rear differential mounted on a rear housing portion. The two housing portions are pivotally coupled to one another along a vertical axis. To transmit power to each differential assembly, a drive line extends across the articulation point. To account for changes in length of the drive line as the vehicle articulates, a portion of the drive line includes a telescoping drive shaft. This drive shaft is provided with universal couplings at either end to account for axial misalignment.

As shown in FIG. 2A which illustrates a prior art telescoping drive shaft, the drive shaft comprises a first drive shaft element 10 telescopicingly receives second drive shaft element 12. The first drive shaft element is provided with internal splines 14 which cooperate with external splines 16 of the second shaft element forming engaging assemblies. In this way, rotational movement can be transmitted between the two drive shaft elements, and, therefore, across the drive line. It should be appreciated that the two drive shaft elements can reciprocate relative to one another.

To assure that the drive shaft elements can reciprocate relative to one another, it is necessary that the splines be adequately lubricated. To accomplish this, lubricating grease is injected through grease fitting 18 into the hollow interior formed by the first shaft element. The lubricating grease is held in this hollow interior which forms a lubricant holding chamber 20. As the drive shaft elements reciprocate with respect to one another, the lubricant is forced along the splines lubricating them. Excess lubricant is exhausted through aperture 24 formed in end plate 26. The assembly is also provided with a seal 28 located at the end of first drive shaft element 10.

Telescoping drive shafts such as the one discussed above have not proved to be entirely satisfactory. The majority of the fresh grease injected into chamber 20 is typically exhausted through aperture 24 and does not reach the intermeshed splines.

SUMMARY OF THE INVENTION

The present invention is directed to a method of supplying fresh lubricant to the intermeshed splines. This is accomplished by forming a passage in the second drive shaft element which provides a conduit for the lubricating grease from the lubricating chamber to the intermeshed splines. In addition, the exhaust aperture in the first drive shaft element is eliminated so that a lubricating grease is forced up through the spline assembly where it can exit through the non-positive seal.

The subject telescoping drive shaft assembly comprises a first shaft element that is similar to the prior art except that the exhaust aperture in the end plate is eliminated. The second drive shaft element is provided with the lubricating passage which starts at the lateral end face of the drive shaft element and extends to the end of the splines. A portion of the passage extends along the central longitudinal axis of the second drive shaft element and from there extends radially outward through a plurality of passages to the splines.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of the log skidder having a telescoping drive shaft.

FIG. 2A is a cross sectional side view of a prior art telescoping drive shaft.

FIG. 2B is a cross sectional side view of the subject telescoping drive shaft.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a four-wheel drive articulated log skidder 100 having a telescoping drive shaft 108. Although the subject drive shaft is illustrated as being included in a logging skidder, it can also be used in other articulated vehicles such as four-wheel drive articulated loaders and four-wheel drive articulated agricultural tractors. Skidder 100 is provided with a front frame portion 101 from which extends wheel 102 and a rear frame portion 103 from which extends wheels 104. The skidder is articulated along a vertical axis defined by pivots 105. The front frame portion houses the front differential which is used to drive the front wheels whereas the rear frame portion is provided with a rear differential for driving the rear wheels. Both of these differentials are interconnected by a drive line that includes the telescoping drive shaft 108. A power supply, such as an internal combustion engine, is housed together with a transmission in the front frame portion and rotates the drive line.

The first drive shaft element 110 is identical to the prior art drive shaft element except that end plate 126 is not provided with an exhaust aperture. This drive shaft element is provided with a universal coupling 130 so that it can be coupled to other portions of the drive line.

The second drive shaft element 112 is substantially similar to the prior art drive shaft element except that it is provided with lubricating passage 150. This lubricating passage extends from lateral end face 152 along the central longitudinal axis defined by the second drive shaft element. A plurality of radially extending passages extend off this main passage for directing grease to the spline engaging assemblies 116 and 114. Lubricating grease is injected into chamber 120 through grease fitting 118 and is exhausted through seal 128.

As with the first drive shaft element 110, the second drive shaft element 112 is also provided with a universal coupling assembly 132.

The external splines of the second drive shaft element 112 extend from the lateral end face 152 longitudinally along the drive shaft element. The radially extending lubricating passages supply grease to the termination point of the splines 116.

As the telescoping drive shaft elements move with respect to one another the intermeshed splines are lubricated by fresh grease from chamber 120. As the elements move together grease from chamber 120 is forced between the splines and through lubricating passage 150 to the termination point of splines 166. As the drive shaft elements are drawn apart, lubricating grease stored between the termination point and seal 128 is directed through the splines and passage 150.

Seal 128 is not a positive seal, but rather a lint wiper, and as such can exhaust excess grease. Seal 128 may comprise a felt washer, or be formed from other similar soft materials.

This invention should not be limited by the above described embodiments, but should be limited solely by the claims that follow.

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