Two-speed PTO stub shaft exchange improvements

A power take-off assembly for a work vehicle including an improved power take-off shaft for installation and removal. The power take off shaft is extended and a cut out section on the first end of the shaft is provided to engage an extended portion of a spring loaded mechanism. Once the cut out section securely fits over the extended portion, the spring loaded mechanism is prevented from axially moving in a rightward direction, thus enabling the spring to hold the gear collar in place to engage the high speed gear. The PTO stub shaft has an extended end with protruding shoulders which serve to capture the snap ring between the stub shaft and the output shaft so that when the stub is moved axially the shoulders will pull the snap ring into the groove on the output shaft which securely fastens the stub shaft. A cut-out section on the front end surface of the output shaft is also provided to allow clearance for the tool to squeeze the snap ring tabs during installation and removal.

FIELD OF THE INVENTION

The present invention relates generally to a reversible two speed PTO Stub Shaft, and more specifically to an improved PTO Stub Shaft for a cheaper and efficient installation process.

BACKGROUND OF THE INVENTION

Power Take-Off Shafts or PTOs are used on agricultural vehicles such as tractors to provide power from the engine to agricultural implements. As the use of PTOs developed over the years, the industry developed a standard for two speed PTOs comprising gear speeds of 1000 and 540 rpms. Thus in order to accommodate industry standards of a particular implement relative to the appropriate gear speed, it is necessary to provide a power take-off assembly which allows quick and easy installation of a proper PTO assemblies, the output shaft has a internally splined portion adapted to axially receive the externally splined reversible power take off shaft to prevent relative rotational movement between the power take-off stub shaft and output shaft. The desired PTO shaft speed is typically determined by the configuration of the PTO shaft end inserted into the output shaft. When reversible PTO shafts are used, as in the case of the present invention, the outer end portion is adapted for engagement with the implement for the selected speed, while the configuration of the inner end portion positions a shifting mechanism against the force of a spring loaded mechanism to selectively engage the proper gear speed.

PTO shafts that are described above are often maintained in place by a locking mechanism, typically a flanged locking mechanism, and arranged externally of the output shaft to which the PTO shaft is coupled. One disadvantage of a PTO shaft and current flanged locking mechanisms is that it tends to be tedious and time consuming to install, which may require the use of an additional person or an additional hand.

Other known PTO shafts are maintained in place by an internal snap ring configured to engage an interior portion of the output shaft. Because of the high force required to compress the snap-ring for installation, special tools such as pliers are usually required to reverse the PTO shaft end. To perform the installation using a snap ring, an operator must push the PTO stub shaft to overcome the high axial force of the spring loaded shifting mechanism (e.g. spring loaded plunger), and at the same time install the snap ring.

It therefore remains desirable to provide an improved PTO stub shaft design that will provide for a quick and secure installation of the PTO stub shaft to the output shaft in a desired orientation without the use of pliers.

SUMMARY OF THE INVENTION

In view of the above, and in accordance with one aspect of the present invention, one object of the invention is to improve the installation and removal process of the two speed reversible PTO stub shaft by enhancing the stub shaft design to enable the operator to easily insert the stub shaft into the output shaft against a spring loaded mechanism by twisting the shaft to align the gear collar teeth to the appropriate gear.

Another object of this invention is to quickly and easily install or remove the power take-off shaft by providing a recess on the front interior top end portion of the output shaft to capture or contain the snap ring which is fastened around the PTO stub shaft. This allows the installer to let go of the tool used to squeeze the snap ring and use both hands to insert the stub shaft against the collar return spring and twist the shaft to align the collar teeth to the gear.

A further object of the invention is to extend the end of the stub shaft and add protruding shoulders in order to further capture or contain a snap ring.

Another object of the invention is to modify the output shaft design by providing a cut out section on the front end surface of the output shaft to allow for snap ring tabs clearance.

Additional objects, advantages, and novel features of the invention will become apparent to those skilled in the art upon examination of the following detailed description of the preferred embodiments of the invention when read in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT

While the present invention is susceptible of embodiments in various forms, there is shown in the drawings and will hereinafter be described a preferred embodiment of the invention with the understanding that the present disclosure is to be considered as setting forth an exemplification of the invention which is not intended to limit the invention to the specific embodiment illustrated.

Referring now to the drawings, wherein like reference numerals refer to like parts throughout the several views, there is shown inFIG. 1a PTO assembly10. A gear collar14is located between a first gear16and a second gear18and is capable of sliding axially between a first speed and a second speed, respectively 1000 rpm and 540 rpm.

FIGS. 1-3show a snap ring24fastened around the outer surface of a PTO stub shaft12. A PTO output shaft20has an internal spline38and an installation surface50. The PTO stub shaft12has a first recess52and an external spline60, wherein the external spline60engages with the internal spline38. Once the snap ring24is aligned and seated within a PTO output shaft recess28, the snap ring24becomes locked and axial movement of the PTO stub shaft12is limited. The PTO stub shaft12has a first end32and a second end34. When the first end32is installed towards a spring loaded mechanism22, the first end32compresses the spring loaded mechanism22. However, when the bore58is installed towards the spring loaded mechanism22, the second end34does not compress the spring loaded mechanism22. This is because the shape of the bore58is complementary to the shape of a member56. The spring loaded mechanism22comprises a spring26, the gear collar14, and the member56. The spring26and the gear collar14are in alignment with the PTO output shaft20. The spring26urges the gear collar14, which is mounted about the PTO output shaft20, towards the PTO stub shaft12. The member56is between the PTO stub shaft12and the gear collar14, and further, it is concentric with the gear collar14.

The operation of the foregoing preferred embodiment of the invention will now be described with reference toFIGS. 1 and 3. InFIG. 1, the PTO stub shaft12having a preferred extended end of9mm, is shown at an initial installation point wherein the PTO stub shaft12is moved axially until the PTO stub shaft12locks into the internal spline38of the PTO output shaft20. The snap ring24fastened around the outer surface of the PTO stub shaft12is simultaneously seated within the PTO output shaft recess28. This improved process enables the work vehicle operator or installer to use both hands on the PTO stub shaft12to overcome the high force of the spring26during installation and force the gear collar14proximally or rightward to engage the first speed as shown inFIG. 3to condition the PTO output shaft20and the PTO stub shaft12to rotate at the first speed of 1000 rpm. The installation surface50extends axially away from the PTO output shaft recess28a distance that is further than any other portion of the PTO output shaft20. When installing the PTO stub shaft12to rotate at a first speed, the installation surface50and the first recess52sandwich the snap ring24before the PTO stub shaft12compresses the spring loaded mechanism22. Then, after the PTO stub shaft12engages the spring loaded mechanism22, the snap ring24seats in the PTO output shaft recess28. The length of the PTO stub shaft12is determined by how much gripping area is desired by the operator to ease the PTO stub shaft12installation and removal processes.

InFIG. 2, the PTO stub shaft12does not compress the spring loaded mechanism22. Still, the PTO stub shaft12and the installation surface50sandwich and seat the snap rind24in the first recess52. A protruding shoulder30is attached near the center of the PTO stub shaft12between the first and second ends32,34and acts as a means for limiting the snap ring24from moving axially. Further, as shown inFIG. 2, the PTO stub shaft12is moved closer to the PTO output shaft recess28on the interior bottom surface of the PTO output shaft20and the snap ring24, once aligned, will seat itself within the PTO output shaft recess28of the PTO output shaft20, thereby locking the snap ring24and the PTO stub shaft12in place to prevent axial movement of the PTO stub shaft12.

FIG. 3shows the PTO stub shaft12in a locked installation position and oriented to rotate at 540 rpm. In this position, the spring loaded mechanism22is fully engaged by the PTO stub shaft12and the force of the spring26is fully exerted in a leftward axial direction. Once this force is exerted, the internal spline38and the PTO output shaft recess28on the PTO output shaft20both operate to capture the PTO stub shaft12and prevent the PTO stub shaft12from moving axially.

If it is desired to change the speed by reversing the PTO stub shaft12, the first end32is inserted into the PTO output shaft20. The operator will compress the snap ring24using a tool similar to pliers, and the PTO stub shaft12will be removed. The PTO stub shaft12comprises a second recess54. When installing the PTO stub shaft12to rotate at a second speed, the installation surface50and the second recess54sandwich the snap ring24before the PTO stub shaft12compresses the spring loaded mechanism22. Then, after the PTO stub shaft12engages the spring loaded mechanism22, the snap ring24seats in the PTO output shaft recess28.

FIG. 4illustrates a front view of the PTO stub shaft12and the snap ring24with tabs48fastened on the outer surface of the PTO stub shaft. The front end surface of the PTO output shaft20is provided with a cut out section36to allow for clearance of the snap ring24with tabs48as the PTO stub shaft12is installed.

From the foregoing, it will be observed that numerous modifications and variations can be affected without departing from the true spirit and scope of the novel concept of the present invention. It will be appreciated that the present disclosure is intended as an exemplification of the invention, and is not intended to limit the invention to the specific embodiment illustrated. The disclosure is intended to cover by appended claims all such modifications as fall within the scope of the claims.