Shaft assembly which retains a reversible shaft

[0002] The present invention generally relates to a shaft assembly, and more specifically to shaft assembly which retains a reversible shaft.

[0003] In some applications, it is desirable to be able to change the interface between a drive shaft and a device being driven such that a variety of such devices may be powered by a common drive source. One such application is a power take-off shaft on an agricultural tractor. The power take-off shaft may be needed to drive a variety of implements, such as sprayers or planters, depending on an operator's needs. Typically, agricultural implements fall into two classes, Category II or Category III implements. Some operators may have considerable investment in either Category II implements or Category III implements and may want to invest money into the other category of implements for another application. A drawback to this situation is that the operator typically cannot afford a separate tractor to operate each type of implement.

[0004] Additionally, a tractor owner who does own both types of implements wants to be able to interchange between Category II and Category III implements quickly and easily. Unsecuring the existing shaft and securing a new shaft into place may require service tools and may be time consuming. A drawback to requiring the operator to maintain a large number of tools for the interchange operation is that lack of a required tool could make the interchange operation more time consuming which could adversely affect the operators productivity.

[0005] What is needed therefore is a shaft assembly which retains a reversible shaft which overcomes the above-mentioned drawbacks.

[0006] In accordance with a first aspect of the present invention, there is provided a removable shaft assembly including a drive shaft having internal splines defined therein and an output shaft positioned within the drive shaft and having a first set of external splines defined thereon adapted to engage the internal splines of the drive shaft. The assembly further includes a cap axially aligned with the drive shaft having internal splines defined thereon which are adapted to prevent an axial movement of the output shaft relative to the drive shaft when the cap is in a first position and to allow axial movement of the output shaft relative to the drive shaft when the cap is in a second position. The output shaft may be removed from the drive shaft when the cap is placed in the first position by axially sliding the first set of external splines through the internal splines of the cap.

[0007] In accordance with a second aspect of the present invention, there is provided a method of operating a removable shaft assembly. The method includes the steps of providing a drive shaft having internal splines defined therein and positioning a output shaft having a first set of external splines defined thereon within the drive shaft. The method yet further includes the step of axially aligning a cap having internal splines defined thereon with the drive shaft which prevent a axial movement of the output shaft relative to the drive shaft when the cap in a first position, and allow axial movement of the output shaft relative to the drive shaft when the cap is in a second position. The method still further includes the step of removing the output shaft from the drive shaft when the cap is placed in the first position by axially sliding the first set of external splines through the internal splines of the cap.

[0008] In accordance with a third aspect of the present invention, there is provided a work machine having an engine, a transmission driven by the engine with a transmission output shaft and a power takeoff assembly driven by the transmission output shaft and powering a drive shaft having internal splines defined therein. The work machine further includes an output shaft positioned within the drive shaft and having a first set of external splines defined thereon adapted to engage the internal splines of the drive shaft. The work machine yet further includes a cap axially aligned with the drive shaft having an internal splines defined thereon which are adapted to prevent a axial movement of the output shaft relative to the drive shaft when the cap in a first position and allow axial movement of the output shaft relative to the drive shaft when the cap is in a second position. The output shaft may be removed from the drive shaft when the cap is placed in the first position by axially sliding the first set of external splines through the internal splines of the cap.

[0009] FIG. 1 is a partially cutaway side view of a work machine; and

[0010] FIG. 2 is an exploded view of a reversible shaft assembly used in the work machine of FIG. 1.

[0011] While the invention is susceptible to various modifications and alternative forms, a specific embodiment thereof has been shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

[0012] Referring now to FIG. 1, there is shown a agricultural tractor, or work machine 10, that incorporates the features of the present invention therein. The work machine 10 includes an engine 12 which drives an engine output shaft 14. The engine output shaft 14 drives a transmission 16. The transmission 16 is operable to select one of a number of gear ratios between the engine output shaft 14 and a transmission output shaft 18. The transmission is connected to a power take-off assembly 20 as is customary. The power take-off assembly 20 includes a clutch 21 operative to transfer power from the transmission to a drive shaft 22 when the clutch 21 is in the engaged state and to prevent power transfer between the transmission and the drive shaft 22 when the clutch 21 is in the disengaged state.

[0013] Referring now to FIG. 2, there is shown an exploded view of a removable shaft assembly 30 which includes the drive shaft 22, an output shaft 24, a cap 26, a torsion spring 28 and a snap ring 29. The drive shaft 22 has a set of internal splines 32 defined therein. The output shaft 24 has a first set of external splines 34 defined thereon which are adapted to engage the internal splines 32 defined in the drive shaft 22. When the output shaft 24 is placed within the drive shaft 22, rotation of the drive shaft 22 in the general direction of arrow 99 will cause the output shaft 24 to also rotate in the general direction of arrow 99 whereas rotation of the output shaft 24 in the general direction of arrow 100 will also cause the drive shaft 22 to rotate in the general direction of arrow 100.

[0014] The cap 26 is axially aligned with the drive shaft 22. The cap 26 has internal splines 36 defined therein which are adapted to prevent an axial movement of the output shaft 24 relative to the drive shaft 22 when the cap 26 is in a first position. The splines 36 are further adapted to allow axial movement of the output shaft 24 relative to the drive shaft when the cap is in a second position. In particular, the internal splines 32 of the drive shaft 22 are not axially aligned with the internal splines of the cap 26 when the cap 26 is in the first position, and the internal splines 32 of the drive shaft 22 are axially aligned with the internal splines of the cap 26 when the cap 26 is in the second position. It should be appreciated that the output shaft 24 may be either inserted or removed by axially sliding the first set of external splines 34 of the output shaft 24 through the internal splines 36 of the cap 26 when the cap 26 is in the second position.

[0015] The torsion spring 28 serves as a biasing member between the drive shaft 22 and the cap 26. A pin 40 secures a first end 38 of the torsion spring 28 to the drive shaft 22 via a hole 42. A second end 44 of the torsion spring 28 is secured to the cap 26 via a pin 46. The pin 46 engages a slot 48 defined in the drive shaft 22. It should be appreciated that by securing the first end 38 of the torsion spring 28 to the drive shaft 22 and securing the second end 44 of the torsion spring 26 to the cap 26, the torsion spring 28 applies a bias force to cap 26 which causes the cap 26 to rotate relative to the drive shaft 22 in the general direction of arrow 100. It should further be appreciated that biasing the cap 26 in the general direction of arrow 100 places the cap 26 in the first position which prevents a an axial movement of the output shaft 24 relative to the drive shaft 22.

[0016] The cap 26 is further secured to the drive shaft 22 by snap ring 29. In particular, a first groove 50 is defined on an inner surface of the drive shaft 22 and a second groove is 52 is defined in an outer surface of cap 26. To attach the cap 26 to the drive shaft 22, the snap ring 29 is compressed and the outer surface of the cap 26 is placed within the inner surface of the drive shaft 22. When the first groove 50 of the drive shaft 22 becomes aligned with the second groove 52 of the cap 26, the snap ring 29 expands within the grooves 50, 52 to secure the cap 26 to the drive shaft 22.

[0017] The output shaft 24 further has a second set of external splines 54 defined on a first end portion 56. The second set of external splines 54 are adapted to drive a first set of implements. In particular, the first set of implements may be Catagory II agricultural implements as defined by American Society of Agricultural Engineers Standard ASAE S203.13 or ASAE S207.12. Similarly, the output shaft 24 further has a third set of external splines 58 defined on a second end portion 60. The third set of external splines 58 are adapted to drive a second set of implements. In particular, the second set of implements may be Catagory III agricultural implements as defined by American Society of Agricultural Engineers Standard ASAE S203.13 or ASAE S207.12.

[0018] Industrial Applicability

[0019] In operation, the output shaft 24 may be positioned within the drive shaft 22 by manually rotating the cap 26 in the general direction of arrow 99, overcoming the biasing force of torsion spring 26, from the first position to the second position. To prepare the work machine 10 to use Category II implement, the output shaft 24 is positioned such that the second end portion 60 is axially slid through the drive shaft 22 and cap 26 such that the first end portion 56 extends out from the work machine 10 to drive implements, as shown in FIG. 1. To secure the output shaft 24 to the drive shaft 22, the cap is released and the biasing force of the torsion spring 28 returns the cap 26 to the first position which prevents the output shaft 24 from moving axially relative to the drive shaft 22.

[0020] When it is desired drive a Category III implement, the output shaft 24 is first removed from the drive shaft 22 by rotating the cap 26 in the general direction of arrow 99, overcoming the biasing force of torsion spring 28, from the first position to the second position. The output shaft is then flipped 180 degrees such that the first end portion 56 is inserted into the drive shaft 22 and the second end portion 60 extends out from the work machine 10. To secure the output shaft 24 to the drive shaft 22, the cap 26 is released and the biasing force of the torsion spring 28 returns the cap 26 to the first position which prevents the output shaft 24 from moving axially relative to the drive shaft 22. It should be appreciated that this configuration allows and operator to easily configure the output shaft 22 to drive either Catagory II and Catagory III implements without the use of any tools.

[0021] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.