Patent Application
20100115903
The invention described in this patent application was not the subject of federally funded research or development.
The present invention pertains to flail mowers; more particularly, the present invention pertains to the drive system for the rotating cutter shaft assembly to which the vegetation-cutting flail knives are attached.
The disclosed invention is best understood by understanding the environment in which it operates. A flail mower assembly 100, as shown in
The belts in the prior art belt and pulley drive systems of flail mower assemblies stretch and wear. Eventually the belts stretch and wear to the point of rendering prior art belt and pulley drive systems non-functional. As the belts in the prior art belt and pulley drive systems wear over time, the horsepower delivered to the rotating cutter shaft assembly of a flail mower assembly is reduced because of belt slippage with respect to the pulleys. Thus, power transfer to the rotating cutter shaft assembly 124, as shown in
Further failure may occur with the belt tensioning mechanism in prior art belt and pulley drive systems. An example of a prior art belt tensioning system 210 appears in
Accordingly, a need remains in the art for a flail mower assembly drive system which costs less to maintain, that reduces power loss caused by belt slippage, has fewer moving parts, and provides greater operating efficiency.
The disclosed flail mower assembly drive system and method of the present invention overcomes the efficiency loss and maintenance problems associated with prior art belt and pulley drive systems for flail mower assemblies. Further, the disclosed flail mower assembly drive system cost less to maintain, eliminates power loss of belt and pulley systems, has fewer moving parts, and provides greater operating efficiency.
The disclosed flail mower assembly drive system is a direct drive system. Specifically, the flow of rotational power from the drive motor is connected directly to the rotating cutter shaft assembly to which the flail knives are hindgedly mounted.
In the disclosed flail mower assembly drive system, the motor is attached to the housing portion which surrounds the rotating cutter drive shaft assembly of the flail mower assembly. Specifically, a combination bearing housing and motor mount is attached to the housing for the flail mower assembly. By Incorporating a bearing housing within the motor mount the size of the drive system assembly is reduced, thereby allowing the flail mower assembly 100 to operate closer to the tractor. Such positioning enables cutting of foliage growing close to the path of the tractor.
The output shaft of the motor which provides rotational power to the rotating cutter shaft assembly is externally splined. This externally splined shaft mates with an internally splined collar affixed to the driven end of the rotating cutter shaft assembly. Specifically, the internally splined collar is connected to the rotating cutter shaft assembly by a thermal interfitment within a recess or counterbore formed in the end of a stub shaft positioned on the driven end of the rotating cutter shaft assembly. In an alternate embodiment, the internally splined collar may also be welded to the stub shaft on the driven end of rotating cutter shaft assembly in addition to the thermal interfitment of the internally splined collar within the recess formed in the stub shaft portion of the rotating cutter shaft assembly.
A still better understanding of the drive system for providing rotational power to the rotating cutter shaft assembly portion of a flail mower assembly may be had by reference to the drawing figures wherein:
The present invention is a direct drive system 10 for the rotating cutter shaft assembly 124 portion of a flail mower assembly 100. As shown in
The disclosed direct drive system 10 is better understood by the realization that the rotating cutter shaft assembly 124 includes a hollow tubular shaft 125 with a first stub shaft or solid cylindrical member 126 mounted within a disc 131. This disc 131 is affixed within the hollow tubular shaft 125 at the driven end of the rotating cutter shaft assembly 124. A second stub shaft or solid cylindrical member 127 is mounted within a disc 133. The disc 133 is affixed within the hollow tubular shaft 125 at the non-driven end of the rotating cutter shaft assembly 124. When the rotating cutter shaft assembly 124 is turned by the motor 20, the flail knives 122 move outwardly by centrifugal force. The moving ends of the rotating flail knives 122 then cut the grasses and the small brush over which the flail mower assembly 100 passes.
To enable proper spinning and minimization of vibration of the rotating cutter shaft assembly 124, the long axis or axis of rotation of the hollow tubular shaft 125, the long axis or axis of rotation of the first solid cylindrical member 126 and the long axis or axis of rotation of the second solid cylindrical member 127 must all be substantially co-axial.
Formed within the end of the first solid cylindrical member 126 and co-axial with its long axis is a recess or counterbore 32. Within the recess or counterbore 32 is positioned an internally splined collar 40. The internally splined collar 40 is held in place within the first solid cylindrical member 126 by the use of a thermal interfitment. Specifically, the internal diameter dimension of the recess or counterbore 32 is caused to expand by heating the first solid cylindrical member 126 to approximately 400° F. and then inserting the unheated internally splined collar 40 therein. The first solid cylindrical member 126 and the internally spliced collar 40 are then allowed to reach the same temperature. The reduction in size of the recess 32 during the cooling process forms a thermal interfitment between the first solid cylindrical member and the internally splined collar 40. This thermal interfitment is strong enough to transmit the torque provided by the motor 20 through the connection of the external splines on the output shaft 22 of the motor 20 with the internal splines within the internally splined collar 40, thence through the thermal interfitment, thereby causing the rotating cutter shaft assembly 124 to turn as one with the externally splined output shaft 22 of the motor 20. Accordingly, the flail mower assembly drive system 10 of the present invention is a direct drive system from the motor 20 to the rotating cutter shaft assembly 124.
If needed, it has also been found that the internally splined collar 40 may also be welded 42 into position within the recess or counterbore 32 of the first solid cylindrical number 126 after the thermal interfitment of the splined collar 40 within the recess or counterbore 32 is completed. As previously indicated, a hydraulic motor 20 is used in the preferred embodiment however, those of ordinary skill in the art will understand that the disclosed invention may also provide a direct drive system for a flail mower enabling use with other types of motors, such as an electric motor.
The advantage provided by the thermal interfitment of the internally splined collar 40 within the recess or counterbore 32 is in manufacturing cost. If it were necessary to form internal splines within the counterbore of the first solid cylindrical member 126, when positioned within the hollow tubular shaft 125, a large machine would be required. According to the present invention, only the internally splined collar 40 need be machined and then affixed within the counterbore 32 to be co-axial with the long axis of the first solid cylindrical member 126.
As shown in
Rotation of the externally splined output shaft 22 within the internally splined collar 40 causes the rotating cutter shaft assembly 124 to turn. When the rotating cutter shaft assembly 124 turns, the ends of the flail knives 122 engage and shorten the length of the grass and brush with which they come into contact.
Shown in
While the foregoing invention has been described according to its preferred and alternate embodiments, those of ordinary skill in the art will understand that still other embodiments have been enabled by the foregoing disclosure. Such other embodiments shall fall within the scope and meaning of the appended claims.
