Patent Application
20080060331
The grass mowing machine may be a self-propelled trim mower 10 including a traction vehicle 11 adapted to carry and operate three reel-type cutting units 20, 30 and 40. The traction vehicle may have three wheels 12, 13 and 14 supporting a frame 15 with controls 16, operator station 17, and engine compartment 18 mounted on the frame.
Alternatively, the present invention may be used for grass mowing machines other than trim mowers, including but not limited to fairway mowers that carry five cutting units, and various other grass mowing machines with two or more cutting units. The mechanism for offsetting cutting units also may be used with rotary cutting units instead of reel-type cutting units.
In one embodiment, each cutting unit 20, 30 and 40 is connected to a lift arm 21, 31 and 41. The same lift arm that is used for offsetting the cutting unit is also used for lifting and lowering the cutting unit. Each lift arm has a first leg 22, 32 and 42 pivotably mounted to the traction vehicle on a first pivot axis and a second leg 24, 34 and 44 pivotably mounted to the cutting unit on a second pivot axis. The first leg of the lift arm may be rotated in a first direction to lower the cutting unit to a mowing position offset to the left of the traction vehicle, in a second direction to lower the cutting unit to a mowing position offset to the right of the traction vehicle, and to an intermediate position between the first and second positions to raise the cutting unit.
In one embodiment, each lift arm 21, 31 and 41 may have a “Z” shape with a first leg 22, 32 and 42, a second leg 24, 34 and 44, and a neck 23, 33 and 43 extending between the first and second legs. First leg 22, 32 and 42 of each “Z”-shaped lift arm provides a first generally horizontal pivot axis mounted to tool bar 50, 60 on traction vehicle 11. Second leg 24, 34 and 44 of each “Z”-shaped lift arm may provide a second generally horizontal pivot axis about which a cutting unit is mounted, which may be parallel to the first pivot axis. The second leg of the lift arm may be inserted through sleeve 25, 35 and 45 on the cutting unit. Each sleeve may include one or more bearings to facilitate rotation of the second leg of the lift arm on the second pivot axis as the cutting unit is raised or lowered. Lift arms 21, 31 and 41 may pivot radially about first pivot axes 22, 32 and 42 on the traction vehicle, allowing cutting units 20, 30 and 40 to pivot radially about second pivot axes 24, 34 and 44. As a result, cutting units 20, 30 and 40 may have the same orientation in the raised, transport position and the lowered, mowing position.
In one embodiment, if cutting unit 20, 30 and 40 is in a raised, transport position, the lift arm for that cutting unit may be generally vertical so that the first pivot axis 22, 32 and 42 is directly below and behind the second pivot axis 24, 34 and 44. Each cutting unit may be raised above the ground surface to a maximum height by approximately the length of neck 23, 33 and 43 of the lift arm.
In one embodiment, each of the cutting units 20, 30 and 40 may be mounted to lift arms 21, 31 and 41 in the same manner. Optionally, one or more cutting units, such as heavier or wider cutting units (i.e., having widths greater than about 26 inches), may be mounted to a pair of lift arms that act together to support the same cutting unit.
In one embodiment, lift arms 21, 31 and 41 may be rotated, either electrically or hydraulically, in the same direction to raise or lower cutting units 20, 30 and 40. In both the raised and lowered positions, lift arms 21, 31 and 41 may maintain the position and spacing of each cutting unit relative to the other cutting units. Maintaining the relative position of the cutting units prevents unlapping when they are lowered, and prevents contact between cutting units when they are raised.
In one embodiment, lift arms 21, 31 and 41 may be rotated in a first direction to lower cutting units 20, 30 and 40, and simultaneously position them in a mowing position offset to the left side of the traction vehicle. Lift arms 21, 31 and 41 may be rotated in a second direction to lower cutting units 20, 30 and 40 and position them in a mowing position offset to the right side of the traction vehicle. Lift arms 21, 31 and 41 may be rotated to a center position to lift the cutting units to a raised or transport position. The mechanism of the present invention also may lock lift arms 21, 31 and 41 in the raised or transport position.
In one embodiment, the mechanism may be operated by an operator's selection of a left/right switch, to offset the cutting units to mowing positions on the left and right sides of the traction vehicle. The lift arms may be released when the lift arms are in the mowing position, so that the cutting units can be free floating to follow ground contours. For example, if a hydraulic cylinder is used to turn each lift arm, the hydraulic cylinder may be configured so that each cutting unit may float in both of the lowered mowing positions, offset left or right. A passage across the piston in the hydraulic cylinder may open if the cutting unit is in a mowing position, allowing hydraulic fluid to flow to either side of the piston. Additionally, each cutting unit may be locked in the raised, transport position. For example, this may be done by blocking the cylinder stroke mechanically or hydraulically when the cuffing units are in the raised position. Additionally, a shaft encoder may be used to indicate the position of the lift arm.
In one embodiment, the first end of each lift arm 21, 31 may be pivotably mounted to the traction vehicle through tool bar 50, and the first end of lift arm 41 may be pivotably mounted through tool bar 60. Sprockets 26, 36 and 46 may be mounted to the first leg 22, 32 and 42 of each lift arm. Idler sprockets 27, 37 and 47 also may be pivotably mounted to tool bars 50 and 60 respectively. A standard roller chain 28, 38 and 48 may engage each pair of sprockets.
In one embodiment, the chain and sprockets may move the cutting units clockwise or counterclockwise to offset them to cutting positions offset to the left and the right of the traction vehicle. To power the chain movement, double acting hydraulic cylinders 29, 39 and 49 with rods extending from each end thereof may be interconnected to chains 28, 38 and 48. Each double acting hydraulic cylinder may have a port on each side of a piston. The piston in each double acting cylinder may provide sufficient force to move the chain in either direction, rotating the sprockets in a first direction to offset the cutting unit to the left, in a second direction to offset the cutting unit to the right, or raise the cutting unit in an intermediate position.
In one embodiment, the ports on a first side of the piston in each hydraulic cylinder may be connected to common valve 55, and the ports on the second side of the piston in each hydraulic cylinder may be connected to a common valve 56. Valves 55 and 56 may be used o control and regulate hydraulic flow and operate the hydraulic cylinders in unison to raise and lower the cutting units together in unison. Thus, the conduit and cylinder used to raise and lower each cutting unit may be subject to the same hydraulic pressure and flow.
Alternatively, a hydraulic rotary actuator may be used instead of a hydraulic cylinder, chain and sprockets for turning the first leg of the lift arm for each cutting unit. For example, a hydraulic rotary actuator may be mounted directly to the tool bar so that it can engage the first leg of each lift arm. In still another embodiment, an electric motor may be used to offset and raise the cutting units. The electric motor may be mounted to the tool bar where it can engage the first leg of each lift arm.
In one embodiment, each lift arm can turn in an arc of about 180 degrees between the lowered left position and the lowered right position. The neck portion of the lift arm may have a length of between about six inches and about twelve inches for most cutting units, and this length provides the maximum offset for each cutting unit to either the left or right side of the traction vehicle. The length of the neck portion of each lift arm also may be limited by the amount of clearance under the frame of the traction vehicle available for a raised cutting unit, and the need for each cutting unit to be located in front of a tire in the offset position so the grass is mowed before the tire rolls over it.
Having described a preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.
