A mowing machine

Abstract: A mowing machine for cutting plants with radially protruding blades of upper (3) and lower (4) blade disks which are coaxially disposed and rotated under the hood that is disposed at the end of a handle. The upper blade disk has a ring gear (8), the lower blade disk has a sun gear (7), and a small gear (9) is provided between the ring gear and the sun gear and meshes these gears so as to rotate the ring and sun gears in the opposite directions, thus rotating the upper and lower blade disks in the opposite directions by driving the small gear for producing a shearing force that cuts the plants.

Description: (Field of the Invention) The present invention relates to a mowing machine of the type that uses a high-revving engine or motor as its power source, whose revolution is reduced at a large reduction ratio to drive an upper blade disk and a lower blade disk in opposite directions so that blades protruding from the edges of the two blade disks cut plants in such a way that scissors cut materials. (Prior Art) As a rotary drive mechanism of a mowing machine for rotatably driving an upper blade disk and a lower blade disk in opposite directions, a planetary gear reduction mechanism comprising a sun gear, a ring gear and planet gears is disclosed in Japanese Patent Publication No. 28818/1995. In this mechanism, the engine revolution is reduced first by a worm and a worm wheel and then by the planetary gear reduction mechanism to obtain a target revolution. The problem with the reduction mechanism according to this prior art is that it employs many gears, resulting in a heavy mowing machine, which is inconvenient for a worker to handle when using it. A mowing machine as defined in the preamble of claim 1 is known from US-A-2,976,665. In this prior art mowing machine the engine is connected via a flexible drive shaft 22 to the center shaft which carries the lower blade disk. Accordingly, the rotary speed of the blade disks is equal or similar to that of the engine and thus undesirably high, unless a separate reduction gear is used, which would make the machine more heavy. US-A-2,826,889 discloses a machine for lawn edging and trimming which has counter rotating upper and lower blade disks carried by a ring gear and a sun gear, respectively, which are rotatably mounted on a solid central shaft. A single pinion arranged between said ring and sun gears and meshing therewith has its shaft connected to a drive engine to impart rotation in opposite directions to said sun and ring gears. No further rotary objects are interposed between said sun and ring gears to support them against radial and/or axial play. (Object of the invention) It is an object of the invention to provide a mowing machine of the kind defined in the preamble of claim 1, which has a simple reduction mechanism that is capable obtaining a desired revolution lower than that of the engine and at the same time obtains improved support of the sun and ring gears for smooth rotation using a light-weight structure. (Solution of the object) According to the invention, the aforementioned object is achieved with a mowing machine as defined in claim 1. The dependent claims relate to further advantageous features of the invention. More specifically, a plate-shaped main unit case is employed, and gears, which constitute the power transmission mechanism, are hung from the plate-shaped main unit case. The main unit case is provided with vertical supporting bars arranged in a plurality of positions on a circle made by connecting all the points having a specific distance from the center of the main unit case, and below the main unit case, a sun gear equipped with a lower blade disk and a ring gear equipped with an upper blade disk are disposed coaxially with said circle. At least some of the plurality of supporting bars standing vertically on the main unit case axially support rotary objects, specifically rollers. or small gears, that circumscribe the sun gear and inscribe the ring gear. All of these rotary objects can be small gears, but at least one of them is a small gear that meshes with both the sun gear and the ring gear, and each supporting bar is provided with a holding means that prevent axial play of the small gear, sun gear and ring gear. This allows the sun gear and the ring gear to rotate in opposite directions via the small gear. Therefore by rotatably driving at least one of the small gears by the power source such as an engine or a motor, the high speed revolution of the small gear is reduced at a large reduction ratio determined by the gear ratios of the sun gear to the small gear and of the ring gear to the small gear, enabling the upper blade disk and the lower blade disk to be rotatably driven in opposite directions at said large reduction ratio. The main unit case can be of a plate or disk shape, but in the interests of a lighter weight, it should be annular with a through hole provided in its center portion and the sun gear should also be provided with a center hole to make it an annular gear with external teeth. The small gear, the sun gear, and the ring gear are configured so that their axial play is inhibited. Specifically, the supporting bars fasten an annular upper supporting plate and an annular lower supporting plate to the main unit case via spacers in such a way that the supporting plates face each other at a certain distance. Moreover, between the upper supporting plate and the upper surface of the small gear an upper roller is provided, and between the lower supporting plate and the lower surface of the small gear a lower roller is provided so as to inhibit the vertical movement of the small gear. Furthermore, guide plates of a diameter larger than that of the small gear are fastened on the upper and lower surfaces of the small gear so that the small gear and the sun gear are not disengaged from each other. (Description of the Embodiments) Embodiments of the mowing machine in accordance with the present invention will now be described with reference to the accompanying drawings. (Brief Description of the Drawings) FIG. 1 is a longitudinal sectional view of the main unit portion of a mowing machine according to one embodiment of the present invention. FIG. 2 is an exploded perspective view of the main unit portion of the mowing machine shown in FIG. 1. FIG. 3 is a plan view of the power transmission mechanism of the main unit of the mowing machine shown in FIG. 1. FIG. 4 is a perspective view of the entire mowing machine according to the embodiment shown in FIG. 1. FIG. 5 is a longitudinal sectional view of the main unit portion of a mowing machine according to another embodiment. FIG. 6 is a schematic plan view showing a gear configuration in the reduction mechanism of the embodiment shown in FIG. 5. FIG. 7 is a longitudinal sectional view of the main unit portion of a mowing machine according to another embodiment. FIG. 8 is a perspective view of the entire mowing machine shown in FIG. 7. As shown in FIG. 4, in the mowing machine of the present invention, the revolution of the power source, e.g., an engine 2, mounted at the base portion of handle 1 is reduced and transmitted to an upper blade disk 3 and a lower blade disk 4. At this time upper blade disk 3 and lower blade disk 4 rotate in opposite directions. The operator holds handle 1 when mowing. Blades 3a established on the upper blade disk 3 and blades 4a established on the lower blade disk 4 cut plants in such a way that scissors cut materials. FIG. 1 is a longitudinal sectional view showing only the main unit, which is mounted at the tip of the handle 1, of the mowing machine. The handle is attached to the main unit obliquely from above. On main unit case 5, which is provided with a through hole 5a in its center portion to make it annular, vertical supporting bars, 6 are established in a plurality of positions (twelve equally spaced out positions in the illustrated examples) on a circle made by connecting all the points having a specific distance from center 0. Below main unit case 5, a sun gear 7 (an annular gear with external teeth) having an external diameter smaller than that of the circle and a ring gear 8 (an annular gear with internal teeth) having an internal diameter larger than that of the circle are disposed. At least two or more supporting bars 6 axially support rotary objects, e.g., rollers or small gears 9, that circumscribe the sun gear and inscribe the ring gear, so that the sun gear 7 and the ring gear 8 smoothly rotate in opposite directions around center 0, with no horizontal play. Both main unit case 5 and sun gear 7 may be solid-disk-shaped, but by making them annular, a through hole that runs through the center portion of the unit can be formed. This through hole not only makes the whole unit lighter, but provides a further advantage that chips generated during the mowing operation can be removed through it. FIG. 3 is a plan view showing a gear mechanism. On a circle made by connecting all the points having a specific distance from center 0, supporting bars 6 are disposed in twelve equally spaced out positions, with every other supporting bar 6 provided with a small gear 9, and one of such small gears (i.e., the gear at the extreme right in this drawing) is used as the driving gear. It is also possible to employ multiple small gears as driving gears. Small gears other than the driving gear are idle gears, which contribute to the smooth rotation of the sun gear 7 and the ring gear 8. For smooth driving of the gears, a plurality, preferably three or more, of small gears 9, including the idle gears, may be employed. In FIG. 3, 6A indicates the shaft of the small gear functioning as the driving gear. Shaft 6A is extended upward, where a bevel gear 10 is mounted. The revolution of the engine is transmitted to the bevel gear 10 via a power-transmission means (shaft, flexible shaft, etc.) attached to the handle 1 of the mowing machine. In the illustrated example, a small bevel gear driven at a high speed by the engine meshes with the bevel gear 10, which is larger, mounted on the shaft 6A to effect a first-stage reduction at the input stage. When the driving gear is rotatably driven, sun gear 7, to which lower blade disk 4 is united, and ring gear 8, to which upper blade disk 3 is united, rotate in opposite directions, performing a mowing operation with blades 3a of upper blade disk 3 and blades 4a of lower blade disk 4. Upper blade disk 3 is united to ring gear 8 via pins 11, etc., in a detachable manner on the outer edge of ring gear 8. On the other hand, in order to unite lower blade disk 4 to sun gear 7, a lower coupling plate 12 that extends outward beneath small gears 9 is fastened to the lower surface of sun gear 7 using bolts, etc., then the sun gear 7 is united in a detachable manner to the edge of the lower coupling plate 12 using attaching pins 13, etc. In the illustrated examples, bolts are used as supporting bars 6. A specific example using such supporting bars 6 to vertically support the entire mechanism will now be described. Beneath the main unit case 5, an annular upper supporting plate 14 with edges protruding downward and an annular lower supporting plate 15 with edges protruding upward are disposed. Main unit case 5, upper supporting plate 14 and lower supporting plate 15 are respectively provided with bolt holes, 5b, 14a, 15a, through which supporting bars 6 (bolts) are inserted from above the main unit case 5. These supporting bars 6 (bolts) are screwed into nuts 17 with spacers 16 inserted between the upper supporting plate 14 and the lower supporting plate 15. Upper supporting plate 14 and lower supporting plate 15 are thus fastened with a certain space between them to the supporting bars 6 vertically established on the main unit case. These supporting bars are disposed in twelve equally spaced out positions, but because the driving gear is disposed in one of these positions, there are actually eleven supporting bars. Small gears 9 that function as idle gears are axially supported by every other supporting bar 6 (altogether five supporting bars according to this drawing), which respectively maintains a certain space between the upper supporting plate 14 and the lower supporting plate 15 using a spacer 16. The supporting bars that do not support small gears 9 function as structural members that add sturdiness to the maintenance of the space between the upper supporting plate 14 and the lower supporting plate 15. An upper roller 18 is disposed between the upper supporting plate 14 and the upper surface of each small gear 9 mounted on each supporting bar 6, and a lower roller 19 is disposed between the lower supporting plate 15 and each small gear 9, so that there is no gap above or below the small gears 9 and that the small gears 9 do not play in the axial direction. As shown in an enlarged view in FIG. 2, the upper surface of small gear 9 comes into contact with a disk-shaped upper guide plate 20, which has a diameter larger than that of small gear 9, whereas the bottom surface comes into contact with a lower guide plate 21, and these guide plates are joined by a metal shaft 22. Accordingly, sun gear 7 and ring gear 8 meshing with small gear 9 are respectively held on the same plane by the upper guide plate 20 and lower guide plate 21 so that their engagement with small gear 9 is maintained. Corresponding to this configuration of the small gears, the upper roller 18 that prevents play of the small gear is shaped like a downward facing cup, whereas the lower roller 19 is shaped like an upward facing cup. These rollers respectively contact the upper guide plate 20 and lower guide plate 21 that are united with the small gears, thereby preventing the small gears, sun gear and ring gear from playing vertically. The inner and outer edges of the upper supporting plate 14, which protrude downward, and those of the lower supporting plate 15, which protrude upward, are provided with inner and outer annular gaskets 23. The inner gaskets contact the upper and lower surfaces of the sun gear 7, whereas the outer gaskets contact the upper and lower surfaces of the ring gear, thereby forming a sealed meshing space for the small gears 9, sun gear 7 and ring gear 8. For smooth driving of the gears, this meshing space may be filled with lubricant such as grease. In the illustrated embodiments the upper supporting plate 14 and the lower supporting plate 15 have protruding edges, but the edges may also be flat. In this case, a downward protruding tubular gasket is used for the upper supporting plate, and an upward protruding tubular gasket is used for the lower supporting plate. The upper supporting plate 14 and the lower supporting plate 15 not only form the sealed meshing space, but hold the sun gear 7 and the ring gear 8 firmly so that they securely mesh with the small gears in cooperation with the upper and lower guide plates of the small gears. As a holding means for inhibiting axial play of the small gears, sun gear and ring gear, a wide supporting plate may be established at the ends of the supporting bars so as to support the assembly of the small gears, sun gear and ring gear. FIGS. 5 and 6 show simplified embodiments of the present invention. FIG. 5 is a longitudinal sectional view, and FIG. 6 is a plan view showing only the reduction mechanism. As shown in FIG. 6, the reduction mechanism comprises sun gear 7, ring gear 8, which surrounds the sun gear 7, and a plurality of small gears 9 disposed between the sun gear 7 and the ring gear 8 so as to mesh with them. In this embodiment, the sun gear 7 is axially supported by a center shaft 24 established in the center portion of the disk-shaped main unit case 5. On the periphery of the sun gear 7, supporting bars 6 are established vertically with respect to the main unit case 5, and small gears 9 are mounted on them while meshing with the sun gear 7 and ring gear 8. Below the ring gear 8, auxiliary rings 25 are disposed, supporting part of the ring gear 8 from below. These auxiliary rings 25 are mounted on the lower surfaces of the small gears 9 via supporting bars 6, thereby preventing ring gear 8 and sun gear 7 from playing axially. One of these small gears is the driving gear. In the illustrated example, the bevel gear 10 mounted on the shaft 6A of the driving small gear 9 is meshed with a second bevel gear 27 mounted on the tip of a drive shaft 26 running through handle 1. In other words, the revolution of an engine or a motor is transmitted to the small gear 9, which rotates sun gear 7 and ring gear 8 in opposite directions. A lower coupling plate 12, which is fastened to the lower surface of the sun gear 7, has an outer edge that projects outward of the ring gear 8, and lower blade disk 4 is fastened to its upper surface. On the upper surface of the ring gear 8, an upper coupling plate 28 is fastened, and the upper blade disk 3 is fastened to the lower surface of its periphery. As such, the upper blade disk 3 and the lower blade disk 4 rotate in opposite directions to perform mowing in such a way as scissors cut materials. The upper blade disk 3 and the lower blade disk 4 can be of any shape or combination of shapes. FIG. 7 is a longitudinal sectional view of another embodiment. This embodiment is characterized in that small gears 9 are mounted at an oblique angle, and that an annular, or cylindrical, sun gear 7 is utilized. A through hole 5a, which also functions as a supporting barrel, is established vertically in the center portion of the main unit case 5, and the cylindrical sun gear 7 is fitted in the supporting barrel in a rotatable manner, while a lock-nut-like fastening member 29 is screwed onto the lower end of the supporting barrel to prevent sun gear 7 from falling off. The external edge of the sun gear 7 is inclined downward while the internal edge of the ring gear 8 is inclined upward so as to match the inclination of the external edge of the sun gear, and the small gears 9 are disposed between these edges. The external edge of the main unit case 5, which supports the small gears 9, is also inclined downward, and the small gears 9 are supported by supporting bars 6 on the inclined surface. According to this embodiment, the small gear that functions as the driving gear is fastened to the tip of a drive shaft 26 that runs through a handle 1 established at an angle of 90° with respect to the inclined surface of the main unit case 5 as shown in FIGS. 7, 8, and the drive shaft 26 is rotated by an engine 2 mounted at the base of handle 1. In this embodiment, the drive shaft 26, which is disposed obliquely with respect to the rotation axis of the upper and lower blade disks, can directly drive the driving small gear 9, eliminating the need for an input-axis-changing mechanism, such as a bevel gear, flexible shaft, etc. FIG. 8 is a perspective view of the entire mowing machine according to the embodiment shown in FIG. 7. In this mowing machine, handle 1 protrudes obliquely from the donut-shaped main unit, which has a through hole in its center portion, i.e., the center of the mowing blades comprising the upper blade disk 3 and the lower blade disk 4. The worker holds the handle 1 when mowing. At the base of handle 1, a power source such as the engine 2 or a motor is mounted, and at the middle portion of the handle 1, an operation handle 30 is provided. (Effects of the Invention) According to the mowing machine of the present invention a large reduction ratio can be obtained with a simple configuration having a small number of gears for a power transmission mechanism of a mowing machine that mows plants with a plurality of blades protruding from the edges of the upper and lower blade disks by rotating the upper and lower blade disks at a low speed. The reduction mechanism is supported by supporting bars established vertically on the plate-shaped main unit case, achieving a light and easy-to-operate mowing machine. According to the invention, the mowing machine can be made of a simple and easy-to-manufacture configuration comprising a sun gear and small gears, which are ordinary spur gears, and a ring gear, which is an annular internal gear. The entire mowing machine can be made lighter by making the main unit case and sun gear light; moreover the through hole formed in the center portion of the machine effectively removes the chips that are generated and accumulated on the surface of the machine during the mowing operation. Furthermore, the conventional high-speed mowing machines often caused the trouble of mown grass twining round the center shaft of the rotary blades. The invention, on the other hand, can use no center shaft, so there will be much fewer troubles relating to twined grass. According to the invention the meshing condition of the small gears, sun gear and ring gear, which constitute the power transmission mechanism, can be reliably maintained with a simple configuration, contributing to the maintenance of a stable driving condition. According to an embodiment of the invention a sealed space filled with lubricant is formed, so it is possible to realize a smoother running condition. The rotary driving mechanism can also be made fully water proof, so it is possible to perform underwater mowing, which was impossible with the conventional high-speed rotary mowing machine. According to another embodiment of the invention, the driving small gear is mounted obliquely, and it is possible to match the inclination of its rotation axis with the inclination of the handle of the mowing machine. This makes the power transmission mechanism simpler by allowing the driving small gear to be mounted at the tip of the drive shaft, which is directly connected to the power source, e.g., an engine. (Codes) 1: Handle; 2: Engine; 3: Upper blade disk; 4: Lower blade disk; 3a, 4a: Blades; 5: Main unit case; 5a: Through hole; 5b: Bolt hole; 6: Supporting bars; 6A: shaft; 7: Sun gear; 8: Ring gear; 9: Small gear; 10: Bevel gear; 11, 13: Attaching pins; 12: Lower Coupling plate; 14: Upper supporting plate; 15: Lower supporting plate; 14a, 15a: Bolt holes, 16: Spacer; 17: Nut; 18: Upper roller; 19: Lower roller; 20: Upper guide plate; 21: Lower guide plate; 22: Metal shaft; 23: Gasket; 24: Center shaft; 25: Auxiliary ring; 26: Drive shaft; 27: Bevel gear; 28: Upper Coupling plate; 29: Fastening member; 30: Operation handle

Claims: A mowing machine for cutting plants using a plurality of blades (3a, 4a) protruding from the edges of an upper blade disk (3) and a lower blade disk (4), which are coaxially disposed and rotate in opposite directions at a low speed, wherein the mowing machine comprises: below a plate-shaped main unit case (5) provided with vertical supporting bars (6) disposed in a plurality of positions on a circle made by connecting all the points having a specific distance from the center (0) of said main unit case, a sun gear (7) equipped with the lower blade disk (4) and a ring gear (8) equipped with the upper blade disk (3) in such a way that they are coaxial with said circle; rotary objects that circumscribe the sun gear (7) and inscribe the ring gear (8) and are rotatably mounted on at least some of the vertically established supporting bars (6), at least one of said rotary objects being a small gear (9) meshing with both the sun gear (7) and the ring gear (8), characterized in that at least one small gear (9) is a driving gear driven by a power source (2); and holding means (18, 19, 20, 21; 25) provided on each of said supporting bars (6) for preventing axial play of the small, sun and ring gears. A mowing machine as claimed in claim 1, in which a center shaft (24) is established in the center portion of the main unit case and the sun gear (7) is axially mounted on said center shaft. A mowing machine as claimed in claim 1, in which the main unit case (5) is an annular case having a through hole (5a) in its center portion, and the sun gear (7) is an annular external gear, also having a through hole in its center portion, so that there is a vertically running through hole in the center portion of the entire machine. A mowing machine as claimed in claim 3, in which a tubular center shaft is established in the through hole of the main unit case (5), and the sun gear (7) is axially mounted on said center shaft. A mowing machine as claimed in any of claims 1 to 4, in which an annular upper supporting plate (14) and an annular lower supporting plate (15) are supported by the supporting bars (6) in such a way that said upper and lower supporting plates (14, 15) face each other maintaining a certain distance between them via a spacer, each of the small gears (9) is equipped with an upper guide plate (20) and a lower guide plate (21) and meshed with the sun gear (7) and the ring gear (8) so the sun and ring gears (7, 8) do not play vertically, and an upper roller (18) is inserted between the upper supporting plate (14) and the upper surface of each small gear (9) and a lower roller (19) is inserted between the lower supporting plate (15) and the lower surface of each small gear (9), so as to prevent axial play of the small, sun and ring gears. A mowing machine as claimed in claim 5, in which gaskets (23) that come into contact with the surface of the sun gear (7) or ring gear (8) are provided at the internal and external edges of the upper and lower supporting plates (14, 15) so as to form a sealed meshing space for the small, sun and ring gears (9, 7, 8), and said meshing space is filled with lubricant. A mowing machine as claimed in claim 1, in which the external edges of the main unit case (5) and the sun gear (7) are inclined downward, the internal edge of the ring gear (8) is inclined upward, and each small gear (9) is mounted on a shaft (6) that is inclined with respect to the rotating axis of the sun and ring gears (7, 8) so as to mesh with the sun and ring gears.

Inventors: ITOH KAZUO, ITOH, KAZUO, Itoh, Kazuo, c/o Itoh Electric Co., Ltd.
Applicants: ITOH ELECTRIC CO LTD, ITOH ELECTRIC CO., LTD.
Application year: 1998
Main classification: A01D34
IPC codes: A01D34