阅读说明：本技术 往复式割草机单元、系统与方法 (Reciprocating mower units, systems and methods ) 是由 沢入直树 宮沢弘之 于 2019-02-19 设计创作，主要内容包括：一种往复式割草机单元(14),包括布置在壳体(24)内的减速齿轮(54)和曲柄机构(56)。减速齿轮(54)以相对较高的第一旋转速度从传动轴接收输入旋转运动,并以相对较低的第二旋转速度将输出旋转运动传递到齿轮输出轴(58),而曲柄机构(56)将齿轮输出轴(58)的输出旋转运动转换成一对割草刀片(32a、32b)围绕共用振荡轴线(A1)的振荡的反相位运动。往复式割草机单元(14)包括输入轴(48),输入轴设置有用于将输入轴(48)能释放地耦接到传动轴的耦接接口(49)。(A reciprocating mower unit (14) includes a reduction gear (54) and a crank mechanism (56) disposed within a housing (24). The reduction gear (54) receives input rotary motion from the drive shaft at a first relatively high rotational speed and transmits output rotary motion to the gear output shaft (58) at a second relatively low rotational speed, and the crank mechanism (56) converts the output rotary motion of the gear output shaft (58) into oscillatory anti-phase motion of the pair of mowing blades (32a, 32b) about the common oscillation axis (a 1). The reciprocating mower unit (14) comprises an input shaft (48) provided with a coupling interface (49) for releasably coupling the input shaft (48) to a drive shaft.)

1. A reciprocating mower unit (14) configured to be driven by a drive unit (12) via a drive shaft (42) arranged within a drive tube (16), the reciprocating mower unit (14) comprising:

a housing (24);

a reduction gear (54) disposed within the housing (24), the reduction gear (54) configured to receive input rotary motion from the drive shaft (42) at a first relatively high rotational speed and to transmit output rotary motion to a gear output shaft (58) at a second relatively low rotational speed; and

a crank mechanism (56) disposed within the housing, the crank mechanism (56) configured to convert the output rotary motion of the geared output shaft (58) into an oscillating motion of a pair of mowing blades (32a, 32b) oscillating in anti-phase with each other about a common oscillation axis (A1), wherein the reciprocating mower unit (14) is characterized by comprising an input shaft (48) for receiving the input rotary motion from the drive shaft (42), wherein the input shaft (48) is provided with a coupling interface (49) for releasably coupling the input shaft (48) to the drive shaft (42).

2. The reciprocating mower unit as claimed in claim 1 wherein said coupling interface (49) comprises splines (50) for sliding axially into rotational engagement with mating splines (44) of said drive shaft (42).

3. The reciprocating mower unit as claimed in any one of the preceding claims wherein said housing (24) comprises clamping means (26) for clamping said housing (24) to said drive tube (16).

4. A vegetation cutter system (39) comprising:

a drive unit (12) comprising a motor (18) and a drive shaft (42) arranged within a drive tube (16);

a reciprocating mower unit (14) as claimed in any one of the preceding claims; and

a clearing saw unit (38) configured to rotate a clearing saw blade (37), wherein the reciprocating mower unit (14) and the clearing saw unit (38) are configured to be alternately connected to the drive shaft (42).

5. A reciprocating mower unit configured to be driven by a drive unit (12) via a drive shaft (42) arranged within a drive tube (16), the reciprocating mower unit (14) comprising:

a housing (24);

a reduction gear (54) disposed within the housing (24), the reduction gear (54) configured to receive input rotary motion from the drive shaft (42) at a first relatively high rotational speed and to transmit output rotary motion to a gear output shaft (58) at a second relatively low rotational speed; and

a crank mechanism (56) disposed within the housing (24), the crank mechanism (56) configured to convert the output rotary motion of the gear output shaft (58) into an oscillating motion of a pair of mowing blades (32a, 32b) oscillating in anti-phase with each other about a common oscillation axis (A1), wherein the reciprocating mower unit (14) is characterized in that the reduction gear (54) is a two-stage reduction gear including a first gear (68) connected for common rotation with an input shaft (48), a second gear (70) meshed with the first gear (68), a third gear (74) connected for common rotation with the second gear (70), and a fourth gear (76) configured for common rotation with a crank (60 a; 60b) of the crank mechanism (56), and the fourth gear (76) is meshed with the third gear (74), wherein the first gear (68) has a first number of teeth, the second gear (70) has a second number of teeth, the third gear (74) has a third number of teeth, and the fourth gear (76) has a fourth number of teeth, wherein the second gear (70) has more teeth than the first gear (68) and the fourth gear (76) has more teeth than the third gear (74).

6. The reciprocating mower unit as claimed in claim 5 wherein said first gear (68) has 7 to 14 teeth; the second gear (70) has 20 to 30 teeth; the third gear (74) has 11 to 19 teeth, and the fourth gear (76) has 26 to 40 teeth.

7. A reciprocating mower unit configured to be driven by a drive unit (12) via a drive shaft (42) arranged within a drive tube (16), the reciprocating mower unit (14) comprising:

a housing (24);

a reduction gear (54) disposed within the housing (24), the reduction gear (54) configured to receive input rotary motion from the drive shaft (42) at a first relatively high rotational speed and to transmit output rotary motion to a gear output shaft (58) at a second relatively low rotational speed; and

a crank mechanism (56) disposed within the housing (24), the crank mechanism (56) configured to convert the output rotary motion of the geared output shaft (58) into an oscillating motion of a pair of mowing blades (32a, 32b) oscillating in anti-phase with each other about a common oscillation axis (A1), the crank mechanism (56) including a respective four-bar linkage for each of the mowing blades, the four-bar linkage configured to oscillate the respective mowing blade in response to rotation of the geared output shaft (58), each of the four-bar linkages including:

a fixed link (24) located between the rotational axis (A2) of the gear output shaft (58) and the common oscillation axis (A1);

a respective input link (60 a; 60b) configured as a crank attached to the gear output shaft (58);

respective output links (64 a; 64b) configured as cranks journaled for pivoting about the common oscillation axis (A1); and

a respective coupler link (62 a; 62b) interconnecting the respective input link and the respective output link (60a, 64 a; 60b, 64b), wherein, for each of the four-bar linkages, a link ratio between the input link (60 a; 60b) and the fixed link (64 a; 64b) is at least 1: 10.

8. the reciprocating mower unit as claimed in claim 7 having at least 1: a link ratio of 8.

9. A reciprocating mower unit configured to be driven by a drive unit (12) via a drive shaft (42) arranged within a drive tube (16), the reciprocating mower unit (14) comprising:

a housing (24);

a reduction gear (54) disposed within the housing (24), the reduction gear (54) configured to receive input rotary motion from the drive shaft (42) at a first relatively high rotational speed and to transmit output rotary motion to a gear output shaft (58) at a second relatively low rotational speed; and

a crank mechanism (56) disposed within the housing (24), the crank mechanism (56) configured to convert the output rotary motion of the gear output shaft (58) into an oscillating motion of a pair of mowing blades (32a, 32b) oscillating in anti-phase to each other about a common oscillation axis (A1), characterized in that the crank mechanism (56) is configured to oscillate at an oscillation angle (a) of less than 15 °₁；α₂) Oscillating each respective mowing blade about the common oscillation axis (a 1).

10. A reciprocating mower unit configured to be driven by a drive unit (12) via a drive shaft (42) arranged within a drive tube (16), the reciprocating mower unit (14) comprising:

a housing (24);

a reduction gear (54) disposed within the housing (24), the reduction gear (54) configured to receive input rotary motion from the drive shaft (42) at a first relatively high rotational speed and to transmit output rotary motion to a gear output shaft (58) at a second relatively low rotational speed; and

a crank mechanism (56) disposed within the housing (24), the crank mechanism (56) configured to convert the output rotary motion of the gear output shaft (58) into an oscillating motion of a pair of mowing blades (32a, 32b) oscillating in anti-phase with each other about a common oscillation axis (A1); and

a ground-engaging body (84) defining a lowermost surface for resting on the ground when the reciprocating mower unit (14) is in use, wherein the reciprocating mower unit (14) is characterized in that the ground-engaging body (84) is rotationally decoupled from each of the pair of mowing blades (32 a; 32b) with respect to rotation about the common axis of oscillation (A1).

11. The reciprocating mower unit of claim 10 wherein the grounding body (84) is rotationally decoupled from the housing (24).

12. The reciprocating mower unit as claimed in any one of claims 10 to 11 wherein said ground engaging body (84) is axially carried by a blade reciprocating shaft (80 a).

13. The reciprocating mower unit of claim 12 wherein,

the grounding body (84) is axially retained between an upper axial stop (94) and a lower axial stop (90) by a central bore (86) of the grounding body (84), wherein an axial distance between the upper and lower axial stops (94, 90) exceeds a thickness of the grounding body (84) adjacent the central bore (86).

14. The reciprocating mower unit as claimed in claim 13 wherein said upper axial stop is defined by a downwardly facing shoulder (94) of said mowing blade reciprocating shaft (80 a).

15. The reciprocating mower unit as claimed in any one of claims 13 to 14 wherein said lower axial stop (90) is defined by a fastening means abutting a shoulder (92) of said mowing blade reciprocating shaft (80 a).

16. A method of operating a reciprocating mower unit (14) comprising:

driving a pair of mowing blades (32a, 32b) to oscillate about a common oscillation axis (a1) in guided mutually anti-phase movements; and

allowing a grounding body (84) axially retained at a bottom surface thereof by the reciprocating mower unit (14) to remain stationary.

17. A method of operating a reciprocating lawnmower, comprising:

operating a motor (18) of the drive unit (12) at a rotational speed of greater than 8000 revolutions per minute;

operating a drive shaft (42) having a length of at least 1 meter at a rotational speed of the motor (18);

driving a first reduction gear stage with an output rotational movement of the drive shaft (42);

driving a second reduction gear stage with an output rotational motion of the first reduction gear stage; and

-converting the output rotary motion of the second reduction gear stage into an oscillating motion of a pair of mowing blades (32a, 32 b).

Technical Field

The present invention relates to a reciprocating mower unit, a vegetation cutting system comprising such a reciprocating mower unit, and a method of operating a reciprocating mower unit.

Background

US4998401A discloses a reciprocating mower which oscillates a pair of mowing blades in anti-phase to each other about a common oscillation axis. Such a mower facilitates convenient cutting of soft grass and shrubs with a very low risk of kicking stones. However, there is a need for a lawn mower that is more ergonomic and user friendly.

Disclosure of Invention

It is an object of the present invention to solve or at least reduce some or all of the above problems. To this end, according to a first aspect, there is provided a reciprocating mower unit configured to be driven by a drive unit via a drive shaft arranged within a drive tube, the reciprocating mower unit comprising: a housing; a reduction gear disposed within the housing, the reduction gear configured to receive input rotary motion from the drive shaft at a relatively high first rotational speed and to transmit output rotary motion to the gear output shaft at a relatively low second rotational speed; a crank mechanism disposed within the housing, the crank mechanism configured to convert an output rotary motion of the gear output shaft into an oscillating motion of the pair of mowing blades oscillating in mutually opposite phases about the common oscillation axis; and an input shaft for receiving input rotational motion from the drive shaft, wherein the input shaft is provided with a coupling interface for releasably coupling the input shaft to the drive shaft. Such a reciprocating mower unit allows the reciprocating mower unit to be coupled to and decoupled from the drive shaft, which allows the reciprocating mower unit to be connected to a different drive unit and vice versa. Thus, the versatility of the reciprocating mower unit and the drive unit is increased.

According to one embodiment, the coupling interface may comprise splines for sliding axially into rotational engagement with mating splines of the drive shaft. One of the input shaft and the propeller shaft may include a socket provided with internal splines, while the other of the input shaft and the propeller shaft may be provided with external splines.

According to one embodiment, the housing may comprise clamping means for clamping the housing to the transmission tube.

According to a second aspect, part or all of the above mentioned problems are solved or at least alleviated by a plant cutter system comprising: a drive unit including a motor and a drive shaft disposed within the drive tube; a reciprocating mower unit as defined above; and a clearing saw unit configured to rotate the clearing saw blade, wherein the reciprocating mower unit and the clearing saw unit are configured to be alternately connected to the drive shaft.

According to a third aspect, some or all of the above mentioned problems are solved or at least alleviated by a reciprocating lawn mower unit configured to be driven by a drive unit via a drive shaft arranged within a drive tube, the reciprocating lawn mower unit comprising: a housing; a reduction gear disposed within the housing, the reduction gear configured to receive input rotary motion from the drive shaft at a relatively high first rotational speed and to transmit output rotary motion to the gear output shaft at a relatively low second rotational speed; and a crank mechanism disposed within the housing, the crank mechanism being configured to convert an output rotary motion of the gear output shaft into an oscillating motion of the pair of mowing blades oscillating in mutually opposite phases about the common oscillation axis, wherein the reduction gear is a two-stage reduction gear including a first gear connected for common rotation with the input shaft, a second gear meshed with the first gear, a third gear connected for common rotation with the second gear, and a fourth gear configured for common rotation with a crank of the crank mechanism, the fourth gear meshed with the third gear, wherein the first gear has a first number of teeth, the second gear has a second number of teeth, the third gear has a third number of teeth, and the fourth gear has a fourth number of teeth, wherein the second number of teeth is greater than the first number of teeth and the fourth number of teeth is greater than the third number of teeth. Such a two-stage reduction gear allows to obtain a high reduction ratio in the reciprocating mower unit with a compact volume, which reduces the need for any reduction gear in the drive unit. Thus, since the same type of drive unit can be used for e.g. a rotary clearing saw, the manufacturing costs of the drive unit can be reduced. Furthermore, if the reciprocating mower unit is provided with a coupling interface as defined above, a modular system may be obtained, allowing to change between the rotary mower unit and the reciprocating mower unit using the same drive unit. According to an embodiment, the drive unit of such a modular system is completely free of any reduction gear, so that the drive shaft rotates at the rotational speed of the motor. According to an embodiment, the first gear and the second gear may be bevel gears. Thereby, the rotational axis of the first gear wheel may be inclined with respect to the common oscillation axis by an inclination angle allowing connection to an inclined drive shaft. According to an example, the inclination angle may be between 25 ° and 65 °, or between 45 ° and 60 °.

According to one embodiment, the first gear may have 7 to 14 teeth; the second gear may have 20 to 30 teeth; the third gear may have 11 to 19 teeth, and the fourth gear may have 26 to 40 teeth.

According to a fourth aspect, part or all of the above mentioned problems are solved or at least alleviated by a reciprocating lawn mower unit configured to be driven by a drive unit via a drive shaft arranged within a drive tube, the reciprocating lawn mower unit comprising: a housing; a reduction gear disposed within the housing, the reduction gear configured to receive input rotary motion from the drive shaft at a relatively high first rotational speed and to transmit output rotary motion to the gear output shaft at a relatively low second rotational speed; a crank mechanism disposed within the housing, the crank mechanism configured to convert the output rotary motion of the gear output shaft into an oscillating motion in which the pair of mowing blades oscillate in mutually opposite phases about a common oscillation axis, the crank mechanism including a respective four-bar linkage for each mowing blade, the four-bar linkage configured to oscillate the respective blade in response to rotation of the gear output shaft, each of the four-bar linkages including a fixed link between a rotational axis of the gear output shaft and the common oscillation axis; a respective input link configured as a crank attached to the gear output shaft; respective output links configured as cranks journaled for pivoting about a common oscillation axis; and a respective coupler link interconnecting a respective input link and a respective output link, wherein, for each four-bar linkage, the link ratio between the input link and the fixed link is at least 1: 10. it has been found that with such a link ratio a relatively low level of vibration of the tool can be obtained, resulting in a better working environment. According to an embodiment, the link ratio between the input link and the fixed link is at least 1: 13. according to a typical example, the link ratio may be in the range of 1: 13 and 1: 25, respectively. A typical length of the input link may be, for example, between 1.5mm and 3 mm. Typical lengths of the fixed link may for example exceed 31 mm. Alternatively or additionally, the fixed link may be shorter than about 50 mm. The reciprocating mower unit may be provided with a coupling interface and/or a two-stage reduction gear as defined above.

According to an embodiment, the reciprocating mower unit may have at least 1: a link ratio of 8. It has been found that using such a linkage ratio, a relatively low level of vibration of the tool can be obtained in conjunction with a compact and efficient reciprocating mower unit, resulting in a more ergonomic reciprocating mower unit. According to an embodiment, the link ratio between the input link and the coupler link is between 1: 9 and 1: 14, respectively. A typical length of the coupler link may be, for example, between 19mm and 29 mm. A typical length of the output link may be, for example, between 22mm and 29 mm.

According to a fifth aspect, part or all of the above mentioned problems are solved or at least alleviated by a reciprocating lawn mower unit configured to be driven by a drive unit via a drive shaft arranged within a drive tube, the reciprocating lawn mower unit comprising: a housing; a reduction gear disposed within the housing, the reduction gear configured to receive input rotary motion from the drive shaft at a relatively high first rotational speed and to transmit output rotary motion to the gear output shaft at a relatively low second rotational speed; a crank mechanism disposed within the housing, the crank mechanism configured to convert the output rotary motion of the geared output shaft into an oscillating motion in which the pair of mowing blades oscillate in mutually opposite phases about the common oscillation axis, wherein the crank mechanism is configured to oscillate each respective mowing blade about the common oscillation axis at an oscillation angle of less than 15 °. Thereby, a low level of vibration can be obtained. It has been found that an oscillation angle between 6 ° and 13 ° results in a good balance between mowing efficiency and vibration. The reciprocating mower unit may be provided with a coupling interface and/or a two-stage reduction gear and/or a four-bar linkage as defined above.

According to a sixth aspect, some or all of the above mentioned problems are solved or at least alleviated by a reciprocating lawn mower unit configured to be driven by a drive unit via a drive shaft arranged within a drive tube, the reciprocating lawn mower unit comprising: a housing; a reduction gear disposed within the housing, the reduction gear configured to receive input rotary motion from the drive shaft at a relatively high first rotational speed and to transmit output rotary motion to the gear output shaft at a relatively low second rotational speed; a crank mechanism disposed within the housing, the crank mechanism configured to convert an output rotary motion of the gear output shaft into an oscillating motion of the pair of mowing blades oscillating in mutually opposite phases about the common oscillation axis; and a grounding body defining a lowermost surface for resting on the ground when the reciprocating mower unit is in use, wherein the grounding body is rotationally decoupled from each of the pair of mowing blades with respect to rotation about the common oscillation axis. Thereby, vibrations of the tool may be reduced, which results in a better user experience. The reciprocating mower unit may be provided with a coupling interface and/or a two-stage reduction gear and/or a four-bar linkage and/or an oscillation angle as defined above. Alternatively, the grounding body may also be rotationally decoupled from the housing.

According to an embodiment, the grounding body may have a circular outer shape as seen along the common oscillation axis. The grounding body may be made of plastic.

According to an embodiment, the grounding body may be axially carried by the blade reciprocating shaft.

According to an embodiment, the grounding body may be axially retained between the upper and lower axial stops through the central opening of the grounding body, wherein an axial distance between the upper and lower axial stops exceeds a thickness of the grounding body adjacent to the central bore. The upper axial stop may be defined by a downwardly facing shoulder of the mowing blade reciprocating shaft. The lower axial stop may be defined by a fastening means abutting a lower shoulder of the mowing blade reciprocating shaft. The fastening means may comprise, for example, a threaded element, such as a screw or nut, to hold the washer tightly in abutment with the lower axial shoulder. The central opening of the grounding body may be sufficiently larger than, for example, any blade reciprocating shaft passing therethrough to allow the grounding body to freely rotate relative to the blade reciprocating shaft.

According to a seventh aspect, part or all of the above problems are solved or at least alleviated by a method of operating a reciprocating mower unit, the method comprising: driving a pair of mowing blades to oscillate about a common oscillation axis in guided mutually anti-phase movements; and allowing the grounding body, which is axially retained at its bottom surface by the reciprocating mower unit, to remain stationary.

According to an eighth aspect, part or all of the above problems are solved or at least alleviated by a method of operating a reciprocating lawn mower, comprising: operating a motor of the drive unit at a rotational speed of greater than 8000 revolutions per minute; operating a drive shaft having a length of at least 1 meter at the rotational speed of the motor; driving a first reduction gear stage with an output rotational motion of a drive shaft; driving a second reduction gear stage with the output rotational motion of the first reduction gear stage; and converting the output rotary motion of the second reduction gear stage into an oscillating motion of a pair of mowing blades.

It should be noted that embodiments of the invention can be embodied by all possible combinations of features recited in the claims. Further, it will be appreciated that the different embodiments described for the device may all be combined with the method, and vice versa.

Drawings

The above and other objects, features and advantages of the present invention will be better understood by the following illustrative and non-limiting detailed description of preferred embodiments of the invention with reference to the drawings, in which like reference numerals will be used for like elements, wherein:

FIG. 1 is a schematic perspective view of a reciprocating mower;

figure 2 is a plan view of a reciprocating mower unit of the reciprocating mower shown in figure 1, seen from above;

FIG. 3a is a schematic perspective view of a vegetation cutter system including the reciprocating mower unit, the clearing saw unit of FIG. 2 and a drive unit for driving either of the reciprocating mower unit and the clearing saw unit;

FIG. 3b is an enlarged view of a detail of FIG. 3 a;

FIG. 4a is a plan view of the reciprocating mower unit shown in FIG. 2, seen from above, with no mowing blade and the housing top cover removed;

FIG. 4b is a simplified model of a four bar linkage mechanism showing the crank mechanism of the reciprocating mower unit of FIG. 2;

FIG. 5 is a schematic perspective view of the reciprocating mower unit shown in FIG. 2 with the housing removed to reveal moving parts therein;

FIG. 6 is a perspective exploded view of a two-stage reduction gear and crank mechanism of the reciprocating mower unit of FIG. 2;

FIG. 7 is a schematic view of a cross-section of the reciprocating mower unit of FIG. 2 taken along line VII-VII shown in FIG. 4 a; and

figure 8 is a schematic perspective view of the arrangement of the grounding body of the reciprocating mower unit of figure 2.

All the figures are schematic, not necessarily to scale, and generally show only parts which are necessary in order to elucidate the embodiments, wherein other parts may be omitted.

Detailed Description

Figure 1 shows a hand-held reciprocating mower 10 including a drive unit 12 and a reciprocating mower unit 14. The drive unit 12 includes a drive tube 16 and a motor 18 attached to a first end 16a of the drive tube 16. An electric motor 18, which may be, for example, an internal combustion engine or an electric motor, is configured to drive reciprocating mower unit 14 via a drive shaft (not shown) within drive tube 16. The drive unit is also provided with a pair of handles 20a, 20b for holding the reciprocating mower 10, and a trigger 22 for controlling the rotational speed of the motor 18, which typically operates at speeds in excess of 8000 revolutions per minute (rpm) in the case where the motor is an internal combustion engine. The reciprocating mower unit 14 is attached to a second end 16b of the drive tube 16 opposite the first end 16a so that an operator standing in an upright position and holding the reciprocating mower 10 by two handles 20a, 20b can conveniently position the reciprocating mower unit 14 in a position close to the ground and at a safe distance from his/her feet for cutting grass and other vegetation, for example. For this purpose, the drive tube typically has a length of more than about 1 meter.

Turning now to FIG. 2, the reciprocating mower unit 14 includes a housing 24 provided with a clamping arrangement 26 for clamping the housing 24 to the drive tube 16 (FIG. 1). The clamping means comprises a slit 28 in the housing 24 and a clamping screw 30 configured to press the slit 28 together. A crank mechanism (not shown) is arranged inside the housing 24 below the top cover 25; the crank mechanism is configured to oscillate the pair of mowing blades 32a, 32b about the common oscillation axis a1 in anti-phase with each other. The crank mechanism is configured to cause a first lower mowing blade 32a of the pair of mowing blades to oscillate at a first oscillation angle alpha₁Oscillate between defined end positions and cause a second upper mowing blade 32b of the pair of mowing blades to oscillate by a second oscillation angle alpha₂Oscillating between defined end positions. Typically, α₁And alpha₂May be substantially identical; in the example shown, α₁＝α₂Is approximately equal to 9 degrees. The oscillation angle corresponds approximately to half the cutting tooth pitch P, i.e. the mowing blades 32a, 32b are moved relative to each other such that each cutting tooth 34b of the upper mowing blade 32b alternately overlaps two adjacent cutting teeth 34a of the lower mowing blade 32a and vice versa in order to cut vegetation caught in the gap 36 between the mowing blades.

Figure 3a shows the drive unit 12, reciprocating mower unit 14 and clearing saw unit 38. Drive unit 12 includes a cutter unit interface 40a at second end 16b of drive tube 16, and each of reciprocating mower unit 14 and clearing saw unit 38 includes a respective drive unit interface 40b configured to mate with cutter unit interface 40a of drive unit 12. Thus, drive unit 12, reciprocating mower unit 14 and clearing saw unit 38 constitute a modular vegetation cutter system 39, allowing reciprocating mower unit 14 and clearing saw unit 38 to be alternately connected to drive unit 12. Even though the reciprocating mower unit 14 is well suited for grass and shrubs, particularly where bouncing pebbles may cause damage, a rotary clearing saw unit 38 configured to rotate a circular clearing blade 37 at high rotational speeds may be better suited for thicker shrubs and where higher cutting speeds are desired. Due to the modular system 39, both alternatives can be used by the operator with less weight and volume.

Figure 3b shows the cutter unit interface 40a of the drive unit 12 and the drive unit interface 40b of the reciprocating mower unit 14 in more detail. It should be understood that the drive unit interface 40b of the clearing saw unit 38 may be identical to the drive unit interface of the reciprocating mower unit 14. For clarity of illustration, the respective outlines of drive tube 16 of drive unit 12 and housing 24 of reciprocating mower unit 14 are shown in phantom. The drive shaft 42 is disposed inside the drive tube 16 and is connected for rotation by the motor 18 (fig. 1) of the drive unit 12. The free end 43 of the drive shaft 42 is provided with external splines 44 extending axially along the drive shaft 42. The drive unit interface 40b includes a drive tube socket 46 for matingly receiving the free second end 16b of the drive tube 16, and the clamping arrangement 26 allows the width of the gap 28 in the housing 24 to be reduced so that the drive tube 16 is securely clamped in the drive tube socket 46 of the housing 24. The drive unit interface 40b also includes an input shaft 48 having a driveshaft socket 49 provided with internal splines 50 for receiving the splined end 44 of the driveshaft 42. The bearing arrangement 52 radially supports the input shaft 48 within the housing 24.

Figure 4a shows the housing 24 of the reciprocating mower unit 14 (figure 1) with its cover 25 (figure 2) removed, revealing the reduction gear 54 and crank mechanism 56. The reduction gear 54 is configured to reduce the rotational speed delivered by the input shaft 48 (fig. 3b) to a lower rotational speed of a gear output shaft 58 that drives a crank mechanism 56 to reciprocate the blades 32a, 32b (fig. 2). The gear output shaft 58 is configured to rotate about a gear output shaft rotational axis A2, thereby rotating a first upper input crank configured to a first upper crank pin 60a formed on the gear output shaft 58. The upper input crank pin 60a defines an input link of a first upper four-bar linkage including an upper input crank pin 60a, an upper coupler link 62a, and an upper output crank 64a configured to reciprocate about the common oscillation axis a1 in response to rotating the upper input crank pin 60a about the gear output shaft axis of rotation a 2. The upper coupler link 62a is pivotally coupled to the upper input crank pin 60a and the upper output crank pin 66a of the output crank 64a, but otherwise floats. The fourth link of the upper four-bar linkage is defined by a fixed link between the gear output shaft rotational axis a2 and the common oscillation axis a 1. The fixed link is physically represented by the housing 24, which holds the gear output shaft rotational axis A2 and the common oscillation axis A1 in a fixed relationship to each other.

Fig. 4b schematically illustrates the operation of the upper four bar linkage 56. A four bar linkage is shown in two positions, one of which is drawn in phantom. Rotation of the input link 60a about the gear output shaft axis of rotation a2 moves the coupler link 62a, which in turn pivots the output link 64a in a reciprocating manner about the common axis of oscillation a 1. The fixed link 24 does not move. According to the illustrated example, the input link 60a has a length of about 2mm (i.e., the radial center of the crankpin is about 2mm offset from the radial center of the gear output shaft (axis a 2)), the coupler link 62a has a length of about 23mm (i.e., the distance between the pivot axes is about 23mm), the output link 64a has a length of about 25mm, and the fixed link 24 has a length of about 37 mm.

Fig. 5 shows the reduction gear 54 and the crank mechanism 56 with the housing 24 (fig. 4a) removed. The reduction gear 54 is a two-stage reduction gear that includes a first gear 68 attached to the input shaft 48, a second gear 70 attached to an intermediate shaft 72 and meshing with the first gear 68, a third gear 74 attached to the intermediate shaft 72 for common rotation with the second gear 70, and a fourth gear 76 attached to the gear output shaft 58 and meshing with the third gear. The first gear 68 and the second gear 70 are bevel gears; in the view of fig. 5, they are shown without teeth for ease of illustration. In the example shown, the first gear 68 has 11 teeth; the second gear 70 has 26 teeth; the third gear 74 has 15 teeth; and the fourth gear 76 has 33 teeth. Thus, the rotational speed at the mesh between the first gear 68 and the second gear 70 has a first reduction, defining a first stage of the two-stage reduction gear, and the rotational speed at the mesh between the third gear 74 and the fourth gear 76 has a second reduction, defining a second stage of the two-stage reduction gear. The upper and lower ends of the intermediate shaft 72 and the gear output shaft 58 are journaled (journal) in bearings 78, although only the lower bearing is shown in the view of fig. 5. Fig. 5 also shows a first upper four-bar linkage and a second lower four-bar linkage of the crank mechanism 56, which is, however, better shown in the exploded view of fig. 6.

Turning to fig. 6, the second lower four-bar mechanism is also driven by the gear output shaft 58. The input crank is configured as a second lower crankpin 60b formed on the gear output shaft 58, defining the input link of a second lower four-bar linkage. The lower crankpin 60b is 180 degrees out of phase with the upper crankpin 60a with respect to rotation about the gear output shaft axis of rotation a 2. The lower four-bar linkage includes a lower input crank pin 60b, a lower coupler link 62b, and a lower output crank 64b configured to reciprocate about a common oscillation axis a1 in response to rotating the lower input crank pin 60b about a gear output shaft axis of rotation a 2. The lower coupler link 62b is pivotally coupled to the lower input crank pin 60b and the lower output crank pin 66b of the lower output crank 64b, but otherwise floats. The fourth link of the lower four-bar linkage is defined by a fixed link between the gear output shaft rotational axis a2 and the common oscillation axis a1, similar to the upper four-bar linkage, and is physically represented by the housing 24.

The lower output crank 64b is splined to the outer blade reciprocating shaft 80b to reciprocate the outer blade reciprocating shaft 80b about the common oscillation axis a 1. The upper blade support 82b is fixedly connected to the bottom end of the outer blade reciprocating shaft 80 b. Similarly, the upper output crank 64a is connected to the inner blade reciprocating shaft 80a via splines to reciprocate the inner blade reciprocating shaft 80a about the common oscillation axis a1 in anti-phase with the outer blade reciprocating shaft 80 b. The lower blade support 82a is fixedly connected to the bottom end of the inner blade reciprocating shaft 80 a. The inner and outer blade reciprocating shafts 80a, 80b are coaxial, and the inner blade reciprocating shaft 80a extends axially from the lower blade carrier 82a through the outer reciprocating shaft 80b and the lower output crank 64b to engage with the splines of the upper output crank 62 a. Each of the lower blade mount 82a and the upper blade mount 82b holds a respective mowing blade 32a, 32b (fig. 2).

The cross-section of fig. 7 shows various components of the reduction gear 54 and the crank mechanism 56. Although the gear output shaft 58 is not visible in cross section, its axis of rotation a2 is intended to coincide with the center of the fourth gear 76. The input shaft 48 is inclined at an inclination angle alpha of about 55 deg. relative to the common axis of oscillation a1 of the gear output shaft₃For holding the drive tube 16 (fig. 1) at a convenient angle, with the blades 32a, 32b horizontal above the ground.

The cross-section of fig. 7 also shows a grounding body 84 for resting on the ground when reciprocating mower unit 14 is in use. Fig. 8 shows a perspective view of the grounding body 84; it has a circular outer shape as seen along the common oscillation axis a1 and is provided with a circular central hole 86 for receiving a screw 88. The washer 90 forms a lower axial stop for the grounding body 84. Referring back to fig. 7, the screw 88 engages with the internal thread of the inner blade reciprocating shaft 80a such that the screw 88 and the inner blade reciprocating shaft 80a are rigidly connected. The screw 88 holds the washer 90 tightly against the lower axial end 92 of the inner blade reciprocating shaft 80a, and the bottom surface of the lower blade carrier 82a integrally formed with the inner blade reciprocating shaft 80a defines an upper axial stop for the grounding body 84. The axial distance between the upper and lower axial stops exceeds the thickness of the grounding body adjacent the central bore 86. Thereby, the grounding body is rotationally separated from the two blade reciprocating shafts 80a, 80b and the housing 24.

The invention has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the invention, as defined by the appended patent claims.

In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.