CUTTING BLADE FOR A MOWING APPARATUS

Abstract: Disclosed herein is a cutting blade (100) for a mowing ap­ paratus, which comprises a pair of first and second pivotal cutting wheels (100U, 100L) slidably superposed with each other and each provided with a number of grass cutting ed­ ges (11a, 11b) along its circumference, each of the cutting teeth (CT) having a major surface (10), two side edges (11a, 11b) and an ou­ ter periphery edge (12); and mechanism (EN, HP, BL) for re­ ciprocatingly rotating each cutting wheel (100U, 100L) in opposite di­ rections through a predetermined angle, respectively. At least one of the side edges (11a, 11b) of each of the cutting teeth (CT) of the cutting wheels (100U, 100L) is defined by an inclined surface forming an acute angle relative to a major surface (10) of the cutting tooth (CT) so as to form a cutting edge, and the outer peri­ phery edge (12) is defined by a plane substantially perpendicu­ lar to the major surface (10) of the cutting tooth (CT). Namely, there is no sharp edge in the outer peripheries of the teeth of the cutting wheels (100U, 100L) or the free ends of the cutting teeth (CT).

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to the mowing apparatus according to the precharacterizing clause of claim 1 (EP-A1-0 257 566). Description of the Prior Art Conventionally, as a cutting blade for a mowing machine for mowing grass or sprig, a single rotatable cutter wheel which is supported by a cutter support body and is driven by an engine or a motor via a drive shaft passed through a hollow pipe connected between the engine and the cutter support body was used. Therefore, when the worker grips two grip portions by both hands and swings the hollow pipe to and fro, it is possible to mow grass by the single rotating cutter wheel. Specifically, as shown in Fig. 1, the conventional mowing apparatus includes a rotary cutting wheel CW having a number of cutting edges CE at the outer periphery thereof. The rotary cutting wheel CW is rotatably supported by a bearing casing BC (cutter support body) and further driven by an engine EN via a transmission shaft rotatably passed through a hollow pipe HP connected between the bearing casing BC and the engine EN. A handle HA including a first grip G₁ is fixed at roughly the middle of the hollow pipe HP, and a second grip G₂ is directly fitted onto the hollow pipe HP so that the worker can swing the cutting wheel to and fro by griping the grips G1 and G2 by both hands. In more detail with reference to Fig. 2, the transmission shaft TS driven by the engine EN is rotatably supported by two bearings BE provided on a junction point between the bearing casing BC and the hollow pipe HP. At the lowermost end of the transmission shaft TS, a first bevel gear BG₁ is fixed. On the other hand, a wheel shaft WS is also rotatably supported by two bearings BE fixed to the lower side of the bearing casing BC. At the uppermost end of the wheel shaft WS, a second bevel gear BG₂ is formed so as to be in mesh with the first bevel gear BG₁. The cutting wheel CW is pinched between two washers WA₁ and WA₂ and fixed to the wheel shaft WS with a spline SP and a nut N. When the worker grips the two grips G₁ and G₂ and swings the hollow pipe HP to and fro, grass can be mowed by the cutting wheel CW driven by the engine EN at a relatively high speed. In the conventional mowing machine, however, since only the single cutter wheel rotates at a relatively high speed, there exist various problems such that pebblestones may be dangerously kicked off; the machine itself must be swung violently to mow grass; and soft grass usually remains unmowed. In order to overcome the problems in the conventional mowing machine as set forth above, there were proposed some improved mowing apparatus having a cutting blade comprising two superposed cutting wheels, which are for example disclosed in USP No. 3,631,658, USP No. 3,472,007 or EP A1 No. 0 257 566 or the like. The improved mowing apparatus were very convenient since grass could be cut in shearing mode as by a scissors. However, unfortunately, in the cutting blades of the improved mowing apparatuses, there was another problem. Namely, in the cutting blades, each of the teeth of the cutting blade has an acute angle or the outer periphery edge of each teeth has a cutting edge. This means that dangerousness would be increased when the apparatus is used, since the tip portions of the teeth or the outer peripheries of the teeth are likely to contact with the worker or the like during the operation thereof, thus leading to injury of the worker. Further, there is a possibility that grass unnecessary to be cut may be cut by the cutting edge provided on the outer periphery of the tooth. Furthermore, if the cutting edge of the outer periphery of the tooth is inadvertently brought into contact with a hard object, such as a stone, rock or tree, the cutting edge may be damaged due to its fragile structure, thus impairing the cutting ability of the cutting wheels. However, it should be noted that in the mowing apparatus having such a blade structure with two superposed cutting wheels which are oscillatingly and reciprocatingly rotated, it is not necessary to provide a cutting edge at the outer periphery of the tooth or to form the tip portion of the tooth acutely, since grass is cut by cutting edges provided on both side edges of each tooth in such a manner as a scissors. EP-A1-0 257 566 discloses a mowing apparatus wherein the outer peripheral edges of the teeth are formed as a cutting edge and the teeth are straight and located parallel to each other. Forming the peripheral edges of the teeth to have cutting functions means danger of persons to be injured and means, simultaneously, danger of the teeth themselves to be damaged by stands, for example. The object underlying the invention is, therefore, to lessen danger of injuring persons and to lessen danger of damaging the teeth by stands or the like. According to the invention the above object is achieved by the features mentioned in the characterizing clause of claim 1. Preferred embodiments are claimed in the subclaims. DE 32 48 679 discloses a cutting assembly for cutting grass. According to Fig. 1 and 2 blades are provided having outer peripheral edges 4b with cutting properties. Furthermore, said blades are located parallel to each other as illustrated by Fig. 4, 6, 9, 11 and 13. According to Figs. 2 and 3 of US 3,631,658 cutting tips are provided instead of peripheral outer edges. Furthermore, according to Fig. 1 thereof, blades 15 are parallel to each other. According to the present invention having the above structure, since there is no sharp edge in the outer peripheries of the teeth of the cutting wheels or the free ends of the teeth, there is less dangerousness in operation of the cutting blade of the mowing apparatus. Further, it becomes possible to avoid cutting grass unnecessary to be cut by the outer peripheries of the teeth. Furthermore, since there is no fragile portion on the tip portion of the tooth, the strength of the tooth is improved, namely the teeth of the cutting wheels become more resistant to damages than those of conventional cutting wheels. Moreover, since the process of sharpening the free ends of the edge is omitted, the manufacturing cost is accordingly reduced. Further, it is also possible to design the cutting wheels such that the teeth of each of the cutting wheels are slightly bent toward the opposite cutting wheel in such a manner that only the tip portions of the teeth of each cutting wheel elastically contact with each other when the cutting wheels are correctly superposed, whereby contacting portions between the teeth of the first and second cutting wheels are displaceable along the profile of each tooth according to the rotational motion of the cutting wheels. According to the cutting wheel having the above structure, the cutting quality is remarkably improved. The features and advantages of the mowing apparatus according to the present invention over the prior-art machine will be more clearly appreciated from the following description of the preferred embodiments of the invention taken in conjunction with the accompanying drawings in which like reference numerals designate the same or similar elements or sections throughout the figures thereof and in which: BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing an example of prior-art mowing machine; Fig. 2 is an enlarged cross-sectional view showing a rotary cutter wheel and a cutter wheel support body of the prior-art mowing machine; Fig. 3 is a perspective view of a first embodiment of the mowing apparatus according to the present invention; Fig. 4 (A) is a top plan view of the main part of the mowing apparatus in Fig. 3; Fig. 4 (B) is an enlarged view of the tooth. Fig. 5 (A) is an enlarged cross-sectional view showing a pair of pivotal cutting wheels and an essential portion of a drive mechanism of the cutting wheels incorporated in the mowing apparatus in Fig. 3; Fig. 5 (B) is an enlarged cross sectional view of a part of the cutting wheels; Fig. 6 is a cross-sectional view of the main part in Fig. 5(A); Fig. 7 is a cross-sectional view taken along line A-A in Fig. 6; Fig. 8 is a cross-sectional view of a rotational speed reduction mechanism in Fig. 3; Fig. 9 is a cross-sectional view of a pair of pivotal cutting wheels and an essential portion of a drive mechanism of a second embodiment of the mowing apparatus according to the present invention; Fig. 10 is a cross-sectional view of the drive mechanism of a third embodiment; Fig. 11 is a cross-sectional view taken along line B-B in Fig. 10. Fig.12(A) is a side view showing a bent hollow pipe connected between the bearing casing and the engine and so fixed to the bearing casing as to be suitable for use in mowing grass on the ground; and Fig.12 (B) is a similar side view showing the bent hollow pipe so fixed to the bearing casing as to be suitable for use in trimming garden trees. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the attached drawings Figs. 3 to 12, embodiments of the present invention will be described. Figs. 3 to 7 show an embodiment of the mowing apparatus according to the present invention. In Fig. 3, an overall view of the mowing apparatus in which a cutting blade according to the present invention is provided. Namely, the apparatus has a cutting blade 100 comprising a pair of upper and lower cutting wheels 100U and 100L. Each of the cutting wheels 100U and 100L has a plurality of cutting teeth CT along its outer periphery thereof. The upper and lower cutting edges 100U and 100L are slidably superposed with each other and pivotally and reciprocationally driven by an engine EN or an electric motor MO in two mutually opposite directions (clockwise and counterclockwise) in order to mow gross between two cutting teeth CT1 and CT2 of the upper and lower cutting wheels 100U and 100L. That is to say, grass can be cut off in shearing mode, which being different from the prior-art cutter wheel which cuts off grass in chopping mode. In more detail in Figs. 4 and 5, a transmission shaft TS is passed through a hollow pipe HP and rotatably supported by a bearing BE fixed to the lower end of the hollow pipe HP. A first bevel gear BG₁ is fixedly fitted to a square shaft portion 101 formed at the lower end of the transmission shaft TS as in the prior-art shown in Fig. 2. In Figs 5 to 7, a lower cutter wheel support plate 113L is integrally formed on a pivotal cutter wheel shaft 110, which is rotatably supported on a bearing case BC. On the lower surface of the lower cutter wheel support plate 113L, there is provided a cover 122 for positioning the cutting wheels 100U and 100L to a predetermined height from the surface of the ground. This cover 122 is fixed to the lower cutter wheel support plate 113L with a screw 123 so as to protect a screw head of a screw 121 which fixes the lower cutting wheel 100L to the lower cutter wheel support plate 113L. A second bevel gear BG₂ which is in mesh with a first bevel gear BG₁ coupled to an end of the transmission shaft TS is fixed to a crank shaft 104 which is rotatably supported in the bearing case BC through bearings BE. Eccentric cam plates 106U and 106L are fixed to the crank shaft 104 integrally. The pivotal cutter wheel shaft 110 is coupled with an upper arm 111U by means of a spline. A cylindrical member 120 into which the pivotal cutter wheel shaft is rotatably and coaxially inserted is coupled with a lower arm 111L by means of a spline. As shown in Figs. 6 and 7, the cam plates 106U and 106L are connected to the upper and lower arms 111U and 111L through an upper and a lower connecting rods 107U, 107L and pins 112U, 112L, respectively. The upper and lower arms 111U, 111L are coupled to the pivotal cutter wheel shaft 110 and the cylindrical member 120, respectively, by means of splines. An upper and a lower cutting wheels 100U and 100L are formed as a dish-shape, respectively. Each of the cutting wheels has a plurality of cutting teeth along the outer periphery thereof. As shown in Figs. 4(A), 4(B) and 5, each of the teeth CT1 has a major surface portion 10 having two side edges 11a and 11b and an outer periphery edge 12 which corresponds to a free end of the tooth. As shown in Fig. 4(B), each of the side edges 11a and 11b is defined by an inclined surface forming an acute angle relative to the major surface 10 of the tooth CT so as to form a cutting edge. On the other hand, the outer periphery edge 12 of the tooth is defined by a plane substantially perpendicular to the major surface 10 of the tooth. Namely, there is no cutting edge on the outer periphery edge 12 of the tooth CT. This means that it is possible to lessen the dangerousness caused by a cutting edge formed on an outer periphery edge of the tooth of the cutting wheels during operation of the mowing apparatus. Further, this is advantageous because even if the outer periphery of the wheels 100U and 100L is applied to a hard object such as a rock, stone, tree or the like the teeth 13 and 14 would not be easily chipped or otherwise damaged thereby. Furthermore, the strength of the tip portion of each tooth can be improved. Further, as shown in Figs. 5A and 5B, the circumferential portion of each cutting wheel 100U or 100L in which a plurality of cutting teeth CT are provided is slightly bent toward the opposite cutting wheel. Therefore, when the upper and the lower cutting wheels 100U, 100L are mated together in such a manner that the cutting teeth CT of each cutting wheel 100U, 100L are overlapped to each other, the cutting wheels 100U and 100L are contacted with each other only at the tip portions of the cutting teeth CT of the cutting wheels 100U and 100L. This condition is shown in Fig. 5(A). On the other hand, when the cutting wheels 100U and 100L are mutually pivoted and the cutting teeth CT of each cutting wheel 100U, 100L are arranged alternately, the tip portions of cutting teeth CT of each cutting wheel 100U, 100L are slightly engaged with each other as shown in Fig. 5 (B), so that contacting points between the side edge 11a of the tooth CT of the upper cutting wheel 100U and the side edge 11b of the tooth CT of the lower cutting wheel 100L are displaceable along the profile of each cutting tooth CE according to the rotational motion of the cutting wheels 110U and 100L. According to the structure of the cutting wheels described above, a mowing ability of the apparatus is remarkably improved. Further, it becomes possible to prevent grass to be cut from being caught between the cutting wheels. Fig. 8 shows a rotational speed reduction mechanism of this apparatus. This speed reduction mechanism comprises a clutch housing CH mounted on the front portion of the engine EN. In the clutch housing CH, there is provided a drum shaft 141 rotatably and axially supported by a bearing BE. On the rear end of the drum shaft 141, a clutch drum 142 is mounted. The inner surface of the clutch drum 142 can be abutted by a centrifugal force on the outer circumference of a centrifugal clutch 144 which is provided on the front end of a crank shaft 143 of the engine EN. On the front side of the clutch housing CH, there is fixed a flange portion of a cylindrical connection case 145 to which a rear end portion of a hollow pipe HP is coupled through a rubber vibration insulator VI. In the connection case 145, a gear shaft 147 is rotatably and axially supported by means of a bearing BE. On the front end of the gear shaft 147, a transmission shaft TS which passes through the hollow pipe HP is fixed. On the rear end of the gear shaft 147, a large spur gear 148 is integrally fixed which engages with a small spur gear 149. The small spur gear 149 is integrally fixed onto a shaft 151 rotatably and axially supported in the gear case GC. Onto the shaft 151, a large spur gear 150 is also fixed. The large spur gear 150 is engaged with a small spur gear 153 fixed onto a front end portion of the drum shaft 141. Therefore, a rotational force from the engine EN is reducingly transmitted to the transmission shaft TS through the clutch drum 142, drum shaft 141, the small spur gear 153, the large spur gear 150, the shaft 151, the small spur gear 149 and the large spur gear 158 sequentially. According to this embodiment, in order to facilitate the operation of the apparatus by reducing the weight of the head portion thereof where the crank lever mechanism and the cutting blade or the like are provided as much as possible, the rotational speed reduction mechanism is displaced from the head portion of the apparatus to the portion near to the engine, that is near at hand of the operator. Fig. 9 shows a second embodiment of the present invention. In this embodiment, a rotational force from a power source is directly transmitted to the crank shaft 104 without bevel gears. Excepting this structure, this embodiment has the same structure as that of the first embodiment. The mowing apparatus of this embodiment can be used in mowers having a bent hollow pipe through which a flexible cable is rotatably passed. Further, this device can also be used as an attachment of an industrial machine, in which a rotational force is supplied from the upper side of the apparatus to the crank shaft 104. Figs. 10 and 11 show a third embodiment of the mowing apparatus of the present invention. In this embodiment, a crank lever mechanism comprising crank arms 160U and 160L are provided instead of the two circular eccentric cam plates 106U and 106L as described hereinabove. Namely, on the crank shaft 104, the crank arms 160U and 160L are integrally formed. On the crank arm 160U and 160L, crank pins 161U and 161L are eccentrically mounted, respectively, to which connecting rods 107U and 107L are pivotably coupled. The connecting rods 107U, 107L are pivotally coupled with upper and lower arms 111U, 111L, respectively, through pins 112U, 112L. The upper and lower arms 111U, 111L are coupled to the pivotal cutter wheel shaft 110 and the cylindrical member 120, respectively, by means of splines. Therefore, in accordance with the rotation of the crank shaft 104, the upper and lower arms 111U and 111L are mutually pivoted toward the different directions, respectively, through the crank lever mechanism, whereby the cutting wheels 100U and 100L are reciprocatingly pivoted toward the different directions, respectively. Figs. 12(A) and (B) show a fourth embodiment of the mowing machine according to the present invention. In the prior-art mowing machine, the hollow pipe HP connected between the engine EN and the bearing casing BC is formed straight. Therefore, the machine is convenient for mowing grass on the ground, but inconvenient in trimming the upper surface of garden trees or a hedge, for instance. To overcome this problem, the hollow pipe HP is bent at an angle near the bearing casing BC as shown in Fig.12(A). In this case, the transmission shaft is either flexible or includes a flexible portion FS as shown in Fig. 12(A). In use, where the machine is used to mow grass on the ground, a screw 200 shown in Fig.12(A) is loosened, and the hollow pipe HP is fixed relative to the cutting wheels at such a position as shown in Fig.12(A). In contrast with this, where the machine is used to trim a garden tree, the screw 200 is loosened, and the hollow pipe HP is fixed as shown in Fig. 12(B). Furthermore, in the above embodiments, the bearing casing BC is connected to the engine EN via the hollow pipe HP. Without being limited thereto, however, it is also possible to directly connect the engine to the bearing casing (without use of the pipe) to minimize the shape of the machine so that the machine is usable for trimming a low garden tree or lawn. In the above embodiments, it is possible to drive the cutting wheels by an electrical motor or a hydraulic motor in stead of an engine.

Claims: A mowing apparatus comprising: a pair of first and second cutting wheels (100) at least one of which being pivotable about its middle axis, said cutting wheels (100) being slidably superposed one on the other and each including a plurality of cutting teeth (CT) along its circumference, each tooth (CT) having a surface facing corresponding surfaces on the other wheel (100), two side edges (11) and an outer periphery edge (12), wherein the side edges (11) of each tooth (CT) of the cutting wheels (100) forms a profile respectively defined by an inclined surface forming an acute angle relative to the facing surface of the tooth (CT) so as to form a cutting edge; and means for reciprocatingly driving said pivotable cutting wheel(s) (100) relative to the other through a predetermined angle, characterized in that the outer peripheral edge (12) of each tooth (CT) is defined by a plane substantially perpendicular to the facing surface of the tooth (CT); and the cutting teeth (CT) of each of the cutting wheels (100) are slightly bent toward the opposite cutting wheel (100) in such a manner that only the tip portions of said cutting teeth (CT) of each cutting wheel (100) elastically contact with each other in a state in which the cutting wheels (100) are correctly superposed with teeth directly opposed, and that the base portions of the cutting teeth (CT) are in engagement with each other when said (one) cutting wheel(s) is/are pivoted into a state in which the cutting teeth (CT) of the two wheels (100) are arranged alternately, such that the connecting portions between the cutting teeth (CT) of the first and second cutting wheels (100) are displaced along the profile of each cutting edge (11) according to the pivotal motion of said (one) cutting wheel(s) (100). The mowing apparatus of claim 1, characterized in that both of the cutting wheels (100) are pivotable in opposite directions. The mowing apparatus of claim 1 or 2, characterized in that each tooth (CT) has a substantially trapezoidal shape having a short parallel side corresponding to the outer periphery of the tooth (CT) and oblique sides corresponding to the side edges of the tooth (CT).

Inventors: TERAI, AKIO, WADA, MINORU
Applicants: KOMATSU ZENOAH CO.
Application year: 1989
Main classification: A01D34
IPC codes: A01G3, A01D34