MOWING MACHINE

Abstract: To mow even soft grass more tidily in shearing mode without kicking pebbles, a pair of two grass cutting wheels (100L, 100U) are pivotally driven by an engine in two mutually-­ different directions. One cutting wheel is slidably fixed relative to the other cutting wheel for safety. The mowing machine can be used in common to shear off grass on the ground and trim a garten tree by adjusting an angle between a hollow grip pipe and the machine cutting surface.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a mowing machine driven by an engine or the like to mow grass. Description of the Prior Art In a prior-art mowing machine for mowing grass, a single rotatable cutter wheel is supported by a cutter support body and driven by an engine or a motor via a hollow pipe connected between the engine and the cutter support body. 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. In the prior-art 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. A more detailed description of this prior-art mowing machine will be made with reference to the attached drawings under DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS. A further known mowing machine (US-A-3 631 658) comprises a pair of first and second pivotal cutting wheels superposed to each other, wherein a motive power source is arranged on the upper side of the cutting wheels. A means for the conversion of a rotational motion supplied from the power source is arranged on the opposite side of the cutting wheels and provided with a protective cap. This arrangement of the rotational motion converting means leads to a complex structure and to a relatively great effort being necessary for a replacement of cutting wheels. Since the rotational motion converting means is arranged such that it faces the ground there exists an increased possibility that this means can be damaged by stones and similar obstacles lying on a ground to be mown. SUMMARY OF THE INVENTION With these problems in mind, therefore, it is the primary object of the present invention to provide a novel mowing machine which can improve the mowing performance, that is, mow even soft grass more tidily without kicking pebbles. The above-mentioned object is achieved, with a mowing machine according to the features of claim 1. The motive power source is an engine or a motor. An advantageous rotational motion converting means comprises the features of claim 3. Further, a plurality of dish-shaped plate springs are provided for slidably supporting one of the cutting wheels for safety. Furthermore, the two pivotal cutting wheels are driven by an engine through a bent hollow pipe including a universal joint, so that grass on the ground can be mowed and additional garden trees can be trimmed by adjusting the cutting angle relative to the hollow pipe (grips). BRIEF DESCRIPTION OF THE DRAWINGS The features and advantages of the mowing machine according to the present invention over the prior-art machines 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: Fig. 1 is a perspective view showing an example of prior-art mowing machines; 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 showing a first embodiment of the mowing machine according to the present invention; Fig. 4 is an enlarged bottom view showing a pair of pivotal cutting wheels and an essential portion of a drive mechanism incorporated in the mowing machine shown in Fig. 3; Fig. 5 is an enlarged cross-sectional view of the pivotal cutting wheels and the drive mechanism shown in Fig. 4; Fig. 6 is a similar cross-sectional view of the pivotal cutting wheels and the drive mechanism of a second embodiment of the mowing machine according to the present invention; Fig. 7 is a fragmentary enlarged view for assistance in explaining a lower pivotal cutting wheel; Fig. 8(A) is a cross-sectional view showing a dish-shaped plate spring for providing a frictional force between the two upper and lower pivotal cutting wheels; Fig. 8(B) is a top view showing the dish-shaped plate spring; Fig. 9(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. 9(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 To facilitate understanding of the present invention, a brief reference will be made to a prior-art mowing machine, with reference to the attached drawings. In Fig. 1(A), a rotary cutting wheel CW formed with a number of cutting edges CE at the outer periphery thereof is rotatably supported by a bearing casing BC (cutter support body) and further driven by an engine EN via 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 to the hollow pipe HP so that the worker can swing the machine to and fro by griping the hollow pipe HP by both hands. In more detail with reference to Fig. 2, a transmission shaft TS driven by the engine EN is rotatably supported by two bearings BE fixed to 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 prior-art mowing machine, however, since only the single cutting wheel CW rotates at a relatively high speed, there exist various shortcomings such that pebblestones may be kicked and soft gross cannot be well mowed even when the cutting wheel CW is moved violently to and fro. In view of the above description, reference is now made to a first embodiment of a mowing machine according to the present invention. In Fig. 3, the feature of the mowing machine according to the present invention is to drive a pair of upper and lower pivotal cutting wheels 100U and 100L by an engine EN or an electric motor MO in two mutually opposite directions (clockwise and counterclockwise) in order to mow grass between two cutting edges formed along each outer periphery of the two pivotal cutting wheels 100U and 100L. That is to say, grass can be cut off in shearing mode, 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 BE1 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. An intermediate shaft 102 is rotatably supported vertically within the bearing casing BC by two upper and lower bearings BE2 and BE3. A second bevel gear BG₂ is fixed to the intermediate shaft 102 so as to be in mesh with the first bevel gear BG₁. In addition, a small spur gear 103 is formed in the intermediate shaft 102. On the other hand, a cam shaft 104 is rotatably supported within the bearing casing BC by two upper and lower bearings BE4 and BE5. A large spur gear 105 is fixed to the cam shaft 104 at such a position as to engage with the small spur gear 103. Further, two (upper and lower) circular and eccentric cam plates 106U and 106L are fixed to the cam shaft 104 with keys. Here, it should be noted that these two circular cam plates 106U and 106L are eccentrically fixed on both the upper and lower surfaces of the large spur gear 105 in radially symmetrical positional relationship to each other with respect to the center of the cam shaft 104. Further, each of two upper and lower annular connecting rods 107U and 107L is fitted to each of the cam plates 106U and 106L, respectively via each of two upper and lower annular bearings 108U and 108L. A pivotal cutter wheel shaft 110 is also rotatably supported vertically within the bearing casing BC via bearings BE6 and BE7. An upper arm 111U is fixed to the uppermost end of the pivotal cutter wheel shaft 110, and one end of the arm 111U is pivotably connected to an end of the upper annular connecting rod 107U via a pin 112U. Further, a lower cutter wheel support plate 113L is fitted to a square portion 114 of the pivotal center wheel shaft 110 and fixed to the shaft 110 by a nut N. A lower cutting wheel 100L is fixed to the lower cutter wheel support plate 113L with bolts as shown in Fig. 5. On the other hand, a cylindrical member 120 formed with a middle arm 111L and an upper cutter wheel support plate 113U is rotatably fitted to the pivotal center wheel shaft 110. An end of the middle arm 111L is also pivotably connected to an end of the lower annular connecting rod 107L via a pin 112L. Further, an upper cutting wheel 100U is fixed to the upper cutting wheel support plate 113U with bolts as shown in Fig. 5. In operation, when the engine EN is driven, power is transmitted to the cam shaft 104 by way of the transmission shaft TS, the first bevel gear BG₁, the second bevel gear BG₂, the small spur gear 103 and the large spur gear 105, so that the cam shaft 104 rotates. Therefore, the two circular eccentric cam plates 106U and 106L fixed to the cam shaft 104 rotate, so that the two annular connecting rods 107U and 107L are driven reciprocably to and fro in Fig. 4. In this case, since the annular connecting rods 107U and 107L are located in radially symmetrical positional relationship to each other with respect to the center of the cam shaft 104, the two arms 111U and 111L connected to the two connecting rods 107U and 107L respectively are driven in two opposing directions, respectively. As a result, the two upper and lower pivotal cutter wheels 100U and 100L are driven so as to pivot in two different directions, respectively to shear off grass caught between two cutter edges CE of the upper and lower pivotal cutting wheels 100U and 100L. Therefore, it is unnecessary for the worker to chop grass by swinging the machine as in the conventional machine, because the machine according to the present invention mows grass in shear mode as by scissors. Fig. 6 shows a second embodiment of the mowing machine according to the present invention. In the first embodiment shown in Figs. 3, 4 and 5, it is necessary to provide an excessive drive power relief device somewhere for the machine in order to prevent the cutting edges CE from being damaged when a rigid material such as metal piece is caught between the cutting edges. For this purpose, a clutch (not shown) can be provided between the transmission shaft TS and the engine EN. Or else, some parts of the bevel gears, the spur gears, the cam plates, etc. can be slidably mounted on the related parts. For the purpose, in the second embodiment shown in Fig. 6, the lower pivotal cutting wheel 100L is slidably supported relative to the lower cutter wheel support plate 113L by use of a plurality of dish-shaped plate springs DS. In more detail, a lower cutter wheel support plate 113L is fitted to a square shaft portion 114 and fixed thereto by a nut. Further, a cutter wheel push plate 130 is fixed to the cutter wheel support plate 113L by screws with the lower pivotal cutting wheel 100L loosely sandwiched therebetween so as to provide a gap G (shown in Fig. 7) wide enough to allow the lower cutting wheel 100L to be rotatable. Further, a plurality of recesses 131 are formed on the upper surface of the cutter wheel push plate 130. A few dish-shaped springs DS as shown in Figs. 8(A) and (B) are inserted into each recesses 131 in superposed relationship to each other in order to provide appropriate frictional forces between the two upper and lower pivotal cutting wheels 100U and 100L (at the outer peripheries thereof) and between the lower cutter wheel support plate 113L and the lower cutting wheel 100L (at the inner periphery thereof), in dependence upon the elastic force of the springs BS. The frictional forces between the two upper and lower pivotal cutting wheels 100U and 100L are smaller than that between the lower cutter wheel support plate 113L and the lower cutting wheel 100L. Therefore, when an excessive torque or shock is applied to the lower pivotal cutting wheel 100L because of a presence of rigid substance between two cutting edges, the lower pivotal cutting wheel 100L is slidably moved against a frictional force produced by the dish-shaped springs BS relative to the cutter wheel support plate 113L in order to prevent the cutting wheels and other power transmitting parts from being damaged. Further, in the second embodiment shown in Fig. 6, since the upper and lower pivotal cutting wheels 100U and 100L are also formed into a dish shape, the outer peripheries of the two pivotal cutting wheels 100U and 100L are brought into tight contact with each other in dependence upon the elastic force of the cutting wheels themselves, thus it being possible to prevent grass from being sandwiched between cutting edges CE of the two cutting wheels 100U and 100L. Further, it is of course possible to slidably mount the upper pivotal cutting wheel 100U relative to the upper cutter wheel support plate 113U. Figs. 9(A) and (B) show a third 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. 9(A). In this case, the transmission shaft TS is connected via a universal joint UJ or coupling as shown by a circle in Fig. 9(A). In use, where the machine is used to mow grass on the ground, a screw 200 shown in Fig. 9(A) is loosened, and the hollow pipe HP is fixed relative to the cutting wheels at such a position as shown in Fig. 9(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. 9(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. Further, it is of course possible to drive the cutting wheels by a motor in stead of an engine. As described above, in the mowing machine according to the present invention, since the two cutting wheels are pivotably driven by an engine in two opposite rotational directions (clockwise and counterclockwise) at a relatively low speed to cut off grass in shear mode, there exist various advantages as follows: (a) Since the cutting wheels are not driven at a high speed, there exists no danger such that pebblestones are kicked off; (2) Since grass is cut off between two cutter edges in shear mode, even soft grass can easily be sheared off without leaving grass unmowed; (3) Since cutting edges are arranged in every direction, the worker can shear off grass in various directions by simply moving only the cutting wheels straight in any desired directions; (4) Since dish-shaped springs are provided so as to slidably rotate one of the two pivotal cutting wheels relative to its drive in case an excessive force is applied to the wheels, it is possible to prevent the cutting edges from being damaged; (5) Since the two pivotal cutting wheels are formed into a dish shape, it is possible to prevent grass from being sandwiched between two cutting wheels; (6) Since the hollow pipe is bent slightly via a universal joint near the bearing casing, it is possible to use the mowing machine both in mowing grass on the ground and trimming a garden tree.

Claims: A mowing machine comprising: (a) a motive power source (EN, MO) (b) a pair of first and second pivotal cutting wheels (100L, 100U) superposed with each other, each of the wheels (100L, 100U) having a number of grass cutting edges (CE) and a central portion, and the superposed cutting wheels (100L, 100U) having two opposing sides; and (c) means for converting rotational motion supplied from said motive power source (EN, MO) into two pivotal motions to oscillate respectively the first and second pivotal cutting wheels (100L, 100U) in two mutually different rotational directions through a predetermined angle, characterized in that the rotational motion converting means comprises: a cam shaft (104) rotatably driven by the motive power source (EN, MO); a first shaft (110) coupled to the central portion of the first wheel (100L); a second shaft (120) coupled to the central portion of the second wheel (100U) and having a cylindrical shape into which the first shaft (110) is rotatably and coaxially inserted; and a crank mechanism (106U, 107U, 112U, 111U, 106L, 107L, 112L, 111L) provided between the cam shaft (104) and the first and second shafts (110, 120) for converting the rotational motion in the cam shaft (104) into two oppositely and reciprocatingly rotating motions in the first and second shafts (110, 120) to oscillate the first and second wheels (110L, 100U) relative to each other about an axis of the shafts (110, 120) through the predetermined angle, wherein the motive power source (EN, MO) and the rotational motion converting means are mounted on the mowing machine on one of the two opposite sides of the cutting wheels (100L, 100U). The mowing machine as set forth in claim 1, wherein the mowing machine comprises a casing (BC) in which the rotational motion converting means is incorporated. The mowing machine as set forth in claims 1 or 2, wherein the crank mechanism comprises: first and second circular and eccentric cams (106U, 106L) each fixed to the cam shaft (104) in radially symmetrical positional relationship with respect to a center of the cam shaft (104); first and second annular connecting rods (107U, 107L), each slidably fitted to each outer periphery of the first and second circular and eccentric cams (106U, 106L), respectively; and first and second arms (111U, 111L) each pivotally connected to at one end thereof an end of the first connecting rod (107U) and an end of the second connecting rod (107L), respectively, and the first and second arms (111U, 111L) being connected to at the other ends thereof each of the first and second shafts (110, 120), respectively. The mowing machine as set forth in claims 1 to 3, further comprising means for interrupting the reciprocating rotational motion of the cutting wheels when an object is caught between the cutting edges (CE) of the first and second cutting wheels (100L, 100U). The mowing machine as set forth in claim 4, wherein the interrupting means comprises means for supporting one of the cutting wheels (100L) elastically to the other cutting wheel. The mowing machine as set forth in claim 5, wherein the supporting means comprises at least one dish-shaped plate spring (DS). The mowing machine as set forth in claims 1 to 6, which further comprises: a transmission shaft (TS) for transmitting power of said motive power source (EN, MO); a first bevel gear (BG1) fixed to one end of said transmission shaft (TS) remote from the other end connected to said motive power source (EN, MO); an intermediate shaft (102) rotatably supported within said casing (BC); a second bevel gear (BG2) fixed to said intermediate shaft (102) so as to be in mesh with said first bevel gear (BG1); a small spur gear (103) fixed to said intermediate shaft (102); and a large spur gear (105) fixed to said cam shaft (104) so as to be in mesh with said small spur gear (103). The mowing machine as set forth in claims 1 to 7, further comprising means for selectively changing the position of the cutting wheels (100L, 100U) relative to the power source (EG, MO). The mowing machine as set forth in claim 8, wherein the position changing means comprises means for bending the transmission shaft (TS) so that it enters into the casing along a line substantially parallel to the plane of the cutting wheels (100L, 100U). The mowing machine as set forth in claim 9, wherein the transmission shaft bending means comprises a universal joint (UJ). The mowing machine as set forth in claims 1 to 10, wherein said motive power source is an engine (EN) or an electric motor (MO).

Inventors: SATSUMI, SHINROKU, TANIGUCHI, MITSURU, TERAI, AKIO, YOSHINO, JUNICHI
Applicants: KOMATSU ZENOAH CO.
Application year: 1987
Main classification: A01D34
IPC codes: A01D34