Walk-behind lawn mower

Abstract: Self-propelled walk-behind lawn mower (21) having a rear discharge chute (83). The rear wheels (28, 29) of the lawn mower are driven by the engine (32) through an axle (45) which is fixed relative to the outer housing (22) and which extends below the discharge chute so as to not interfere with the flow of grass clippings from the discharge chute. A transmission (44) is provided for driving the rear wheels and is offset to one side of the discharge chute so as to be clear of the path of discharged grass. All four wheels (26, 27, 28, 29) of the mower are simultaneously adjustable and the driven rear wheels are adjustable by pivotal movement of a driving transmission (44) that interconnects the wheels with the driven axle. In addition, a combing arrangement (91) is provided on the outer housing for combing grass upwardly before it reaches the cutting blade (31).

Description: The present invention relates to a lawnmower as indicated in the preamble of claim 1. A common type of lawn mower is the so-called "rotary type". With this type of mower, the cutting blade rotates about a vertically disposed his and is contained within a scroll-shaped outer housing that has an opening which forms a discharge chute through which the cut grass is discharged. This type of lawn mower may be either side or rear discharge type. A disadvantage with the side discharge type is that the catcher bag, which is attached to the side of the lawn mower, obstructs the ability of the mower to be placed close to objects such as trees, curbing or the like and thus substantially diminishes the utility of the mower. Although a rear discharge type of mower overcomes these difficulties, there are certain other problems with the design of rear discharge rotary mowers. One of these has to do with the driving arrangement for the rear wheels, if the mower is of the self-propelled type. If both rear wheels are driven, the shaft for the rear wheels is positioned at a height such that it is in proximity to and extends across the discharge chute opening of the mower. As such, the flow of grass discharge is obstructed and, furthermore, grass may accumulate either on the axle shaft or on its outer housing to further clog the discharge opening. Furthermore, this location for the axle shaft tends to cause the grass clippings to impinge upon and become clogged in the drive arrangement for the axle. In connection with rotary type lawn mowers, they are normally provided with four independently adjustable wheels. Adjustment of the wheels relative to the mower housing accomplishes the cutting height adjustment. Although arrangements have been incorporated wherein more than one wheel may be adjusted simultaneously, when the mower is of the type having powered wheels, the manner of adjustment becomes very complicated. This is particularly true when pairs of wheels are coupled together through a driven axle and those wheels must have their height adjusted. The problem becomes even more acute when the adjustment is achieved in combination with the rear driven wheels of a rear discharge rotary motor. One of the disadvantages of certain types of rotary mowers is that they do not provide a uniform cut of the grass. The reason for this is that the motion of the blade is utilized to attempt to cause the grass to maintain an erect position so that it will be cut uniformly. However, with certain types of grasses or certain conditions, this construction, per se, is not sufficient so as to cause all or the grass to be held erect when being cut. A lawnmower of the type as indicated above is known from DE-A-36 27 208. However, this known lawnmower is unsatisfactory regarding the adjusting mechanism for adjusting the position of the wheels for changing the cutting height of the mower. Accordingly, it is an objective of the present invention, to provide an improved lawnmower of the above mentioned type having an improved adjusting arrangement for adjusting the height of the wheels relative to the housing of the mower. According to the present invention, said objective is performed in that said lever comprises a first forward link and a second rearward link which are with their one ends pivotally connected with said one bellcrank and the second auxiliary transmission means, respectively, and with their other ends pivotally connected with a first arm of another bellcrank which is in turn pivotally supported on the housing between the stub axles of the wheels disposed at the same side of the housing, while a second arm of said other bellcrank which is longer than the first arm thereof, is provided with a handle for adjusting said other bellcrank and operating a locking mechanism for locking said other bellcrank in an adjusted position corresponding to a desired position of the wheels. Accordingly, the danger of fouling of the locking mechanism is reduced. Moreover, the provision of a second bell crank has the advantage that a lever arm can be used, thereby reducing the force necessary for lifting operation. Preferred embodiments of the present invention are laid down in dependent claims. Hereinafter, the present invention will be illustrated and explained in greater detail by means of a preferred embodiment in conjunction with accompanying drawings, wherein: Figure 1 is a side elevational view of a rotary walk-behind self-propelled lawn mower constructed in accordance with an embodiment of the invention. Figure 2 is a top plan view of the lawn mower. Figure 3 is a rear elevational view of the lawn mower. Figure 4 is an enlarged sectional view taken along the line 4-4 of Figure 1 and shows the arrangement for driving the rear wheels. Figure 5 is a cross-sectional view taken along the line 5-5 of Figure 4. Figure 6 is a cross-sectional view taken along the line 6-6 of Figure 2. Figure 7 is a partial cross-sectional view taken along the line 7-7 of Figure 3. Figure 8 is an enlarged top plan view showing the front portion of the mower housing. Figure 9 is a cross-sectional view taken along the line 9-9 of Figure 8. Figure 10 is a cross-sectional view taken along the line 10-10 of Figure 8. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION Referring first generally to Figures 1 through 3, a walk-behind self-propelled rotary lawn mower constructed in accordance with an embodiment of the invention is identified generally by the reference numeral 21. The law mower 21 includes a main body portion, indicated generally by the reference numeral 22 and which maybe formed from a suitable material such as cast aluminum or the like. The main body portion is comprised generally of a forwardly extending inlet part 23, a main part defining a scroll casing 24 and a discharge or trailing portion 25. The parts 23, 24 and 25 are integrally connected to each other. The main body portion 22 is suported for movement along the ground by means of a pair of front wheels 26 and 27. The wheels 26 and 27 are supported on the housing 22 in a manner so as to permit adjustment of the rotational axis of the wheels 26 and 27 relative to the housing 22 for cutting height adjustment. In a similar manner, a pair of rear wheels 28 and 29 are carried by the housing part 25 and are adjustable vertically relative to the main body portion 22 so as to permit cutting height adjustment. As will become apparent, the adjusting mechanisms for the wheels 26, 27, 28 and 29 are interconnected so that the height adjustment of all four corners of the outer housing portion 22 will be achieved simultaneously. This insures against accurate adjustment of all wheels and simplifies the operation. A cutting blade 31 is contained within the scroll part 24 of the main body portion 22 and is rotatable about a vertically extending axis. The manner in which the cutting blade 31 is journaled forms no part of the invention, and for that reason, has not been illustrated in detail. An internal combustion engine, indicated generally by the reference numeral 32 and which may be of any known type is provided for driving the blade 31. To that end, the engine 32 is of the type having its output shaft rotating about a vertically extending axis and the crankshaft or output shaft may be directly connected to the blade 31 for rotation of the blade 31 at the same speed as the engine output shaft. Although the specific form of the engine 32 forms no part of this invention, it should be noted that the engine 32 is provided with an outer protective cowling 33 which cooperates with its air-cooling system. In addition, the engine 32 has a crankcase with a lubricating system which may be filled through a fill opening 34. Furthermore, a fuel tank 35 is positioned rearwardly of the engine and may be directly carried by it. A handle 36 of any known type is affixed to the main body portion 22 in a suitable manner and one which may allow adjustment and/or folding of the handle for storage or convenience. A starter rope 37 for the engine 32 extends rearwardly and is supported at the operator end of the handle 36 in a known manner so that the operator can start the motor 32 from his standing position behind the mower. As has been noted, the mower 21 is of the self-propelled type. To this end, the engine 32 is provided with an auxiliary output shaft 38 which may be driven either directly from the engine output shaft or may be driven from an engine accessory shaft such as the camshaft. In the illustrated embodiment, the auxiliary output shaft 38 rotates about a generally horizontally extending axis. The auxiliary output shaft 38 is coupled by means of a first universal joint 39 to one end of a driveshaft 41. The drive shaft 41 extends rearwardly and downwardly and is coupled at its trailing end to the input end of a second universal joint 42. The output of the second universal joint 42 drives an input shaft 43 of a step-down transmission, indicated generally by the reference numeral 44. The step-down transmission 44 (Figure 4) may be of any known type and drives a rear axle 45 at a reduced speed ratio from the speed of the driveshaft 38. The axle 45 extends transversely across the rear end of the main body portion 22 and is positioned below the discharge chute, as will be described. The rear axle 45 is journaled for rotation about a fixed rotational axis relative to the main body portion 22 by a construction as best understood by reference to Figures 4 and 5. It should be noted from Figure 4 that the transmission 44 is offset to one side of the mower 21, for a reason to be described. This offset places the transmission 44 adjacent the rear wheel 28. There is a tubular shaft 46 that extends between the transmission 44 and toward the rear wheel 28 that carries an outboard bearing 47 so as to journal the adjacent portion of the axle shaft 45 relative to the tube 46. There is a similar longer tube 48 that extends between the opposite side of the transmission 44 and which terminates adjacent the outer remaining rear wheel 29. The outer end of the tube 48 carries a similar bearing for supporting the other end of the rear axle 45. The tubes 46 and 48 are coupled together by means of a bracket assembly 49 for a reason to be described. The tubes 46 and 48 are respectively supported by means of anti-friction bearings 51 carried in brackets 52 that are affixed to the main body portion 22 for rotation of the tubes 46 and 48 about an axis that is coincident with the rotational axis of the rear axle 45. The rear wheels 28 and 29 are each driven from the respective ends of the rear axle 45 by means of auxiliary transmissions, indicated generally by the reference numeral 53 and having a construction as best shown in Figure 4. Each of these auxiliary transmission 53 comprises a transmission casing 54 which may be formed from sheet metal and which is affixed to the respective end of the tubular number 46 or 48. Contained within the auxiliary transmission casing 54 is a sprocket 55 that is affixed to the respective end of the rear axle 45. A chain 56 is trained around the sprocket 55 and a further sprocket 57 that is connected by means of a one-way clutch 58 to a hub 59 of the respective rear wheel 28 or 29 for driving it. The rear wheel hubs 59 are journaled upon a stub axle shaft 61 that is affixed in any suitable manner to the auxiliary transmission casing 54. The use of the auxiliary transmissions 53 for driving the rear wheels 28 and 29 permits the rear axle 45 to be lowered relative to the rotational axis of the rear wheels 28 and 29 and also permits pivotal adjustment of the auxiliary transmissions 53 relative to the rear axle 45 for height adjustment. It should be readily apparent that rotation of the auxiliary transmission assemblies 53 relative to the axis of rotation of the rear axle 45 will cause the stub axle 61 to move through an arc relative to the main body portion 22 so as to permit height adjustment. Also, the auxiliary transmissions 53 are interconnected with each other for simultaneous rotation due to the fact that they are affixed to the tubes 46 and 48 respectively and these tubes are rigidly interconnected for simultaneous rotation by means of the brackets 49. Referring now primarily to Figures 1 and 2, the front part 23 of the main body portion 22 is formed with an upwardly opening recess 62 in which a front axle 63 is positioned. The front axle 63 is journaled at opposite ends relative to the body part 23 by means of supporting brackets 64 which are affixed to the body part 23 in a known manner. Respective bellcranks 65 are affixed to the ends of the front axle 63 and have first arms 66 that carry stub axles 67 which journal the respective front wheels 26 and 27 in a suitable manner. The bellcrank 65 at one side of the mower 21 has a further arm 68 that is pivotally connected to one end of a link 69. The link 69 extends rearwardly and is connected at its rearward end by a pivot pin 71 to a rear link 72. The pivot pin 71 is connected to one arm of a bellcrank 73 that is pivotally supported on the main body portion by a pivot pin 75. The rear end of the link 72 is connected by means of a pivot pin 76 to a lever arm 77 that is rigidly connected to the relative auxiliary transmission casing 54. Hence, the linkage system comprised of the links 69 and 72 will transmit motion from the front bellcrank 65 to the rear transmission casing 54 and vice versa so that the wheels at one side of the mower will be operated simultaneously. In addition, the fact that the front bellcranks are rigidly connected to the axle 63 and the transmission casings 54 are rigidly connected to each other by the axle tubes 46, 48 and brackets 49 insures that the wheels at the other side of the mower 21 will be adjusted simultaneously with those connected by the lines 69 and 72. The bellcrank 73 cooperates with a locking mechanism as shown in Figure 1 for retaining the wheels 26, 27, 28 and 29 in an adjusted position. This locking mechanism includes a slidable sleeve 78 that is suported on the other bellcrank arm and which carries a locking pin 79. The locking pin 79 is adapted to be received in selected notch 81 of a bracket 82 that is affixed to the main body portion 22. The sleeve 78 is urged by a coil spring (not shown) so that the locking pin 79 moves into engagement with a respective one of the notches 81. If an operator desires to achieve height adjustment, the sliding handle 78 is moved so that the pin 79 is free of the notches 81 and the bellcrank 73 is then rotated. Figure 1 shows the mower 21 at maximum cutting height. If the cutting height is to be lowered, the bellcrank 73 is pivoted in a counterclockwise direction which effects counterclockwise rotation of the front bellcranks 56 and the rear auxiliary transmissions 53 so as to lower the respective stub axles 61 and 67. As a result, the cutting height will be lowered. The mechanism can be re-locked in the set adjusted position by releasing the sliding handle 78 whereupon the locking pin 79 will re-enter the appropriate locking notch 81. Referring now primarily to Figures 2 through 4, 6 and 7, the grass discharge chute construction will be described. As has been previously noted, the main body portion 22 has a scroll part 24 in which the cutter blade 31 rotates. The scroll part 24 is configured so as to form a rearwardly opening grass discharge chute 83. As may be seen best in Figure 7, the discharge chute 83 opens into a transversely extending wall 84 of the main body portion 22. The wall 84 is disposed forwardly of a rear wall 85 of the housing assembly with the walls 84 and 85 being connected by a longitudinally extending wall 86. It should be noted that the longitudinally extending wall 86 lies to one side of the main transmission 44 and is spaced outwardly relative to the opening of the discharge chute 83 so that grass clippings that are thrown rearwardly will follow the path indicated by the broken lines 87 and will not impinge upon either the wall 86 or the transmission 84. As a result, clogging of the discharge chute will be avoided and the transmission will not become clogged with the grass clippings since it is protected from them both by the outer casing of the transmission 44 and by the walls 84 and 86 as well as their relationship to the discharge chute 83 and the path of grass discharge. The discharge chute is also defined at its lower end by a plate 90 that extends upwardly so that the cut grass will be directed upwardly over the tube 49. A catcher bag 88 may be mounted on the rear of the main body portion 22 in an appropriate manner so as to receive the grass clippings thrown from the discharge chute 83. Conventionally, rotary mowers employ the forces generated by the cutting blade as a device for causing the grass to move to an erect position so it will be uniformly cut. However, various conditions can prevent the mere suction of the blade from achieving its intended purpose. Therefore the forward or inlet part 23 of the main housing portion 22 is configured as shown in Figures 8 through 10 so as to achieve a combing or raking function on the grass that will tend to cause it to move to an erect position and to insure that the suction of the blades can lift the grass into an erect position for cutting. As may be best seen in Figure 8 through 10, the inlet part 23 has a generally boxed shape that is defined at its rear end by a depending wall 89 of the scroll portion 24. This depending wall has a serrated lower edge 91 that will act at as a comb or rake so as to remove foreign particles from the grass and also to comb or rake the grass upwardly so as to facilitate cutting. It has been found that this construction will give a much more satisfactory and uniform cut heighth. It should be readily apparent from the foregoing description that the described mower is extremely effective in providing a good grass cut, ease of adjustment and operates in such a way that the discharge chute, even though rearwardly facing is not obstructed by the rear axle of the mower regardless of the height. Although an embodiment of the invention has been illustrated and described, various changes and modifications may be made without departing from the scope of the invention, as defined by the appended claims.

Claims: A rotary walk-behind lawn mower having an outer housing (24), a rotating cutting blade (31) contained within said outer housing (24), and rotatable about a generally vertically extending axis, a power unit (32) carried by said outer housing (24) for driving said cutting blade (31), said outer housing (24) defining a discharge chute (83) through which grass cut by said cutting blade (31) is discharged, a plurality of wheels (26-29) journaled relative to said outer housing (24) by a front axle (63) for rotatably coupling two of said wheels (26,27) and a rear axle (45) for rotatably coupling a further two of said wheels (28,29), means (38,39,41-44) for driving said rear axle (45) from said engine (32), first and second auxiliary transmission means (53) for driving said further two wheels (28,29) from respective ends of said rear axle (45), said first and second auxiliary transmission means (53) being pivotal about said rear axle (45) for adjusting the height said outer housing (24) relative to said further two wheels (28,29), wherein two bellcranks (65) are affixed to both ends of the front axle (63), said bellcranks (65) having first arms (66) that carry stub axles (67) which journal the front wheels (26,27), one of said bellcranks (65) having another arm (68) that is pivotally connected to a lever extending rearwardly to couple the height adjusting movement of rear and front wheels, characterised in that said lever comprises a first forward link (69) and a second rearward link (72) which are with their one ends pivotally connected with said one bellcrank (65) and the second auxiliary transmission means (53), respectively, and with their other ends pivotally connected with a first arm of another bellcrank (73) which is in turn pivotally supported on the housing (24) between the stub axles (61, 67) of the wheels disposed at the same side of the housing (24), while a second arm of said other bellcrank (73) which is longer than the first arm thereof, is provided with a handle (78) for adjusting said other bellcrank (73) and operating a locking mechanism (79, 81, 82) for locking said other bellcrank (73) in an adjusted position corresponding to a desired position of the wheels (26 to 29). A rotary walk-behind lawn mower as claimed in claim 1, characterised in that the diameter of the rear wheels (28,29) is larger than the diameter of the front wheels (26,27), and that the pivot axis (45) of the auxiliary transmission means (53) is disposed rearward and beneath with respect to the axes of rotation of said rear wheels (28,29). A rotary walk-behind lawn mower as claimed in claims 1 or 2, characterised in that , said rear axle (45) being journaled by said outer housing (24) and extending across and beneath said discharge chute (83). A rotary walk-behind lawn mower as claimed in at least one of claims 1 to 3, characterised in that , the first and second transmission means rotatably coupling the respective wheels (28,29) to the rear axle (45) are chain-drive transmissions (53) contained within a respective housing (54) journaling the associated wheels (28,29), and said housing (54) is pivotal about the rear axle (45). A rotary walk-behind lawn mower as claimed in at least one of the preceding claims 1 to 4, characterised in that , the rear axle (45) is driven from the engine (32) through a step-down transmission (44), that rotatably supported tube portions (46,48) extend substantially between the step-down transmission (44) and the opposite housing (54) of chain-drive transmissions (53), and that said tube portions (46,48) surrounding the corresponding portions of the rear axle (45) are interconnected with each other for joint rotation. A rotary walk-behind lawn mower as claimed in at least one of the preceding claims 1 to 5, characterised by means (46,48,49) for interconnecting the chain-drive transmission housings (54) for simultaneously pivotal movement. A rotary walk-behind lawn mower as claimed in at least one of the preceding claims 1 to 6, characterised in that , the discharge chute (83) opens rearwardly and is defined by a wall of the outer housing (24), and that the step-down transmission (44) for driving said rear axle (45) from said power unit (32) is positioned on the side of a wall away from said discharge chute (83). A rotary walk-behind lawn mower as claimed in at least one of the preceding claims 1 to 7, characterised in that , the step-down transmission (44) is disposed to one side of the discharge chute (83) and is offset from the path of the discharge of grass from said discharge chute (83). A rotary walk-behind lawn mower as claimed in at least one of the preceding claims 1 to 8, characterised in that , the first and second rear wheels (28,29) are journaled by stub axles (61) fixed relative to the respective transmission housing (54). A rotary walk-behind lawn mower as claimed in at least one of the preceding claims 1 to 9, characterised in that , the discharge chute (83) extends above and to one side of the rear axle (45). A rotary walk-behind lawn mower as claimed in at least one of the preceding claims 1 to 10, characterised by , main transmission means for driving the rear axle from the power unit (32) and wherein the outer housing (24) defines a dividing wall extending between the step-down transmission (44) and said discharge chute (83). A rotary walk-behind lawn mower as claimed in at least one of the preceding claims 1 to 11, characterised in that , the outer housing (24) being formed with an inlet end (23) which leads to said cutting blade (31) and which is formed with a plurality of teeth for combing grass upwardly before reaching said cutting blade (31).

Inventors: MIKOME KIYOTAKA, MIYAZAKI MITSUO, MORISHITA MASAHIRO, MIKOME, KIYOTAKA, MIYAZAKI, MITSUO, MORISHITA, MASAHIRO
Applicants: YAMAHA MOTOR CO LTD, YAMAHA MOTOR CO., LTD.
Application year: 1988
Main classification: A01D34
IPC codes: A01D34