US2181781A - Lawn mower - Google Patents

Description

Nv. 28, 1939. K. A. cAsPERssoN 1 LAWN MowER Filed July l, 1938 2 Sheets-Sheet l Patented Nov. 28, 1939 UNITED ES LAWN MOWER IApplication July 1, 1938, Serial --N0. 217,033 In Sweden December 8, 1936 My invention relatesi to lawn-mowers oi the class in which movable knives-are arrangedv to circle in relation to the stationary knife for cooperation therewith.

The main-object-of the invention'is vto improve mowers of the type referred to and to remove certain drawbacks of mowers heretofore used, In conventional-'mowers of said typeY the circling knivesare iixedto they rotary element or elements Vby which-they are carried. In crosssection: the plane sides-of the knives coincide or A approximately coincide -withthe rotation surface along which the knivesmove during their circling motion When a knife xed as referred to descends from a point on a level with the centre towards-the stationary knife the plane of the knife is successively changed from a substantially verticalposition to -a substantially horizontal position. As ay result the-knifehits the grass by its outer face due to this change of position whereby the grass is deflected forwardly and escapes cutting or takes a position which is disadvantageous for the-cutting operation. Due to the improvement eifected by my present invention this draw-back is removed.

A further object ofl my invention is to provide for a certain movement of the movable knives, in addition to the circling movement thereof in order to obtain a more efficient cutting operation than in conventional mowers.

The invention provides a mower of a construction in which the stationary knife or cutter-bar is combinedwith movable knives for cooperation therewith, and includes means to impart circling motion to themovable knives,.and` guide means to cause said movablevknives'to; rotateabout their longitudinal axis .simultaneously withtheir circling motion.

Theinvention further consists. in the particular construction, arrangementof parts, and cornbinations thereof hereinafter described and claimed.

An embodiment offthe invention is shown by 45 way of example in the accompanying drawings in which y Figures .1, 2, 3 land 4 illustrate the means effecting the knife movement and itsvoperation diagrammatically; Figs. land 2fare-.cross-sec- 50 tional views, and Fig. Slis a partfsectional view;

Fig. 4 is a Adetail view.

Fig. 5 is -an elevation off-a lawn-mower constructed Aaccording to the invention.

Fig. 6 is apart, crossfseQtonalvie-w ofthe ma- 55 chine illustratedin Fig. 5.

Fig. 7 is a part-sectional view ofthe machine as seen from the rear.

Fig. 8 is a horizontal sectional yView offene lateral portion of the. machine.

Fig. 9 shows a knife in elevation. 5

Fig. l0 is a part-sectional view of aA modified form of guide means for theiknives.

In the diagrammaticfFiguresl1A, the numeral I designates the shaft about which the knivesk 2 circle. Preferably, each knife has. its bar-shaped 10- rear edge portion 3 journalled rotatably relatively to two .armsll and-5 secured to the shaftfl and spacedapart a quarter of Va revolutionrelatively to each other. The knife2-will thus have a longitudinal inclined positionwhich -isrequired 15 for' the cutting operation. kFixed cna tr-unnion ii extending from the end of the'knifethrough the arm 4 is a bell-crank lever 'l and journalled thereon is a roller 8 which is .adapted to move in a circular groove 9 in astationary. element It. 20 Thegroovei is eccentric. relative tothe shaft I, the eccentricity being` equal to the radius. of.` the bell-crank lever I. The last-mentionedarrangement provides for the .guidance of the knives referred to, aswill be .described hereinafter. .2.5

The position of the arm 4 marked by a in Fig. l, and. thebell-cranklever 'Ltur-ntheknife 2 to a position most suitable for thecutting operation. 4When the arm 4 moves'from. the position a, to the position b` in a direction .as shown bythe 30 arrow I I, theroller moves in thegroove 9 and as aresult thebell-crank leverrl and the knife .secured thereto are forced to rotate in relation to the arm 4. Since the radius of the bell-crank lever and the eccentricity between the .shaft I 3 5 and the .groove 9 are equal, the bell-crank lever and the knife maintain the angular position relatively to the horizontal line shownin .theposition a of thearm 4. In the angular position c of the Aarm i the knife'. maintains the-same po- 40 sition and .eifectsthe cutting operation by engagement with the stationary knife .I2 in such position. In the position d of the arm. 4 and in the position-.e the knife still maintains zthesame angular position. rIhe plane of the.-knifethus 45 maintains the position suitable for the cutting operation during the Whole revolution. 'The knivesfthus maintain a constant angularpositionrelatively to the horizontal line and have their cutting l-edges directed rdownward or inclined downward. The ,knives Aareadvanced between the grass-stalkswiththeir edgesforemost andvhave no tendency of unduly v cleflecting the grass, and no diiiioulty. is experienced in Cutting relativelyhighgrass. After Qlliing '1.21.16 zkrlYeS 55 ascend, maintaining the position referred to they will act as shovels on the grass which has been cut and throw it rearwardly for collection in a magazine or basket arranged in the mower in a conventional manner. Consequently, the usual disadvantage that the grass which has been cut is carried along by the knives is prevented.

The oblique position of the knife shown in Fig. 3 is necessary as already stated above to obtain a good shearing action against the stationary knife I2. place in such a manner that the circling knife initially hits the stationary knife at one end thereof, and the point ofcontact between thev knives then moves therealong successively during the movement. This and the fact that the knives 2 maintain their angular position during the circling movement require an arc-shaped form of the knife edges, as shown in Fig. 3.

A particular advantage of the described ar-` rangement of the movable knives relatively to the stationary knives is that during the cutting operation the movable knife in its cooperation with the stationaryknife, in addition to the shearing action which is present for example in usual scissors, performs such a cutting action which occurs for example in using a carving knife because the `edge of the movable knife moves longitudinally relatively to the stationary knife to a certain degree during each revolutio-n. This feature will be clear on considering the movement of a point of the movable knife edge during one revolution, as for instance the point a: in Fig. 3. After the knife has rotated one half revolution from the position shown in full lines to the position shown in dotted lines in Fig. 3, the point .r has rotated to a position marked and simultaneously has moved laterally a distance y. This lateral or axial movement of the knife edge relatively to the main shaftl I is directed toward the point of intersection between the edges of the stationary knife and themovable knife when said knives are cooperating, and as a result the movable knife tends to catch the grass between the knives and pull it into the angle therebetween. The relative movement of the knives as described is favourable to the cutting operation.

The mower constructed for use as shown in Figs. 5-9 corresponds in all essentials to the diagrammatic Figures 1 4, Fig. 5 illustrating an assembly of the mower construction on a reduced scale. Consequently, I designates the' shaft about which the knives 2 circle. The arms l5 and 5 carrying the knives are shown in Figs. 7 and 8. The bell-cranks connected to the arms d and rotatable in relation thereto are designated by 'I and the rollers by 8. The guide groove 9 for the rollers is formed in the stationary frame I0 of the mower. The stationary knife I2 is clamped on an adjustable element in a conventional manner. The shaft I is carried by ball bearings IB in the frame Ill as shown in Fig. 8. One of the ground Wheels II of the mower has formed thereon an internal gear I8 which meshes with a pinion I9 keyed to the shaft I. A ground roll 2D of conventional type supports the rear portion of the mower. In order to permit the rear edge portion 3 of each knife 2 to be pivoted in the arms 4 and 5 each knife has, at one end thereof, a trunnion 6 extending through the arm 4, and at the opposite end a tapering hole 2| engaged by the end of an adjustable set screw 22 as shown in Fig. 7. 'Ihis screw permits theknife to be easily removed and mounted in place and also to The cutting operation in fact takesl I set it in a position so as to prevent any undue slack and clearance during the rotation.

A construction of the groove 9 to fit exactly to the rollers 8 would cause considerable friction when the rollers move in the groove. Such friction may be avoided by constructing the guide means as in the modiiication shown in Figure l0. Ihe single roller is replaced in this construction by two rollers 8a and 3b one engaging the outer wall 9a of the groove 9, and the other engaging the inner wall 9b thereof. It will be noted that the walls 9a and 9b forming races for the rollers 8a and 8b converge outwardly, and that the diameter of the one roller, 8b, is larger than that of the other roller, 8a. The construction permits the rollers to be set in correct position for rolling against the walls of the groove by axial displacement of the shaft 3 of the knife such axial displacement being elected by means of a set screw as described with reference to the element 22 in connection with the foregoing embodiment.

The invention is not limited tothe exact construction shown in the drawings and described with reference thereto but may be modified in comparison therewith in several respects within the scope defined by the claims.

What I claim is:

1. In a lawn mower, a iixed cutter bar, a plurality of knives, rotatable means supporting said knives in circumferential spaced relations 'to be moved successively adjacent the cutter bar, each knife being longitudinally rotatable with respect to said supporting means, fixed guide means, and means associated with each knife and said guide means for rotatingv the knives with respect to said supporting means during rota,- tion thereof. v

2. In a lawn mower, a iixed cutter bar, a rotatable reel shaft, arms'carried by said reel shaft, a knife carried by the arms and mounted for longitudinal rotation with respect thereto for cooperation with the cutter bar, guide means arranged eccentrically with respect to the axis of said reel shaft, and means carried by said knife engaging said guide means for rotating said knife longitudinally during rotation of the reel shaft.

3. In a lawn mower, a fixed cutter bar, a plurality of knives, rotatable means supporting said knives in circumferential spaced relations to be moved successively adjacent the cutter bar, each knife being longitudinally rotatable with respect to said supporting means, fixed 'circular guide means arranged eccent'rically with respect to the axis of said rotatable supporting means, and a bell crank lever carried by each knife engaging said guide means for rotating the knives with respect to said supporting means during rotation thereof.

4. In a lawn mower, a fixed cutterv bar, a plurality of knives, rotatable means supporting said knives in circumferential spaced relations to be moved successively adjacent the cutter bar, each knife being longitudinally rotatable with respect to s'aid supporting means, fixed circular guide means arranged eccentrically with respect to the axis of said rotatable supporting means, a bell crank lever carried by eachknife engaging said guide means for rotating the knives with respect to said supporting means during rotation thereof, and the radius of said bell crank levers being equal to the eccentric displacement of the guide means with respect to theaxis of the rotatable supporting means.

5. In a lawn mower, a frame, a cutter bar alswel j iixed to the frame, rotatable means supporting said knives in circumferential spaced relations to be moved successively adjacent the cutter bar, each knife being longitudinally rotatable with respect to said supporting means, said frame having a circular groove therein arranged eccentrically with respect to the axis of said rotatable supporting means, a bell crank lever secured to each knife, and a roller carried by each bell crank lever each engaging said groove for rotating each knife with respect to said supporting means during rotation thereof.

6. In a lawn mower, a frame, a cutter bar fixed to the frame, rotatable means supporting said knives in circumferential spaced relations to be moved successively adjacent the cutter bar, each knife being longitudinally rotatable with respect to said supporting means, said frame having a circular groove therein arranged eccentrically with respect to the axis of said rotatable supporting means, a bell crank lever secured to each knife, a roller carried by each bell crank lever each engaging said groove for rotating each knife with respect to said supporting means during'rotation thereof, and means for axially adjusting the positions of said knives and bell crank levers with respect to saidl groove.

7. In a lawn mower, a xed cutter bar, a rotatable reel shaft, circumferentially*y spaced arms carried by said reel shaft, a knife blade' having an arcuate shaped cutting edge carried by two circumferentially spaced arms and mounted for longitudinal rotation with respect thereto for cooperation with the cutter bar, guide means arranged eccentrically with respect to the axis of said reel shaft, and means carried by said knife engaging said guide means for rotating said knife longitudinally during rotation of the reel shaft, whereby the arcuate shaped cutting edge of the knife blade moves longitudinally with respect to the xed cutter bar during yrotation of said reel shaft.

KARL ALBERT CASPERssoN.

Images