US3514932A - Adjusting device for oscillating cutter mechanism - Google Patents

Description

June 2, 1 970 A. HOROWITZ ET AL 3,514,932

ADJUSTING DEVICE FOR OSCILLATING CUTTER MECHANISM Filed May 5, 1967 F l G] KCw 30 F l (5.4

INVENTORS ALEXANDRE HOROWITZ BY BERNARD J. BEUSINK AGENT United States Patent U.S. Cl. 56-293 4 Claims ABSTRACT OF THE DISCLOSURE The drive arms of the oscillating knives of the cutter mechanism are adjustably connected to the bearing block within the reciprocating drive bar by means of a second spring urged wedge-shaped block slidably contacting the bearing block to displace same and thereby control the degree of contact between the oscillating and stationary knives.

'lhis invention relates to mowing machines, more particularly to a machine having pivotal knives driven about a hinge in an oscillating manner, in which at least one knife of each of the pair of knives cooperating during the cutting operation is arranged so as to be tiltable.

The use of such tiltable knives advantageously provides a reaction force produced by the pressure on the article to be out which results in a moment about the tilting axis of the knives so that during the cutting operation, the relative pressure of the knives is larger; accordingly the cutting force exerted is greater. Thus, under no-load conditions, the relative pressure of the knives need be only small and considerable frictional losses are avoided. Consequently, it would be desirable to support the driving arm of the tiltable knife in a resilient manner, for example, in a driving point, so that the knife is continuously pressed with a slight resilient force. However, this cannot be achieved without the use of further means, since the said reaction pressure of the article to be out also results in a component which tends to depress the said resilient support so that so strong a resilient force would have to be applied that the advantage of avoiding frictional losses under no-load conditions becomes illusive.

The invention has for an object to provide a solution of this problem and is characterized in that an adjusting device for a driving arm of the tiltable knife is used which influences the relative pressure of the cutting edges and which comprises two blocks slidably guided in directions at right angles to each other and pressed against each other by a spring, one of which blocks engages an arm of the tiltable knife, these blocks slidably engaging each other by bevelled surfaces which extend in a direction lying between the said directions at right angles to each other.

Thus, as will be described hereinafter, an adjusting position can be obtained in which under no-load conditions the cutting edges are pressed together with a relatively slight force; when needed an increase of the pressure component on the resilient support of the driving arm is automatically provided. Any unnecessary clearance 3,514,932 Patented June 2, 1970 around the driving point, such as would be caused by wear, is also automatically eliminated by readjustment.

The invention will now be described more fully with reference to embodiments outlined in the drawing, and further advantageous details will be disclosed.

FIG. 1 is a diagrammatic perspective view of a knife of a series of knives for a drive bar driven in a reciprocatory manner,

FIG. 2 shows diagrammatically the drive point with the spring-urged sleeve arrangement,

FIG. 3 shows the spring indirectly acting on the drive point,

FIG. 4 shows a modification in which an overload protecting device is incorporated,

FIG. 1 shows a knife 1 having a drive arm 2 and forming part of a series of such knives in a cutter bar which supports stationary lower knives one pair of which, located on either side of the knife 1, are denoted by 3 and 4. The cutter bar itself is not shown, but the arrangement is shown in a coordinate system XYZ, in which the counter-knives 3 and 4 lie in the XY plane and the hinge 5. of the arm 2 lies in the Z-axis and is journalled in a wall of the cutter bar coinciding with the YZ-plane. Projection lines indicate that the knife 1 has an inclination with respect to the XY-plane and in effect goes through said plane. The centre line 6 of the driving arm has an even larger inclination with respect to the XYZ-plane in which the cutting operation is carried out.

The figure further shows the arrangement of a drive bar 7 journalled in the cutter bar (not shown) and moving in a reciprocatory manner in its longitudinal direction. This drive bar supports bearing block 9, in which block the drive point 8 of the drive arm 2 of each knife 1 of the series of driven bilaterally operating knives is included.

In operation, when the knife 1 moves to the right at the instant illustrated in FIG. 1, the cutting effect is performed in point 10.

A cutting resistance Ks introduces a moment about the centre line 6 of the arm 2, which moment tends to tilt the upper knife 1. The lower knife 4 hampers this tilting by exerting a force K on the upper knife. The equilibrium of moments results in K =Ks tan a.

Consequently the pressure by which the knives are pressed together in the area in which grass blades are cut, may theoretically be zero under no-load conditions of the knives. The opposite cutting edge of the knife, i.e. the side adjacent knife 3 in FIG. 1, which cutting edge is inoperative during the stroke of the knife 1 to the right may also theoretically be under no-load conditions. The frictional losses under no-load conditions are consequently considerably reduced; nevertheless the relative pressure of the knives at the area of the cutting operation remain sufficient to prevent deviations, since said pressure is automatically adapted to the larger or smaller force required for the moving operation at the relevant instant. If it is desired that the knives continuously engage each other with a slight resilient relative pressure, even under noload conditions, an arrangement as shown in FIG. 2 would be preferred. This figure shows diagrammatically that the drive point 8 of knife arm 2 shown in FIG. 1 enclosed between vertical guides 11 in the bearing block 9 which in turn is arranged in the drive bar 7. The ballshaped arm end 8 bears on a supporting plate 12 consti- 3 tuted by the head of a sleeve 13 which is vertically displaceable in guides and is pressed upwards by a spring 14.

The moving knife 1 is thus continuously pressed on the stationary counter-knives 3 and 4 with a force exerted by the spring 14. However, this pressure must be sufiicient to produce the maximum K occurring under full-load conditions. Moreover, this spring pressure will result in pressure forces on the two cutting edges of the upper knife 1. Thus, idling losses and wear occur to an extent which is a considerable disadvantage.

FIG. 3 shows another embodiment in which a spring cooperates (indirectly) with the drive bar 7. The ball or drive point 8 in this case bears on a block 17 which is displaceable between two parallel guides and 16 and which bears on an inclined surface 18 of a wedge-shaped body 19 which is displaceable along a guiding path 20 of the drive bar 7 in a direction in which it is laterally urged by a spring 21 with a force P.

In the basic adjusting position, a slight elastic pressure of the upper knife on the lower knives is obtained under no-load conditions and this pressure force can be kept at a low value, nevertheless an increase of the force K is possible according to the need.

If the coefficients of friction along the surfaces 18 and 20 are denoted by J} and f respectively, and the wedge inclination (which is chosen to be small) is denoted by (p, with the coefficient of friction f for the vertical guiding (15, 16) being neglected, the force K exerted on the ball 8 when the supporting surface 22 is moved upwards can be expressed as follows:

and when said surface is moved downwards:

P tan (f1+f2) By varying p, f and f any ratio between Pt and Pt can be chosen, in other words, with a small force Pt for the resilient pressure, under no-load conditions, Pl, can be adjusted to a value exceeding the normal values of K and K FIG. 4 shows an embodiment in which a modification of the embodiment of FIG. 3 is combined with a spring system providing a protecting device in the load transmission that becomes operative when a driven knife is blocked.

The driving point 8 of the drive arm for each knife driven in an oscillatory manner is included in a bearing block 23 fulfilling the function of one of the blocks 17 and 19 pressed against each other by a spring (cf. FIG. 3). The other of the blocks engaging each other by bevelled surfaces 24 is a block 25. These two blocks 23 and 25 are also guided so as to be displaceable each in a direction of two directions at right angles to each other, that is to say the block 25 in the drive bar 7 in the longitudinal direction of said bar and the other block in a direction at right angles thereto along the wall of a cupped spring washer 26. The spring 27 ensures that the block 25 is resiliently pressed with the force P.

However, this spring also fulfils a function in the protecting spring system which becomes operative, for example, when a stone arrives between the driven knife and a counter-knife, as a result of which the driven knife is blocked. If a given value of the force to be transmitted by the drive bar 7 to the drive point 8 is then exceeded, the assembly of blocks 23 and 25 deviates with respect to the driving bar 7 against spring pressure, that is to say that the reciprocatory movement of the drive bar 7 can be continued (while driving the non-blocked knives of the series of knives) but the driving point of the blocked knife remains stationary, while the driving force exerted thereon does not exceed the force produced by the spring pressure P. In order to permit of obtaining this relative deviation in both directions (for a bilaterally operating knife) when the force P is exceeded, the assembly 23,

25 of the blocks bears on one side on a cupped spring washer 26 which is pressed against a stop 30 in the driving arm by a spring 29 engaging said arm at 28. Consequently, the cupped spring washer '26 can deviate against the pressure of said spring 29. The stress of the springs 27 and 29 is chosen so that the spring 29 exerts a force 2P. Since the assembly 23, 25 is pressed with the force P of the spring 27 by its other side against the cupped string washer 26, the cupped spring washer will relatively deviate to the right when the driving force on the drive point 8 exceeds the value P upon movement of the drive bar 7 to the left.

As stated, however, the spring 27 also fulfils the function of the spring 21 in FIG. 3. The angle 0 of the bevelled contact surface .24 between the two blocks 23 and 25 to the direction of the force P, however, is chosen to be considerably larger than in FIG. 3.

Thus, the readjusting effect exerted on the block 23 by the spring force P (cf. FIG. 3) can be achieved in the most desirable manner, although in contrast to the embodiment of FIG. 3, the force P has been fixed before hand at a comparatively high value because of the additional function of said spring as a device for protecting the knife edge and other parts from being overloaded in case the knife is blocked.

The aforesaid formulae for K can be applied with a sufiiciently accurate approximation for a small angle (,0 whilst neglecting given factors, but this is not the case for larger values of (p (for example 70 to If in this case, the coefficient of friction f of the vertical guiding of the block 23 (along the cupped spring washer 26) is taken into account but if f (guide of block 25 in drive bar 7) is neglected, the following formula can be derived.

The use of a large angle (,0 further affords the advantage that a given readjustment can be achieved by displacing the block 25 only through a very small distance with respect to the block 23. The force P is not notably varied (due to variation in length of the spring 27) so that the readjusting effect is the same in all circumstances.

What is claimed is:

1. An oscillating cutter assembly comprising first knife means, movable second knife means interposed between said first knife means, knife drive arm means connected at one end to said second knife means and at the other end to a reciprocating drive bar means, hinge means interposed between said knife arm ends providing a pivot around which said second knife means oscillates and tilts, wherein said connection between the knife arm means and the reciprocating drive bar means includes a drive point means on one end of said knife drive arm, bearing block means mounted within said drive bar and accommodating said drive point means and drive point biasing means including an angular shaped body biasingly coacting with the bearing block for urging said second knife means into contact with said first knife means.

2. An oscillating cutter assembly according to claim 1 wherein said drive point biasing means further comprises a support block and a spring biased wedge block, said support block having one end in engagement with said drive point and the other end in engagement with said spring biased wedge block.

3. An oscillating cutter assembly according to claim 1 wherein said bearing block slidingly engages said drive bar means, said bearing block movably receiving said drive point means; said drive point biasing means further includes an adjusting block means positioned laterally adjacent said bearing block means with the abutting faces of said bearing block and said adjusting block means defining a complementary angled connection; a spring means for biasingly interconnecting said bearing block with said reciprocating drive bar and for biasingly interconnecting said adjusting block and said drive bar whereby said complementary abutting forces are in biased sliding contact thereby applying a biasing force to said drive arm for urging said second knife means into contact with said first knife means.

4. An oscillating cutter assembly according to claim 3 wherein said spring means includes a pair of springs, with the first of said springs biasingly interconnecting said drive bar and said adjusting block and the second of said springs biasingly interconnecting said drive bar and said bearing block thereby forcing said adjusting block and said bearing block into abutting engagement for providing a biasing force to said drive arm for urging said second knife means into contact with said first knife means and for providing a connection "between said bearing block and said drive arm which permits relative motion therebetween when a predetermined force is applied to said bearing block.

References Cited UNITED STATES PATENTS ROBERT PESHOCK, Primary Examiner J. N. ESKOVITZ, Assistant Examiner US. Cl. X.R. 56298

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