WO1992017997A1

WO1992017997A1 - Cutting device for a rotary mower

Info

Publication number: WO1992017997A1
Application number: PCT/NL1992/000057
Authority: WO
Inventors: Alexander Jan Vogelenzang
Original assignee: Vogelenzang Alexander J
Priority date: 1991-04-09
Filing date: 1992-03-26
Publication date: 1992-10-29
Also published as: AU1554692A

Abstract

The invention comprises a cutting device for a rotary mower for mowing of grass and other crops consisting of one or more mowing rotors. Such mowing rotors are usually equipped with two or more at even distances protruding cutting elements. According to the invention the mowing rotors are equipped at their periphery with two or more oblong curved cutting segments (9 and 10) which cover a third to a fifteenth of the mowing rotor's periphery (8) and are the cutting edges of the cutting segments (12), seen from above, at the periphery approximately spirally shaped, in such way that when mowing the smallest diameter, seen in the running direction, comes first, while the difference between the smallest and the largest diameter (20) does not exceed 60 millimiters and the cutting edges have a cutting profile preferably sharpened at the underside.

Description

Cutting device for a rotary mower.

The invention concerns a cutting device for a rotary mower for mowing grass and other crops.

Rotary mowers are equipped with one or more mowing rotors, each with two or more at even distances at the periphery protuding cutting elements, usually called blades which are, seen in the rotational direction sharpened and are radially or at a small angle to the radial, free swinging or firmly attached. The advantage of rotary mowers is the simple construction and they allow high working speeds.

One can regard as a disadvantage the danger for bystanders and users by flying stones and other in the area present solid objects which are thrown away by the at a high speed moving protruding blades. Another disadvantage is that the blades become quickly blunt by wear. It is therefore necessary to replace blunt blades frequently as they wear especially quick at the outer ends. The discharge of the cut crop is unfavourable as at each cutting cycle the cutting process of the blades is from the rear to the front whereby they also transport cut crop, influencing the cutting action unfavourably. The invention intends to eliminate the above mentioned drawbacks and disadvantages. To remedy this, each mowing rotor is equipped with two or more oblong curved cutting segments, stretching over a third to a fifteenth of the periphery of the mowing rotor and the cutting edges of the cutting segments, seen from above, are at the periphery spirally shaped in such a way that the smallest diameter comes, seen in rotational direction, first and the difference between the smallest and larges half diameter does not exceed 60 mi 11 imeters and the cutting edges have a cutting and corrugated profile which is preferably sharpened at the under side. As there are with this construction no radially protruding blades which cannot collide at great speed perpendicular against sol id objects, the danger of flying stones, etc. is avoided. The wear pattern of the cutting segments

SUBST.TUTE SHEET Is passing off evenly over the whole cutting edge by which the lifetime increases. In addition the sharpness of the cutting edge is being influenced favourably by the wear at the under side. Below the invention will be explained more fully with help of annexed illustrations.

Fig. 1 is a view from above of nearly crescent shaped plane being the projection of the surface that is cut at a given travel speed and rotations per minute at a blade on the front side of a rotary mower. Fig. 2 is a view from above of a mowing rotor with two cutting segments according to the invention. Fig. 3 are tangential views of sections along the lines

I - I and II - II from fig. 2 of the cutting segments. Fig. * is a view in direction of arrow II from fig. 3. Fig. 5 is a view in direction of arrow III from fig.

3. Fig. 6 is a view from above for clarifying the cutting pattern of a cutting segment in combination with a fixation of the segment as indicated in claim

8.

In fig. 1 the shaded crescent shaped area 1 is that which at a given travel speed and rotations per minute being mowed with a rotary mower to which are attached two or more cutting segments at even distances on the periphery of the mowing rotor. In this the inner circumscription 2 the circumference of the so called cutting circle of the previous blade passage and the l ine 3 the cutting circle of the following blade passage. Travel is in the direction of arrow .^• and the rotation in that of arrow

5. Actually both lines 2 and 3 are part of a cycloid which is described by the periphery of the blades. The largest width 6 of the crescent shaped area is in front of the rotorshaft 7 and is also indicated as bite-size

6. The bite-size is equal to the distance 7-7 ' in which 7 and 7' are the spots where the shaft is at the end of each half turn.

SUBSTITUTE SHEET In fig. 2, 8 is the mowing rotor and 9 and 10 the cutting segments fixed near the periphery of the mowing rotor 8. The cutting circle 11 is the circle described by the largest diameter of the cutting segments 9 and 10. The cutting edge 12 of the cutting segments is adapted in such a way that by each length unit during a single passage as much as possible a uniform area of the crescent shaped area (1 fig. 1) is being mowed and is, seen from above, spirally shaped in which the smallest diameter in rotational direction comes first.

The wavy edge with radial waves of the cutting segments has a width 14 (see also fig. 3).

In fig. 3 one can see the difference in slope of the obl ique downward pointing teeth and of the over its length warped cutting segment 9, in which the edge 12 is sharpened in such way that comes into being a so called free running angle 15 with the horizontal plane.

The distance 20 is the difference in distance between the beginning and the end of the spirally shaped cutting segment with the rotorshaft. The in fig. 4 In the direction of the arrow II from fig. 3 shown view of the wavy-edge shows that the pressed waves 13 have a more or less Irregular angular section have a short side 16 and a long one 17 in such a way that after one sided sharpening under an angle (15 fig. 3) one gets a corrugated periphery from which the teeth have the profile of an unequally sided trapeze (fig. 5).

In fig. 6 a cutting segment 9 is shown positioned in the first part of the cutting traject with such a circumference 12 that each length unit of it mows at a certain speed and rotations per minute nearly the same surface. It has been taken into account with this that during the cutting cycle for mowing the crescent shaped area a certain distance is covered by the mower. One can see clearly that the front part 18 of the cutting segment 9 starts mowing only after a part of the to cover half turn and that the rear part 19 determines the circumference 3 of the cut circle over approximately 180° and should as such work over a very small cutting depth. Fixation of the cutting segments to the mowing rotor is by a central

SUBSTITUTE SHEET 20 and two rotorpins fitting in the keyholes 21 and of the cutting segments from which 23 is the center gravity.

SUBSTITUTE SHEET

Claims

Patent claims

1. Cutting device for rotary mowers for mowing of grass and other crops, characterised by mowing rotors and equipped at their periphery with two or more oblong curved cutting segments which cover a third to a fifteenth of the circumference of the mowing rotor and the cutting edges of the cutting segments, seen from above, are at their periphery more or less spirally shaped in such a way that when mowing the smallest diameter, seen in rotational direction, runs in front and the difference between the smallest and the largest half diameter does not exceed 60 mill imeters and the cutting edges have a cutting or corrugated profile which are preferably sharpened at the under side.

2. Cutting device as defined in claim 1, characterised by somewhat bent down cutting segments in which the slope in rotational direction along the cutting segment increases so the cutting edge, seen from above, is nearly spirally shaped in such way that when mowing the smallest diameter runs in front at rotational direction and the cutting edge has a cutting or corrugated profile which is preferably sharpened at the under s ide.

3. Cutting device as defined in claim 1 and 2, character ised by having the periphery of the mowing rotor at the fixing points more or less similar to the more or less spirally cutting edge which these cutting segments require and is equipped with a somewhat downward pointing periphery in such a way that oblong curved as a cone section conceived cutting segments can be fixed and the cutting edge is nearly spirally shaped.

4. Cutting device as defined in claims 2 and 3, characterised by cutting segments having a small angle with the horizontal plane.

5. Cutting device as defined In claims 2 and 3, character ised by cutting segments with a wavy periphery in which the waves show a corrugated or unequally sided trapeze profile where the steep side of a tooth or unequally sided trapeze comes first in rotational direction.

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6. Cutting device as defined in claims 1 - 5, characterised by rotary mowers with near each other placed synchronised driven mowing rotors with segments at the periphery have sufficient distance for getting a mowing overlap with the next rotor.

7. Cutting device as defined in claims 2 - 6, characterised that cutting segments are sharpened at the under side in a plane making a small angle with the horizontal piane.

8. Cutting device as defined in claims 1 - 7, characterised that cutting segments are fixed by means of two keyholes to rotor pins and the segment can pivot around a third pin and the center of gravity is at such a spot with respect to the third pin that the centrifugal force in combination with the cutting resistence fix the segment securely.

9. Cutting device as defined in claims 1 - 8, characterised that the mowing rotor is cone shaped with a large top angle.

_SUB_ST_ITUTE SHEET Cutting device for rotary mower.

The invention comprises a cutting device for a rotary mower, for mowing of grass and other crops consisting of one or more mowing rotors. Such mowjng rotors are usually equipped with two or more at even distances protruding cutting elements. According to the invention the mowing rotors are equipped at their periphery with two or more oblong curved cutting segments (9 and 10) which cover a third to a fifteenth of the mowing rotor's periphery (8) _nd are the cutting edges.of the cutting segments (12), seen from above, at the periphery approximately spirally shaped, in such way that when mowing the smallest diameter, seen in the running direction, comes first, while the difference between the smallest and the largest diameter (20) does not exceed 60 mill imeters and the have a cutting profile preferably sharpened

ide.

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