GB2291822A

GB2291822A - Cutting blade for a garden waste shredder

Info

Publication number: GB2291822A
Application number: GB9512136A
Authority: GB
Inventors: Erwin Karg
Original assignee: LESCHA MASCHF GmbH
Current assignee: LESCHA MASCHF GmbH
Priority date: 1994-08-04
Filing date: 1995-06-15
Publication date: 1996-02-07
Also published as: FR2723326A1; ATA116995A; DE4427700A1; GB9512136D0; AT403667B; DE4427700C2

Description

2291822 DEVICE FOR CHOPPING GARDEN- REFU The invention relates to a device

for chopping garden refuse or the like, with a feed chute and a discharge chute between which a carrier disc, which is motor driven via a shaft, is arranged, carrying at least one blade arranged over a discharge slot and cooperating with a fixed rest.

Choppers of this kind have one or more blades with straight cutting edges which chop the material with a percussive cutting action similar to the blows of an axe. These choppers are very noisy in operation. It has now been found that a major factor contributing to the noise is the percussive cutting action of the blades.

With this as its starting-point, the invention has the object of providing a chopping machine of the abovementioned kind which affords a marked reduction in noise level while largely retaining the existing construction of the unit.

According to the invention this is achieved by providing at least the cutting edge of each blade with a spiral profile running in towards the shaft of the carrier disc.

The invention provides an oblique shearing cut, with the cutting edge of the blade engaging with the material to be chopped over a large angle of rotation of the carrier disc, so that its engagement with the material is relatively extended compared with conventional choppers. Such a cutting action has been found to cause much less noise during chopping. The spiral configuration of the blade produces an "inward shift" effect on the material to be cut, particularly on the thicker stems, with the result that, for a given motor torque, they are cut off nearer to the centre of the cutter disc, that is nearer to the point of maximum cutting force ( = peripheral force). A further advantage of the invention lies in the fact that existing choppers can be equipped with these blades by replacing the carrier disc.

Advantageously the profile of the cutting edge of the blade is made to encircle the shaft. This makes it easy to increase the angle of rotation over which the cutting edge of the blade acts on the material to be chopped.

Preferably, where a single blade is used, the profile of the cutting edge is made to encircle the shaft through a sector of approximately 36T. This results in a quiet and gentle cutting action without unduly reducing the strength and stability of the carrier disc.

According to another configuration of the invention, where two blades are used, the profile of each cutting edge is made to encircle the shaft through a sector of approximately 1800. Such an arrangement is capable of increasing the throughput of material to be chopped. The carrier disc with blades can 20 easily be balanced.

By way of example, two specific embodiments of the invention will now be described, with reference to the accompany drawings, in which:

Figure 1 shows a longitudinal section through a chopper according to the invention; Figure 2 is a view from above of the chopper shown in Figure 1, with filling hopper removed; Figure 3 is a view of a carrier disc from above; Figure 4 shows a section along the line IV-IV in Figure 3; and Figure 5 shows a further embodiment of a carrier disc in a similar view to Figure 3.

The chopper shown in Figure 1 and 2 has a feed chute 1 which is fixed to a cover 2 of a housing 3. A carrier disc 4 is rotatably arranged in the housing 3, and can be driven via a shaft 5 by a motor 6, conveniently an electric motor, at some 1400 to 3000 rpm. Instead of a horizontal carrier disc, it would also be possible to provide a carrier disc set at an oblique angle to the feed chute. A discharge chute 7 also opens into the housing 3. The housing 3 is supported on three legs 8. A filling hopper 9 can be mounted on the feed chute 1.

A blade 10 with a cutting edge 11 is mounted on the carrier disc 4.

The blade 10 is conveniently connected to the carrier disc 4 by bolts 12, making it easily replaceable. The cutting edge 11 of the blade has a spiral profile which from a portion 11 a adjacent to the outer rim of the carrier disc 4 runs in towards the shaft 5. The profile of the cutting edge 11 may be made in the form of a segment of a spiral. Alternatively, the profile may be built up of segments of circles of different radii and with centres offset with respect to the shaft 5. As illustrated, the profile of the cutting edge 11 advantageously extends from an area of the carrier disc 4 which carries the portion 11 a, located on one side of the shaft 5, to an area diametrically opposite. Thus the cutting edge 11 encircles the shaft, in this case through approximately 3600, in order that during one revolution of the carrier disc 4 the cutting edge 11 engages with the material to be chopped over as long a 5 period as possible.

In the illustrated embodiment, the entire blade 10 has a spiral shape, so that its width is constant over its whole extent. Since the profile 13 of the back of the blade 10 is unimportant, this may have some other shape. For example, it may at least partly follow the rim of the carrier disc 4.

Also provided is a discharge slot 14, which is likewise made in a spiral curve to match the cutting edge 11. Whilst discharge slots with other shapes are possible, the illustrated discharge slot 14 causes minimal weakening of the carrier disc 4, without impairment of function. The outer boundary 15 of the discharge slot 14 is set back with respect to the cutting edge 11 of the blade 10, so that the cutting edge 11 partly overhangs the discharge slot 14. This assists the snag-free discharge of chopped material. As can be seen from Figure 3, the discharge slot 14 terminates in front of the edge portion 11 a of the blade 10. This avoids weakening of the carrier disc 4 in the rim area. In operation, with the carrier disc 4 turning in the direction of the arrow a, the blade 10 cooperates with an angled rest 16 fitted to the wall of the feed chute 1.

As the carrier disc 4 together with the blade 10 rotates in operation, the blade performs a slicing cut ftom the outside inwards on the material which rests against the rest 16. The extension of cutting time to a full revolution of the carrier disc 4 results in a considerable reduction in noise.

-5 In the embodiment shown in Figure 5, a carrier disc 20 which carries two blades 21, 22 is mounted on the shaft 5. The blades 21, 22 have cutting edges 23, 24. Here again each cutting edge 23, 24 is curved in a spiral which runs in towards the shaft 5. Each of the cutting edges 23, 24 extends over not quite 1800 around the shaft 5. As in the first embodiment, the blades 21, 22 are made in one piece and have a spiral shape. The same applies to the discharge slots 25, 26 provided under the blades. In principle, more than two blades can be used. However, the cutting edge of each blade should then encircle the shaft 5 through at least 900.

Instead of one-piece blades, blades composed of segments individually connected to the carrier disc may also be used.

It is possible to use blade segments with straight cutting edges forming a polygonal train, approximating to a spiral, in the assembled condition.

As the above remarks show, the invention is not limited to the illustrated embodiments.

-6

Claims

1. A device for chopping garden refuse or the like, with a feed chute and a discharge chute between which a carrier disc, which is motor driven via a shaft, is arranged, carrying at least one blade arranged over a discharge slot and cooperating with a fixed rest, at least the cutting edge of each blade having a spiral profile running in towards the shaft of the carrier disc.

2. A device according to Claim 1, in which the profile of the cutting edge of the blade encircles the shaft.

3. A device according to Claim 1 or 2, where a single blade is used, the profile of the cutting edge encircling the shaft through approximately 36T.

4. A device according to Claim 1 or 2, where two blades are used, the profile of the cutting edge of each blade encircling the shaft through approximately 180'.

5. A device according to any one of the preceding claims, in which each 20 blade is made in one piece, and is curved in a spiral.

6. A device according to any one of Claims 1 to 4, in which the blade is made up of a number of segments.

7. A device according to Claim 6, in which the cutting edges of the blade segments are straight, and form an approximately spiral polygonal train.

8. A device according to any one of the preceding claims, in which each discharge slot is shaped in a spiral curve to match the cutting edge of the blade.

9. A device according to any one of the preceding Claims, in which the cutting edge of the blade overhangs the outer boundary of the discharge slot.

10. A device according to any one of the preceding claims, in which the discharge slot within the carrier disc is made shorter in the edge region of the 10 carrier disc than the cutting edge of the blade.

11. A device for chopping garden refuse or the like, constructed and arranged substantially as herein described, with reference to Figures 1 to 4, or Figure 5 of the accompanying drawings.