Disc harrow.

DESCRIPTION

The invention relates to a disc harrow comprising a frame and at least one disc, which disc fixed by means of a number of bolts to a hub journalled in the frame, wherein the shanks of said bolts extend into bores formed in said disc and bores formed in said hub over at least part of their length, which latter bores are aligned with the bores in the disc.

Disc harrows have been known for several decades, an embodiment of such a disc harrow is known from EP 1 616 466, for example.

With the known disc harrows, each of the discs is usually fixed to a hub, which is rotatably supported in the frame of the disc harrow. The axes of rotation of the discs usually extend at an angle to the intended direction of movement of the harrow, such that contact with the soil to be tilled sets the discs rotating.

As a result of this arrangement of the discs with their axes of rotation extending at an angle to the intended direction of movement, the bolts by means of which the discs are fixed to the hub are loaded in tension and in shear.

The discs are usually made of a material which is significantly harder than the material of which the bolts are made. As a result, there is a danger that the bolt shanks will be compressed under the influence of the load exerted on the bolts via the discs and that the discs will come loose and the bolts may shear off, with all its adverse consequences.

The object of the invention is to provide a disc harrow of the above kind in which the above drawbacks of the prior art can be significantly reduced if not eliminated altogether.

According to the invention this object can be accomplished in that at least one pin is provided, which pin extends with a tight fit into the hub and into recesses formed in the disc over at least part of its length, and in that the recess in the disc is in open communication at one end with a central hole formed in the disc.

Especially said latter aspect facilitates the forming of the recess.

Using the construction according to the invention, it is possible to use a pin whose material quality is significantly better than that of the bolt being used, enabling the pin to take up at least part of the loads exerted on the bolts and

thus prevent the bolts from deforming and/or shearing off undesirably.

If the disc and the pin have at least substantially the same degree of hardness, the disc and the pin cannot undesirably deform each other.

Another aspect of the invention relates to a disc in particular intended for use in a disc harrow having the above-described features.

The invention will now be explained in more detail with reference to the appended figures.

Figure 1 is a perspective view of a disc and means supporting said disc, in which the various parts are shown spaced from each other. Figure 2 is a perspective view of the disc, seen in another direction than in figure 1 .

Figure 3 is a larger-scale view of the encircled part A of the disc that is shown in figure 2.

The disc 1 shown in the figures comprises a dish-shaped portion 2, in the centre of which a flange 3 being in one piece with the dish-shaped portion 3 is formed. Usual recesses 4 are formed in the outer circumference of the dish-shaped part 2. The flange 3 is provided with a number of bolt holes 6 extending through the flange, which bolt holes are arranged on a pitch circle. A hub 7 is provided for supporting the disc 1 , which hub is substantially made up of a flange corresponding to the flange 3 and an axle journal 9. Threaded holes 10 corresponding to the holes 6, which extend through the flange 8, are formed in said flange 8. The axle journal 9 can be mounted in a sleeve 15 in a usual manner by means of bearings 1 1 , a sealing ring 12, a lock nut 13 and a cap 14, which sleeve 15 is mounted to the end of an arm 16. A support 17 is mounted to the end of the arm 16 remote from the sleeve 15, by means of which support the arm 16 can be attached to a frame (not shown) of the disc harrow.

The two flanges 3 and 8 can be fixed together by means of bolts 18, in such a manner that the shanks of said bolts extend through bores 6 formed in the flanges 3 and are screwed into the threaded bores 10. The bolts 18 will then be locked by means of self-locking nuts 19 to be screwed onto the bolts.

A disc-shaped projection 20 on the flange 8 is received with a tight fit in a central hole 21 formed in the flange 3.

The construction as described above is conventionally used with disc harrows.

According to the invention, a further hole 22 is provided in the flange 8 at a position spaced from the bolt holes 10, in which further hole an end of a pin 23 can be received with a tight fit, for example with a press fit.

Furthermore, a more or less U-shaped recess 24 is formed in the flange 3 of the disc 1 , which recess is in open communication at one end with the central hole 21 formed in the flange 3 of the disc 1. The construction is such that the end of the pin 23 that projects outside the flange 8 can be received in the recess 24 formed in the flange 3 with a tight fit. The pin 23 will be made of a significantly higher-grade steel than the bolts 18. As a result, the pin 23 will be better able to take up shear forces and pressure forces than the bolts 18, and the pin 23 will relieve the bolts at least in part of shear forces and pressure forces. The pin is preferably made of a material having a hardness at least substantially equal to the hardness of the disc 1 , in order to prevent the part 3 from eating into the material of part 23, and vice versa, as well as possible.