Crop threshing or separating – Tooth structure – Mounting means
Patent
1993-06-10
1995-02-14
Suchfield, George A.
Crop threshing or separating
Tooth structure
Mounting means
56128, A01D 4500
Patent
active
053890388
DESCRIPTION:
BRIEF SUMMARY
This invention relates to crop strippers for detaching and harvesting crops from standing plants. Such strippers are best known for stripping grain from the heads of cereal crops such as wheat and herbage crops such as grass seed, but they can also be used to harvest crops such as rice, safflower, milo and peas, or to strip leaves, young shoots or blossom, for example, from the stems of crops.
WO86/01972 describes a crop stripper comprising a rotary drum which has its axis of rotation extending generally horizontally and transversely to the direction of advance through a crop. The drum is provided at its periphery with a number of axial rows or combs of projecting teeth at equispaced intervals about its periphery. As the machine advances through a standing grain crop, the drum is rotated with its lower periphery turning in the direction of advance. The stems of the crop are trapped in the spaces between the projecting teeth and as they are drawn around the drum the grain is stripped from the heads of the plants.
The teeth are required to deflect easily, both to avoid damage from contact with obstacles or the ground, and to allow them to yield to the resistance of the plant stems through which they are drawn. On that account, it is customary to make the teeth of plastics. It is found, however, that they wear very rapidly when handling some crops and require frequent replacement because their stripping efficiency is then affected.
According to one aspect of the present invention, a stripper drum for a crop stripper has a plurality of axially extending rows of teeth, the rows being mounted at spaced intervals about the periphery of the drum with the teeth projecting outwards, and registering with said teeth there is a series of projecting elements of smaller radial extent, said elements forming openings that register with the gaps between the teeth at their roots.
With the teeth formed from a flexible plastics material, such as polyethylene, and the projecting elements from an abrasion resistant material such as metal, it is found that by shaping said openings to substantially conform with the gaps between the teeth or to overlap the edges of said gaps, it is possible to protect the plastics teeth against premature wear without in any way affecting their flexibility and operating efficiency. The projecting elements can themselves be of relatively thin sheet metal because they can be protected against excessive bending loads by the flexible teeth.
Furthermore, although it has been found necessary in the past to form the teeth of crop strippers' drums from plastics material in order to give them adequate flexibility it now is found that metal teeth can be made sufficiently flexible, especially if the shape of the stripping openings at their roots can be formed by the associated smaller radial elements, independently of the teeth themselves. The possibility of making the teeth of metal brings the additional advantage that friction from the crop is reduced and therefore the power requirement is reduced.
In some crops rigid teeth can be used because there is little or no risk of the teeth being overstressed: nevertheless there can be advantages in such circumstances in providing the projecting elements as aforesaid, in register with the teeth. Where flexibility of the teeth is significant it may be required to keep the width of the teeth small and it is desirable that the metal itself should be capable of large elastic deformations, e.g. being a spring steel. The limitation of the width of a tooth is most effective in increasing flexibility if it is done at the tooth root, but that can increase the gap between the teeth to an undesirable extent from the point of view of stripping efficiency. However, the smaller elements can be formed with openings significantly smaller than the gaps at the tooth roots and so provide the operative stripping surfaces in that region.
For grain stripping in particular, the flexible teeth preferably taper towards their outer radial extremities so that the gap between them widens towar
REFERENCES:
patent: 5036653 (1991-08-01), Klinner
patent: 5044147 (1991-09-01), Klinner
McCredie Paul J.
Shelbourne Keith H.
Griggs Dennis T.
Shelbourne Reynolds Engineering Ltd.
Suchfield George A.
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