Harvesters – Cutting – Rotating cutting-reel type
Patent
1992-05-13
1994-03-15
Bagnell, David J.
Harvesters
Cutting
Rotating cutting-reel type
29891, 56294, 56DIG20, A01D 3452
Patent
active
052937348
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to bottom blades for the type of grass cutting unit that has a rotating cutting reel.
These bottom blades are subject to high wear rates because of the almost continuous engagement with the rotating cutting reel over extended periods of use. Friction, particularly where the cutting reel is not correctly adjusted, can lead to thermal distortion of the bottom blade, this distortion in some cases becoming permanent.
SUMMARY OF THE INVENTION
It is an object of this invention to provide an inexpensive method of producing an improved bottom blade which has a low wear rate, and less susceptibility to thermal distortion.
Accordingly, the present invention consists in a method of producing a bottom blade for a grass cutting unit, comprising the steps of forming an elongate mounting element of relatively low hardness; welding thereto an elongate wear strip of relatively high hardness, the wear strip being positioned with an elongate edge thereof substantially aligned with an elongate edge of the mounting element and, subsequent to said welding step, forming a bend in the mounting element along a bend line parallel to the length of the strip.
Preferably, the wear strip undergoes a hardening step before said welding step.
Suitably, said welding step comprises an electron beam welding process.
Advantageously, the step of forming the elongate mounting portion includes a bending step to produce an inclined lip, the welding step comprising the welding of the wear strip to said lip and the subsequent bending step serving to increase the inclination of said lip relative to the body of the mounting portion.
In a bottom blade according to this invention, the elongate plate of the bottom blade need not be formed of hardenable material and can, for example, be formed of an inexpensive mild steel. The material for the wear strip can be chosen to optimize the wear and thermal properties, without regard to factors such as the expense of producing an entire bottom blade out of the material or the toughness required in the mounting portion of the bottom blade. Thus, the wear strip can in one example be formed of high speed steel which retains its properties at elevated temperatures.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described by way of example with reference to the accompanying drawings in which:
FIG. 1 is an illustration of a conventional bottom blade in use;
FIG. 2 is an end view of a conventional bottom blade;
FIGS. 3, 4 and 5 are respectively plan, front and side views of a bottom blade produced according to this invention;
FIG. 6 illustrates a bottom blade according to this invention in use;
FIG. 7 is a scrap view illustrating a feature of the construction of the bottom blade according to this invention;
FIGS. 8 and 9 are respectively plan and end views of a modified bottom blade according to this invention at an intermediate stage in manufacture;
FIG. 10 is an end view of the bottom blade shown in FIGS. 8 and 9, in its final form; and
FIGS. 11 and 12 are end views of a further modified bottom blade according to this invention at intermediate and final stages of manufacture, respectively.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrates a conventional grass cutting unit having a cutting reel 1 with a series of blades 2 arranged about a shaft 3 which is rotatably mounted in bearings 4. A bottom blade 5 is attached to a bottom block 6 and cooperates with the rotating blades to shear or cut grass. The bearings 4 and the bottom block 6 are mounted in the cutting unit so that the relative orientation of the rotating blades 2 and the bottom blade 5 can be adjusted and accurately maintained.
A conventional bottom blade is normally made from a high carbon alloy steel. Referring to FIG. 2, the lip portion 9 is generally induction hardened to provide a wear resistant cutting edge. Through the inclination of the lip to the body of the blade, an edge 8 is presented to the cutting reel with the thickness at this point being in the circ
REFERENCES:
patent: 1348471 (1920-08-01), Aspinwall
patent: 1355509 (1919-12-01), Ross
patent: 2045386 (1936-06-01), Gottschalk
patent: 2183545 (1939-12-01), Clemson
patent: 2557897 (1951-06-01), Sullivan
patent: 2583543 (1952-01-01), Boyce et al.
patent: 3635271 (1972-01-01), Markham
patent: 3805660 (1974-04-01), Burrough
Bagnell David J.
Ransomes Sims & Jefferies Limited
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