GB2129264A - Mowers - Google Patents

Abstract

A flail-type of mower has the individual cutters mounted on the ends of spring or torsion arms 12, 18 which hold the cutters 24, 26 at a spaced position from the shaft 10 but allow deflection against obstructions. This enables the shaft to be rotated at a relatively low speed as compared to that required with a convention flail mower. <IMAGE>

Description

SPECIFICATION Mowers This invention relates to mowers particularly for grass and scrub cutting. A mower construction which is widely used for this purpose is known as a flail mower and comprises a shaft provided with a helically (usually but not essentially) arranged pattern of individual flails each of which is freely pivoted at its inner end adjacent the shaft and has a hooked or bent end provided with the cutting edge. When the shaft is rotated, typically at a speed between 2000 and 2500 r.p.m., the flails swing out and form a rotating "cylinder" of cutting surfaces. It will be appreciated that if a flail hits an obstacle which cannot be cut, the flail can at least theoretically deflect about its pivot to a position even tangential to the shaft instead of extending substantially radially of the shaft.In fact, the rotational speed has to be sufficiently high for the cutters to be effective and not deflect even when dealing with material within the design capacity of the mower. Substantial power is required to rotate the rotor at a speed sufficient to extend the cutters to the near radial position and provide adequate impact force at the cutting edge.

The object of the present invention is to provide a mower having similar capabilities to the flail mower but requiring less energy in operation.

In accordance with the invention a mower comprises a shaft and a plurality of cutters arranged along and or about the shaft, each cutter being mounted on an end of a corresponding torsion arm extending from the shaft.

By these means, the cutters may be located at least in the vicinity of the required position even when the shaft is stationary, and in the event of impact with an object beyond the design cutting power of the system, can deflect due to the torsion effect, and so escape damage.

The torsion arm may be a tail of a helical torsion spring. Conveniently the torsion arms are provided in pairs as tails of a pair of oppositely wound helical torsion springs formed from single length of spring rod, and with an attachment eye formed between said adjacent ends.

The cutters per se may be similar to flails but of relatively short length (radially of the shaft in use) and freely pivoted at the ends of the torsion arms.

This provides a further degree of protection in the event of potential damage.

One embodiment of the invention is illustrated in the accompanying drawings wherein: Figure 1 is a fragmentary elevation showing a portion of the mower shaft, with only one complete pair of torsion arms and accompanying cutters shown in full line and a second pair part shown in chain dot line, other ones which would be mounted on the shaft being omitted for clarity; and Figure 2 is a cross section of the same shaft again showing only one torsion arm in full line and another in dash line, yet others being omitted in the interest of clarity.

In the drawings, the shaft 10 is tubular. Each torsion arm 12 extends generally tangentially of the integral spring soil 14, and the opposite tail of the same coil is integral with an attachment eye 1 6 by means of which the torsion set is fixed to the shaft. Torsion arm 1 8 is similarly located in relation to a second but opposite hand coil 20 integral with the same attachment eye 1 6.

The outer end of each torsion arm such as 12 is formed with a further eye or hook end 22 on which a pair of back-to-back flails 24, 26 are freely pivoted. The arms 12, 1 8 are curved along their length so that in the event of extreme deflection in an anticlockwise direction as seen in Figure 2, a mid portion 28 can conform closely to the shaft surface.

It will be appreciated that during deflection energy is stored in the spring coil 14 (or 20) which returns the arm to the illustrated position when the deflecting force is released, without requiring energy input from the drive shaft 10.

It is believed that a cutter constructed as described can be run at greatly reduced rotor speed as compared to a comparable conventional flail mower, resulting not only in reduced power requirements but eliminating many vibration problems encountered with a traditional mower.

1. A mower comprising a shaft and a plurality of cutters arranged along and/or about the shaft, each cutter being mounted on an end of a corresponding torsion arm extending from the shaft.

2. A mower as claimed in Claim 1 wherein the torsion arm is a tail of a helical torsion spring.

3. A mower as claimed in Claim 2 wherein torsion arms are provided in pairs as tails of a pair of oppositely wound helical torsion springs formed from a single length of spring rod.

4. A mower as claimed in Claim 3 wherein an attachment eye is formed between the pair of torsion springs for fixing the same to a shaft.

5. A mower substantially as described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Mowers This invention relates to mowers particularly for grass and scrub cutting. A mower construction which is widely used for this purpose is known as a flail mower and comprises a shaft provided with a helically (usually but not essentially) arranged pattern of individual flails each of which is freely pivoted at its inner end adjacent the shaft and has a hooked or bent end provided with the cutting edge. When the shaft is rotated, typically at a speed between 2000 and 2500 r.p.m., the flails swing out and form a rotating "cylinder" of cutting surfaces. It will be appreciated that if a flail hits an obstacle which cannot be cut, the flail can at least theoretically deflect about its pivot to a position even tangential to the shaft instead of extending substantially radially of the shaft.In fact, the rotational speed has to be sufficiently high for the cutters to be effective and not deflect even when dealing with material within the design capacity of the mower. Substantial power is required to rotate the rotor at a speed sufficient to extend the cutters to the near radial position and provide adequate impact force at the cutting edge. The object of the present invention is to provide a mower having similar capabilities to the flail mower but requiring less energy in operation. In accordance with the invention a mower comprises a shaft and a plurality of cutters arranged along and or about the shaft, each cutter being mounted on an end of a corresponding torsion arm extending from the shaft. By these means, the cutters may be located at least in the vicinity of the required position even when the shaft is stationary, and in the event of impact with an object beyond the design cutting power of the system, can deflect due to the torsion effect, and so escape damage. The torsion arm may be a tail of a helical torsion spring. Conveniently the torsion arms are provided in pairs as tails of a pair of oppositely wound helical torsion springs formed from single length of spring rod, and with an attachment eye formed between said adjacent ends. The cutters per se may be similar to flails but of relatively short length (radially of the shaft in use) and freely pivoted at the ends of the torsion arms. This provides a further degree of protection in the event of potential damage. One embodiment of the invention is illustrated in the accompanying drawings wherein: Figure 1 is a fragmentary elevation showing a portion of the mower shaft, with only one complete pair of torsion arms and accompanying cutters shown in full line and a second pair part shown in chain dot line, other ones which would be mounted on the shaft being omitted for clarity; and Figure 2 is a cross section of the same shaft again showing only one torsion arm in full line and another in dash line, yet others being omitted in the interest of clarity. In the drawings, the shaft 10 is tubular. Each torsion arm 12 extends generally tangentially of the integral spring soil 14, and the opposite tail of the same coil is integral with an attachment eye 1 6 by means of which the torsion set is fixed to the shaft. Torsion arm 1 8 is similarly located in relation to a second but opposite hand coil 20 integral with the same attachment eye 1 6. The outer end of each torsion arm such as 12 is formed with a further eye or hook end 22 on which a pair of back-to-back flails 24, 26 are freely pivoted. The arms 12, 1 8 are curved along their length so that in the event of extreme deflection in an anticlockwise direction as seen in Figure 2, a mid portion 28 can conform closely to the shaft surface. It will be appreciated that during deflection energy is stored in the spring coil 14 (or 20) which returns the arm to the illustrated position when the deflecting force is released, without requiring energy input from the drive shaft 10. It is believed that a cutter constructed as described can be run at greatly reduced rotor speed as compared to a comparable conventional flail mower, resulting not only in reduced power requirements but eliminating many vibration problems encountered with a traditional mower. CLAIMS

1. A mower comprising a shaft and a plurality of cutters arranged along and/or about the shaft, each cutter being mounted on an end of a corresponding torsion arm extending from the shaft.

2. A mower as claimed in Claim 1 wherein the torsion arm is a tail of a helical torsion spring.

3. A mower as claimed in Claim 2 wherein torsion arms are provided in pairs as tails of a pair of oppositely wound helical torsion springs formed from a single length of spring rod.

4. A mower as claimed in Claim 3 wherein an attachment eye is formed between the pair of torsion springs for fixing the same to a shaft.

5. A mower substantially as described with reference to the accompanying drawings.