GB2115667A - Mowers - Google Patents

Abstract

The cutting head of a mower is angled by a rack and pinion mechanism. The pinion (22) is fast with the head and the rack (24) is displaced by the ram (26). This maintains a constant mechanical advantage facilitating fine and accurate control. <IMAGE>

Description

SPECIFICATION Mowers This invention relates to mowers of the kind in which a cutting head is carried on one end of a boom or system of arms to extend laterally of a tractor, e.g. for road verge trimming. In order to cope with embankments, hedge sides and tops, the cutting head needs to be precisely angled with respect to the arm or boom as well as positioned for height and reach. This is done by providing a hydraulic ram or rams effective on each pivot. In a complete system with two arms, there are at least three rams, i.e. one between the tractor and the first arm, a second between the first and second arms, and a third to control the head angle. It is control of the head angle which is the most difficult for various reasons.

One reason is the differing mechanical advantage at different extensions of the ram (different angles between the ram and the arm) which means that a given movement of the valve controlling hydraulic flow will give different results at different points in the range of movement. If linkages are used between the ram and head, as is usual, then a little wear on the pivot pins may lead to the head moving jerkily and so on. Fine accurate and responsive control is then impossible.

The object of the invention is to provide a new system for head control which can give more accurate control in simpler fashion.

In accordance with the invention a mower comprises a cutter head mounted on the end of a boom or system of arms for projecting the head laterally of a tractor, and means for controlling the angle of the head relative to the boom or arms comprising a pinion fast with the cutter head and journalled on the boom or arms, and a rack carried by said boom or arms and ram displaced to turn the pinion.

By these means the angle between the ram and arm remains constant, and the mechanical advantage is invariable. The rack teeth may be of simple shape to minimise the effect of tolerance or wear between them and the pinion. Unit axial ram displacement will cause equiangular pinion rotation irrespective of the points in the range.

The invention is illustrated in the accompanying drawings in which Figure 1 is an elevation of a tractor and mower; and Figure 2 is a fragmentary elevation on an increased scale showing the cutting head.

Referring to Figure 1, the cutting head 10 is pivoted to the end of the outer arm 1 2 which is in turn pivoted to the inner arm 14 and the latter is pivoted on the tractor. A first hydraulic ram 1 6 controls the position of the arm 14 relative to the tractor, a second hydraulic ram 1 8 controls the angle of the arm 12 relative to the arm 14, and the head is pivoted to the arm 1 2 on the shaft 20.

Referring to Figure 2, the shaft 20 which is fixed to the cutting head and journalled on the arm 12 carries an angularly fast pinion 22 meshed with a rack 24 formed on the ram or piston rod of the hydraulic cylinder 26. Extension or contraction of the ram turns the pinion so as to adjust the angle of the cutting head relative to the arm 12.

1. A mower comprising a cutter head mounted on the end of a boom or system of arms for projecting the head laterally of a tractor, and means for controlling the angle of the head relative to the boom or arms comprising pinion fast with the cutter head and journalled on the boom or arms, and a rack carried by said boom or arms and ram displaced to turn the pinion.

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

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

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Mowers This invention relates to mowers of the kind in which a cutting head is carried on one end of a boom or system of arms to extend laterally of a tractor, e.g. for road verge trimming. In order to cope with embankments, hedge sides and tops, the cutting head needs to be precisely angled with respect to the arm or boom as well as positioned for height and reach. This is done by providing a hydraulic ram or rams effective on each pivot. In a complete system with two arms, there are at least three rams, i.e. one between the tractor and the first arm, a second between the first and second arms, and a third to control the head angle. It is control of the head angle which is the most difficult for various reasons. One reason is the differing mechanical advantage at different extensions of the ram (different angles between the ram and the arm) which means that a given movement of the valve controlling hydraulic flow will give different results at different points in the range of movement. If linkages are used between the ram and head, as is usual, then a little wear on the pivot pins may lead to the head moving jerkily and so on. Fine accurate and responsive control is then impossible. The object of the invention is to provide a new system for head control which can give more accurate control in simpler fashion. In accordance with the invention a mower comprises a cutter head mounted on the end of a boom or system of arms for projecting the head laterally of a tractor, and means for controlling the angle of the head relative to the boom or arms comprising a pinion fast with the cutter head and journalled on the boom or arms, and a rack carried by said boom or arms and ram displaced to turn the pinion. By these means the angle between the ram and arm remains constant, and the mechanical advantage is invariable. The rack teeth may be of simple shape to minimise the effect of tolerance or wear between them and the pinion. Unit axial ram displacement will cause equiangular pinion rotation irrespective of the points in the range. The invention is illustrated in the accompanying drawings in which Figure 1 is an elevation of a tractor and mower; and Figure 2 is a fragmentary elevation on an increased scale showing the cutting head. Referring to Figure 1, the cutting head 10 is pivoted to the end of the outer arm 1 2 which is in turn pivoted to the inner arm 14 and the latter is pivoted on the tractor. A first hydraulic ram 1 6 controls the position of the arm 14 relative to the tractor, a second hydraulic ram 1 8 controls the angle of the arm 12 relative to the arm 14, and the head is pivoted to the arm 1 2 on the shaft 20. Referring to Figure 2, the shaft 20 which is fixed to the cutting head and journalled on the arm 12 carries an angularly fast pinion 22 meshed with a rack 24 formed on the ram or piston rod of the hydraulic cylinder 26. Extension or contraction of the ram turns the pinion so as to adjust the angle of the cutting head relative to the arm 12. CLAIMS

1. A mower comprising a cutter head mounted on the end of a boom or system of arms for projecting the head laterally of a tractor, and means for controlling the angle of the head relative to the boom or arms comprising pinion fast with the cutter head and journalled on the boom or arms, and a rack carried by said boom or arms and ram displaced to turn the pinion.

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