GB2115261A - Levelling device - Google Patents

Abstract

There is described a levelling device for mounting on a tractor in order to assist in the digging and laying of drains. The levelling device comprises first sighting means 10 height- adjustably mounted on the tractor and second and third sighting means 12, 14 which may be positioned along a desired line to determine the level to be maintained. A cable 20 connects the adjustable sighting-means 10 to the implement 30. <IMAGE>

Description

SPECIFICATION Levelling device This invention relates to a levelling device.

The invention has particular application in assisting in the positioning of a tractor drawn implement, such as a drainer, at a desired depth to ensure the correct drain gradient is obtained.

According to the present invention there is provided a levelling device comprising a first sighting means slidably movable on a support mounted on a tractor, cable means for attaching said sighting means to an implement mounted on the tractor, the depth of which implement is to be controlled, and second and third sighting means for determining the level to be maintained.

Preferably, said first sight means is a variable cross-head and said second and third sight means are fixed cross-heads.

Preferably also, said implement is a drainer.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:- Fig. 1 illustrates schematically a levelling device made in accordance with the present invention; and Fig. 2 shows one example of a variable cross-head.

Referring to the drawings, a levelling device comprises a first sighting means in the form of a variable cross-head 10 slidably mounted on a vertical shaft 11 fixed to the front end of a tractor 1.

The variable cross-head is connected by means of a cable20orthe like to a rear mounted implement 30 in the form of a drainer. In the digging of drains a specified gradientisto be maintained and to this end, second and third, fixed cross-heads 12,14 are provided for positioning at two spaced pointsfrom the tractor along a desired line.

In use, the operator sets the drainer30atthe working depth at one end of the drain to be dug. The variable cross-head 10 is set at a comfortable eye level and the cable 20 is connected to the drainer 30 without slack. The height ofthe cross-head 10 to the ground is then measured.

The second,fixed cross-head 12 isthen set in the ground at the height of the movable cross-head 10 plus an additional amount representing the desired gradient of the drain. The third, fixed cross-head 14 is then aligned with the first cross-head 10 and second cross-head 1 2to give a reference line.

The tractor is then driven along the drain line, adjusting the height of the drainer 30 by means of the hydraulic control, to ensure that the three cross heads remain aligned. In this way accurate drain digging is achieved.

Modifications and improvements may be incorpo rated without departing from the scope of the invention.

1. A levelling device comprising a first sighting means slidably movable on a support mounted on a tractor, cable means for attaching said sighting means to an implement mounted on the tractor, the depth of which implement is to be controlled, and second and third sighting means for determining the level to be maintained.

2. A levelling device as claimed in claim 1 wherein thefirst sight means is constituted by a crneshead which is height-adjustable on said support.

3. A levelling device as claimed in either preced- ing clatrnwherein the second and third sighting means arefixed to cross-heads.

4. A levelling device as claimed in any preceding claim wherein said implement is a drain digging device.

5. A levelling device substantially as hereinbefore' 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 Levelling device This invention relates to a levelling device. The invention has particular application in assisting in the positioning of a tractor drawn implement, such as a drainer, at a desired depth to ensure the correct drain gradient is obtained. According to the present invention there is provided a levelling device comprising a first sighting means slidably movable on a support mounted on a tractor, cable means for attaching said sighting means to an implement mounted on the tractor, the depth of which implement is to be controlled, and second and third sighting means for determining the level to be maintained. Preferably, said first sight means is a variable cross-head and said second and third sight means are fixed cross-heads. Preferably also, said implement is a drainer. Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:- Fig. 1 illustrates schematically a levelling device made in accordance with the present invention; and Fig. 2 shows one example of a variable cross-head. Referring to the drawings, a levelling device comprises a first sighting means in the form of a variable cross-head 10 slidably mounted on a vertical shaft 11 fixed to the front end of a tractor 1. The variable cross-head is connected by means of a cable20orthe like to a rear mounted implement 30 in the form of a drainer. In the digging of drains a specified gradientisto be maintained and to this end, second and third, fixed cross-heads 12,14 are provided for positioning at two spaced pointsfrom the tractor along a desired line. In use, the operator sets the drainer30atthe working depth at one end of the drain to be dug. The variable cross-head 10 is set at a comfortable eye level and the cable 20 is connected to the drainer 30 without slack. The height ofthe cross-head 10 to the ground is then measured. The second,fixed cross-head 12 isthen set in the ground at the height of the movable cross-head 10 plus an additional amount representing the desired gradient of the drain. The third, fixed cross-head 14 is then aligned with the first cross-head 10 and second cross-head 1 2to give a reference line. The tractor is then driven along the drain line, adjusting the height of the drainer 30 by means of the hydraulic control, to ensure that the three cross heads remain aligned. In this way accurate drain digging is achieved. Modifications and improvements may be incorpo rated without departing from the scope of the invention. CLAIMS

1. A levelling device comprising a first sighting means slidably movable on a support mounted on a tractor, cable means for attaching said sighting means to an implement mounted on the tractor, the depth of which implement is to be controlled, and second and third sighting means for determining the level to be maintained.

2. A levelling device as claimed in claim 1 wherein thefirst sight means is constituted by a crneshead which is height-adjustable on said support.

3. A levelling device as claimed in either preced- ing clatrnwherein the second and third sighting means arefixed to cross-heads.

4. A levelling device as claimed in any preceding claim wherein said implement is a drain digging device.

5. A levelling device substantially as hereinbefore' described with reference to the accompanying drawings.