GB2084269A - Hydraulically operated folding drawbars of agricultural trailers - Google Patents

Abstract

The drawbar 3 of a trailer 1 is arranged to fold downwards when necessary (hydraulic cylinder 5 causing the drawbar to swing about pivot 4 on frame member 2 between the positions shown in Fig. 1 and Fig. 2) with concomitant detent action (of a line 12 e.g. a rope or cable) to prevent actuation of an overrun brake of the trailer (via linkage 11) by holding a brake lever 8 in its basic position against reverse force applied to the lever (at arm 9) by a towing eye 6. When the drawbar 3 is swung back to its unfolded position (Fig. 1) the lever 8 is automatically released (line 12 going slack) to ensure that the overrun brake will operate during road travel. <IMAGE>

Description

SPECIFICATION Hydraulically operated folding drawbars of agricultural trailers The invention relates to hydraulically operated folding (downwardly pivotable) drawbars of agricultural trailers, such drawbars being advantageous when, for example, the trailer is to be run into a flat or surface silo for unloading.

A problem arises, however, in that, the drawbar having an overrun brake actuating device, with known drawbar arrangements, the towing eye has first to be moved into its fully drawn-out position and then locked therein by a manually actuated device. Otherwise, with the drawbar folded down, the overrun brake would come into action owing to the reverse force acting on the towing eye, preventing further movement of the trailer.

A disadvantage with known constructions is the cumbersome manipulation as well as, more especially, the possibility that the towing eye may be left in the locked condition after the drawbar has been swung back into position again, with the result that when the trailer is running on roads the absolutely necessary safety arrangement provided by the automatically acting overrun brake apparatus is absent. Serious accidents may occur as a consequence.

The invention has as its object to provide a constructionally simple arrangement with which the overrun brake apparatus is automatically rendered inoperative when the drawbar is folded down and is automatically returned to an operative condition when the drawbar is swung back again.

According to the present invention there is provided a folding drawbar as defined in claim 1 of the ciaims appended to this specification.

Further features of the invention are indicated in the subordinate claim(s) and in the following description in which a constructional example is described in some detail with reference to the accompanying drawings wherein: Fig. 1 shows a folding drawbar swung into its upper position; and Fig. 2 shows it in its lowered or folded-down position.

The trailer belonging to this constructional example is fundamentally of known type in its structure and function and its details are not of importance to the present invention, so it will not be described herein and only the front part of the vehicle frame 1 of such a trailer is shown.

A folding drawbar 3 is mounted on the front transverse frame member 2 of the vehicle frame 1 in such manner as to be pivotable in a vertical plane about a horizontal pivot pin 4 by means of a hydraulic cylinder 5 pivotably connected to the folding drawbar 3 and to the vehicle frame 1.

The towing eye 6 is guided in the drawbar 3 so as to be longitudinally movable and, when pulled by the tractor, is held in its drawn-out position which is limited by an abutment (not shown).

When the tractor is braked, the towing eye is displaced in the direction of the inner end of the drawbar by the thrust of the hitched-on trailer.

When this happens, a two-arm brake lever 8, which is mounted on a pivot 7 in the drawbar 3 and abuts with one arm 9 on the rear end of the towing eye 6 and whose other arm 10 is pivotably connected to the linkage 11 leading to the braking apparatus of the trailer, is moved pivotally in such a manner that the trailer is automatically braked.

There is further connected pivotably to the arm 10 of the two-arm brake lever 8 a line 12 (which may be a rope or a cable) whose other end is secured to the vehicle frame 1. The line 12 is of such length that in the normal position of the drawbar, i.e. when the drawbar is swung into the upper position relatively to the vehicle frame 1, the said line hangs down loosely, whereas in the position to which the drawbar 3 is swung down by the hydraulic cylinder 5 the line is tensioned. Thus in the latter position the line 12 acts as detent means such that the brake lever 8 is prevented from moving pivotally and is thus held in a position in which the trailer brake apparatus is inoperative.

This ensures that, without any contribution by the tractor driver, the overrun brake apparatus is rendered inoperative when the drawbar 3 is folded down but is rendered operative in the normal position of the drawbar 3, i.e. for travelling on roads.

1. Hydraulically operated folding drawbar of an agricultural trailer with an automatically operating overrun brake apparatus, comprising a brake lever which is mounted to be movable in the drawbar and which is connected by linkage means to the brake apparatus of the trailer, the brake lever being movable by abutment on a rear portion of a towing eye of the drawbar when the latter is displaced longitudinally rearwards, characterised in that, when the drawbar is swung down, the brake lever is held in its basic position, wherein it does not act on the vehicle brake apparatus, by detent means connected to the frame of the vehicle, and when the drawbar is swung back the said brake lever is automatically released again from the detent means.

2. Hydraulically operated folding drawbar according to claim 1, characterised in that, the brake lever being a two-arm lever which is mounted to be pivotable about a pivot pin and whereof one arm engages the towing eye, detent means comprising a line which is connected to the second arm in such manner that it is loose when the drawbar is not folded and is tensioned when the drawbar is folded down.

3. A folding drawbar substantially as herein described with reference to the accompanying drawings.

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

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Hydraulically operated folding drawbars of agricultural trailers The invention relates to hydraulically operated folding (downwardly pivotable) drawbars of agricultural trailers, such drawbars being advantageous when, for example, the trailer is to be run into a flat or surface silo for unloading. A problem arises, however, in that, the drawbar having an overrun brake actuating device, with known drawbar arrangements, the towing eye has first to be moved into its fully drawn-out position and then locked therein by a manually actuated device. Otherwise, with the drawbar folded down, the overrun brake would come into action owing to the reverse force acting on the towing eye, preventing further movement of the trailer. A disadvantage with known constructions is the cumbersome manipulation as well as, more especially, the possibility that the towing eye may be left in the locked condition after the drawbar has been swung back into position again, with the result that when the trailer is running on roads the absolutely necessary safety arrangement provided by the automatically acting overrun brake apparatus is absent. Serious accidents may occur as a consequence. The invention has as its object to provide a constructionally simple arrangement with which the overrun brake apparatus is automatically rendered inoperative when the drawbar is folded down and is automatically returned to an operative condition when the drawbar is swung back again. According to the present invention there is provided a folding drawbar as defined in claim 1 of the ciaims appended to this specification. Further features of the invention are indicated in the subordinate claim(s) and in the following description in which a constructional example is described in some detail with reference to the accompanying drawings wherein: Fig. 1 shows a folding drawbar swung into its upper position; and Fig. 2 shows it in its lowered or folded-down position. The trailer belonging to this constructional example is fundamentally of known type in its structure and function and its details are not of importance to the present invention, so it will not be described herein and only the front part of the vehicle frame 1 of such a trailer is shown. A folding drawbar 3 is mounted on the front transverse frame member 2 of the vehicle frame 1 in such manner as to be pivotable in a vertical plane about a horizontal pivot pin 4 by means of a hydraulic cylinder 5 pivotably connected to the folding drawbar 3 and to the vehicle frame 1. The towing eye 6 is guided in the drawbar 3 so as to be longitudinally movable and, when pulled by the tractor, is held in its drawn-out position which is limited by an abutment (not shown). When the tractor is braked, the towing eye is displaced in the direction of the inner end of the drawbar by the thrust of the hitched-on trailer. When this happens, a two-arm brake lever 8, which is mounted on a pivot 7 in the drawbar 3 and abuts with one arm 9 on the rear end of the towing eye 6 and whose other arm 10 is pivotably connected to the linkage 11 leading to the braking apparatus of the trailer, is moved pivotally in such a manner that the trailer is automatically braked. There is further connected pivotably to the arm 10 of the two-arm brake lever 8 a line 12 (which may be a rope or a cable) whose other end is secured to the vehicle frame 1. The line 12 is of such length that in the normal position of the drawbar, i.e. when the drawbar is swung into the upper position relatively to the vehicle frame 1, the said line hangs down loosely, whereas in the position to which the drawbar 3 is swung down by the hydraulic cylinder 5 the line is tensioned. Thus in the latter position the line 12 acts as detent means such that the brake lever 8 is prevented from moving pivotally and is thus held in a position in which the trailer brake apparatus is inoperative. This ensures that, without any contribution by the tractor driver, the overrun brake apparatus is rendered inoperative when the drawbar 3 is folded down but is rendered operative in the normal position of the drawbar 3, i.e. for travelling on roads. CLAIMS

1. Hydraulically operated folding drawbar of an agricultural trailer with an automatically operating overrun brake apparatus, comprising a brake lever which is mounted to be movable in the drawbar and which is connected by linkage means to the brake apparatus of the trailer, the brake lever being movable by abutment on a rear portion of a towing eye of the drawbar when the latter is displaced longitudinally rearwards, characterised in that, when the drawbar is swung down, the brake lever is held in its basic position, wherein it does not act on the vehicle brake apparatus, by detent means connected to the frame of the vehicle, and when the drawbar is swung back the said brake lever is automatically released again from the detent means.

2. Hydraulically operated folding drawbar according to claim 1, characterised in that, the brake lever being a two-arm lever which is mounted to be pivotable about a pivot pin and whereof one arm engages the towing eye, detent means comprising a line which is connected to the second arm in such manner that it is loose when the drawbar is not folded and is tensioned when the drawbar is folded down.

3. A folding drawbar substantially as herein described with reference to the accompanying drawings.