GB2170383A

GB2170383A - Plough with semi-automatic overload safeguard

Info

Publication number: GB2170383A
Application number: GB08525523A
Authority: GB
Inventors: Laak Theo Van; Gottfried Giesen
Original assignee: Lemken GmbH and Co KG
Current assignee: Lemken GmbH and Co KG
Priority date: 1985-01-31
Filing date: 1985-10-16
Publication date: 1986-08-06
Also published as: DK37786D0; GB2170383B; DK37786A; GB8525523D0; CH667366A5; FR2576740B1; DE3503135A1; FR2576740A1; ATA264585A; DE3503135C2

Abstract

The plough comprises an overload protection device having a roller 7 disposed between the tool stem 5 and the locking element 14 and rolling freely on the rolling faces 11, 12. When the plough share carried by the stem experiences a load the stem pivots and distorts the locking element and the stem in the region of its contact with the roller. On an overload, this distortion will be followed by the roller moving with its locking element and out of engagement with the stem. As illustrated, the rolling face 12 or the stem is provided by a surface of a leaf spring 22. <IMAGE>

Description

SPECIFICATION Plough with semi-automatic overload safeguard The invention relates to a device for protecting ploughs and other soil-working implements against overload with a roller disposed directly or indirectly between the tool stem and the locking element and rolling freely on the rolling faces.

Such overload safeguards are used to avoid deformation or destruction of the plough frame or plough bottom for example, should either strike stones or strong roots or the like. Whereas in the case of the so-called fully automatic overload safeguards, the tool stem or for example the plough bottom, together with the tool stem, will be pivoted about a point upon encountering a correspondingly large rock or root and then pushed back into its starting position, it is necessary in the case of the socalled semi-automatic overload safeguards to stop the tractor unit and push the outwardly pivoted tool stem back into its working position, while it is braced on or in the ground. In the case of known semi-automatic overload safeguards, the tool stem is, as a rule, held in the normal position by strong springs and a ratchet or the like.When an obstacle is struck, the ratchet disengages after it has overcome the preset spring pressure and the tool stem pivots rearwards about a pivot point. It has been found to be difficult to use the spring in order accurately to adjust the point at which the tool stem swings out with the tool connected to it. This is particularly true because the effect of the overload safeguard is altered after just a very short time due to rust and other influences.

An overload safeguard is known (DAS 10 90 895) in which the tool stem carrying the working implement is pivotable about an axis and between two plates, an upper lever arm of this tool stem being provided with a groove into which engages the roller on a detentwhich is bent over resiliently to a U-shape and which is mounted to be likewise pivotable on the plates. In the case of one embodiment of this overload safeguard, the roller provided in the detent also lies in recesses in the two plates which are provided with oblique faces on one side. In the case of another embodiment, instead of these oblique faces, a link is articulatingly connected to the end of the detent and is fixed to the plates in such a way as to be pivotable about a journal.If a considerable force acts on the ploughshare, then the tool stem carrying it is pivoted somewhat about its pivoting axis. This results in the detent which is bent into a U-shape being somewhat deformed so that the distance between the pivoting axis of the detent and the roller changes, i.e. according to the location of the pivoting axis of the detent in relation to the pivoting axis of the tool stem it is either increased or decreased. This yielding of the detent results in the roller provided at the other end arriving against the oblique faces on the plates and when a certain force is exceeded, the roller is pressed out of the groove in the tool stem, so that it releases the tool stem. The same function as these oblique faces on the plates is fulfilled by a link engaging the end of the detent.A disadvantage of this is that between the roller and the carrying plates on the one hand and the roller and the tool stem on the other, considerable friction forces occur so that considerable wear and tearwill result. Therefore, after a short time the device operates in an unreliable manner, particularly since adjustment of the exact triggering force is not possible. For the rest, functioning is possible only if the oblique faces are manufactured to a degree of accuracy which is unusually high for agricultural machinery.

A roller is also the working medium of the overload safeguard known from DAS 12 04 445, which is mounted freely between ratchet and tool stem. By reason of this free mounting of the roller, friction is intended to be reduced or should only occur in the triggering range as rolling friction. The ratchet is pretensioned with a powerful spring so that the overload safeguard is triggered only when the spring force is overcome. By virtue of the considerable pretensioning force of the spring, it is only possible with considerable difficulty to pivot the tool stem against the fo rce of the spring and back into its working position once it has been triggered. Furthermore, the known overload safeguard requires considerable space for accommodation ofthe individual components.In consequence, the free spaces between the articulation on the plough frame and the tools are very restricted but are very important to the work of ploughing. In addition, the weight of the plough fitted with such an overload safeguard becomes so great that these ploughs can only be used in conjunction with large tractors, i.e. tractors having considerable tractive capacity.

Instead of a strong spring, an overload safeguard known from DAS 12 47 726 has a flexible detent which is mounted at one end to be rotatable on the supporting part and to be connected to the tool stem via a mounted roller. Under load, deformation causes the detent to slip out of the roller. The detent itself is again pretensioned by a spring so that the entire system is subject to considerable friction influences both by reason of the spring force and also by reason of the mounting of the roller and the other parts. According to the lubrication, so the system triggers more or less early, so that an accurate adjustment is not feasible here, either.

Another disadvantage is the considerable space required for the individual components, so that the free space already mentioned above becomes considerably restricted.

Despite these described disadvantages, these semi-automatic overload safeguards are substantially more favourably costed than the fully automatic stone safeguards which, by reason of the automatic facilities required and the weight this involves, usually have to cope with fewer furrows than standard units, by virtue of the limited lifting capacity of the tractor. For the rest though, they do cause less time loss and are easier to use than the known shear-off safeguards where, when there is a break, the tractor driver has to leave the tractor and fit a new shearing pin.

The invention is therefore based on the problem of providing a simple compact lightweight semiautomatic overload safeguard for earth-working implements, particularly ploughs.

According to the invention, the problem is resolved in that the locking element and tool stem between which the roller is located is in the region of its rolling faces constructed so that it undergoes a variation in angle when under load.

This lock or the roller is according to the invention so mounted that when an overload occurs only the rolling friction has to be overcome in order to trigger the device. The solution according to the invention achieves this in that the two faces or parts between which the roller is located undergo a variation in angle, initiating and at the same time facilitating the rolling process.

Thus, the point of response of the overload safeguard can on the one hand be accurately predetermined and on the other accurately maintained. The roller itself and its function is not affected by any rust formation or the like.

Therefore, environmentai conditions cannot have a negative effect on the functional efficiency of the overload safeguard.

According to an expedient development of the invention, locking element and tool stem are in the region of their rolling faces so constructed or located that at the moment of being triggered, their normals extend virtually parallel with each other.

Consequently, the locking element and tool stem in any case support the roller in linearfashion so that friction is minimised. This linear contact of the roller with the locking element on the one hand and the tool stem on the other is, according to this expedient embodiment, maintained actually at the moment of triggering, so that optimum conditions obtain at this decisive moment.

In this respect, it has been found expedient for the normals of the rolling faces or of the parts carrying the rolling faces to extend virtually parallel with one another. From the outset, this guarantees an optimum triggering process, the abovedescribed linear contact between locking element and roller on the one hand and tool stem and roller on the other always being present.

In the working position, the roller is held particularly expediently between the two parallel rolling faces in that the locking element is constructed as a hook pivotable out of a predeterminable dead centre position and adapted to brace the roller on both sides. Together with the tool stem, the roller is therefore enclosed on three sides, the hook determining by its shape and location the dead centre position out of which the roller has to be moved in order to free the locking element or the hook and thus the tool stem. When this dead centre position is overcome, the hook yields as a locking element or is pressed away so that locking of the tool stem, brought about solely by the roller, is released and the tool stem is capable of moving aside before the obstruction in the soil.

The overload safeguard can be easily, accurately and expediently adjusted or readjusted in keeping with circumstances since according to an advantageous embodiment of the invention the hook is held by an eccentric screw about which it is adapted to pivot. In this way, the dead centre position can be changed and with it the moment of response of the overload safeguard. Another possibility is that the pivot point about which the hook is pivotable may be movable. In this way, too, it is possible to vary the dead centre position and adapt it expediently to whatever circumstances apply. The mounting ofthe roller which is favourable for the full effect of the overload safeguard is for itto be held between tool stem and locking element but loosely although secured against falling out. Thus, only minimal forces of rolling friction can act on the roller.Any unintentional falling of the roller out sideways when the overload safeguard responds is according to a development of the invention prevented in that it is secured by guides which prevent it slipping out sideways. These guides have nothing to do with the actual functioning of the overload safeguard so they cannot affect the accuracy of response. They function only as a safeguard if the roller slips beyond its predetermined clearance, without any disadvantageous forces acting on the overload safeguard. The variation in angle which occurs under load can be brought about particularly favourably if the part of the tool stem which supports the roller is resiliently constructed, for example as a leaf spring. It is expedient for the leaf spring to be exchangeable to facilitate fitment or if necessary to facilitate exchange.Since also the hook is resilient, i.e. consists for example of spring steel, it is ensured that if a loading occurs, the rolling faces or their normals extend virtually parallel with one another and shift so that when the predetermined load is reached, the roller can respond and disengage the locking element.

The action of the leaf spring is favoured because the leaf spring is clamped at the end and braced on the tool stem at a distance from the rolling face. In this way, the leaf spring is virtually pretensioned because when it responds, i.e. when the tip is loaded, it bellies up in the centre in order thus to assist response of the locking element at the predetermined point.

Pivoting of the tool stem back into the starting position and re-engagement of the locking element are substantially facilitated in that the head face of the tool stem is constructed as a run-up ramp.

Thus, upon re-engagement, the roller runs on the oblique head face and back into the engaged position so that even in the event of sudden loadings during pushing back of the tractor, no deformation of the roller can occur.

If two tool stems are disposed opposite each other, for example in the case of a rotary plough, pivoting of the hook out of its supported position due to gravity is prevented in that the oppositely disposed locking elements, constructed as hooks, of two tool stems are braced on each other through a spacer, for example a spring. This spring is only so dimensioned that whichever hook happens to be associated with the tool which is not in the operative position is maintained in its hold position.

This spring and its rating, i.e. its strength, are not required for functioning of the overload safeguard itself.

The invention is in particular characterised in that a simple and accurately operating semi-automatic overload safeguard is provided which is advantageously of rugged construction and of which the efficiency is not adversely affected by environmental influences. The trigger point or moment of release can be accurately predetermined, so that the efficacy of the overload safeguard is substantially improved. Another advantage is that by relatively simple measures and by using structurally simple parts, it becomes possible to vary the point of response of the overload safeguard so that it is possible to adapt to conditions in the field.

Further details and advantages of the object of the invention will become evident from the ensuing description of the accompanying drawings which show a preferred example of embodiment, together with the details and components necessary therefor.

In the drawings: Fig. 1 is a side view of an overload safeguard in the working position;.

Fig. 2 shows an'overload safeguard at the moment of release; Fig. 3 shows the mounting of the locking element, and Fig. 4 shows two superposed overload safeguards.

In the case of the overload safeguard shown in section in Figs. 1 to 4, this is a safeguard for ploughs 1. Fig. 4 shows an overload safeguard suitable or envisaged for rotary ploughs.

The tool stem 5 is mounted on the plough frame 2 and secured by the overload safeguard. The safety feature is a locking element 6. A roller 7 is disposed between the locking element 6 and the tool stem 5, in fact in such a way that only in the region of the rolling faces 11, 12 does it have contact with the tool stem 5 on the one hand and the locking element 6 on the other. The roller 7 and also the roller 9 according to Fig. 4 are cylindrical and are prevented from falling out of the overload safeguard by laterally disposed guides which are not shown here.

The locking element 6, whether in the single form according to Fig. 1 or the double version shown in Fig. 4, where it is designated 8, is constructed as a hook 14 which, via its back portion 15 and together with the angle 18, prevents unintentional slipping out of the roller 7, 9. The hook 14 is connected to the housing 29 or plough frame 2 by an eccentric screw 16 or even a simple screw. The eccentric screw 16 is so located that the hook 14 is in a dead centre position which ensures that the hook can only move out of its position when it encounters a specific force or overload. By means of the eccentric screw 16, the relevant point of rotation can be so varied just by turning the screw that the dead centre position becomes correspondingly altered.With a variation in dead centre position, the response point of the overload safeguard is changed and/or adapted to suit the circumstances.

The angle 18 is mounted on the tool stem 5 by the supporting screw 19. The supporting screw 19 thus at the same time supports the leaf spring 22 by which the rolling faces 11, 12 acting on the roller 7,9 can be altered under load, just as they are by the hook 14 or its construction.

The efficiency of the leaf spring 22 is provided on the one hand by the setback 23 in the region of the tip 24 and also by the fact that it is fixed at one end, 25. Furthermore, the angle 18 has a recess 27 which allows the leaf spring 22 to belly out, as shown in Fig. 2. The head face 28 of the tool stem 5 is made sloping so that when the overload safeguard reengages, the roller 7,9 is able to slide along it and so facilitate engagement.

Fig. 2 shows the overload safeguard in Fig. 1 at the moment of being released, and it is clear that both the hook 14 and also the leaf spring 22 become so bent in the region of the rolling face 11,12 that they extend virtually parallel with each other so that there is still linear contact between tool stem 5 or locking element 6,8 and the roller 7,9. Upon the point shown here being further exceeded, the hook 14 is released so that it jumps back together with the roller 7 and releases the tool stem 5. The overload safeguard will then have responded and can be restored to the locking position by the implement or the plough 1 being pushed backwards.

Fig. 3 shows the construction of the eccentric screw 16 by which the hook 14 is fixed on the plough frame 2.

Finally, Fig. 4 shows a development of the invention for example in the case of a rotary plough, where the two locking elements 6, 8 supporting the rollers 7,9 are so braced by the spacer 10, in this case a spring, that they cannot be pivoted out of the supporting position by their own weight.

Claims

1. A device for protecting ploughs and other soilworking implements against overload with a roller disposed directly or indirectly between the tool stem and the locking element and rolling freely on the rolling faces, characterised in that the locking element (6, 8) and tool stem (5) between which the roller (7,9) is located is in the region of its rolling faces (11, 12) constructed so that it undergoes a variation in angle when under load.

2. A device according to Claim 1, characterised in that the locking element (6,8) and tool stem (5) are in the region of their rolling faces (11, 12) so constructed or located that at the moment of being triggered, their normals extend virtually parallel with each other.

3. A device according to Claim 1 and Claim 2, characterised in that also in the position of rest the normals of the rolling faces (1 1;12) or of the parts carrying the rolling faces extend virtually parallel with one another.

4. A device according to Claim 1, characterised in that the locking element (6,8) is constructed as a hook (14) pivotable out of a predeterminable dead centre position and adapted to brace the roller (7, 9) on both sides.

5. Device according to Claim 1 and Claim 4, characterised in that the hook (14) is held by an eccentric screw (16) about which it is adapted to pivot.

6. Device according to Claim 1, characterised in that the roller (7, 9) lies loosely between tool stem (5) and locking element (6, 8) and is in any event secured against falling out.

7. Device according to Claim 6, characterised in that the roller (7, 9) is secured by guides so that it cannot slip out sideways.

8. Device according to Claim 1, characterised in that the part of the tool stem (5) which supports the roller (7, 9) is resilient, being preferably constructed as a leaf spring (22).

9. Device according to Claim 8, characterised in thatthe leaf spring (22) is of interchangeable construction.

10. Device according to Claim 8, characterised in that the leaf spring (22) is clamped atthe end (25) and is supported on the tool stem (5) at a distance from the rolling face (11, 12).

11. Device according to Claim 1, characterised in thatthe head face (28) of the tool stem (5) is constructed as a run-up ramp.

12. Device according to Claim 1 and Claim 4, characterised in that when locking elements (6, 8) constructed as hooks (14) and provided on two tool stems (5) are mounted opposite each other, they are braced against each other by a spacer (10), preferably a spring.

13. A device for protecting ploughs and other soilworking implements against overload as claimed in Claim 1, substantially as herein described with reference to and as illustrated by the example shown in the accompanying drawings.