GB2040656A - Agricultural seed drills - Google Patents

Abstract

An agricultural seed drill comprises a first frame 10 for connection to a towing vehicle, a second frame 14, and a pivotal connection between the two frames 10 and 14. Arm assemblies 18 are independently pivotally mounted on the second frame 14 and each arm assembly carries at least one disc 22 and at least one roller 24. Front springs 26 and rear springs 28 acting between the arm assemblies 18 and the second frame 14 are disposed respectively forward of the transverse axis of the roller 24 and rearward of the transverse axis. The springs 26 and 28 are arranged such that the depth of operation of discs 22 is substantially independent of the weight of material in a container which is supported on the second frame 14. <IMAGE>

Description

SPECIFICATION Agricultural seed drills This invention relates to agricultural sowing of seeds by a technique of slit sowing, in which seeds are implanted in slits or narrow slots cut in the ground.

In particular the invention is concerned with apparatus (hereinafter referred to as "apparatus of the kind set forth") for seeding ground in the use of which seeds from container means mounted on a frame assembly connected to a towing vehicle are delivered through tubes to slits which are cut and opened in the ground by a plurality of discs mounted on the frame assembly for rotation about generally transverse axes, roller means mounted on the frame assembly in a position rearwardly of the discs for rotation about a transverse axis being adapted to compact the ground and close the slits after seeds have been implanted therein.

There is known an apparatus of the kind set forth in which the frame assembly comprises first and second relatively movable frames, of which the first frame comprises a draw bar for connection to a towing vehicle, and the second frame forms a mounting for a plurality of transversely spaced, longitudinally extending, arm assemblies carrying the discs, the arm assemblies being located below the frames and being urged downwardly away from the second frame by resilient means, and a resilient connection being provided between the first and second frames by adjustment of which the loading applied to the discs can be varied to control penetration of the discs into the ground and the depth of the slits thus produced.

An apparatus as described in the last preceding paragraph is hereinafter referred to as an "apparatus of the particular kind set forth". One example of an apparatus of the particular kind set forth is described in U.K. Patent Specification No. 1 218 785, in which the second frame is pivotally mounted on the first frame. Front and rear compression springs are located between each of the arm assemblies and the second frame, and each arm assembly trails from a transverse shaft, carried by the second frame, to which it is pivotally connected. The angular disposition of the second frame on the first frame can be adjusted, to vary the loading on the discs, by a screw arrangement to which the second frame is resiliently connected. The container means comprises both a seed box and a fertilizer box for fertilizer.

In use of a seed drill as described in Specification number 1 218785 it has been found that as sowing progresses adjustments have to be made in order to keep adequate weight on the discs, to provide the desired penetration of the ground, whilst maintaining sufficient weight on the roller means for compaction of the ground after seeding. This difficulty arises because the weight of material (seed and, optionally, fertilizer) in the container means decreases as sowing progresses, and as a result the distribution of weight on to the discs and rollers changes. The situation is complicated by the fact that the varying weight distribution also affects the loading on the towing point of a tractor towing the drill, with the result that the attitude of the tractor may vary, also to affect the loading on the discs.

It is an object of the present invention to provide an apparatus of the particular kind set forth in the use of which less difficulty arises with varying weight distribution as sowing progresses.

According to my invention in apparatus of the kind set forth the frame assembly comprises a first frame for connection to a towing vehicle, a second frame, and a pivotal connection between the two frames, the arm assemblies are independently pivotally mounted on the second frame, and each arm assembly carries at least one of the discs and at least one roller of the roller means, and the resilient means comprise front and rear springs acting between the arm assemblies and the second frame, the front springs being mounted forward of the transverse axis of the roller means and the rear springs being mounted rearward of the transverse axis of the roller means, the front and rear springs being so constructed and arranged that the loading on the discs is substantially independent of the weight of the material in the container means which is supported on the second frame.

This is achieved by convenient selection of the strengths of the front and rear springs.

The weight of the material in the container means is taken by the rollers and a draw-bar of a towing vehicle in proportions dependent upon the distance of the container means from the draw-bar and from the axis of rotation of the rollers.

The loading on the discs is substantially dependent upon a pre-load imparted to the front springs by moving the first frame angularly with respectto the second frame about the pivotal connection between the frames which is located at the rear ends of the frames remote from the draw-bar.

Only a single pivotal connection is provided between each arm assembly and the second frame and such a connection is located at the forward end of the second frame, the arm assemblies and the second frame being otherwise unconnected apart from the provision of the front and rear springs.

The relative spring strengths are preferably chosen in accordance with the position of the container means on the second frame. It is advantageous for the rear springs to be as weak as possible so that the rollers are able to follow closely the contours of the ground. This, in turn, dictates the strength of the front springs.

Preferably the container means is disposed on the second frame at a location such that, in a normal attitude of the apparatus during a sowing operation the centre of gravity of material in the container means remains substantially vertically above the transverse axis of rotation of the roller means as sowing progresses.

By arranging the container means close to, or substantially vertically above, the transverse axis of rotation of the roller means ensures that a smaller proportion of the weight is taken by the draw-bar, and a larger proportion of the roller means.

There now follows a description, to be read with reference to the accompanying drawings, of an agricultural seed drill which illustrates the invention by way of example.

In the accompanying drawings; Figure 1 is a diagrammatic view in side elevation of the drill in a first position of adjustment; Figure 2 is a view similar to Figure 1 but with the drill in a second position of adjustment.

The drill is constructed very similarly to that described with reference to Figures 1 to 7 of U.K.

Patent Specification number 1 218785. The drill is an apparatus of the particular kind set forth with a frame assembly comprising a first frame 10, comprising a draw bar 12 for connection to a towing vehicle, and a second frame 14 which is pivotally mounted, at 16, on the first frame. A plurality of arm assemblies 18 (one only visible in the drawings) are located beneath the frames and are independently pivotally mounted, at 20, on the second frame, so as to trail from the pivotal mountings 20. Each arm assembly carries rotatably mounted discs 22 and two rollers 24, one disc and one roller being mounted on each side of the arm assembly. One front spring 26 and one rear spring 28 act between each arm assembly 18 and the second frame 14, the front springs 26 being mounted in front of a common transverse axis of rotation of the rollers 24 and the rear springs 28 being mounted behind the transverse axis of the rollers. The resilient connection between the first and second frames, for adjustment of the loading applied to the discs 22 in use of the drill, comprises a rotatable screw member 30 threadedly mounted in a trunnion block 32 on the first frame 10. The second frame 14 is secured to a second trunnion block 34 through which the screw member 30 extends. The second trunnion block 34 is freely slidable along the screw member 30 and is resiliently located between two abutments on the screw member by compression springs 36 and 38.

By rotation of the screw member 30, the angular adjustment of the second frame 14 on the first frame 10 can be varied to vary the loading on the discs 22.

The drill comprises container means in the form of a seed box 40 mounted on the second frame 14 to contain a supply of seeds to be dispensed in use of the drill. Means for dispensing the seeds from the seed box, and directing the seeds into slits cut in the ground by the discs 22, is constructed and arranged substantially as in the aforementioned drill described in Specification number 1 218785.

The drill shown in the drawings differs from the aforementioned drill described in Specification No. 1 218785 in the arrangement of the front springs 26 and the rear springs 28, and in the mounting of the arm assemblies 18 on the second frame 14.

As shown in Figure 2 there are no pivotal mountings between the rear ends of the arm assemblies 18 and the second frame, and, apart from the front springs 26 and the rear springs 28, the arm assemblies are connected to the second frame 14 only by the pivotal connection 20 attheirforward ends. Also the spring constants of the front and rear springs 26 and 28 are selected so that the weight of the material in the container means is transferred through them to the rollers 24 and the draw-bar with substantially none of that weight being transferred to the discs. It follows therefore that the loading on the discs 22, and in consequence the penetration of the discs 22 in the ground during a drilling operation, is independent of the loading on the second frame 14 and is determined solely by operation of the screw member 30 to urge the frames 10 and 14 relatively towards each other as shown in Figure 2, thereby preloading the front springs 26.

Preferably the container means is arranged on the frame assembly so that in the normal attitude of the drill during a sowing operation the centre of gravity of material in the container means is vertically above the transverse axis of rotation of the rollers 24 (as indicated by the chain-dot line 42), and will so remain as sowing progresses and the weight of material in the container means falls. As a consequence the loading from the draw baw 12 on the towing point of a towing vehicle does not vary with weight of material in the container means.

It will be appreciated that although the container means of the drill shown in the drawings is in the form of a single seed box 40, the container could take various alternative forms arranged so that the centre of gravity of material therein remained vertically above the axis of the rollers 24 during a sowing operation. For example, the container means might comprise a seed box and a separate fertilizer box, the two boxes being located on opposite sides of the axis of the rollers 24 but being balanced about the axis so that the centre of gravity of all the material in the two boxes remains vertically over the axis during sowing. Alternatively the container means could be in the form of a single box which iscompartmented to accommodate more than one material.

As referred to above the springs 26 and 28 have spring constants such that the loading on the discs 22 is substantially independent of the weight of material in the container means. When a load is applied to the second frame 14 by material in the container means, some of this load is applied to the rear springs 28. The applied load causes a compression of the rear springs 28, and accordingly the second frame is lowered at its rear end. The loading from the draw bar 12 on the towing point remaining constant, the height above the ground of the front end of the draw bar can be considered to be constant. The front springs 26 are mid-way between the towing point and the rear springs 28, and accordingly a lowering of the rear end of the second frame 14 by a certain distance is accompanied by a lowering of the second frame at the front springs 26 by one half of that distance. In order that the discs 22 should not thus be lowered, which lowering (which would alter with the load in the container means) would affect the loading on the discs 22 during a sowing operation, it is necessary that the effect should be cancelled out by the tendency for the arm assemblies 18to pivot about the axis of the rollers 24 due to the load from the springs 28. In the drill shown in the drawings, the front springs 26 are such that they will deflect 1 inch (2.54 cm.) for each 56 pounds (25.4 kg.) of loading, and the rear springs 28 are such that they will deflect 1 inch (2.54 cm.) for each 63 pounds (28.6 kg.) of loading. The distance from the axis of the rollers 24 to the front springs 26 is 36 inches (91.4 cm.) and to the rear springs 28 is 16 inches (40.6 cm.). A load of 260 pounds (118keg) in the container means acting through vertically above the transverse axis of rotation of the rollers 24 is balanced by the rollers 24 and this is taken up by the rear springs 28 180 pounds (81.6 kg) and the front springs 2680 pounds (36.4 kg).

The rear springs 28 will compress 180/63 = 2.86 inches (7.55 cm) because the rear springs 28 compress an extra 2.86 inches (7.55 cm) the front springs 26 will have to compress half of this amount i.e. an extra 1.43 inches (3.75 cm) so that the same loading of 70 pounds (31.8 kg) will be maintained on the front springs 26 to keep the required depth of penetration of the discs 22. The front springs 26 with a load of 80 pounds (36.4 kg) will compress 80/56 = 1.43 inches (3.75 cm). This is calculated compression required to maintain the system in equilibrium. That is, to maintain a constant applied pressure to the front springs 26 (disc depth control) no matter what weight is applied to the frame assembly: This is irrespective of the quantity of seed and/or fertilizer in the respective boxes. Suppose the weight were reduced to 130 pounds (59 kg). Then a load of 90 pounds (40.8 kg) on the rear spring would compress (or lower) it 90/63 = 1.43 inches (3.75 cm).

To maintain the proper depth control the front springs 26 would have to compress (or lower) half this amount i.e. .715 inches (1.90 cm).

Since there is a load of 40 pounds (18.2 kg) on the front springs 26 then they would each compress (or lower) 40/56 = .715 inches (1.90 cm).

By having the weight of the seeds and/or fertilizer boxes balanced about the rollers 24 no extra weight is added to or taken from the draw-bar hitch point no matter whether the boxes are empty or full.

If the weight of the seed and/or fertilizer boxes is moved forward on the main frame say to halfway between the draw-bar hitch point and the rollers 24, then half this weight would be taken up on the draw-bar and half on the rollers 24. Depth control would still be maintained by using the same spring arrangement as above but would be influenced by the weight on the draw-bar.

This extra weight on the draw-bar could vary from nothing to 1000 pounds (454 kg) and could perhaps affect the height of the hitch point and thus the depth control of the drill.

Claims (5)

1. Apparatus of the kind set forth in which the frame assembly comprises a first frame for connection to a towing vehicle, a second frame, and a pivotal connection between the two frames, the arm assemblies are independently pivotally mounted on the second frame, and each arm assembly carries at least one of the discs and at least one roller of the roller means, and the resilient means comprise front and rear springs acting between the arm assemblies and the second frame, the front springs being mounted forward of the transverse axis of the roller means and the rear springs being mounted rearward of the transverse axis of the roller means, the front and rear springs being so constructed and arranged that the loading on the discs is substantially independent of the weight of the material in the container means which is supported on the second frame.

2. Apparatus as claimed in c!aim 1, in which only a single pivotal connection is provided between each arm assembly and the second frame and such a connection is located at the forward end of the second frame, the arm assemblies and the second frame being otherwise unconnected apart from the provision of the front and rear springs.

3. Apparatus as claimed in claim 1 or claim 2, in which the relative spring strengths are chosen in accordance with the position of the container means on the second frame.

4. Apparatus as claimed in any preceding claim in which the container means is disposed on the second frame at a location such that, in a normal attitude of the apparatus during a sowing operation, the centre of gravity of material in the container means remains substantially vertically above the transverse axis of rotation of the roller means as sowing progresses.

5. Apparatus of the kind set forth substantially as described herein with reference to and as illustrated in the accompanying drawings.