GB2265809A - Injecting slurry into soil - Google Patents

Abstract

An injector for intermittently injecting a slurry into soil comprises a leg 16 extending downwards from a support structure such that if the support structure is moved above the soil surface in a generally horizontal predetermined direction the lower end of the leg is pulled through the soil. The lower end of the leg supports a blade 20 extending transversely to the direction of movement through the soil and arranged to lift soil through which it is pulled. The lower end of the leg is caused to move cyclically relative to the support such that the depth of the blade beneath the support structure and hence beneath the soil varies cyclically. Slurry is supplied to the lower end of the leg through passageway 21 extending along or within the leg. The supply of slurry to each to leg is intermittent. <IMAGE>

Description

FLUID PRODUCT SOIL INJECTION The present invention relates to an injector for injecting a fluid product into soil and a method for operating such an injector.

It is well known to inject fluid products such as sewage slurry into the ground by pulling a downwardly extending leg through the ground so as to loosen the ground and injecting fluid product immediately behind the leg. Generally an array of downwardly extending legs is supported on a common support structure that is carried by a tractor, fluid product being injected behind each of the legs. Fluid product is supplied to each of the legs from a common slurry tank which is pressurised to force the slurry down parallel passageways extending to each of the legs.

The disposal of sewage sludge is an ever increasing problem and disposal by injection into the soil is a preferred solution to this problem. Unfortunately, as environmental protection regulations with regard to run-off of slurry into ditches and water courses have become more stringent, it is has become progressively more difficult to comply with those regulations.

With conventional injection apparatus, slurry is pumped continuously to each leg of the injector arrangement. If each leg was to receive a carefully metered supply of slurry such that the volume of slurry supplied for a given distance of movement of that leg through the soil could be tightly controlled the risk of run-off would be considerably reduced. Unfortunately it is not easy to distribute slurry through a series of parallel small diameter passageways given the nature of the product and there is a tendency for one or more of the passageways to become blocked. Thus even if a constant total rate of supply of slurry can be maintained the supply of slurry to each leg cannot be accurately predicted.As a result it is not unusual when using conventional slurry injection equipment to see slurry appearing on the surface or being left unabsorbed in relatively large soil cavities from which it can be washed by rain.

It would be possible to overcome the problem outlined above by using highly accurate metering equipment on each leg so that the problem of differential distribution between different legs can be avoided. Such a solution would however result in an unduly complex and expensive assembly.

If an injector was provided with a single leg the problem of differential fluid distribution would be avoided but nevertheless it would be difficult to accurately meter continuously the volumes of fluid product to be delivered to that single leg. Thus even with a single leg injector expensive components would be required to ensure that the injected fluid product was delivered in the appropriate volumes. Given the nature of for example sewage sludge the composition of which cannot be accurately determined in advance this is not an easily solved problem.

International Patent Application No. W087/04893 describes a subsoil aerator which is particularly effective as a means for loosening and aerating soil. In the described aerator, a plurality of legs are supported so as to extend downwards from a support structure which is carried by a tractor above the soil surface. The lower end of each leg supports a blade extending transversely to the direction of movement of the tractor and arranged so as to lift soil through which it is pulled. The lower end of the leg is moved cyclically in an elliptical path such that the depth of the blade beneath the support structure also varies cyclically, the legs moving out of phase so that the pulling force required from the tractor is minimised. It has been found that the described subsoil aerator is particularly good at breaking up soil.

It is an object of the present invention to provide an injector for injecting a fluid product into soil in such a manner that the risk of fluid product run-off is minimised.

According to the present invention, there is provided an injector for injecting a fluid product into soil, comprising a support structure which in use is moved above the soil surface in a generally horizontal predetermined direction, at least one leg extending downwards from the support structure and having a lower end which in use is pulled through the soil, a fluid product supply passageway extending to the lower end of the leg, and means for supplying fluid product to the passageway, wherein the fluid product supply means is arranged to intermittently supply fluid product to the passageway.

Preferably two or more legs are arranged on the support structure, each leg being provided with a respective fluid product passageway, and fluid product being supplied intermittently to each leg such that each leg receives fluid product in turn. Fluid product may be distributed to the leg such that the supply of fluid product to one leg is terminated shortly after the initiation of the supply of fluid product to a second leg. Preferably the legs are driven relative to the support structure such that the depth of the legs beneath the surface vary cyclically. Fluid product may be supplied in synchronism with movements of the lower ends of the legs. Fluid product may be supplied to each leg for a period corresponding to a single upward movement of that leg but alternatively fluid product may be supplied for a period corresponding to one or more complete cycles of the leg movement.

The legs may be driven from a common power supply which also drives a fluid product distributor. The distributor may be in the form of an outer tube having a series of axially spaced outlet ports each connected to a respective leg, and a coaxial inner tube driven by the same power supply and having a series of axially spaced inlet ports.

Each outlet port is axially aligned with a respective inlet port, the outlet ports being radially aligned and the inlet ports being radially offset so as to provide the desired intermittent fluid supply to each of the legs in turn.

The present invention also provides a method for operating a fluid injector of the type referred to above.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side view of an embodiment of the invention hitched to the back of an agricultural tractor; Figure 2 is a view of a support frame and depending legs of the embodiment of Figure 1 looking rearwardly; Figure 3 is a more detailed illustration of the interconnection between one of the legs shown in Figures 1 and the support frame on which it is mounted; Figure 4 is a view of part of the leg shown in Figure 3 taken on the lines 4-4; Figure 5 schematically illustrates the movement imparted to the tip of the leg shown in Figure 3 during use of the device; and Figure 6 schematically illustrates the operation of a distributor connected to the legs of embodiment described in Figures 1 and 2.

Referring to Figures 1 to 3, the illustrated embodiment of the invention comprises a support frame fabricated from square sectioned steel tube and including a front member 1, two substantially identical side members 2 and a rear member supporting upwardly extending brackets 3. Two plates 4 extend upwardly from the front member 1 to a top bracket 5 and a bracing link 6 extends from the bracket 5 to the rear member. When the frame is hitched to a towing vehicle as shown in Figure 1, an upper link 7 is pivotally connected to the bracket 5 and two lower links 8 are pivotally connected to the front member 1.

The links 7 and 8 are connected to conventional brackets on the towing vehicle, for example upper towing pivot 9. The vertical position of the frame can be controlled by lifting the links 8 so that they pivot about their points of connection to the towing vehicle.

The lifting mechanism is of conventional design and accordingly is not described in detail herein The front member 1 of the frame supports a gear box 10 having a splined input shaft coupled to power takeoff 11 of the towing vehicle by a transmission shaft 12. Toothed wheels 13 are supported on an output shaft of the gear box and drive a cam shaft 14 via chains 15. The cam shaft 14 is supported on suitable bearings mounted on the frame. The cam shaft drives four legs 16 which extend downwards from the support frame 1 as best illustrated in Figure 2.

As best seen from Figure 3, the cam shaft 14 extends through circular apertures 17 in each of the legs 16. Each leg is also connected to a respective bracket 3 by a pivotal link 18. In the regions of the cam shaft 14 which pass through the apertures 17 in the legs 16, the cam shaft 14 supports four cams 19. If we identify the legs shown in Figure 2 as first, second, third and fourth legs counting from the lefthand side, then the cams engaging the first and third legs are in phase, the cams engaging the second and fourth legs are in phase, but the two sets of in phase cams are 1800 out of phase with each other relative to the cam shaft. Thus as the cam shaft 14 rotates the cams 19 about the cam shaft axis, the centres of the apertures 17 execute a circular motion about the cam shaft axis.This has the effect of moving the leg in a vertical plane parallel to the direction in which the leg is dragged through the ground.

Blades 20 are supported adjacent the bottom ends of each of the legs 16. The blades 20 are best shown in Figure 4 and extend transversely to the direction of motion of the legs to a maximum distance of for example 15 centimetres on either side of the legs and extend in a direction parallel to the direction of motion of the legs to a distance of for example 20 centimetres. The blades 20 may subtend an angle with the horizontal of approximately 250.

If the vehicle to which the legs 16 are secured is stationary, the lower ends of the legs 16 perform an oscillatory motion in which the leg tip follow an elliptical path schematically illustrated in Figure 5.

The maximum horizontal displacement relative to the support frame may be for example in the range of 20 to 50 mm whereas the maximum displacement in the vertical direction may be of the order of 10 to 15 mm.

When the legs are pulled through the soil, the precise path followed by any one point on the legs depends on the speed of the vehicle which is pulling the legs. If the vehicle speed is low, then the legs move backwards and forwards through the soil in a direction parallel to the direction of vehicle motion. If the vehicle speed is relatively high, then the legs always are moving in the direction of motion of the vehicle but the speed of motion in that direction varies as the leg reciprocates relative to the support frame. The greater the maximum displacement of the leg relative to the support frame in the horizontal direction, the greater the vehicle speed at which leg movement through the soil is always in one direction.

Each leg supports a fluid passageway in the form of a pipe 21 extending down the rearward edge of the leg. The pipe 21 could of course be formed by an integral passageway within the body of the leg. The bottom end of the passageway 21 terminates adjacent the lower end of the leg and fluid to be injected is supplied under pressure through the passageway 21.

During each upward movement of the blades 20 supported by any one leg, a cavity is formed in the soil beneath the lifted blades.

Depending on the soil type, there would generally also be some tearing of the earth in front of and to each side of the leg so that the cavity beneath the blades 20 communicates with cavities extending forwards and to either side. Fluid pumped into the cavity beneath the blades 20 thus generally flows into the communicating cavities. As the leg is moved forward and lowered the tendency is for the fluid beneath and around the blades 20 to be thoroughly mixed with finely broken particles of soil. Thus rather than the fluid product rr.erely being injected into a cavity which remains dimensionally reasonably stable, the fluid product is in effect mixed with the soil around the leg.

In the arrangement described which has four legs, all of the legs could be continuously supplied with fluid from a common supply source, e.g. a pressurised container of slurry. If this approach were adopted however any blockage in one of the passageways 21 would result in all the delivered slurry going to the other three legs and thus there could be no confidence that the slurry was being evenly distributed through all of the four legs. Given that the rate of supply of slurry to each leg must be relatively low to avoid the risk of run-off, if a continuous supply system is used the passageways 21 or at least ports leading to those passageways must be relatively small, exacerbating the problem of maintaining even distribution.

These problems are overcome in accordance with the present invention by supplying slurry in pulses intermittently to each of the legs and in particular by distributing slurry to each of the legs in turn so that for only short periods is it possible for slurry to flow to more than one of the legs.

Referring now to Figure 6, this illustrates the operation of a slurry distributor having four outlet ports each connected to a respective passageway 21 mounted on a respective leg. The distributor comprises an outer tube 22 which is stationary and fixed to the support frame shown in Figure 1. The outer tube 22 defines four axially spaced but radially aligned outlet ports 23, each outlet port 23 being connected to a respective passageway 21. A tubular rotor 24 is coaxially disposed within the tube 22, the rotor 24 defining four inlet ports 25. The ports 25 are axially spaced apart so that each of the ports 25 is axially aligned with a respective outlet port 23. The ports 25 are radially displaced by multiples of 900 such that any one time at least one of the inlet ports 25 is at least partially aligned with a respective outlet port 23.

In use, the inner tube 24 is rotated in the direction indicated by arrows in Figure 6a, 6b and 6c. Pressurised slurry is supplied to the interior of the inner tube 24. Starting with the relative orientation of the inner and outer tube shown in Figure 6a, it can be seen that one of the inlet ports 25 is just beginning to communicate with the respective outlet port 23. At this time the inlet port 25 which is 900 in advance of that shown in Figure 6a is just breaking communication with its respective outlet port 23.

Figure 6b shows the distributor after a 450 as compared with Figure 6a. It will be seen that the ports 23 and 25 are fully aligned enabling a substantial flow of slurry to the respective leg. Figure 6c shows the distributor after a further 450 rotation, the illustrated inlet port 25 just breaking communication with the outlet port 23. At this time the inlet port 25 which is 900 behind that shown in Figure 6c is just beginning to communication with its respective outlet port 23.

In order to ensure that the flow of product does not actually stop at any one time, the ports are arranged such that each inlet port communicates with its respective outlet port for a rotation of 92.75 of the inner tube. This approach minimises the likelihood of blockages becoming established in the slurry distribution system.

Thus with the distributor operating as discussed with reference to Figure 6, the distribution of slurry to the four legs shown in Figure 2 is such that any one time only one of the four legs is receiving slurry except for a short period of overlap between the legs said from adjacent inlet ports 25 on the inner tube 24. Various timing relationships can of course be established. For example a system could be arranged such that slurry is supplied to each leg only during periods of motion of that leg during which the leg tip is lifting relative to the soil. In one experimental apparatus however the inner tube 24 is driven through a 1 to 8 reduction gear from the cam shaft which drives the leg 16 and accordingly with such an arrangement each leg receives a pulse of slurry, the pulse having a duration corresponding to the time taken for the cam shaft 14 to rotate twice.

In the experimental arrangement, slurry is delivered to the last most leg in Figure 2, then to the third leg in Figure 2, then to the second leg in Figure 2, and then to the fourth leg in Figure 2. The full cycle is repeated for each eight revolutions of the cam shaft 14. With the experimental arrangement, injected slurry has been found to be incorporated into the soil through which the legs have been dragged and there is minimal risk of run-off of slurry as a result.

The relationship between leg movement and slurry injection can be finely adjusted by simply rotating the outer tube 22 about its axis.

Thus if the outer tube 22 is secured to the support frame by u bolts simple slackening of the u bolt enables appropriate timing adjustments to be made.

With the experimental equipment described above, the cam shaft 14 has been driven at 540 revolutions per minute and this has provided excellent results given a tractor forward speed of the order of 2 to 3 miles per hour. The angle subtended by the blades 20 has been adjusted, a steeper angle being appropriate in softer soils.

Claims (15)

CLAIMS:

1. An injector for injecting a fluid product into soil, comprising a support structure which in use is moved above the soil surface in a generally horizontal predetermined direction, at least one leg extending downwards from the support structure and having a lower end which in use is pulled through the soil, a fluid product supply passageway extending to the lower end of the leg, and means for supplying fluid product to the passageway, wherein the fluid product supply means is arranged to intermittently supply fluid product to the passageway.

2. An injector according to claim 1, wherein the lower end of the leg supports at least one blade extending transversely to the predetermined direction and arranged to lift soil through which the lower end of the leg is pulled.

3. An injector according to claim 2, comprising means for causing the lower end of the leg to move cyclically relative to the support structure such that the depth of the blade beneath the support structure varies cyclically.

4. An injector according to claim 3, wherein the fluid product supply means operates in synchronism with movements of the lower end of the leg relative to the support structure.

5. An injector according to claim 4, wherein the fluid supply means is arranged to supply fluid product to the leg each time the leg moves vertically upwards such that fluid product is delivered into a cavity formed beneath the leg as a result of its upward movement.

6. An injector according to any one of claims 3, 4 or 5, wherein the lower end of the leg moves along a substantially elliptical path relative to the support structure.

7. An injector according to any one of claims 3, 4, 5 or 6, wherein the fluid product supply means delivers fluid product to the leg once in each of a predetermined number of cycles of movement of the lower end of the leg.

8. An injector according to any preceding claim, wherein a plurality of legs extend downwards from the support structure, each leg being provided with a respective fluid product passageway, and the fluid product supply means being arranged to supply fluid product intermittently to each leg in turn.

9. An injector according to claim 8, wherein the fluid product supply means is arranged to terminate the supply of fluid product to a first leg after initiation of the supply of fluid product to a second leg.

10. An injector according to claim 8 or 9, wherein the fluid product is distributed to each leg from a distributor driven from the common power supply.

11. An injector according to claim 10, wherein the distributor comprises an outer tube having a series of axially spaced outlet ports each connected to a respective leg passageway, and a co-axial inner tube driven by said power supply and having a series of axially spaced inlet ports, each outlet port being axially aligned with a respective inlet port, pressurised fluid product being supplied to the interior of the inner tube, and the relative offset between each axially aligned pair of ports being selected to determine the timing of supply of fluid product to the legs.

12. An injector according to claim 11, wherein the outlet ports are radially aligned.

13. A method for injecting a fluid product into soil, wherein a support structure which supports at least one downwardly extending leg is moved above the soil surface in a generally horizontal predetermined direction such that a lower end of the leg is pulled through the soil, and fluid product is supplied to a supply passageway extending to the lower end of the leg, the fluid product being supplied intermittently.

14. An injector for injecting a fluid product into soil substantially as hereinbefore described with reference to the accompanying drawings.

15. A method for injecting a fluid product into soil substantially as hereinbefore described with reference to the accompanying drawings.