Downforce Control Assembly for a Row Unit of a Disc Planter

Abstract

Abstract The present invention is directed to a downforce control assembly 10 of a row unit 11 of a disc planter. The downforce control assembly 10 is associated with a gauge wheel 13 arranged to cooperate with an opening disc 15 which creates a seed furrow in soil at a target depth. The downforce control assembly 10 generally comprises: 1. a mechanical sensor 12 associated with the gauge wheel 13, the mechanical sensor 12 arranged for sensor movement dependent on a reaction force to the gauge wheel 13; 2. a coupling assembly 14 connected to the mechanical sensor 12 and arranged for coupling displacement dependent on the sensor movement in the mechanical sensor 12; 3. a downforce control valve 16 connected to the coupling assembly 14; 4. a downforce system or airbag 21 operatively coupled to the downforce control valve 16 and arranged in response to the coupling displacement to automatically apply a downforce on the row unit 11 via the downforce system 21, said downforce being effectively in maintaining the reaction force to the gauge wheel 13 substantially constant. Abstract 2021225138 30 Aug 2021 1. 2. 3. 4. constant. 20 21 22 51 38 3 0 A ug 2 02 12021225138 30 Aug 2021 21 10 25 13 17 10 15 0) FIGURE 1A 23 13 19 11

Description

Technical Field [0001 ] The present invention is broadly directed to a downforce control assembly for a row unit of a disc planter. Background of Invention

[0002] In a conventional row unit of a disc planter the height of the furrow-opening disc relative to an associated gauge wheel broadly determines the target depth of the seed furrow. However, this assumes the gauge wheel maintains contact with the soil which depends on the conditions within the field and the resistance of the soil to the associated opening disc. If the soil is particularly firm or heavy the opening disc, without sufficient downforce to overcome the relatively high resistance of the soil, will not create the seed furrow at the target depth for that row unit. In order to address this potential problem, the disc planter may include a downforce system which applies a downforce to one or more of the row units to ensure the associated gauge wheels maintain contact with the soil and the respective opening discs achieve the target depth of the seed furrow.

[0003] The downforce system, once it is manually adjusted for the required downforce, is static or substantially constant including a mechanical spring which in addition to the weight of the row unit provides an additional downforce proportional to the mechanical spring. This static downforce system does not compensate for varying conditions within a field which means the depth of the seed furrow will be different depending on the resistance provided by the soil to the row unit. The static downforce system may be manually adjusted so that the downforce is varied depending on the expected firmness of the soil to which the row unit is to be applied. Alternatively, in attempting to address this problem with the static downforce system, the downforce system is active including a load cell on one or more row units for measuring gauge wheel load. The active downforce system then electronically controls airbags / liftbags or hydraulic rams to apply a variable downforce to the relevant row unit(s) depending on the measured load. These active downforce 2021225138 30 Aug 2021 systems are relatively complicated in construction and often expensive to both install and potentially maintain. Summary of Invention

[0004] According to the present invention there is provided a downforce control assembly for a row unit of a disc planter, said downforce control assembly comprising: a mechanical sensor associated with a gauge wheel of the row unit, said sensor at least in part being arranged for sensor movement dependent on a reaction force applied to the gauge wheel; a coupling assembly connected to the mechanical sensor and arranged for coupling displacement dependent on the sensor movement in the mechanical sensor; a downforce control valve connected to the coupling assembly; a downforce system operatively coupled to the downforce control valve which in response to the coupling displacement applies a downforce on the row unit via the downforce system, said downforce being effective in maintaining the reaction force applied to the gauge wheel substantially constant.

[0005] Preferably the mechanical sensor includes an outer casing housing a resiliently deformable core. More preferably, under the influence of the reaction force applied to the gauge wheel, a force is applied to the outer casing causing the outer casing to deform the deformable core providing the sensor movement in the mechanical sensor.

[0006] Preferably the mechanical sensor also includes a pair of washer plates mounted within the outer casing on opposing sides of the deformable core. More preferably the mechanical sensor also includes an elongate fastener arranged coaxial with the outer casing and the washer plates for mounting of the mechanical sensor to the row unit. Still more preferably the washer plates about at least part of their perimeter surface are radially spaced from the outer casing thereby permitting the sensor movement in the mechanical sensor. Even more preferably at least one of the washer plates includes an opposing pair of ridges on its perimeter surface, said opposing ridges configured to contact an internal surface of the outer casing thereby 2021225138 30 Aug 2021 limiting the sensor movement of the mechanical sensor in a direction generally perpendicular to the opposing pair of ridges.

[0007] Preferably the coupling assembly includes a lever arm at a proximal end connected to the mechanical sensor and at a distal end connected to a coupling arm which connects to the downforce control valve. More preferably the coupling assembly also includes a fulcrum member about which the lever arm rocks increasing the sensor movement in the mechanical sensor to the coupling displacement of the coupling assembly.

[0008] Preferably the downforce control valve is operatively coupled to the coupling arm for proportional control of the downforce system depending on the coupling displacement of the coupling assembly. More preferably the downforce control valve provides pneumatic control of the downforce system which is pneumatically driven.

[0009] Preferably the downforce control assembly also comprises a height adjuster assembly associated with the gauge wheel wherein height adjustment of the gauge wheel relative to a frame or frame sub-assembly of the row unit is effected by actuation of said adjuster assembly. More preferably the height adjuster assembly includes locking means arranged to retain the gauge wheel at a required height adjustment relative to the frame or frame sub-assembly.

[0010] Preferably the height adjuster assembly includes: an adjuster cam pivotally mounted about a cam axis to the frame or frame sub-assembly of the row unit; a tilting sub-assembly associated with the gauge wheel for height adjustment of the gauge wheel relative to the frame, said tilting sub-assembly (i) pivotally mounted to either the frame or frame sub-assembly for tilting of the tilting sub-assembly about a tilt axis radially separated from the cam axis, and (ii) being operatively coupled to the adjuster cam whereby pivoting of the adjuster cam about the cam axis provides sliding contact of said cam with the tilting sub-assembly thereby tilting the tilting sub-assembly about the tilt axis providing the height adjustment of the gauge wheel relative to the frame or frame sub-assembly. More preferably the adjuster cam includes an arcuate slot arranged to receive the locking 2021225138 30 Aug 2021 means fixed to the tilting sub-assembly and designed to releasably engage the adjuster cam to lock the tilting sub-assembly thereby retaining the gauge wheel at the required height adjustment relative to the frame or frame sub-assembly. Preferably the adjuster cam is arranged for pivoting about the outer casing thereby tilting the tilting sub-assembly and the associated gauge wheel for retention at the required height adjustment via the locking means. More preferably the force applied to the outer casing is applied via the adjuster cam which is locked to the tilting subassembly at the required height adjustment. Alternatively the mechanical sensor is mounted about the tilt axis of the tilting sub-assembly wherein the force resulting from the reaction force applied to the gauge wheel is applied to said mechanical sensor via the tilting sub-assembly to provide the movement in the mechanical sensor. Brief Description of Drawings [0011 ] In order to achieve a better understanding of the nature of the present invention a preferred embodiment of a downforce control assembly for a row unit of a disc planter will now be described, by way of example only, with reference to the accompanying drawings in which: Figures 1A and 1B are isometric assembly views from either side of a row unit of a disc planter, the row unit incorporating a downforce control assembly of a preferred embodiment of the invention; Figure 2 is an isometric view from an inner side of the downforce control assembly taken from the preferred embodiment of figure 1; Figure 3 is a top view of the downforce control assembly of the preferred embodiment of figures 1 and 2; Figure 4 is an isometric view from an outer side of the downforce control assembly of the preferred embodiment of the preceding figures; Figures 5A and 5B are exploded isometric views of the downforce control assembly of the preferred embodiment of the preceding figures. 2021225138 30 Aug 2021 Detailed Description

[0012] As seen in figure 1, there is a downforce control assembly 10 of a preferred embodiment of a row unit 11 of a disc planter (not shown). It will be understood that the downforce control assembly 10 is associated with a gauge wheel 13 arranged to cooperate with an opening disc 15 which creates a seed furrow in soil at a target depth (not shown). The opening disc 15 is rigidly fixed to a frame 17 of the row unit 11 at a fixed height relative to the frame 17. The height of the gauge wheel 13 may be adjusted relative to the opening disc 15 to affect the depth of the seed furrow. In an alternative arrangement (not shown), the height of a press wheel 19 of the row unit 11 may be adjusted relative to the opening disc to affect the depth of the seed furrow. In a further arrangement (not shown), the gauge wheel may follow and be located substantially in line with the opening disc whereby it serves the function of both a gauge and a press wheel and can be height-adjusted relative to the associated opening disc. In each of these arrangements, the row unit 11 is one of a plurality of row units connected alongside one another to a toolbar of a main frame of the disc planter (not shown). The row unit frame 17 of this example swings in a pivoting action about a row unit headstock 25 which is rigidly attached to the toolbar of the main frame, this pivoting action permits active control of the variable downforce applied to the associated row unit 11.

[0013] As best seen in figures 2 to 4, the downforce control assembly 10 of this embodiment generally comprises: 1. a mechanical sensor 12 associated with the gauge wheel 13 of the row unit 11, the mechanical sensor 12 at least in part being arranged for sensor movement dependent on a reaction force applied to the gauge wheel 13; 2. a coupling assembly 14 connected to the mechanical sensor 12 and arranged for coupling displacement dependent on the sensor movement in the mechanical sensor 12; 3.    a downforce control valve 16 connected to the coupling assembly 14; 4.    a downforce system shown partly as airbag 21 operatively coupled to the downforce control valve 16 and arranged in response to the coupling displacement to automatically apply a downforce on the row unit 11 via the 2021225138 30 Aug 2021 downforce system 21, said downforce being effective in maintaining the reaction force applied to the gauge wheel 13 substantially constant.

[0014] The downforce control valve 16 is thus operatively coupled to the downforce system 21 which automatically applies the downforce on the opening disc 15 of the row unit 11 with the reaction or residual force largely being applied to the gauge wheel 13. In this embodiment the downforce system 21 operatively couples between the row unit headstock 25 and the row unit frame 17 which under the influence of the downforce system 21 pivots about said headstock 25 The downforce applied to the row unit 11 is thus active in maintaining the reaction force applied to the gauge wheel 13 substantially constant. It will be understood that, by maintaining the reaction force applied to the gauge wheel 13 constant, the gauge wheel 13 maintains uniform contact with the soil surface during planting or other field operation. Thus, the automatic and variable downforce applied to the row unit 11 ensures the associated opening disc 15 penetrates the soil to create the furrow at the target and substantially uniform planting or seeding depth.

[0015] It will be understood that operation of the downforce control assembly 10 in relatively firm soil requires the application of relatively high active downforces to the row unit 11 to achieve the target seeding depth for the opening disc 15 of that row unit 11. On the other hand, in less firm soil the active downforce automatically applied to the row unit 11 will be relatively low to achieve the equivalent and uniform seeding depth. For example, in order to actively maintain the reaction or residual force applied to the gauge wheel 13 via the soil substantially constant at around 30 to 40 kilograms for: 1. relatively firm soil or heavy ground, the application of an active downforce at around 155kg (pressure applied to the row unit 11 via the downforce system) is required based on reactive forces on the associated opening disc 15 at around 120kg; 2. less firm soil, the application of an active downforce at around 65kg (pressure released from the row unit via the downforce system) is required based on reactive forces on the associated opening disc 15 at around 30kg. 2021225138 30 Aug 2021

[0016] It is to be understood that the active downforce applied to the row unit may vary from the values disclosed depending largely on the reactive forces applied by the ground engaging / contacting and planter components.

[0017] Although not illustrated, the downforce control assembly 10 may also include a static counterbalance spring for use in relatively soft soil conditions where in the absence of the counterbalance spring the reaction force on the gauge wheel would be too high. The counterbalance spring applies an upward counterbalance force sufficient to largely remove the weight of the associated row unit. This is necessary when the reaction force on the gauge wheel is too high even when the pressure is fully released from the downforce system. The counterbalance spring is connected between the swinging frame 17 of the row unit 11 and the associated fixed headstock 25 whereby the weight of the row unit 11 is transferred via the headstock 25 and associated toolbar to the main frame of the machine or its wheels (not shown).

[0018] In an alternative embodiment not illustrated, the active downforce system may be reversed and function as an active up-force system where the force automatically exerted on the row unit is upward. This would mean the optional static counterbalance spring is reversed in its placement and action whereby it forces the row unit downward. In this variation, the application and release of pressure on the row unit via the up-force system is opposite to that disclosed in the preferred embodiment. Under firm soil conditions the up-force system releases pressure from the associated airbag so that the counterbalance spring applies a relatively high downforce to the row unit whereas under less firm soil conditions the downforce system applies increased pressure to the associated airbag so that the counterbalance spring applies a relatively low downforce to the row unit.

[0019] In this embodiment the downforce control valve 16 is operatively coupled to the downforce system for its control depending on the coupling displacement of the coupling assembly 14. The downforce control valve 16 of this example provides direct pneumatic control of the downforce system which includes conventional airbags or air springs such as 21 inflated by an air compressor under the control of the downforce control valve 16. 2021225138 30 Aug 2021

[0020] The mechanical sensor 12 of the downforce control assembly 10 may be incorporated in each of the row units 11 or their respective gauge wheels 15. Although not shown, in an alternative arrangement a single row unit from a section of the row units may incorporate a shared mechanical sensor for that section. In this alternative arrangement, the row unit with the shared mechanical sensor is controlled by an airbag dedicated to that row unit whereas the other row units without a mechanical sensor are controlled by slave airbags dedicated to respective of the other row units relying on the shared mechanical sensor. In a further variation not shown, the airbags or other downforce mechanisms may together be controlled via a common pneumatic system which communicates with a plurality of mechanical sensors via a shared proportional relay valve whereby the reaction force applied to the associated gauge wheels is effectively averaged across the corresponding row units. This is an advantage in the event that one of the row units or its mechanical sensor detects rogue “data” wherein the downforce system continues to effectively operate with the rogue “data” being offset by the reaction force detected on the remaining row units. [0021 ] The chosen configuration for the downforce control assembly 10 for the row units of the disc planter may vary depending on a number of factors including the required “resolution” of the system. For example, the differences in row-to-row soil resistance may require a high resolution system where the downforce control assembly 10 is incorporated in each of the adjacent row units. In any event, it is to be understood that the downforce control assembly 10 provides near real-time control of the downforce applied to the row unit to achieve the target seeding depth. It will be understood that this active control of the row unit(s) is effected by detection of the reaction force on the relevant gauge wheel via the mechanical sensor associated with said wheel.

[0022] As seen in figures 1 to 4, the downforce control assembly 10 of this embodiment also comprises a height adjuster assembly 20 associated with the gauge wheel 13. The height adjuster assembly 20 is actuated to effect height adjustment of the gauge wheel 13 relative to the frame 17 of the row unit 11. In this example the height adjuster 20 includes locking means 22 arranged to retain the gauge wheel 13 at a required height adjustment relative to the frame 17. It is to be understood that 2021225138 30 Aug 2021 locking of the locking means 22 is required for effective operation of the downforce control assembly 10. In this embodiment the height adjuster 20 includes: 1. an adjuster cam 24 pivotally mounted about a cam axis 26 to a frame subassembly 28 of the row unit 11; 2. a tilting sub-assembly 30 associated with the gauge wheel 13 for height adjustment, and pivotally mounted to a mounting bracket 31 of the frame 17 (see figure 1) for tilting of the tilting sub-assembly 30 about a tilt axis 32 radially separated from the cam axis 26.

[0023] The tilting sub-assembly 30 is operatively coupled to the adjuster cam 24 whereby pivoting of the adjuster cam 24 about the pivot axis 26 provides sliding contact of the adjuster cam 24 with the tilting sub-assembly 30. This sliding contact effects tilting of the tilting sub-assembly 30 about the tilt axis 32 providing the height adjustment of the gauge wheel 13 relative to the frame 17. The adjuster cam 24 of this example includes an arcuate slot 34 arranged to receive the locking means 22 fixed to the tilting sub-assembly 30. The locking means 22 of this embodiment includes an elongate fastener arrangement designed to releasably engage or clamp the adjuster cam 24 to lock the tilting sub-assembly 30 thereby retaining the gauge wheel 13 at the required height adjustment relative to the frame 17.

[0024] As best seen in the exploded views of figure 5A and 5B, the mechanical sensor 12 of this embodiment includes an outer casing 36 housing a resiliently deformable core 38. The adjuster cam 24 is arranged for pivoting about the outer casing 36 thereby tilting the tilting sub-assembly 30 and the associated gauge wheel 13 for subsequent retention at the required height adjustment via the locking means 22. In this locked mode, under the influence of the reaction force applied to the gauge wheel 13, a force is applied to the outer casing 36 via the adjuster cam 24 and the associated tilting sub-assembly 30 to which it is locked. It will be understood that this force causes the outer casing 36 to deform the deformable core 38 providing the sensor movement in the mechanical sensor 12. In this example the sensor movement is generally defined by a radial movement relative to the cam axis 26 at which the adjuster cam 24 is restrained. This radial movement results from 2021225138 30 Aug 2021 compression or decompression of the deformable core 38 and will vary depending on various factors including: 1.     the radial separation between the cam axis 26 and the tilt axis 32; 2.    the elastic modulus of the deformable core 38 which depending on the force applied to the outer casing 36 will influence the extent of the radial movement of the outer casing 36.

[0025] In this embodiment the mechanical sensor 12 also includes a pair of washer plates 40a and 40b mounted within the outer casing 36 on opposing sides of the deformable core 38. The washer plates 40a / b are arranged to co-axially support the deformable core 38 within the outer casing 36 via an elongate fastener 42 which effects mounting of the mechanical sensor 12 to the frame sub-assembly 28 at the cam axis 26 of the adjuster cam 24. The washer plates 40a / b about at least part of their perimeter surface are radially spaced from the outer casing 36 thereby permitting the radial movement in the mechanical sensor 12.

[0026] In this embodiment one of the washer plates 40b includes a radial arm 44 arranged for fixing to a mounting bracket 45 of the frame sub-assembly 28. The radial arm 44 is also configured to engage a keyway (not shown) in the outer casing 36 to limit rotation of the outer casing 36 on pivoting of the adjuster cam 24 about the outer casing 36 during height adjustment of the gauge wheel 13. In this example, the washer plates 40a / b each include an opposing pair of ridges 46a and 46b on their perimeter surface. The opposing ridges such as 46a / b are configured to contact an internal surface of the outer casing 36 thereby promoting the radial movement of the mechanical sensor 12 in a direction generally perpendicular to an imaginary line passing through the opposing pair of ridges 46a / b. That is, the opposing pair of ridges 46a / b restrict radial movement of the outer casing 36 in a direction in general alignment with the opposing pair of ridges 46a / b. The mechanical sensor 12 is thus designed to detect and respond to reaction forces applied to the associated gauge wheel 13 largely removing any other forces applied to the mechanical sensor 12 and otherwise resulting in its movement.

[0027] Returning to figures 1 to 4, the coupling assembly 14 of this embodiment includes a lever arm sub-assembly 48 at a proximal end connected to the mechanical 2021225138 30 Aug 2021 sensor 12 or in this example a pair of lugs 50a and 50b integral with the outer casing 36. The lever arm 48 at a distal end is connected to coupling arm 52 connected to the downforce control valve 16. The coupling assembly 14 also includes a fulcrum member 54 mounted to the frame sub-assembly 28 and about which the lever arm 48 rocks under the influence of the mechanical sensor 12. In particular, it will be understood that the reaction force on the gauge wheel 13 associated with the downforce control assembly 10 causes the radial sensor movement in the outer casing 36 wherein: 1. the lever arm 48 rocks about the fulcrum member 54 causing coupling displacement in the coupling arm 52; 2. the coupling arm 52 at its distal end transmits the coupling displacement to the downforce control valve 16.

[0028] In this example it is likely that the radial or other sensor movement in the mechanical sensor 12 will, depending on the reaction forces applied to the gauge wheel 13, vary from approximately zero to 3mm either side of neutral where there is no deformation or compression of the deformable core 38. In this embodiment the lever arm 48 and fulcrum member 54 are arranged to provide a ratio of around 5:1 wherein the distal end of the lever arm 48 is expected to rock from between zero to 15mm either side of neutral. This arrangement of the lever arm 48 and fulcrum member 54 amplifies the otherwise relatively small movement in the mechanical sensor 12. This amplified and rocking displacement translates to approximately the same coupling displacement at the distal end of the coupling arm 52. This coupling displacement results in part rotation or swinging of an actuator arm 58 connected to the downforce control valve 16. It is expected that this actuator displacement will activate the downforce control valve 16 from its closed to open positions for proportional control of the downforce system 21 to which it is operatively coupled.

[0029] It will be understood that the downforce control assembly 10 may periodically (say seasonally) be mechanically calibrated to adjust the applied downforce. That is, the downforce assembly 10 may be manually adjusted so that either side of a threshold movement in the mechanical sensor 12 (associated with a sensed reaction force on the associated gauge wheel 13) the downforce control valve 2021225138 30 Aug 2021 16 either applies or releases air from the downforce control system or airbag 21 associated with the corresponding row unit 11. For example, if the reaction force on the gauge wheel 13 (detected by the mechanical sensor 12) is less than 20 kg the control valve 16 is mechanically adjusted to add air to the airbag 21. Likewise, if the reaction force on the gauge wheel 13 (detected by the mechanical sensor 12) is greater than 20 kg the control valve 16 is mechanically adjusted to release air from the airbag 21. This mechanical adjustment or calibration may be achieved by adjusting the length of the coupling arm 58 which controls opening and closure of the control valve 16.

[0030] In this embodiment the height adjuster assembly 20 associated with the downforce control assembly 10 is otherwise constructed as detailed in the specification of the applicant’s co-pending Australian provisional patent application. It is to be understood that the disclosures of this co-pending application tilted “Height Adjuster Assembly for a Row Unit of a Disc Planter” are to be considered included herein by way of this reference.

[0031] Now that a preferred embodiment of the invention has been described it will be understood that the downforce control assembly for a disc planter has at least the following advantages over the admitted prior art: 1. the downforce control assembly is relatively simple in its construction and operation relying upon a mechanical rather than electronic sensor; 2. the downforce control assembly applies near real-time downforce control providing uniform pressure or reaction force on the gauge wheel promoting seeding at targeted depths for soils of varied resistances to opening discs; 3. the downforce control assembly is relatively accurate in detecting reaction forces applied to an associated gauge wheel for application of the required downforce for uniform seeding at the require depth; 4. the downforce control assembly can be retrofitted to some existing downforce systems being pneumatically driven; 5. the downforce control assembly lends itself to calibration or adjustment to influence the downforce applied to the associated row unit. 2021225138 30 Aug 2021

[0032] Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. For example, the mechanical sensor may be mounted about the tilt axis rather than the cam axis wherein the force resulting from the reaction force applied to the gauge wheel is applied to the mechanical sensor via the tilting sub-assembly. Alternatively, the mechanical sensor may be directly coupled to the gauge wheel arm for transmission of the forces resulting from the reaction force applied to the gauge wheel. The mechanical sensor may deflect in a rotational rather than translational movement in effectively detecting reaction forces applied to the gauge wheel. This alternative rotational or twisting movement in the mechanical sensor would likewise be transferred to the downforce control valve via a coupling assembly. Alternatively it is possible that the mechanical sensor may connect directly to the downforce control valve without a coupling assembly. The downforce system may be hydraulic rather than the pneumatic system of the described embodiment. Finally and as described in more detail above, the active downforce system may be reversed and function as an active up-force system where the force automatically exerted on the row unit is upward.

[0033] All such variations and modifications are to be considered within the scope of the present invention the nature of which is to be determined from the foregoing description.

Claims

1. A downforce control assembly for a row unit of a disc planter, said downforce control assembly comprising:a mechanical sensor associated with a gauge wheel of the row unit, said sensor at least in part being arranged for sensor movement dependent on a reaction force applied to the gauge wheel;a coupling assembly connected to the mechanical sensor and arranged for coupling displacement dependent on the sensor movement in the mechanical sensor;a downforce control valve connected to the coupling assembly;a downforce system operatively coupled to the downforce control valve which in response to the coupling displacement applies a downforce on the row unit via the downforce system, said downforce being effective in maintaining the reaction force applied to the gauge wheel substantially constant.

2. A downforce control assembly as claimed in claim 1 wherein the mechanical sensor includes an outer casing housing a resiliently deformable core.

3. A downforce control assembly as claimed in claim 2 wherein, under the influence of the reaction force applied to the gauge wheel, a force is applied to the outer casing causing the outer casing to deform the deformable core providing the sensor movement in the mechanical sensor.

4. A downforce control assembly as claimed in either of claims 2 or 3 wherein the mechanical sensor also includes a pair of washer plates mounted within the outer casing on opposing sides of the deformable core.

5. A downforce control assembly as claimed in claim 4 wherein the mechanical sensor also includes an elongate fastener arranged coaxial with the outer casing and the washer plates for mounting of the mechanical sensor to the row unit.

6. A downforce control assembly as claimed in either of claims 4 or 5 wherein the washer plates about at least part of their perimeter surface are radially spaced from the outer casing thereby permitting the sensor movement in the mechanical sensor.2021225138 30 Aug 20217.    A downforce control assembly as claimed in any one of claims 4 to 6 whereinat least one of the washer plates includes an opposing pair of ridges on its perimeter surface, said opposing ridges configured to contact an internal surface of the outer casing thereby limiting the sensor movement of the mechanical sensor in a direction generally perpendicular to the opposing pair of ridges.

8. A downforce control assembly as claimed in any one of the preceding claims wherein the coupling assembly includes a lever arm at a proximal end connected to the mechanical sensor and at a distal end connected to a coupling arm which connects to the downforce control valve.

9. A downforce control assembly as claimed in claim 8 wherein the coupling assembly also includes a fulcrum member about which the lever arm rocks increasing the sensor movement in the mechanical sensor to the coupling displacement of the coupling assembly.

10. A downforce control assembly as claimed in either of claims 8 or 9 wherein the downforce control valve is operatively coupled to the coupling arm for proportional control of the downforce system depending on the coupling displacement of the coupling assembly.

11. A downforce control assembly as claimed in any one of the preceding claims wherein the downforce control valve provides pneumatic control of the downforce system which is pneumatically driven.

12. A downforce control assembly as claimed in any one of the preceding claims wherein the downforce control assembly also comprises a height adjuster assembly associated with the gauge wheel wherein height adjustment of the gauge wheel relative to a frame or frame sub-assembly of the row unit is effected by actuation of said adjuster assembly.

13. A downforce control assembly as claimed in claim 12 wherein the height adjuster assembly includes locking means arranged to retain the gauge wheel at a required height adjustment relative to the frame or frame sub-assembly.2021225138 30 Aug 202114. A downforce control assembly as claimed in either of claims 12 or 13 wherein the height adjuster assembly includes:an adjuster cam pivotally mounted about a cam axis to the frame or frame sub-assembly of the row unit;a tilting sub-assembly associated with the gauge wheel for height adjustment of the gauge wheel relative to the frame, said tilting sub-assembly (i) pivotally mounted to either the frame or frame sub-assembly for tilting of the tilting sub-assembly about a tilt axis radially separated from the cam axis, and (ii) being operatively coupled to the adjuster cam whereby pivoting of the adjuster cam about the cam axis provides sliding contact of said cam with the tilting sub-assembly thereby tilting the tilting sub-assembly about the tilt axis providing the height adjustment of the gauge wheel relative to the frame or frame sub-assembly.

15. A downforce control assembly as claimed in claim 14 wherein the adjuster cam includes an arcuate slot arranged to receive the locking means fixed to the tilting subassembly and designed to releasably engage the adjuster cam to lock the tilting subassembly thereby retaining the gauge wheel at the required height adjustment relative to the frame or frame sub-assembly.

16. A downforce control assembly as claimed in either of claims 14 or 15 wherein the adjuster cam is arranged for pivoting about the outer casing thereby tilting the tilting sub-assembly and the associated gauge wheel for retention at the required height adjustment via the locking means.

17. A downforce control assembly as claimed in claim 16 wherein the force applied to the outer casing is applied via the adjuster cam which is locked to the tilting subassembly at the required height adjustment.

18. A downforce control assembly as claimed in claim 16 wherein the mechanical sensor is mounted about the tilt axis of the tilting sub-assembly wherein the force resulting from the reaction force applied to the gauge wheel is applied to said mechanical sensor via the tilting sub-assembly to provide the movement in the mechanical sensor.

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