Agricultural drills

An agricultural drill having a plurality of seed dispensing units 6 that are driven through rotary shaft means 8 that extends across the width of the drill and is driven by a drive mechanism 9 at one end, said shaft means 8 comprising two coaxial shafts that each drive the seed dispensing units 6 associated with half the width of the drill and that are connected together by a quick release coupling 25 that couples the shafts together for rotation and can be released to stop rotation of that shaft remote from the drive mechanism 9. The quick release coupling 25 comprises a bayonet type coupling in which a radially projecting pin 28 associated with one shaft 8 engages in an axially and circumferentially extending slot 27 associated with the other shaft 8, said slot 27 being shaped so that it cooperates with the pin 28 and produces a wedge action that urges the two shafts 8 into axial abutting engagement when they are driven.

TECHNICAL FIELD 
This invention relates to agricultural drills. 
BACKGROUND ART 
It is now common practice to provide agricultural drills with tramlining 
devices that operate to leave selected rows unsown in selected bouts so as 
to produce tracks or tramlines in the subsequent crop for the passage of a 
vehicle when treating the crop such as by spreading or spraying fertilizer 
or insecticide. 
Generally, the subsequent crop treatment covers two or more drill bouts in 
one pass of the treatment vehicle, and the treated width conveniently 
coincides with the edges of the drill bouts. However, a situation can 
arise in which the treated width does not coincide with the edges of the 
drill bouts and half of the first drill bout will not be treated by the 
first pass of the treatment vehicle. An agricultural drill has therefore 
been proposed in West German Patent Specification No. DE-2924625 to allow 
half a bout width to be sown. Said drill has a plurality of seed 
dispensing units that are spaced across the width of the drill and are 
driven by a drive mechanism comprising two coaxial drive shafts each 
extending over one half the width of the drill and each being selectively 
driveable so as to sow half a width either side of the centre line of a 
drill bout or to sow a full width bout. Each drive shaft is driven through 
a corresponding clutch mechanism at the centre of the drill comprising a 
first gearwheel on the shaft, a second gearwheel on a pivoted arm that is 
operated to engage or disengage said first and second gearwheels, and a 
third gearwheel in constant mesh with the second gearwheel and which is 
carried on an input drive shaft coaxial with the pivoted arms. Thus, two 
clutch mechanisms are provided to control drive to the adjacent inner ends 
of both seed unit drive shafts, and an input drive shaft transfers drive 
from the side of the drill to these clutches. 
Agricultural drills are also known, for example as shown in U.S. Pat. No. 
3,620,419, in which a plurality of seed dispensing units are driven by a 
common drive shaft that is axially adjustable to vary the feed rate of the 
dispensing units. 
An object of the present invention is to provide an agricultural drill 
having a drive mechanism for the seed dispensing units which is adapted to 
allow either a full or half a bout width to be sown but which is simpler 
than the known drive mechanism of this type employing two coaxial drive 
shafts each associated with a respective half of the drill width. A 
further object is to provide that said drive mechanism is adapted so that 
it allows adjustment of the feed rate of the seed dispensing units through 
axial adjustment of said drive shafts driving said units. 
SUMMARY OF THE INVENTION 
This object is achieved according to the invention by providing an 
agricultural drill having a plurality of seed dispensing units that are 
spaced across the width of the drill, two coaxial drive shafts each 
extending across a respective half of the width of the drill and each 
being in driving engagement with the seed dispensing units associated with 
said respective half of the width of the drill, and a drive mechanism at 
one end of the drill that serves to drive one or both drive shafts 
characterised in that the drive mechanism is adapted for driving 
engagement with that end of one drive shaft nearest the drive mechanism 
and in that a quick release drive coupling is provided between the two 
drive shafts comprising a radially projecting pin associated with one 
shaft and a slotted member associated with the other shaft the pin being 
engageable in an axially and circumferentially extending slot formed in 
said slotted member so that it cooperates with the pin to produce a wedge 
action that urges the two shafts axially into abutting engagement when 
they are driven. 
The drill can therefore be used to sow half a bout along the edge of a 
field by simply releasing the coupling between the two halves of the seed 
dispenser drive shaft. This coupling is then reconnected so that the drill 
sows full width bouts thereafter. The advantage of this coupling is that 
it is relatively simple and makes use of the angular reaction force 
between the two shafts to maintain them in axial engagement. This is an 
important feature if the drive shafts are axially adjustable to vary the 
feed rate of the seed dispensing units, because any variation in the axial 
spacing of the drive shafts will produce differences between the feed 
rates of the seed dispensing units associated with the two drive shafts.

BEST MODE OF CARRYING OUT THE INVENTION 
The illustrated drill comprises a chassis 1, a tractor drawbar 2 and a pair 
of landwheels 3. A plurality of coulters 4 are pivotally connected to the 
front beam of the chassis so as to trail therefrom, and a 
hydraulically-operated actuation system (not shown) is provided to force 
the coulters into work to form seed furrows. 
A seed hopper 5 is mounted on the chassis across its width and a plurality 
of individual seed dispensing units 6 are mounted on the underside of the 
hopper 5 so as to dispense seed that is delivered to a furrow produced by 
a respective coulter 4. The seed dispensing units, as shown in FIGS. 2 and 
3, each comprising a rotary metering member 7 that is keyed on a drive 
shaft 8 that is common to all of the units and is rotatably driven at the 
left-hand end by a drive mechanism 9 coupled to the adjacent landwheel 3. 
The metering member 7 is rotatably mounted in the side walls of a housing 
10 that opens upwards and communicates with the hopper 5 through an 
opening in the bottom wall 11 of the hopper. Seed entering the housing 
from the hopper is dispensed from the housing to the respective coulter by 
the action of a fluted roll 12 that forms part of the metering member 7. 
The rate at which the seed is dispensed is varied by axial adjustment of 
the metering member 7 within the housing so as to vary the effective width 
of the fluted roll 12 within the housing. An adjustment mechanism 13 
controls the axial setting of the drive shaft 8 and thereby controls the 
axial setting of all the metering members simultaneously so that the feed 
rate for all the seed dispensing units 6 is the same. As shown in FIG. 2, 
the adjustment mechanism 13 comprises a lever 14 connected in a pivot 15 
to the bottom wall 11 of the hopper and engaging a channel 16 in a 
cylindrical block 17 keyed to the drive shaft 8. Axial movement of the 
drive shaft 8 relative to the drive mechanism 9 is accomodated by a 
sliding connection 18 (FIG. 3) comprising a rectangular tubular sleeve 19 
that is axially slidable in a drive gear 20 of the drive mechanism 
journalled in a plate 21 connected to the end of the hopper 5. The sleeve 
19 carries a boss 22 at its inner end that mates with the drive shaft 8 
and has an end face 23 which abuts the end of the adjacent fluted roll 12. 
A pin 24 holds the drive shaft 8 and boss 22 in axial engagement. 
The seed dispensing units and the drive mechanism for them are described in 
more detail in U.S. Pat. No. 3,260,419 which is incorporated herein by 
reference. 
In the known seed dispensing mechanism, there is a one-piece drive shaft 
that extends the full width of the drill so that all of the dispensing 
units are driven together at all times. However, the drive shaft 8 in the 
illustrated embodiment of the invention is formed in two coaxial sections 
that are connected at the centre of the drill by a quick release coupling 
25 that enables the two to be uncoupled so that only one is driven by the 
drive mechanism 9, thereby allowing half a bout to be sown. 
The quick release coupling 25 is illustrated in FIGS. 5 to 8 and comprises 
a socket member 26 that is mounted on the end of the right-hand section of 
shaft 8 and is adapted to receive the adjacent end of the left-hand 
section of shaft 8. The socket member 26 is formed with two curved slots 
27 in its side wall diametrically opposite one another. These slots 27 
open outwards at the free edge of the side wall and curve inwards 
circumferentially of the side wall in the sense of rotation of the shaft 
when being driven, this direction being indicated by an arrow in FIG. 5. 
A pin 28 is inserted diametrically through the left-hand section of shaft 8 
near its free end, and the projecting ends of this pin 28 cooperate with 
the slots 27 in the manner of a bayonet connection, as shown in FIG. 5. 
Further, because of the curved nature of the slots 27, the rotary driving 
action of the left-hand section of the shaft produces a wedging action of 
the pin against the sides of the slots 27 and thereby serves to pull the 
two sections of the shaft axially into end-to-end abutting engagement. The 
pin 28 does not engage the end of slots 27 in order to ensure that the 
wedging action persists when the two sections of the drive shaft 8 abut 
end-to-end. 
The importance of this feature arises from the fact that the shaft 8 is 
movable axially so as to move the rotary metering units within the seed 
dispensing units and thereby adjust the rate at which they dispense seed. 
Thus, the two sections of the shaft 8 need to be kept in a fixed axial 
relationship relative to one another if the feed rate adjustments of the 
seed dispensing units associated with each section are not to get out of 
step. 
The socket member 26 is slidably mounted on the right-hand section of shaft 
8. A pin 29 is inserted transversly through the end of the shaft 8 so that 
its ends project and act as a detent to retain the socket member on the 
shaft. The ends of the pin 29 are received in a transverse slot 30 in the 
base 31 of the socket member when the latter is fully extended for 
coupling, as shown in FIG. 7, the free end of the shaft 8 then projecting 
slightly into the central cavity 23 of the socket member for abutting 
engagement with the free end of the left-hand section of shaft 8. Grooves 
33 formed longitudinally in the internal surface of the side wall 34 of 
the socket member accommodate the ends of the pin 29. 
A spring loaded ball-bearing detent 35 is provided in a recess 36 in the 
base 31 of the socket member so as to engage the shaft 8 and cooperate 
with a transverse hole 37 in the shaft to define a retracted position (see 
FIG. 5) in which the socket member 26 is free of the pin 28 for 
uncoupling. An elastomer block 38 in recess 36 urges the ball-bearing 35 
into engagement with the shaft. 
In the illustrated embodiment, the seed dispenser drive mechanism 9 is 
shown on the left-hand side of the drill so that when the socket member 26 
is retracted to uncouple the two sections of shaft 8, only the left-hand 
section is driven and operates the seed dispensing units 6 over the 
left-hand half of the drill to sow half a bout width along the left-hand 
side of the bout. This is illustrated in FIG. 4 for the first bout of the 
drill along the left-hand side of a field. The socket member 26 is then 
extended to engage the pin 28 in slots 27 and thereby couple the two 
sections of the shaft together. The second and successive bouts are then 
sown as full width bouts as shown in FIG. 4. 
On the third bout tramlines 39 are formed by operating a tramlining 
mechanism that serves to cut-off the supply of seed from two of the seed 
dispensing units equally spaced on each side of the centre line of the 
bout. The tramlining mechanism is represented schematically at 40 in FIG. 
1 and comprises shutters that are insertable into the channel 4 (FIG. 2) 
between the housing 10 and the bottom wall 11 of the hopper to cut-off the 
supply of seed to the housing 10. The details of the tramlining mechanism 
are not relevant to the present invention, but a suitable tramlining 
system is shown in U.S. Pat. No. 4,289,256. 
The tramlining mechanism is operated again to produce tramlines 39 on the 
seventh bout and on each successive fourth bout thereafter. In this way, 
tramlines are produced down the centre of successive strips of land four 
bouts wide, as indicated by the lateral arrows W in FIG. 4. In particular 
the first strip of land down the left-hand side of the field is exactly 
four bouts wide because of the first bout being half a bout. Thus, a 
treatment vehicle such as a tractor carrying spraying equipment, can use 
the tramlines in spraying each four bout strip in one pass without missing 
or wasting spray materials down the left-hand edge of the field. 
It will be appreciated that the illustated drill that forms tramlines down 
the centre of a bout, will need to sow a first half width bout whenever 
the tramlines are formed in the centre of strips that are an even number 
of bouts wide, but not when the tramlines are formed in the centre of 
strips that are an odd number of bouts wide. 
The illustrated example of strips four bouts wide is a common situation 
produced when using a 3 metre drill together with a 12 metre sprayer. 
The illustrated drill has been shown without fertiliser dispensing units, 
but it will be appreciated that these can be easily provided below the 
rear section of the hopper in the same manner as the seed dispensing units 
6, and the hopper divided by an internal transverse central partition into 
seed and fertiliser hoppers. The fertiliser dispensing units will have a 
common transverse drive shaft and this will be split into two sections 
with a quick release coupling 25 between them in the same manner as the 
drive shaft 8. The two drive shafts will then be coupled and uncoupled 
together to sow a full width or half width bout as necessary.