Note: Descriptions are shown in the official language in which they were submitted.
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SAFETY CIRC~IT FOR THE DRIVE MOTOR OF A TRACTOR
BACKGROUND OF THE INVENTION
This invention relates to a safety circuit for
controlling the drive motor of a tractor and implement
combination.
A tractor and implement combination for example a
swather or a mower includes a drive motor and a transmission
system for transmitting drive power from the motor to drlve the
tractor and to drive the implement. Safety circuits are often
provided in an arrangement of this type for example which
prevent operation of the starter motor to start the engine when
the implement drive system is engaged. Seat switches are also
known which can operate to stop the engine if the operator
leaves the seat for any reason.
SUMMARY OF THE INVENTION
It is an object of the present invention to
provide an improved safety circuit arrangement for a tractor
and implement combination.
According to the invention, therefore, there is
provided a tractor for moving and driving an agricultural
implement comprising a tractor body, an implement, means
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connecting the implement to the tractor body for transportation
with the tractor body in movement across the ground, first
drive means for driving operation of the implement, manually
movable first operator means movable from the first deactivated
position to a second position actuating said first dcive means,
second drive means for driving movement of said tractor body
across the ground, manually movable second operator means
movable from first deactivated position to a second position
actuating said second drive means, drive motor means for
developing power for transmission to said first and second
drive means, an electrically operated starter motor for
commencing operation of said drive motor means, an electrically
operated control system for allowing commencement and
continuation of operation of said drive motor means, seat
mounted on the tractor body for an operator such that said
flrst and second operator means are manually actuable by the
operator when seated, and a safety circuit for controlling
operation of said drive motor means, said safety circuit
including a first switch movable to a safety switch condition
in response to movement of said first operator means to the
first position thereof, a second switch movable to a safety
switch condition in response to movement of said second
operator means to the first position thereof, a third switch
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circuit movable to a safety switch condition in response to the
presence of the operator in the seat, and control circuit means
arranged to prevent actuation of said starter motor except when
said first and second switches are both in the safety switch
condition thereof and arranged to prevent said control system
from allowing operation of said drive motor means except when
either both said first and second switches together are in the
safety switch condition thereof or when the third switch
circuit is in the safety switch condition thereof.
One embodiment of the invention will now be
described in conjunction with the accompanying drawings in
which:
DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic illustration of the
safety circuit of a tractor and implement combination according
to the present invention.
Figure 2 i9 a schematic side elevational view of
a tractor and implement combination incorporating the safety
switches of the circuit of Figure 1.
In the drawings like characters of reference
indicate corresponding part~ in the different figures.
DETAILED DESCRIPTION
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Turning fir~tly to Figure 2, there is shown
schematically a tractor and implement combination in the form
of a self-propelled swather having a tractor unit lO and an
implement 11 constituted by a swather header. The tractor unit
10 includes a frame 12 and ground wheels 13 and ]4 generally
the front of which is driven to propel the tractor by a
hydraulic drive system 15. The rear wheel 14 is generally a
castor wheel which is free to rotate so the steering and drive
system for the tractor is provided by the control of the
hydraulic fluid to the hydraulic drive system 15 to the front
wheel.
The tractor further includes a motor 16 mounted
within a housing 17. The motor includes a conventional
electric starter motor 18 and a control system l9 which
controls the continued operation of the motor.
In relation to diesel engines, the control system
19 will be constituted by the fuel pump system which must
receive power from an electrical supply of the engine to
continue to 3upply the pressurized fuel to the engine to
maintain the engine in operation. In respect of a gasoline
engine, the control system is constituted by the conventional
ignition system. The term control system i~ used herein for
convenience to indicate either of these systems and of course
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generally the control system is actuated by the operator by
moving a key actuated switch to a "run" position.
The tractor unit further includes an operator
seat 20 mounted within a cab 21. The seat includes a seat
switch 22 for sensing the presence of the operator.
The controls to the tractor unit include a
steering system schematically indicated at 23 and first and
second levers 24 and 25 respectively which actuate the
implement and the drive to the tractor respectively. These
again are shown schematically and simply illustrate a lever
operable by the operator when seated in the seat. The lever 25
is operable to control the transmission of the tractor from a
neutral position to forward and reverse positions. This acts
to control supply of hydraulic fluid from a pump 26 driven by
the engine 16 to the drive system 15. The lever 24 controls a
drive system of the header schematically indicated at 34. The
lever 24 include~ a first switch 27 responsive to movement of
the lever to a first inoperative position of the implement.
The lever 25 includes a second switch 28 responsive to movement
of the lever 25 to a neutral position of the transmission~
The implement shown schematically includes a
frame 30, a reel 31, a draper 32 and a sickle knife 33. The
details of the drive 34 are not shown for convenience of
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illustration but in practice can include a mechanical belt
drive from the engine to the knife system and a hydraulic drive
system to the reel and draper.
Referring now to Figure 1 a safety circuit for
controlling actuation of the starter 18 and the control system
19 is provided and incorporating the seat switch 22, the clutch
switch 27 responsive to movement of the implement actuation
lever 24 to the inoperative position, the second switch 28
responsive to movement of the drive transmission lever 25 to
the neutral position and a further bypass switch 35 which is
manually operated and is shown in Figure 2 attached to the
lever 25. The switch 35 can then therefore be operated
manually to the closed position but automatically moves to the
open position in response to movement of the lever 25 out of
the neutral position. Thus when the transmission lever 25 is
in a drive position, the bypass 35 is automatically moved to an
open condition as indicated schematically in Figure 2.
The circuit further includes the vehicle battery
36 and an ignition switch 37 which is alao shown schematically
in Figure 2. The circuit further includes a fuse 38, a timer
39, a first relay 40 and a second relay 41 which are shown only
in Figure 1.
The clutch switch 27 and the transmission neutral
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switch 28 are both of the type which are moved to the closed
circuit condition in response to movement of the associated
lever to the inoperative or neutral position. The seat switch
22 is also of a type which is moved to the closed circuit
condition on detection of the presence of the operator on the
seat.
The relay 40 includes a coil 40A actuating an
armature 40B movable from an open circuit condition to a closed
circuit condition in an electrical connection with a contact
40C. Movement of the relay 40 therefore by actuation of the
coil thereof causes connection of a voltage across the starter
motor 18 from the battery 36 to ground.
The relay 41 includes a coil 41A actuating an
armature 41B movable between the first contact 41C and the
second contact 41D. The first contact 41C is cannected in a
circuit through the seat switch 22 to the control system 19 to
supply power to the control system when the seat switch is in
the closed position. The contact 41D is connected directly to
the control system to provide power thereto when the coil 41A
i9 actuated to move the armature to the contact 41D. The power
for the control system is taken from a line 42 on the
downstream side of the fuse 38. A third route for the power to
the control system can be supplied through a line 43 into the
,
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timer 39 for connection across a five second delay connector
from contact 1 to contact 6 of the timer, but after the five
seconds is timed out, the contact is disconnected and the
control system connected from contact 6 to contact 2 to ground.
In operation in an initial condition of the
machine, the clutch switch 27 is moved to the closed position
by disengagement of the drive to the implement and the
transmission neutral switch 28 is moved to the closed condition
by movement of the transmission to the neutral position. The
position of the bypass switch will normally in this condition
be open as the operator will not want to operate the bypass at
this time. The operator may or may not be seated in the seat
in which case the seat switch will either be in the closed
position or in the open position which is not important at this
time.
With the switches 27 and 28 therefore closed,
power from the ignition switch 37 i9 connected through a start
line through the coil 48 and the switches 27 and 28 to ground
thus actuating the coil 48 to pull the armature to complete the
contact to the starter motor. The starter motor can thus be
actuated by movement of the ignition switch to the start
position by the operator.
At the same time power is supplied on the line 42
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from the run contact to the ignition switch which again passes
through the switches 27 and 28 to ground thus actuating the
coil 41A and moving the armature 41B into electrical engagement
with the contact 41D to supply power to the control system 19
regardless of the condition of the seat switch or the timer.
In this condition therefore the ignition switch
27 can be actuated to start and to operate the motor 16 in the
conventional manner. Once started, the operator can move the
transmission into drive by actuating the lever 25 and/or the
implement drive by actuating the lever 24 in which case one or
both of the switches 27 and 28 will be moved to the open
condition. When this occurs, the coil 41A of the relay 41 is
deactuated so that the armature moves to the contact 41C. In
thi9 condition therefore power is supplied to the control
system 19 only through the seat switch 22. If the operator
therefore moves from the seat thus opening the seat switch 22,
power is no longer supplied to the control system through the
ralay. At this time therefore, the timer comes into play and
provides connection through the line 43 to the control system
for the time period for example of five seconds. After the
timer has timed out, the control system is disconnected and the
motor will stop. The timer of course allows the operator to
adjust his position or temporarily stand without the engine
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instantaneously stopping which would of course be an
inconvenience. The timer does not however allow a long enough
period for him to leave his seat and move to a location outside
the cab or away from the normal operator position which of
course could present him into a dangerous location. It is
therefore not possible for the operator to leave the seat while
either the implement is running or the transmission is not in
neutral so that there is no danger that the operator will leave
the seat while for example the machine is halted due to
resistance on the wheels but is not actually in the neutral
position of the drive system. This can of course be very
dangerous in that the operator can believe that the machine is
properly halted and, without the system described above could
leave the seat while the machine i~ halted and then find the
machine restart because it was not actually in neutral but it
was merely temporarily halted by the resistance to the wheels
overcoming the power supplied through the transmission system.
The circuit described above is very simple and
yet provides very safe control over the operation of the
machine.
The bypass switch 35 is an optional arrangement
which can be omitted in some of the embodiments of the device.
The bypass switch 35 can be used by the operator manually and
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deliberately to close the switch 35 to provide a circuit
through the switch 35 and through the switch 28 to ground thus
actuating the coil 41A while the clutch switch 27 remains in
open condition. Thus the operator can move the transmission to
neutral but leave the implement running while he leaves the
seat to observe the running of the implement for example to
diagnose problems or noises arising in the implement. The
bypass switch 35 does not however allow the operator to leave
the seat while the transmission is not in neutral. The bypass
switch is also automatically returned to the open condition by
movement of the transmission lever 25 to the operating position
so that the system is returned to its normal safety condition
after the bypass has been used and is no longer required.
Since various modifications can be made in my
invention as hereinabove described, and many apparently widely
different embodiments of same made within the spirit and scope,
it is intended that all matter contained in the accompanying
specification shall be interpreted as illustrative only and not
in a limiting sense.
