GB2227917A

GB2227917A - Height control of a harvester cutting mechanism

Info

Publication number: GB2227917A
Application number: GB9002334A
Authority: GB
Inventors: Joerg Pilz; Hans-Peter Spaida; Gerhard Windisch; Lothar Naether; Christian Noack; Manfred Teichmann
Original assignee: VEB Kombinat Fortschritt Landmaschinen Neustadt (Bestand)
Current assignee: VEB Kombinat Fortschritt Landmaschinen Neustadt (Bestand)
Priority date: 1989-02-10
Filing date: 1990-02-02
Publication date: 1990-08-15
Also published as: GB9002334D0; IT9047600A1; DK33090A; DK33090D0; IT9047600A0; FR2642932A1; DD279807A1; DE4000918A1

Description

HEIGHT CONTROL OF A HARVESTER CUTTING MECHANISM The present invention

relates to a harvester and has particular reference to height control of a ground-tracking cutting mechanism of the harvester.

The cutting mechanism of a harvester should cut the crop to be harvested as closely as possible to the ground and provide a constant stubble height. These objectives may be achieved with relatively little difficulty in the case of even terrain. The harvester cutting mechanism is brought into the appropriate operating position by hand through lower- ing of an associated conveyor shaft. In the case of uneven terrain, however, the cutting mechanism must be constantly adjusted in operating height (DE-AS 2 216 558).

For this purpose it is known to mount ground sensors below the cutting mechanism, the sensors being rotationally movable about an axis.

The movement of the sensors is evaluated for control of the height setting. Height guidance takes place through raising or lowering of the conveyor shaft which at its lower end carries the rigidly fastened cutting mechanism (WP 155 678, DE-PS 22 65 329, DE-PS 24 55 642). The evaluation of the movement of the sensors takes place through travel- measuring systems with reed switches which are switched by a magnet being brought into the proximity of or screened from the switching magnet (DE- AS 22 64 635, DE-05 29 10 139, DE-OS 33 28 506).

It is also known to actuate electrical switches by way of cable pulls from ground sensors (WP 79 878). For the monitoring of other movements, for example monitoring of rotational speed in the case of elevator drives, it is known to mount inductive transmitters for pulse generation in front of a V-belt pulley carrying control elements (WP 140 695). It is also known to so fasten the cutting mechanism to the conveyor shaft that the mechanism can pendulate in direction of travel of the harvester and also transversely thereto and bears by skids on the ground. For this purpose, the cutting mechanism is fastened by a hinge and an intermediate piece to the lowest point of the conveyor shaft. For ground relief, spring elements are mounted between the intermediate piece and the conveyor shaft so that the cutting mechanism slides over the ground. The cutting mechanism itself is fastened to the intermediate piece by a central axle, about which it can pendulate transversely to the direction of movement in accordance with the ground contours. The movement of this ground-tracking cutting mechanism is limited by abutments and thereby effective only in a certain range (WP 120 780, WP 158 114, WP 233 921). In the case of substantial changes in the ground contours, the necessary freedom for pendulation must be achieved through raising or lowering of the conveyor shaft.

For this purpose, it is known to mount hydraulic spring elements between the pendulating cutting mechanism and the conveyor shaft and associate this with reed switches which are switched by an iron plate fastened to the piston rod of the spring element. The reed switches effect lowering or raising of the conveyor shaft through switching of valves as soon as the cutting mechanism approaches an abutment. Moreover, movable ground sensors are provided and effect a rapid reaction of the conveyor shaft to ground profile changes (DD-AP 156 939).

The hydraulic spring legs serve for support of the cutting mechanism, for adjustment of the height of the cutting mechanism on pressure loading by way of a pressure store, and for measurement value determination on reaching the tilting range limits. The movement of the 1 cutting mechanism is strongly damped by the pressure store, so that it does not follow every ground profile change immediately. Since the hydraulic spring legs are also utilised for movement of the cutting mechanism, they must be mounted underneath the cutting mechanism. How- ever, the effectiveness of the measuring equipment is thereby substantially restricted. It is very sluggish in accordance with the damping of the spring legs, and is exposed to contamination due to the proximity of the ground. In the alterantive, reference is made to use of ground sensors which are movable about an axis and which are loaded by spring pressure. These sensors follow each ground contour and, by way of limit switches, control the movement of the conveyor shaft as well as of the spring legs. Consequently, there is a risk of countercontrol and oscillation of the mowing table.

There is therefore a need for control means for a ground-tracking cutting mechanism, which may permit free movement of the cutting mechanism in accordance with the ground profile, may react rapidly and automatically to contour changes and which is not impaired by dust. Preferably such control means shall enhance the range of movement of the cutting mechanism, which preferably can pendulate transversely to and longitudinally of the direction of travel, through controlled raising and lowering of the conveyor shaft in accordance with the ground profile. For preference such control means should be able to be manual ly overriden and should permit use of the cutting mechanism without ground contact.

According to the present invention there is provided a harvester comprising a height-adjustable conveying shaft for harvested stock, a ground-tracking cutting mechanism mounted on the front of the 1 1 shaft for limited upward and downward pendulating movement relative to the shaft, load-relieving means supporting the cutting mechanism, and height control means comprising first and second signal generating devices so actuable by means mechanically coupled to the cutting mechanism as to generate first and second signals respectively indicative of reaching of travel limit positions by the mechanism, a third signal generating device to generate a third signal indicative of shaft height position, logic circuit means responsible to the third and first or third and second signals to generate a control signal for rais- ing or lowering of the shaft, manually operable means to cause a control signal for raising or lowering of the shaft to be provided independently of the signals of the signal generating devices, adjusting means controllable by the control signals to correspondingly raise or lower the shaft, and means to block response of the logic circuit means to the first to third signals.

In a preferred embodiment, the cutting mechanism is mounted to be pendulating both transversely to and longitudinally of the direction of travel, while being retained by springs to relieve the ground and limited by abutments in its movement in the range of pendulation. The height control means comprises signal generating devices in the form of two initiators connected by a cable pull with the cutting mechanism and serving to signal the reaching of the limits of the range of pendulation of the cutting mechanism and a shaft height initiator which checks the conveyor shaft movement and in its range of response activates the cutting mechanism initiators by way of the logic circuit means. The logic circuit means is followed by way of a two-channel switching amplifier and by respective electromagnetic valves in each of a channel for raising and a channel for lowering of the conveyor shaft. Connected to the inputs of the logic circuit means are the outputs of the cutting mechanism initiators, the output of the shaft height initiator, manual control keys which are also connected with the inputs of the switching amplifier and override the height guidance circuit, and an initiator switch to render the signals of the cutting mechanism initiators ineffective.

The cutting mechanism initiators preferably comprise a fixedly mounted first initiator actuable by a metal strip, which is movable in front of the initiator and which is pivotable through a semicircle and connected with the cutting mechanism by a cable pull, and an adjustable second initiator which is disposed opposite the first initiator on the pivot arc of the metal strip and is arranged to be wiped by the strip. The shaft height initiator can be fixedly settable or fastened on a base member movable by a cable pull or other linkage from the driver's cab. Mounted in front is a switch plate which is rotatable out of the range of engagement of the initiator through the movement of the conveyor shaft.

After switching-on of the height control means, initially no signal is delivered to the electromagnetic valves. The logic circuit means is activated after depression of the manual control key for lowering of the conveyor shaft. The corresponding feed to the switching amplifier is driven by low potential through the manual control key. The logic circuit means, due to the driving with low potential, holds the feed at this potential level, which is maintained by the connection of the feed to the input of the logic circuit means. When the conveyor shaft is lowered to such an extent that the switch plate moves in front of the shaft height initiator, this provides a signal which sets the afore-mentioned feed to high potential so that the switching amplifier no longer drives the corresponding valve. A time delay in that case has the effect that the conveyor shaft is lowered beyond the set switch- ing point until reaching a setting of the switach plate in front of the shaft height initiator and the cutting mechanism hassecure ground tracking. The signal from the shaft height initiator opens the inputs for the first and second initiators so that their signals control the valves without the self-holding taking place by way of the manual control key line. The manual control keys override the signals of the initiators through direct action on the switching amplifier. When operating the cutting mechanism without ground tracking, the initiator switch is closed. Thereby, no signals are delivered by the first and second initiators to the valves. The conveyor shaft is controlled in its height by the manual control keys and by the signals from the shaft height initiator.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, in which:

Fig. 1 is a schematic side elevation of the front part of a combine harvester embodying the invention; Fig. 2 is a block schematic diagram for height control means of a cutting mechanism of the harvester.

Fig. 3 is a partly sectional view of first and second initiators of the control means; and Fig. 4 is a partly sectional view of a third initiator of the control means.

i Referring now to the drawings, there is shown part of a combine harvester 2 which includes a cutting mechanism carried by a pivot frame 3. The frame 3 is articulated to a lower transverse carrier 4 of a conveyor shaft 5. Relief springs 7, which are arranged between the conveyor shaft 5 and an upper transverse carrier 6 of the pivot frame 3, have the effect that the cutting mechanism 1 sliding on skids 8 is movable relieved of ground pressure within a limited pivotal angle of the pivot frame 3. When travelling over uneven ground, the cutting mechanism 1 is guided upwardly or downwardly by way of the skids 8 and in that case tilted by the pivot frame 3 about the lower transverse carrier 4. The tilting movement of the frame 3 is limited to the rear and front by mechanical abutments (not shown) and is transmitted by a cable pull 9 to an initiator assembly 10 arranged below the driver's cab. On each occasion before reaching the front or rear abutment of the frame 3, lowering or raising movement of the conveyor shaft 5 is initiated by the initiator assembly 10, actuated by means of the cable pull 9, in conjunction with a logic circuit 27 connected thereto and a switching amplifier 28. The frame 3 with the cutting mechanism 1 is thus pivoted in the respectively opposite direction and the lowering or raising movement is thereby switched off through the initiator assembly 10.

These movements are controlled by the height control or guidance system illustrated in block schematic form in Fig. 2. Initiators 205 and 20H of the assembly 10 are connected to inputs E1 and E2 of the logic circuit 27. A shaft height initiator 26 is connected to an input E3 of the circuit 27. A manual control key 29 and a manual control key 30 connect inputs E4 and E6 with an earth line. An initiator switch 31 is connected to the input E5. The height guidance system is switched on by way of a switch 32. The logic circuit 27 is followed by a switching amplifier 28, which amplifies the signals in a channel 11raising" as well as in a channel "lowering". An electromagnetic valve 33 in the channel "raising" and an electromagnetic valve 34 in the channel "lowering" are connected through the amplifier 28. The amplifier 28 is supplied with energy independently of the energy supply for the initiators 20S, 20H and 26 and the logic circuit 27. The key 30 is connected directly with the channel "raising" and the key 29 directly with the channel "lowering" ahead of the inputs of the amplifier.

Consequently, the conveyor shaft 5 can be moved by way of the keys 29 and 30 even when the height guidance system is switched off. When the height guidance system is switched on after closing of the switch 32, then it is activated with the conveyor shaft 5 raised through brief depression of the key 29. In that case, the channel "lowering" is applied to earth potential and the input E4 of the logic circuit 27 is set. The channel "lowering" is held at low poteenti a] due to the return to the input E4 until the shaft height initiator 26 delivers a signal.

This effects resetting of the input E4 and thereby causes the channel "lowering" to be at high potential. Due to a time delay, this signal is supplied only when the cutting mechanism 1 has secure ground contact. The signals of the initiators 205 and 20H are now freed for control of the valves 33 and 34. Controlled by the initiators 20S and 20H, the conveyor shaft 5 raises and lowers so that the pivot frame 3 is disposed in a central setting within its range of tilting. When guiding the cutting mechanism 1 without ground contact during the harvest, the t control signals of the initiators 20S and 20H are blocked through closing of the initiator off-switch 31. The conveyor shaft 5 is brought, through brief actuation of the manual control key 29, into the operating range, which is fixed or settable through actuation of a cable pull or linkage (not shown), of the shaft height initiator 26 and held therein by this.

The initiator assembly 10, illustrated in Fig. 3, consists of the parts of base member 11, a mount 12, a ring 13, an arresting pin 14, a bolt 15, a torsion spring 16, a bearing 17, a cable pulley 18, a metal switching plate 19 and the two inductive initiators 20S and 20H. The member 11 is firmly connected with the frame of the harvester 2. The initiator 20S, the bolt 15 and the mount 12 with the second initiator 20H are fastened to the member 11. The cable pulley 18, at which the switch plate 19 is fastened, is mounted to be rotatable on the bolt 15.

Fastened to the cable pulley 18 is the cable pull 9 (not shown in Fig. 3), which is tensioned by the spring 16. The spring is fixed at one end in the cable pulley 18 and at the other end in the ring 13 locked to the member 11. The ring 13 is situated between the member 11 and a collar of the bolt 15 and is arrested by means of a pin 14 inserted into one of a plurality of holes arranged concentrically with the bolt 15 in the member 11. The restoring force of the spring 16 depends on the choice of the hole for reception of the pin 14. The spacing of the active area of each initiator 20S and 20H from the switching plate 19 is set to the optimum value. By loosening of the securing nut of the bolt 15 and rotation of the mount 12, the angular spacing of the initiator 20H on the mount 12 from an initiator 20S on the member 11 is settable and thereby also the switching point spacing of the two intiators 20S and 20H.

4 1 4 - The shaft height initiator mount 21 is illustrated in Fig. 4. It is firmly connected with the frame of the harvester 2 by a bearing block 22 disposed above the conveyor shaft 5. On its spigot, a switch p] ate 23, consi sting of a hub and a sector-shaped sheet metal p] ate, is arranged to be rotatable parallelly to the plane of movement of a side surface of the conveyor shaft 5 and is connected with the conveyor shaft 5 by way of a coupling rod 24.

The inductive shaft height initiator 26 is fastened to the spigot of the bearing block 22 to be fixedly settable in desired position on a circular arc about this axis parallelly to the axis of the bearing block 22 by means of a mount 25. The mount 25 can also be arranged to be rotatable about the spigot of the bearing block 22 and settable from the driver's cab by means of levers and linkages, by a cable pull and restoring spring, or by another form of transmission means.

-1 i

Claims

1. A harvester comprising a height-adjustable conveying shaft for harvested stock, a ground-tracking cutting mechanism mounted on the front of the shaft for limited upward and downward pendulating movement relative to the shaft, load-relieving means supporting the cutting mechanism, and height control means comprising first and second signal generating devices so actuable by means mechanically coupled to the cutting mechanism as to generate first and second signals respectively indicative of reaching of travel limit positions by the mechanism, a third signal generating device to generate a third signal indicative of shaft height position, logic circuit means responsive to the third and first or third and second signals to generate a control signal for raising or lowering of the shaft, manually operable means to cause a control signal for raising or lowering of the shaft to be provided in- dependently of the signals of the signal generating devices, adjusting means controllable by the control signals to correspondingly raise or lower the shaft, and means to block response of the logic circuit means to the first to third signals.

2. A harvester as claimed in claim 1, wherein the cutting mechanism is additionally mounted on-the shaft for lateral pendulating movement.

3. A harvester as claimed in either claim 1 or claim 2, the loadrelieving means comprising springs.

4. A harvester as claimed in any one of the preceding claims, wherein the mechanical coupling is provided by a cable pull.

5. A harvester as claimed in any one of the preceding claims, comprising a two-channel switching amplifier to amplify the control signals.

6. A harvester as claimed in any one of the preceding claims, the adjusting means comprising a respective electromagnetic switch to initiate each of raising and lowering of the shaft.

7. A harvester as claimed in claim 5, the manually operable means comprising a respective manual control key for each of a control signal for raising the shaft and a control signal for lowering the shaft, the keys being connected to inputs of the amplifier and inputs of the logic circuit means.

8. A harvester as claimed in any one of the preceding claims, wherein the means to block response comprises a switch connected to an input of the logic circuit means.

9. A harvester as claimed in claim 4, wherein the first and second signal generating devices are disposed at an adjustable spacing from each other and actuable by a pivotable switching plate driven by the cable pull.

10. A harvester as claimed in any one of the preceding claims, wherein the third signal generating device is actuable by a respective pivotable switching plate driven by movement in height of the conveyor shaft.

1

11. A harvester as claimed in claim 10, comprising means to adjust the position of the third signal generating device.

12. A harvester substantially as hereinbefore described with reference to the accompanying drawings.

Published 1990 at The Patent Office. State House. 6671 High Holborn. Londor WC1R4TP- Further copies maybe obtained from The Patent OTIce Sales Branch. St Mary Cray. Orpington, Kent BR5 3RD Printed by Multiplex techruques ltd. St Mary Cray, Kent. Con. 1 '87