CA1117626A - Depth limit control system for agricultural implements - Google Patents
Depth limit control system for agricultural implementsInfo
- Publication number
- CA1117626A CA1117626A CA000336599A CA336599A CA1117626A CA 1117626 A CA1117626 A CA 1117626A CA 000336599 A CA000336599 A CA 000336599A CA 336599 A CA336599 A CA 336599A CA 1117626 A CA1117626 A CA 1117626A
- Authority
- CA
- Canada
- Prior art keywords
- control
- valve
- working element
- limit
- cylinders
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- A—HUMAN NECESSITIES
- A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
- A01B—SOIL WORKING IN AGRICULTURE OR FORESTRY; PARTS, DETAILS, OR ACCESSORIES OF AGRICULTURAL MACHINES OR IMPLEMENTS, IN GENERAL
- A01B63/00—Lifting or adjusting devices or arrangements for agricultural machines or implements
- A01B63/14—Lifting or adjusting devices or arrangements for agricultural machines or implements for implements drawn by animals or tractors
- A01B63/16—Lifting or adjusting devices or arrangements for agricultural machines or implements for implements drawn by animals or tractors with wheels adjustable relatively to the frame
- A01B63/22—Lifting or adjusting devices or arrangements for agricultural machines or implements for implements drawn by animals or tractors with wheels adjustable relatively to the frame operated by hydraulic or pneumatic means
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- Life Sciences & Earth Sciences (AREA)
- Zoology (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Soil Sciences (AREA)
- Environmental Sciences (AREA)
- Lifting Devices For Agricultural Implements (AREA)
Abstract
DEPTH LIMIT CONTROL SYSTEM FOR AGRICULTURAL IMPLEMENTS
ABSTRACT OF THE DISCLOSURE
A depth limit control system is provided including an electrically operative valve which is connected in series between one or more working cylinders integral with a trail behind implement frame supporting discs, plow bottoms or other agricultural implements, and a manually controlled valve which controls flow of fluid to and from the cylinders.
The electrically operative valve is controlled from a com-parator circuit which compares the outputs of transducers which develop signals respectively corresponding to a manu-ally adjustable limit and to the vertical position of the agricultural implement, the electrically operative valve being so operated when the manually adjustable limit is reached so as to prevent further lowering of the agricultur-al implement.
ABSTRACT OF THE DISCLOSURE
A depth limit control system is provided including an electrically operative valve which is connected in series between one or more working cylinders integral with a trail behind implement frame supporting discs, plow bottoms or other agricultural implements, and a manually controlled valve which controls flow of fluid to and from the cylinders.
The electrically operative valve is controlled from a com-parator circuit which compares the outputs of transducers which develop signals respectively corresponding to a manu-ally adjustable limit and to the vertical position of the agricultural implement, the electrically operative valve being so operated when the manually adjustable limit is reached so as to prevent further lowering of the agricultur-al implement.
Description
1~76Z6 DEPT~ LIMIT CONTROL SYSTEM FOR AGRICULTURAL IMPLEMENTS
BACK5ROUND OF THE IN~ENTION
Field of the Invention This invention relates to a control system for an agricultural implement and more particularly to a control system which is readily adjustable and which facilitates accurate control of the positioning and movement of a work-ing element while being economically manufacturable and relatively simple and straightforward in construction and operation. The control system can be readily applied to existing implements of various designs or can be incor-porated during manufacture.
Description of the Prior Art In agricultural implements such as plows, harrows and the like, the plow bottoms, discs or other working elements must be controllably movable upwardly or downwardly during operation to adjust for varying soil conditions and must be movable to a fully raised position for travel or to clear an obstacle. Hydraulic systems are generally used and in a typical system, a manually adjustable valve controls flow of a fluid to and from a hydraulic cylinder which operates a rockshaft arranged to control the vertical posi-tion of discs or plow bottoms. The hydraulic cylinder maybe double-acting or may be single-acting with the force of gravity being relied upon to effect downward movement of the workins implement.
Systems have been proposed which rely on mechan-ical stops. These systems cannot be ad~usted during opera-.~ ,~, ,.
":
tion. The operatox must dismount, predict some incrementalchange in depth, then make a mechanical change which may require tools.
Systems have also been proposed using, in place of 5 the manually operated valve, an electrically operated valve controlled from a command potentiometer operated by the operator.
Systems using a manually operated valve are, in general, very rugged and highly reliable while being rela-10 tively inexpensive to manufacture, but they have limita-tions. For example, when a plow bottom is raised to clear an obstacle or at the end of a row, it requires considerable care and expertise to rapidly return the plow bottom to the optimum plowing level. Electrically controlled systems are 15 more easily controlled and might provide greater flexibility but those heretofore proposed have been relatively expensive and have other disadvantages, including increased power consumption and no "limp-home" or manual override and back-up provisions.
SUMMARY OF THE INVENTION
This invention was evolved with the general object of overcoming disadvantages and shortcomings of prior art arrangements and of providing a system which is readily adjustable and which facilitates accurate control of the movement and positioning of a working element of an agri-cultural implement while being relatively simple in con-struction and operation and economically manufacturable.
In accordance with this invention, a secondary control is applied to a hydraulic system which raises and lowers a working element of an agricultural implement and which is controlled from a main raise-lower control manually adjustable by an operator. The secondary control includes electrically opexated valve means for connection to the hydraulic system, a limit control means for establishing a manually set limit on lowering movement of the working element and an electrical system for controlling the valve 176~
means from the limit control means to limit lowering move-ment of the working element in accordance with the manually set limit. With this comparatively simple arrangement, the hydraulic system can be operated in normal fashion from the main raise-lower control but the operator can set whatever limit is desired on the lowering movement by setting the secondary control. In operating a disc harrow, for example, he can use the main control in determining the optimum depth for existing soil conditions and he may then set the secon-dary control to operate at that depth. Then when encounter-ing an obstacle or at the end of a row, he can use the main control to lift the harrow and thereafter use it for lower-ing until the limit position is reached and then continue operation at the optimum depth. Thus a "memory" operation is obtained and accurate, reliable and efficient control is facilitated.
The electr cal system includes transducers for develop-ing signals corresponding to the manually set limit and to the vertical position of the working element and a comparator means 20 for comparing such signals to control the secondary valve means.
The transducers in a preferred embodiment are potentiometers operating as voltage dividers to develop analog signals which are compared by a high gain differential amplifier. Preferably, positive feedback means are provided for producing a bi-stable 25 h~steretic switchin~ operation and a high degree of stability and reliability in operation.
With the electrical control, the depth control means can be readily in~talled in proximity to the o~era-tor's station of a tractor and in proximity to the main .30 raise-lower control, facilitating adjustment whenever desired and permitting adjustment during movement of the implement. Indicator means may be associated with the depth control means, permitting use thereof as a monitor to in-dicate when a desired depth has been reached as well as an 35 indication of actual depth.
In accordance with a specific feature, the secon-dary electrically operated valve means is connected in _ 4 ~ 1~7~Z6 series with a main valve of the hydraulic system which is coupled between a pump and at least one working cylinder coupled mechanically to the working element. The hydraulic system may thus be of a standard highly reliable type such ; as one usiny a manually adjustable spool valve and the arrangement can be readily installed on an existing imple-ment or can be readily incorporated during manufactur~ of an implement without change in its basic design.
In accordance with specific featu~es, the secon--O dary valve is located between the main valve and the workins cylinder or cylinders and preferably it is located close to the wor~ing cylinder or cylinders and on the "drop side" to increase accuracy of control especially when a master-slave cylinder arrangement is used, and also to provide additional resistance against "leak-down" of an implement dur~ng opera-tion.
This invention contemplates other objects, fea-tures and advantages which will become more fully apparent from the following detailed description taken in conjunction O with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
.
FIGURE 1 is a perspective view illustrating a depth control arrangement according to the invention, shown applied to a trail behind self-supported disc harrow imple-ment;
FIGURE 2 is a view illustrating diagrammaticallythe hydraulic system o the implement and the coupling of the depth control arrangement thereto; and FIGURE 3 is a circuit diagram of an electrical ,0 system of the depth control arrangement of the invention.
DESCRIPTION OF A PREFERRED EMBODIME NT
Reference numeral 10 generally designates a depth monitoring and control system constructed in accordance with - the principles of this invention and shown diagrammatically ,~....
1~L176Z6 as applied to a trail behind disc harrow implement generally designated 11 which is drawn by a tractor generally desig-nated 12 and which includes working elements in the form of discs 13. It will be understood that the invention may be applied in controlling the position of working elements of other types of agricultural implements and may be used, for example, in controlling the position of the bottoms of plows, the headers of combines, the buckets of loaders, and backhoes, the blades of scrapers, etc.
A hydraulic system is used for raising and lower-ing the discs, controlled by a lift control valve 14 located in the operator's cab of the tractor 12 and operated by a control lever lS.
In accordance with the invention, depth control means are provided, including a unlt 16 located in the cab of the tractsr and including an adjustment knob 18 for establishing a manually set limit on lowering movement of the discs 13. In a typical operation, the operator, through operation of the control lever lS, determines the optimum level for the discs 13 according to prevailing soil condi-tions with the knob 18 being positioned to set the corres-ponding limit on lowering movement. Then, whenever an obstruction or hazard is encountered or when turning at the end of a row, the lever 15 is operated to raise the discs 13. After the obstruction or hazard is cleared or after the turn is completed, the lever 15 is again operated to lower the discs until the set limit is reached, the discs 13 being then positioned and thereafter maintained at the optimum depth as previously set by the operator. No readjustment is necessary~
It is noted that a graduated scale 19 (Figure 3) is located adjacent the knob 18 so that the setting for any particular condition of operation may be noted and there-after the knob 18 may be positioned at the same setting whenever desired.
In the illustrated disc harrow implement generally designated 11, the discs 13 are carried from a frame struc-1~7~Z6-- 6 --ture 20 supported ~rom a pair of inner support wheels 21 and
BACK5ROUND OF THE IN~ENTION
Field of the Invention This invention relates to a control system for an agricultural implement and more particularly to a control system which is readily adjustable and which facilitates accurate control of the positioning and movement of a work-ing element while being economically manufacturable and relatively simple and straightforward in construction and operation. The control system can be readily applied to existing implements of various designs or can be incor-porated during manufacture.
Description of the Prior Art In agricultural implements such as plows, harrows and the like, the plow bottoms, discs or other working elements must be controllably movable upwardly or downwardly during operation to adjust for varying soil conditions and must be movable to a fully raised position for travel or to clear an obstacle. Hydraulic systems are generally used and in a typical system, a manually adjustable valve controls flow of a fluid to and from a hydraulic cylinder which operates a rockshaft arranged to control the vertical posi-tion of discs or plow bottoms. The hydraulic cylinder maybe double-acting or may be single-acting with the force of gravity being relied upon to effect downward movement of the workins implement.
Systems have been proposed which rely on mechan-ical stops. These systems cannot be ad~usted during opera-.~ ,~, ,.
":
tion. The operatox must dismount, predict some incrementalchange in depth, then make a mechanical change which may require tools.
Systems have also been proposed using, in place of 5 the manually operated valve, an electrically operated valve controlled from a command potentiometer operated by the operator.
Systems using a manually operated valve are, in general, very rugged and highly reliable while being rela-10 tively inexpensive to manufacture, but they have limita-tions. For example, when a plow bottom is raised to clear an obstacle or at the end of a row, it requires considerable care and expertise to rapidly return the plow bottom to the optimum plowing level. Electrically controlled systems are 15 more easily controlled and might provide greater flexibility but those heretofore proposed have been relatively expensive and have other disadvantages, including increased power consumption and no "limp-home" or manual override and back-up provisions.
SUMMARY OF THE INVENTION
This invention was evolved with the general object of overcoming disadvantages and shortcomings of prior art arrangements and of providing a system which is readily adjustable and which facilitates accurate control of the movement and positioning of a working element of an agri-cultural implement while being relatively simple in con-struction and operation and economically manufacturable.
In accordance with this invention, a secondary control is applied to a hydraulic system which raises and lowers a working element of an agricultural implement and which is controlled from a main raise-lower control manually adjustable by an operator. The secondary control includes electrically opexated valve means for connection to the hydraulic system, a limit control means for establishing a manually set limit on lowering movement of the working element and an electrical system for controlling the valve 176~
means from the limit control means to limit lowering move-ment of the working element in accordance with the manually set limit. With this comparatively simple arrangement, the hydraulic system can be operated in normal fashion from the main raise-lower control but the operator can set whatever limit is desired on the lowering movement by setting the secondary control. In operating a disc harrow, for example, he can use the main control in determining the optimum depth for existing soil conditions and he may then set the secon-dary control to operate at that depth. Then when encounter-ing an obstacle or at the end of a row, he can use the main control to lift the harrow and thereafter use it for lower-ing until the limit position is reached and then continue operation at the optimum depth. Thus a "memory" operation is obtained and accurate, reliable and efficient control is facilitated.
The electr cal system includes transducers for develop-ing signals corresponding to the manually set limit and to the vertical position of the working element and a comparator means 20 for comparing such signals to control the secondary valve means.
The transducers in a preferred embodiment are potentiometers operating as voltage dividers to develop analog signals which are compared by a high gain differential amplifier. Preferably, positive feedback means are provided for producing a bi-stable 25 h~steretic switchin~ operation and a high degree of stability and reliability in operation.
With the electrical control, the depth control means can be readily in~talled in proximity to the o~era-tor's station of a tractor and in proximity to the main .30 raise-lower control, facilitating adjustment whenever desired and permitting adjustment during movement of the implement. Indicator means may be associated with the depth control means, permitting use thereof as a monitor to in-dicate when a desired depth has been reached as well as an 35 indication of actual depth.
In accordance with a specific feature, the secon-dary electrically operated valve means is connected in _ 4 ~ 1~7~Z6 series with a main valve of the hydraulic system which is coupled between a pump and at least one working cylinder coupled mechanically to the working element. The hydraulic system may thus be of a standard highly reliable type such ; as one usiny a manually adjustable spool valve and the arrangement can be readily installed on an existing imple-ment or can be readily incorporated during manufactur~ of an implement without change in its basic design.
In accordance with specific featu~es, the secon--O dary valve is located between the main valve and the workins cylinder or cylinders and preferably it is located close to the wor~ing cylinder or cylinders and on the "drop side" to increase accuracy of control especially when a master-slave cylinder arrangement is used, and also to provide additional resistance against "leak-down" of an implement dur~ng opera-tion.
This invention contemplates other objects, fea-tures and advantages which will become more fully apparent from the following detailed description taken in conjunction O with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
.
FIGURE 1 is a perspective view illustrating a depth control arrangement according to the invention, shown applied to a trail behind self-supported disc harrow imple-ment;
FIGURE 2 is a view illustrating diagrammaticallythe hydraulic system o the implement and the coupling of the depth control arrangement thereto; and FIGURE 3 is a circuit diagram of an electrical ,0 system of the depth control arrangement of the invention.
DESCRIPTION OF A PREFERRED EMBODIME NT
Reference numeral 10 generally designates a depth monitoring and control system constructed in accordance with - the principles of this invention and shown diagrammatically ,~....
1~L176Z6 as applied to a trail behind disc harrow implement generally designated 11 which is drawn by a tractor generally desig-nated 12 and which includes working elements in the form of discs 13. It will be understood that the invention may be applied in controlling the position of working elements of other types of agricultural implements and may be used, for example, in controlling the position of the bottoms of plows, the headers of combines, the buckets of loaders, and backhoes, the blades of scrapers, etc.
A hydraulic system is used for raising and lower-ing the discs, controlled by a lift control valve 14 located in the operator's cab of the tractor 12 and operated by a control lever lS.
In accordance with the invention, depth control means are provided, including a unlt 16 located in the cab of the tractsr and including an adjustment knob 18 for establishing a manually set limit on lowering movement of the discs 13. In a typical operation, the operator, through operation of the control lever lS, determines the optimum level for the discs 13 according to prevailing soil condi-tions with the knob 18 being positioned to set the corres-ponding limit on lowering movement. Then, whenever an obstruction or hazard is encountered or when turning at the end of a row, the lever 15 is operated to raise the discs 13. After the obstruction or hazard is cleared or after the turn is completed, the lever 15 is again operated to lower the discs until the set limit is reached, the discs 13 being then positioned and thereafter maintained at the optimum depth as previously set by the operator. No readjustment is necessary~
It is noted that a graduated scale 19 (Figure 3) is located adjacent the knob 18 so that the setting for any particular condition of operation may be noted and there-after the knob 18 may be positioned at the same setting whenever desired.
In the illustrated disc harrow implement generally designated 11, the discs 13 are carried from a frame struc-1~7~Z6-- 6 --ture 20 supported ~rom a pair of inner support wheels 21 and
2? and a pair of outer support wheels 23 and 24. The inner wheels 21 and 22 are supported on axles of arms which are secured to a rockshaft 26 actuated ky a pair of hydraulic 5 cylinders 27 and 28. The outer wheels 23 and 24 are sup-ported in a similar manner from shafts actuated by a palr of hydraulic cyllnders 29 and 30. As best seen in Figure 2 in conjunction with Figure l the frame structure 20 and thereby the discs 13 are raised by supplying fluid under pressure 10 through lines 31 and 32 to the cylinders 27 and 28 from which fluid is supplied through lines 33 and 34 to cylinders 29 and 30. Fluid flows from cylinders 29 and 30 through lines 35 and 36 to reservoir 40 when cylinders 29 and 30 are being filled.
To lower the discs 13, the operation is reversed with fluid flowing through lines 35 and 36 to cylinders 29 and 30, with fluid flowing from cylinders 29 and 30 through lines 33 and 34 to cylinders 27 and 28 and with fluid flow-ing from cylinders 27 and 28 through lines 31 and 32 eventu-ally to the reservoir 40.
Figure 2 shows a pump 39 that has an inlet con~
nected to the reservoir 40, the outlet of pump 39 and the reservoir 40 being connected through lines 41 and 42 re-spectively to the lift control valve 14. Lift control valve 14 is connected through a line 43 to lines 31 and 32 and through a line 44 to lines 35 and 36.
In the system of this invention, a secondary valve 45 is provided which is operated by a solenoid 46 and which is preferably located on the implement generally designated 11 close to the cylinders 27 and 28. The manner of flow through valve 45 is indicated diagrammatically in Figure 2.
When solenoid 46 is deenergized, fluid may flow in either direction as indicated by double ended arrow 47. r~en solenoid 46 is energized, a check valve 48 is operative, permitting flow from line 43 to lines 31 and 32 for raising of the discs 13 but blocking flow in the reverse direction to prevent lowering of the discs 13.
~1176Z~;
The liEt control valve 14 has -three positions. In a neutral position, fluid flows in a recirculating path from line 41 to line 42, as indicated by arrow 50 with fluid flow to or from lines 43 and 44 being blocked, as indicated by lines 51 and 52. In a "raise" position, fluid flows from line 41 to line 43 and from line 44 to line 42 is indicated by arrows 53 and 54. In a "lower" position, fluid flows from line 41 to line 44 and from line 43 to line 42 as indicated by crossed arrows 55 and 56.
In Figure 3 it can be seen that the operating solenoid 46 for the valve 45 is connected to terminals 57 and 58, terminal 57 being connected through a fuse 59 to a positive supply terminal 60 of the tractor electrical system and also connected through a protective diode 61 to ground.
Terminal 58 is connected to the collector of a transistor 62, the emitter of which is connected to ground. A protec-tive diode 63 and an indicator lamp 64 are connected between terminals 57 and 58, in parallel with the solenoid 46. Lamp 64 is preferably positioned in the unit 16 adjacent the adjustment knob 18 within view of the operator, signalling to him that the pre-set optimum depth has been reached.
The base of the transistor 62 is connected through a resistor 65 to the output of an operational amplifier 66 which has a plus input connected to the movable contact of a potentiometer 68 which is connected between ground and an output line 69 of a regulated voltage supply 70 connected to ` the terminal 57. The potentiometer 68 forms a depth or level sensing transducer, the movable contact thereof being mechanically connected to the rockshaft 26 in a manner such as to move toward the grounded end of the resistance element and away from the supply end thereof in response to rotation of the rockshaft 26 in a direction to raise the frame struc-ture 20 and discs 13.
The minus input of the operational amplifier 66 is connected through a resistor 72 to the terminal 58 and is also connected through a resistor 73 to the movable contact of a potentiometer 74 which has end terminals connected .lL,~.~ 7t;~
through fixed resistors 75 and 76 to ground and to the regulated voltage supply line 69. Potentiometer 74 forms a depth limit control transducer, its movable contact being mechanically connected to knob 18.
In operation, when the control lever 15 (Figure 2) of valve 14 is moved to a "raise" position, fluid flows from the pump outlet through line 41 and through passage 53 of valve 14, thence through line 43 and through passage 47 through valve 45 and thence through lines 31 and 32 to 10 cylinders 27 and 28. Fluid flows from cylinders 27 and 28 to cylinders 29 and 30 through lines 33 and 3A and return -flow is from cylinders 29 and 30 and through lines 35 and 36, through line 44, through a path through valve 14 as represented by passage 54 and thence through line 42 to the 15 reservoir 40.
When the control lever 15 of valve 14 is moved to a "lower" position, fluid flows from the outlet of pump 39 through line 41, thence through the path through control valve 14 as represented by passage 55 and through line 44 20 and lines 35 and 36 to cylinders 29 and 30. Fluid flows through lines 33 and 34 from cylinders 29 and 30 to cylin-ders 27 and 28 respectively and return flow is from cylin-ders 27 and 28 through lines 31 and 32, through the passage 47 of valve 45 and through line 43, the passage 54 through 25 valve 14 and through line 42 to reservoir 40.
When the discs 13 (Figure l) are fully raised, the movable contact of the depth sensing potentiometer 68 (Figure 3) is at a limit of its movement toward the grounded end of the resistance element thereof and the voltage 30 applied to the plus input of the amplifier 66 is at a minimum. As the discs 13 are lowered, the voltage applied to the plus input of amplifier 66 increases and at a certain position, determined by the setting of the potentiometer 74, the voltage applied to the plus input is more positive than
To lower the discs 13, the operation is reversed with fluid flowing through lines 35 and 36 to cylinders 29 and 30, with fluid flowing from cylinders 29 and 30 through lines 33 and 34 to cylinders 27 and 28 and with fluid flow-ing from cylinders 27 and 28 through lines 31 and 32 eventu-ally to the reservoir 40.
Figure 2 shows a pump 39 that has an inlet con~
nected to the reservoir 40, the outlet of pump 39 and the reservoir 40 being connected through lines 41 and 42 re-spectively to the lift control valve 14. Lift control valve 14 is connected through a line 43 to lines 31 and 32 and through a line 44 to lines 35 and 36.
In the system of this invention, a secondary valve 45 is provided which is operated by a solenoid 46 and which is preferably located on the implement generally designated 11 close to the cylinders 27 and 28. The manner of flow through valve 45 is indicated diagrammatically in Figure 2.
When solenoid 46 is deenergized, fluid may flow in either direction as indicated by double ended arrow 47. r~en solenoid 46 is energized, a check valve 48 is operative, permitting flow from line 43 to lines 31 and 32 for raising of the discs 13 but blocking flow in the reverse direction to prevent lowering of the discs 13.
~1176Z~;
The liEt control valve 14 has -three positions. In a neutral position, fluid flows in a recirculating path from line 41 to line 42, as indicated by arrow 50 with fluid flow to or from lines 43 and 44 being blocked, as indicated by lines 51 and 52. In a "raise" position, fluid flows from line 41 to line 43 and from line 44 to line 42 is indicated by arrows 53 and 54. In a "lower" position, fluid flows from line 41 to line 44 and from line 43 to line 42 as indicated by crossed arrows 55 and 56.
In Figure 3 it can be seen that the operating solenoid 46 for the valve 45 is connected to terminals 57 and 58, terminal 57 being connected through a fuse 59 to a positive supply terminal 60 of the tractor electrical system and also connected through a protective diode 61 to ground.
Terminal 58 is connected to the collector of a transistor 62, the emitter of which is connected to ground. A protec-tive diode 63 and an indicator lamp 64 are connected between terminals 57 and 58, in parallel with the solenoid 46. Lamp 64 is preferably positioned in the unit 16 adjacent the adjustment knob 18 within view of the operator, signalling to him that the pre-set optimum depth has been reached.
The base of the transistor 62 is connected through a resistor 65 to the output of an operational amplifier 66 which has a plus input connected to the movable contact of a potentiometer 68 which is connected between ground and an output line 69 of a regulated voltage supply 70 connected to ` the terminal 57. The potentiometer 68 forms a depth or level sensing transducer, the movable contact thereof being mechanically connected to the rockshaft 26 in a manner such as to move toward the grounded end of the resistance element and away from the supply end thereof in response to rotation of the rockshaft 26 in a direction to raise the frame struc-ture 20 and discs 13.
The minus input of the operational amplifier 66 is connected through a resistor 72 to the terminal 58 and is also connected through a resistor 73 to the movable contact of a potentiometer 74 which has end terminals connected .lL,~.~ 7t;~
through fixed resistors 75 and 76 to ground and to the regulated voltage supply line 69. Potentiometer 74 forms a depth limit control transducer, its movable contact being mechanically connected to knob 18.
In operation, when the control lever 15 (Figure 2) of valve 14 is moved to a "raise" position, fluid flows from the pump outlet through line 41 and through passage 53 of valve 14, thence through line 43 and through passage 47 through valve 45 and thence through lines 31 and 32 to 10 cylinders 27 and 28. Fluid flows from cylinders 27 and 28 to cylinders 29 and 30 through lines 33 and 3A and return -flow is from cylinders 29 and 30 and through lines 35 and 36, through line 44, through a path through valve 14 as represented by passage 54 and thence through line 42 to the 15 reservoir 40.
When the control lever 15 of valve 14 is moved to a "lower" position, fluid flows from the outlet of pump 39 through line 41, thence through the path through control valve 14 as represented by passage 55 and through line 44 20 and lines 35 and 36 to cylinders 29 and 30. Fluid flows through lines 33 and 34 from cylinders 29 and 30 to cylin-ders 27 and 28 respectively and return flow is from cylin-ders 27 and 28 through lines 31 and 32, through the passage 47 of valve 45 and through line 43, the passage 54 through 25 valve 14 and through line 42 to reservoir 40.
When the discs 13 (Figure l) are fully raised, the movable contact of the depth sensing potentiometer 68 (Figure 3) is at a limit of its movement toward the grounded end of the resistance element thereof and the voltage 30 applied to the plus input of the amplifier 66 is at a minimum. As the discs 13 are lowered, the voltage applied to the plus input of amplifier 66 increases and at a certain position, determined by the setting of the potentiometer 74, the voltage applied to the plus input is more positive than
3~ that applied to the minus input. The amplifier 66 then - produces a positive output vol-age which is applied to the base of transistor 62 which then conducts heavily to ener-gize the solenoid 46 and operate the valve 45.
1~76~6 g When valve 45 is so operated, flow from cylinders 27 and 28 (Figure 2) and through lines 31 and 32 is blocked by the check valve 48 and with flow from cylinders 27 and 2 being blocked, flow from cylinders 29 and 30 and through 5 lines 33 and 34 is also blocked. Thus downward movement of the discs 13 is limited, the limit position being determined by the setting o~ the potentiometer 74, adjustable through the adjustment knob 18. When the limit is reached, the control lever 15 may be released to allow the valve 14 to be 10 operated to its neutral position ~y suitable spring means associated with the valve.
It is noted that the potential of the collector of transistor 62 and terminal 58 is substantially equal to the potential of terminal 57 when transistor 62 is non-conduc-tive and drops to close to ground potential when transistor62 conducts heavily. Through the resistor 72, which pro-vides positive feedback, the potential of the minus input of amplifier 66 is shifted in a negative direction from a value slightly above to a va~ue slightly below the potential of the contact of potentiometer 74. Thus, once the plus input of amplifier 66 becomes only very slightly more positive than its minus input, the positive feedbac~ insures that it will rapidly become much more positive to cause the ampli-fier to produce a positive output with a high degree of stability. Similarly, the amplifier is rapidly cut off when the plus input becomes only very slightly more nega~ive than the minus input and the circuit has a bi-sta~le operation, hysteretic operation~ This feature is lmportant in avoiding oscillatory operations which t~e system may have a tendency to produce such as hydraulic "bouncing" caused by the accu-mulator effect of flexible hydraulic lines, or electric signal fluctuations.
It will be understood that modifications and variations may be effected without departing from the spirit and scope of the novel concepts of this invention.
1~76~6 g When valve 45 is so operated, flow from cylinders 27 and 28 (Figure 2) and through lines 31 and 32 is blocked by the check valve 48 and with flow from cylinders 27 and 2 being blocked, flow from cylinders 29 and 30 and through 5 lines 33 and 34 is also blocked. Thus downward movement of the discs 13 is limited, the limit position being determined by the setting o~ the potentiometer 74, adjustable through the adjustment knob 18. When the limit is reached, the control lever 15 may be released to allow the valve 14 to be 10 operated to its neutral position ~y suitable spring means associated with the valve.
It is noted that the potential of the collector of transistor 62 and terminal 58 is substantially equal to the potential of terminal 57 when transistor 62 is non-conduc-tive and drops to close to ground potential when transistor62 conducts heavily. Through the resistor 72, which pro-vides positive feedback, the potential of the minus input of amplifier 66 is shifted in a negative direction from a value slightly above to a va~ue slightly below the potential of the contact of potentiometer 74. Thus, once the plus input of amplifier 66 becomes only very slightly more positive than its minus input, the positive feedbac~ insures that it will rapidly become much more positive to cause the ampli-fier to produce a positive output with a high degree of stability. Similarly, the amplifier is rapidly cut off when the plus input becomes only very slightly more nega~ive than the minus input and the circuit has a bi-sta~le operation, hysteretic operation~ This feature is lmportant in avoiding oscillatory operations which t~e system may have a tendency to produce such as hydraulic "bouncing" caused by the accu-mulator effect of flexible hydraulic lines, or electric signal fluctuations.
It will be understood that modifications and variations may be effected without departing from the spirit and scope of the novel concepts of this invention.
Claims (5)
1. In a control for an agricultural implement including a frame, supporting wheel means supported on said frame, a working element supported from said frame for raising and lowering movements relative to said supporting wheel means, a main raise-lower control manually adjustable by an operator, and a hydraulic system controlled from said control for raising and lowering said working element, secondary limit control means for establishing a manually set limit on lowering movement of said working element, auxiliary elect-rically operated valve means for connection to said hydraulic system,and an electrical system for controlling said auxiliary valve means from said secondary limit control means for limiting lowering movement of said working element in accordance with said manually set limit; said electrical system comprising first transducer means associated with said secondary limit control means for developing a first electric signal corresponding to said manually set limit, second transducer means coupled to said working element for develop-ing a second electrical signal corresponding to the vertical position of said working element, and comparator means for comparing said first and second electrical signals and arranged for developing an output signal when the value of said second electrical signal is less than that of said first electrical signal, and means responsive to said output signal for operating said auxiliary valve means; said first and second electrical signals being analog signals and said comparator means including a high-gain differential amplifier.
2. In a control as defined in Claim 1, positive feedback means coupled to said differential amplifier for producing a bi-stable hysteretic switching operation.
3. In a control as defined in Claim 1, said first and second transducers being potentiometers operable as voltage dividers.
4. In a control as defined in Claim 2, said first and second transducers being potentiometers operable as voltage dividers.
5. In a control as defined in Claim 1, 2 or 3 wherein said hydraulic system includes a hydraulic cylinder coupled mechanically to said working element, a pump, and a main valve between said pump and said cylinder and operated by said main raise-lower control, said auxiliary electrically operated valve means being coupled in series between said main valve between said pump and said cylinder.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US95110678A | 1978-10-13 | 1978-10-13 | |
| US951,106 | 1978-10-13 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1117626A true CA1117626A (en) | 1982-02-02 |
Family
ID=25491273
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000336599A Expired CA1117626A (en) | 1978-10-13 | 1979-09-28 | Depth limit control system for agricultural implements |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU5160679A (en) |
| CA (1) | CA1117626A (en) |
| FR (1) | FR2438409A1 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3213615A1 (en) * | 2016-03-02 | 2017-09-06 | Deere & Company | Agricultural implement, work machine with such and a method for controlling the implement |
| US10667454B2 (en) | 2016-03-02 | 2020-06-02 | Deere & Company | Hydraulic control system of an implement for a work machine and method thereof |
| US10750653B2 (en) | 2016-03-02 | 2020-08-25 | Deere & Company | Automated leveling and depth control system of a work machine and method thereof |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4337959A (en) * | 1980-06-05 | 1982-07-06 | International Harvester Co. | Self-leveling and height control hydraulic system |
| FR2568088B1 (en) * | 1984-07-26 | 1988-06-24 | Stark Crister | ADJUSTING APPARATUS FOR AGRICULTURAL MACHINE TOOLS |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3630290A (en) * | 1969-04-28 | 1971-12-28 | Deere & Co | Hydraulic power lift system for tractor and implement |
| JPS5139447B2 (en) * | 1971-09-06 | 1976-10-28 | ||
| US3731746A (en) * | 1971-11-18 | 1973-05-08 | Allis Chalmers | Weight transfer hitch |
| US4053018A (en) * | 1973-05-23 | 1977-10-11 | Kabushiki Kaisha Komatsu Seisakusho | Automatic control system for earth-moving equipment |
-
1979
- 1979-09-28 CA CA000336599A patent/CA1117626A/en not_active Expired
- 1979-10-09 AU AU51606/79A patent/AU5160679A/en not_active Abandoned
- 1979-10-10 FR FR7925202A patent/FR2438409A1/en not_active Withdrawn
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3213615A1 (en) * | 2016-03-02 | 2017-09-06 | Deere & Company | Agricultural implement, work machine with such and a method for controlling the implement |
| US9961823B2 (en) | 2016-03-02 | 2018-05-08 | Deere & Company | Hydraulic control system of an implement for a work machine and method thereof |
| US10667454B2 (en) | 2016-03-02 | 2020-06-02 | Deere & Company | Hydraulic control system of an implement for a work machine and method thereof |
| US10750653B2 (en) | 2016-03-02 | 2020-08-25 | Deere & Company | Automated leveling and depth control system of a work machine and method thereof |
| US12089516B2 (en) | 2016-03-02 | 2024-09-17 | Deere & Company | Automated leveling and depth control system of a work machine and method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| AU5160679A (en) | 1980-04-17 |
| FR2438409A1 (en) | 1980-05-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |