GB1603204A - Three point linkage for agricultural tractors - Google Patents

Three point linkage for agricultural tractors Download PDF

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Publication number
GB1603204A
GB1603204A GB1296877A GB1296877A GB1603204A GB 1603204 A GB1603204 A GB 1603204A GB 1296877 A GB1296877 A GB 1296877A GB 1296877 A GB1296877 A GB 1296877A GB 1603204 A GB1603204 A GB 1603204A
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United Kingdom
Prior art keywords
ram
valve
control valve
piston
duct
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
Application number
GB1296877A
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Durkan P J
Original Assignee
Durkan P J
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Durkan P J filed Critical Durkan P J
Priority to GB1296877A priority Critical patent/GB1603204A/en
Publication of GB1603204A publication Critical patent/GB1603204A/en
Expired legal-status Critical Current

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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
    • A01B59/00—Devices specially adapted for connection between animals or tractors and agricultural machines or implements
    • A01B59/002—Details, component parts
    • A01B59/004—Length-adjustable links

Description

(54) THREE POINT LINKAGE FOR AGRICULTURAL TRACTORS (71) I, PETER JOHN DURKAN, a British subject of Hookers Farm, Bolney, Haywards Heath, Sussex, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a three point linkage for agricultural tractors of the type having two draft links pivotally connected to the rear of the tractor and extending rearwardly therefrom, an hydraulically actuated mechanism connected to the draft links to raise and lower them through a draft link control valve operable by the driver and a third link pivoted to the tractor above and between the draft links and extending rearwardly, all three links having at their free ends means on which can be mounted agricultural tools such as ploughs.
In using such tools on tractors, as for example in ploughing, it is desirable not only to raise and lower the tools, but to raise or lower one side of the tools with respect to the other. Three point linkages are known in which the latter operation is possible while the draft links are stationary. The forces applied to such linkages are very substantial and in ploughing for example such forces vary with the depth of the plough shares in the soil so that such known linkages have the disadvantage that the tractor driver cannot simultaneously actuate the mechanism to raise and lower the tools and to vary the difference in height of the draft links which can be important to avoid damage to the tools or increase the tractive effort of the tractor.
The main object of the present invention is to provide a three point linkage for agricultural tractors in which this disadvantage is eliminated.
According to the present invention a three point linkage of the above type includes a double acting ram forming part of at least one of the draft links, and a ram control valve in the hydraulic circuit of the draft link hydraulically actuated mechanism, the draft link control valve and the ram control valve being in a single flow and return circuit of the hydraulically actuated mechanism supplied by a pump from a reservoir and each movable independently from operative to inoperative positions in which the flow of fluid in the circuit is controlled by actuation of the valves, the arrangement being such that by operation of one or both valves the draft links and the ram are actuated separately or in unison.
In a preferred construction the ram valve is a spool valve having a single inlet from the pump, and fluid flow lines are provided to each end of the ram cylinder and also an outlet to the draft link control valve, the spool being urged into a neutral position, in which fluid from the pump flows direct to the draft link control valve, and movable into either of two operating positions in which the fluid flows to and from opposite sides of the ram piston and thence to the draft link control valve.
If desired a non-return valve may be provided in the line from the pump to the ram control valve.
In one construction the draft link hydraulically actuated mechanism is coupled directly or indirectly to a piston-cylinder assembly in the tractor rear axle block which contains the draft link control valve, the pump and the reservoir, and ducts are provided from the pump to the ram control valve and from the draft link control valve to the reservoir, and the ram control valve is mounted outside the block or forming part of the block with the pump inlet and return flow outlet therefrom connected respectively to said ducts.
From another aspect of the invention a kit of parts is provided for assembling on a conventional three point linkage of an agricultural tractor of the above type, said kit comprising at least one double acting ram for interposition in one draft link and for connections to the draft link actuating member of the tractor, a ram control valve mountable on the tractor, pressure fluid connections constructed for mounting between the ram control valve and opposite ends of the ram cylinder, pressure fluid connections constructed for mounting between the ram control valve and the pump of the tractor draft link control circuit and between the ram control valve and the draft link actuating circuit of the tractor, and a block providing connections between the ram control valve, the pump and tractor draft link actuating circuit. The ram piston rod may have a levelling indicator to give the tractor driver a visual indication of the position of the ram piston in them ram cylinder.
The invention also includes an agricultural tractor having a linkage of the invention or a linkage formed from a kit of parts according to the invention.
In order that the invention may be more fully understood one construction in accordance therewith will now be destroyed by way of example with reference to the accompanying drawings in which: Fig. 1 is a perspective view of the rear of an agricultural tractor having a three point linkage assembled thereon; Fig. 2 is a diagrammatic side view of Fig.
1, a road wheel being omitted, and showing the hydraulic operating means of the three point linkage; Fig. 3 is a diagrammatic representation of the hydraulic circuit of the mechanism including the ram control valve circuit in the construction of Figs. 1 and 2; Fig. 4 is a cross section on an enlarged scale of a modified construction employing a non-return type valve in the hydraulic circuit of Fig. 3 actuating the double acting ram in Figs. 1 to 3, and Fig. 5 shows diagramatically a modified circuit of Fig. 3 including the non-return valve shown in Fig. 4.
Referring to the drawings, in which the same references are used to designate the same parts in all the Figures, these show a tractor indicated at 1, with rear road wheels 2 mounted on an axle arrangement within an axle casing 3 forming part of or assembled on the engine block 4. Pivoted to the block one at each side are rearwardly extending draft links 5, 6 and above them a third link 7, each of the links having eyes 8 at their rear ends forming the conventional three point linkage to which an agricultural tool, e.g. a plough may be connected. The upper link 7 may be pivoted to the block in one of several positions shown by holes 9 in brackets 10 on the tractor block as is usual.
Each draft link 5, 6 has pivoted to it at a suitable mid-length point 11 an hydraulically actuated draft-link mechanism including connecting means comprising a rod 12 pivoted at 13a to a lever 13 which at its other end is fast on a shaft 14 journalled in and extending through the block 4. Within the block and fast with the shaft 14 is a lever 15 articulated at 16 to the piston rod 17 of a piston 18 sliding in a cylinder 19.
The axle casing 3 has an oil sump 20 from which the fluid, normally oil as an hydraulic fluid, can be pumped by a pump 21 and to which it is returned by a flowpath duct or ducts 22 after passing through an hydraulic circuit to be described.
In at least one of the rods 12 is interposed a double acting ram 23 having a piston 24 sliding in a cylinder 25, the piston and cylinder being connected to the opposite ends of the interrupted -rod 12. Thus by moving the piston in the cylinder the length of the rod 12 can be lengthened or shortened.
Within or outside the block 4 is a draft link mechanism control valve 26 and a ram control valve 27. In the block 4 is a plate 28 having borings therein (not shown) into which lead the pump delivery line 29, which may include a non-return valve 30, and the return duct 22. Bores in the plate 28 connect with lines 31, 32 to the valve 27. These bores are a means of connecting the line 29 and duct 22 within the casing block 4 assembly to the ram control valve 27. The lines 33, 34 from the opposite ends of the ram 23 are connected into the valve 27.
Referring to Fig. 3 this shows a ram control valve 27 having a body 35 and a slider 36, with the pump inlet 29, and outlet ducts 33, 34 to the rams 23 and 37 to the valve 26 and thence into the draft link operating circuit 32a. The slider 36 has ports 38 A.B.C and D in it such that by operation of the handle 39e, against springs 40a and 41 the slider is moved to the right or left of Fig. 3 from the central neutral position shown in Fig. 3 and will couple a fluid flow path from the pump to either side of the ram piston 24 and to the duct 22 leading to the valve 26. In the neutral position the slider provides a direct fluid flow path from the pump to the valve 26 through the lines 29 and 22, and back to the reservoir 20: if the circuit is in the inoperative position with the draft links stationary, the fluid will flow back to the reservoir 20 by the line 32, but when the valve 26 is shifted to make the circuit operative to raise or lower the draft links the fluid flows to the cylinders 19, the oil from beneath the pistons 18 flowing to the reservoir 20. This is normal operation of the linkage, the ram 27 being locked by the static oil in it. Thus irrespective of the operation or not of the ram 23 the cylinder 19 can be supplied with fluid to raise the draft links 5, 6 in unison or, by allowing the fluid at an appropriate time to flow through the duct 22, permit the raised draft links to fall to or towards their lowest position where, by operation of the valves 26 rnd 27 they may be held.
In its neutral position the valve 27 allows the aforesaid operation of the draft links to take place while the ram 23 is inactive and thus rendering the rod 12 solid. Using the lever 39a, the slider 36 is moved to the right in Fig. 3 in the cylinder 35 causing the fluid from the pump to pass through the non-return valve 30 to 33 (or 34 if the lever 39a is moved to the left in Fig. 3) to the ram 23, the fluid displaced in the ram 23 returning in the circuit by 34 or 33 respectively and hence by line 37 to the valve 26. At the same time the valve 27 by appropriate setting will permit fluid to flow into the circuit enabling the cylinder 19 to operate normally, either through or by-passing the ram cylinder 23. A level indicator 39 (Fig. 2) may be provided on the ram piston rod 12 if desired, as shown. A relief line 50 including a pressure relief valve 51 is connected between the line 29 and the line 32.
Referring to Figs. 4 and 5 these show a modification of the construction shown in Figs. 1 and 2 including in Fig. 5 a variation of the top part of Fig. 3 showing the inclusion of the modification of Fig. 2 shown in Fig. 4.
In this modification, a non-return valve 40 is interposed in the outlet duct 34 with a duct connecting the body of the valve 40 above the piston 23 to the outlet duct 33. This nonreturn valve has a body 41 with a bore 42 in which slides a piston or plunger 43 slidably sealed in the bore by a piston ring or O-ring 44 and connected by a duct 43s to the duct 33. A substantially conical baffle 45 is fixed within the hollow interior of the body 41 and has a central opening 46 through which can slide a pin 47 on the plunger 43. A ball 48 held by a light spring 49 against the baffle 45 is provided in the hollow valve body 41, the spring being calibrated to maintain the ball in the conical hollow of the baffle 45 to close the opening 46 when the pressure in the hydraulic circuit (Fig. 3) is zero and the plunger and pin assembly 43, 47 are withdrawn to the left in Figs. 3 and 5. The valve is preferably mounted on the cylinder 23 or incorporated therein.
In operation when the pressure in duct 34 is high the ball 48 is lifted off the baffle 45 against the light pressure of the spring 49 so that oil flows to the underside of the piston 24 in the cylinder 23, and the piston is displaced to the left in Fig. 3. The oil above the piston 24 is expelled from the cylinder 23 through the duct 33, but until the pressure on both sides of the piston 24 is equalised the pressure in the duct 33 causes displacement of the plunger 43 so that the pin 47 passes through the opening 46 to lift the ball off the baffle opening 46. Thus the ball 48 only reseats itself on the baffle opening 46 when the pressure in the underside of the piston is greater than in the top side of the piston and the part of the circuit of Fig. 3 is at rest, thus preventing any material escape of oil from the body 40 into the duct 34.
If desired a valve similar to the valve 40 may be included in the duct 33 and connected through a duct similar to duct 33 to the duct 34.
By means of the aforesaid construction it will be seen that the ram and the piston cylinder assembly 18, 19 can both function with the flow of oil in the hydraulic circuit or one or other can function with the same fluid circuit independently of the other. The operation of the valves by the tractor driver will enable him to actuate the whole arrangement with infinite variability which will enable him to have very fine control of the operation of the tool coupled to the three point linkage.
WHAT I CLAIM IS:- 1. A three point linkage of the type herein set forth including a double acting ram forming part of at least one of the draft links and a ram control valve in the hydraulic circuit of the draft link hydraulically actuated mechanism, the draft link control valve and the ram control valve being in a single flow and return circuit of the hydraulically actuated mechanism supplied by a pump from a reservoir and each movable independently from operative to inoperative positions in which the flow of fluid in the circuit is controlled by actuation of the valves, the arrangement being such that by actuation of one or both valves the draft links and the ram are actuated separately or in unison.
2. A linkage according to Claim 1 wherein the ram valve is a spool valve having a single inlet from the pump, and fluid flow lines are provided to each end of the ram cylinder and also an outlet to the draft link control valve, the spool being urged into a neutral position, in which fluid from the pump flows direct to the draft link control valve, and movable into either of two operating positions in which the fluid flows to and from opposite sides of the ram piston and thence to the draft link control valve.
3. A linkage according to Claim 1 or 2 wherein a non-return- valve is provided in the line from the pump to the ram control valve.
4. A linkage according to any of Claims 1 to 3 wherein the draft link hydraulically actuated mechanism is coupled directly or indirectly to a piston-cylinder assembly in the tractor rear axle block which contains the draft link control valve, the pump and the reservoir, and ducts are provided from the pump to the ram control valve and from the draft link control valve to the reservoir, and the ram control valve is mounted outside the block or forming part of the block with the pump inlet and return flow outlet therefrom connected respectively to said ducts.
5. A linkage according to any of Claims 1 to 4 wherein a non-return valve is provided in one or both of the ducts from the ram to the ram control valve and connected to the other of said ducts thereby preventing back flow of oil through the ram when the ram is inoperative.
6. A three point linkage of the type herein set forth substantially as herein described with reference to Figs. 1 to 3 of the accompanying
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

  1. **WARNING** start of CLMS field may overlap end of DESC **.
    displaced in the ram 23 returning in the circuit by 34 or 33 respectively and hence by line 37 to the valve 26. At the same time the valve 27 by appropriate setting will permit fluid to flow into the circuit enabling the cylinder 19 to operate normally, either through or by-passing the ram cylinder 23. A level indicator 39 (Fig. 2) may be provided on the ram piston rod 12 if desired, as shown. A relief line 50 including a pressure relief valve 51 is connected between the line 29 and the line 32.
    Referring to Figs. 4 and 5 these show a modification of the construction shown in Figs. 1 and 2 including in Fig. 5 a variation of the top part of Fig. 3 showing the inclusion of the modification of Fig. 2 shown in Fig. 4.
    In this modification, a non-return valve 40 is interposed in the outlet duct 34 with a duct connecting the body of the valve 40 above the piston 23 to the outlet duct 33. This nonreturn valve has a body 41 with a bore 42 in which slides a piston or plunger 43 slidably sealed in the bore by a piston ring or O-ring 44 and connected by a duct 43s to the duct 33. A substantially conical baffle 45 is fixed within the hollow interior of the body 41 and has a central opening 46 through which can slide a pin 47 on the plunger 43. A ball 48 held by a light spring 49 against the baffle 45 is provided in the hollow valve body 41, the spring being calibrated to maintain the ball in the conical hollow of the baffle 45 to close the opening 46 when the pressure in the hydraulic circuit (Fig. 3) is zero and the plunger and pin assembly 43, 47 are withdrawn to the left in Figs. 3 and 5. The valve is preferably mounted on the cylinder 23 or incorporated therein.
    In operation when the pressure in duct 34 is high the ball 48 is lifted off the baffle 45 against the light pressure of the spring 49 so that oil flows to the underside of the piston
    24 in the cylinder 23, and the piston is displaced to the left in Fig. 3. The oil above the piston 24 is expelled from the cylinder 23 through the duct 33, but until the pressure on both sides of the piston 24 is equalised the pressure in the duct 33 causes displacement of the plunger 43 so that the pin 47 passes through the opening 46 to lift the ball off the baffle opening 46. Thus the ball 48 only reseats itself on the baffle opening 46 when the pressure in the underside of the piston is greater than in the top side of the piston and the part of the circuit of Fig. 3 is at rest, thus preventing any material escape of oil from the body 40 into the duct 34.
    If desired a valve similar to the valve 40 may be included in the duct 33 and connected through a duct similar to duct 33 to the duct 34.
    By means of the aforesaid construction it will be seen that the ram and the piston cylinder assembly 18, 19 can both function with the flow of oil in the hydraulic circuit or one or other can function with the same fluid circuit independently of the other. The operation of the valves by the tractor driver will enable him to actuate the whole arrangement with infinite variability which will enable him to have very fine control of the operation of the tool coupled to the three point linkage.
    WHAT I CLAIM IS:- 1. A three point linkage of the type herein set forth including a double acting ram forming part of at least one of the draft links and a ram control valve in the hydraulic circuit of the draft link hydraulically actuated mechanism, the draft link control valve and the ram control valve being in a single flow and return circuit of the hydraulically actuated mechanism supplied by a pump from a reservoir and each movable independently from operative to inoperative positions in which the flow of fluid in the circuit is controlled by actuation of the valves, the arrangement being such that by actuation of one or both valves the draft links and the ram are actuated separately or in unison.
  2. 2. A linkage according to Claim 1 wherein the ram valve is a spool valve having a single inlet from the pump, and fluid flow lines are provided to each end of the ram cylinder and also an outlet to the draft link control valve, the spool being urged into a neutral position, in which fluid from the pump flows direct to the draft link control valve, and movable into either of two operating positions in which the fluid flows to and from opposite sides of the ram piston and thence to the draft link control valve.
  3. 3. A linkage according to Claim 1 or 2 wherein a non-return- valve is provided in the line from the pump to the ram control valve.
  4. 4. A linkage according to any of Claims 1 to 3 wherein the draft link hydraulically actuated mechanism is coupled directly or indirectly to a piston-cylinder assembly in the tractor rear axle block which contains the draft link control valve, the pump and the reservoir, and ducts are provided from the pump to the ram control valve and from the draft link control valve to the reservoir, and the ram control valve is mounted outside the block or forming part of the block with the pump inlet and return flow outlet therefrom connected respectively to said ducts.
  5. 5. A linkage according to any of Claims 1 to 4 wherein a non-return valve is provided in one or both of the ducts from the ram to the ram control valve and connected to the other of said ducts thereby preventing back flow of oil through the ram when the ram is inoperative.
  6. 6. A three point linkage of the type herein set forth substantially as herein described with reference to Figs. 1 to 3 of the accompanying
    drawings or as modified in Figures 4 and 5 of the accompanying drawings.
  7. 7. A kit of parts suitable for assembling on a three point linkage of an agricultural tractor of the above type, comprising at least one double acting ram for interposition in one draft link and for connections to the draft link actuating member of the tractor, a ram control valve mountable on the tractor, pressure fluid connections constructed for mounting between the ram control valve and opposite ends of the ram cylinder, pressure fluid connections constructed for mounting between the ram control valve and the pump of the tractor draft link control circuit and between the ram control valve and the draft link actuating circuit of the tractor, and a block providing connections between the ram control valve, the pump and tractor draft link actuating circuit.
  8. 8. An agricultural tractor having assembled thereon a three point linkage according to any of Claims 1 to 6 or a three point linkage on which is assembled the kit according to Claim 7.
GB1296877A 1978-05-31 1978-05-31 Three point linkage for agricultural tractors Expired GB1603204A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB1296877A GB1603204A (en) 1978-05-31 1978-05-31 Three point linkage for agricultural tractors

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1296877A GB1603204A (en) 1978-05-31 1978-05-31 Three point linkage for agricultural tractors

Publications (1)

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GB1603204A true GB1603204A (en) 1981-11-18

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB1296877A Expired GB1603204A (en) 1978-05-31 1978-05-31 Three point linkage for agricultural tractors

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4942928A (en) * 1986-04-09 1990-07-24 Industrias John Deere, S.A. De C.V. Bidirectional moldboard plow with adjustable tilting mechanism
US5020603A (en) * 1990-01-25 1991-06-04 Harrell Danny H Reversible plow
US5024281A (en) * 1990-08-02 1991-06-18 Long Manufacturing N.C., Inc. Reversible moldboard plow
US5720214A (en) * 1996-04-17 1998-02-24 Kanzaki Kokyukoki Mfg. Co., Ltd. Fluid supply assembly for working vehicles
EP2540149A1 (en) * 2011-06-30 2013-01-02 AGCO International GmbH Tractor implement hitch

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4942928A (en) * 1986-04-09 1990-07-24 Industrias John Deere, S.A. De C.V. Bidirectional moldboard plow with adjustable tilting mechanism
US5020603A (en) * 1990-01-25 1991-06-04 Harrell Danny H Reversible plow
US5024281A (en) * 1990-08-02 1991-06-18 Long Manufacturing N.C., Inc. Reversible moldboard plow
US5720214A (en) * 1996-04-17 1998-02-24 Kanzaki Kokyukoki Mfg. Co., Ltd. Fluid supply assembly for working vehicles
EP2540149A1 (en) * 2011-06-30 2013-01-02 AGCO International GmbH Tractor implement hitch

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Legal Events

Date Code Title Description
PS Patent sealed
PCNP Patent ceased through non-payment of renewal fee
728C Application made for restoration (sect. 28/1977)
728R Application refused (sect. 28/1977)