USRE22642E - Tbactob fob agricultural - Google Patents

Description

y 1945. H. G. FERGUSON Re. 22,642

TRACTOR FO R AGRICULTURAL IMPLEMENTS Original Filed April 14, 1943 4 Sheets-Sheet 2 y 1945- H. G. FERGUSON Re. 22,642

TRACTOR FOR AGRICULTURAL IMPLEMENTS Original Filed April 14, 1943 4 Sheets-Sheet 3 21 I/ a 31 h it eiuued May 15. 1945 TRACTOR FOB AGRICULTURAL MLEMENTS Henry-George Ferguson, Belfast, Northern Ireland Original No. 2,356,231, dated August 22, 1944, Se-

rial No. 483,009, April 14, 1943. Application for reissue December- 2, 1944, Serial No. 556,331. In Great Britain July 4, 1941 30 Claims.

This invention relates to tractors having means for the attachment of a soil-working or agricultural implement, and'a power operated control unit for moving said implement up and down with reference to the tractor and supporting it on the tractor and relates more especially to a tractor having means for putting the power unit out of efiective operation in accordance with the principle as disclosed in my prior Patent No. 2,118,181. I

When the implement 01' a tractor as disclosed in the said prior patent encounters an obstruction the excess of draft pressure on the implement operates the oil control valve to allow the oil to escape from the ram so that the tractor is relieved of the implement weight and the driving wheels slip and so damage to the implement and other parts is avoided; Further, the automatic control of'depth by means of the power unit is rendered ineffective so that the power unit does not tend to raise the implement as it normally does in the event of increased draft pressure. With an arrangement operating on the principle described in the said prior patent there is a tendency sometimes for the tractor and implement to oscillate backwards and forwards or shudder when an obstruction is encountered. The cause of this is that when the wheels spin, the draft pressure on the implement is reduced and causes the control valve to return from its oil-release position to oil-admitting position, so that thevoil pressure in the ram is restored and the ram endeavors to lift the implement. If the implement is caught in an overhanging obstruction the tractive grip of the driving wheels is again increased and consequently so is the draft pressure on the implement which again causes .the control valve to move to release the oil and again cause wheel spin. If this cycle is rapidly repeated there is the beforementioned undesirable "shuddering effect and an object of the invention is to obviate this disadvantage.

An object of the invention is to provide a tracoccurs, with means for maintaining said power appreciable time during the consequent decrease of draft pressure consequent on said slipping.

A further object of the invention is'to provide a tractor which has means for the attachment of a soil-working or agricultural implement, a fluid or hydraulic pressure power unit, including a pump, a ram or equivalent pressure operable device and control valve means, said unit supporting the implement on the tractor and said valve means being under the influence of the draft pressure on the implement so as automatically to cause the power unit to raise'or lower the implement tomaintain the draft pressure thereon and/or the depth of cut thereof constant and so as to release the pressure on said device when there is an excess of draft pressure on the implement so that the latter is no longer supported or largely supported by the tractor and slipping of the traction wheels occurs, with means for maintaining said valve means in the pressure release position or in said position for a predetermined time despite the reduction in 4 draft pressure on the implement consequent on inafter referred to.

Fig. 2 is across sectional view to a larger scale of the hydraulic raising and lowering and depth control unit.

Fig. 3 is a corresponding plan view.

Fig. 4 is an elevation to a larger scale of the I hydraulic depth control unit in a difierent position.

Fig. 5 is a corresponding end elevation, and

Figs. 6 and '7 are end and side detail views.

Fig. 8 is an elevation of a modified form.

Fig. 9 is a detail view to a larger scale of the latch in F18. 8.

Fig. 10 shows a modification of the latch in Fig. 7.

Fig. 11 is a modification of the arrangement in Fig. 2.

Referring especially to Fig. 1, the tractor is of the Ford-Ferguson type embodying the Ferguson linkage and implement control system. The

tractor comprises a body casing I and the usual unit out of operation or out of operation for an two rear ground wheels 2, the nearer wheel beleave the cylinder.

ing omitted for clearness. The linkage system comprises an upper compression link 3 and two laterally spaced lower draft links 4, the links-being triangularly spaced and universally attached to the tractor and implement. The tractor embodies a fluid-power unit, described later, which operates. the lifting arm b on the rock shaft 511 and serves to raise and lower the links 4 through the present invention it is not necessary to de-'- scribe the tractor in detail but reference will be made to some of the basic features of the Ferthis occurs the consequent compression in the link 3 due to the soil or draft pressure on theimple'ment compresses the balance spring 24 to a predetermined extent such that the pivot I2 is guson system. The forward convergence of the upper and lower links gives a favorable line of draft tending to keep the implement in the ground as in prior patent specification No.

1,464,130 and the implement is automatically controlled for depth of cut in accordance with the principle set out in my prior Patent No. 1,687,719; the fluid-power unit and depth control being substantially as set forth in my prior Patents Nos. 2,118,180 and 2,118,181 but with structural differences as will be seen from the following description.

The lower links 4 converge forwardly in order to cause the implement to follow .closely the steering of the tractor as in my prior Patent No.

The hydraulic pressure and deptfiicontrol-unit .includes an oil ram consisting o'Fa cylinder 5a connected to an oil pump, not shown, and having a ram or piston I connected to the operating so moved tothe left (Fig. 2) that, under the influence of the spring II, the lever ll rotates about its point of contact with eccentric l5 in a clockwise direction and brings the valve 8 back to the position shown in Fig. 2 and movement of oil ceases. Thereupon the implement carries on working at the predetermined depth. When the lever I1 is returned to the lift position shown in Fig. 2, the lever II is rotated clockwise about th pivot l2 under the action of tensionspring l4 and causes valve 8 to uncover the section port 9 so that oil is pumped into the cylinder and the implement is raised until the ram"| engages the projections and moves the lever I I to the position shown in Fig. 2.

Automatic depth control during operationiseffected by raising or lowering the plow respectively as the implement goes too deep or too she] low and the draft or soil pressure increases or decreases. This control is in response to the swinging movement .of the lever I I about the engagement of its upper end I! with crank l5 as a center produced by the shifting of the pivot I 2 either to the left or right by the corresponding movements of the rod 22. Such swinging movelever 5. The pump is controlled by a valve 8 adapted to control an inlet port ii on the suction side of the pump and outlet port I n and which is connected to a lever ll of duplex form as shown in Fig. 5 and which is pivoted at l2, engaged at l3 by the tension spring I4 and has its top end I! normally kept by said spring against the eccentric or cranked part ii of the shaft Hi on which is mounted the manual control lever I'I., Inasmuch as the pivot I 2 and crank I5 are movable the lever II may be described as a floating lever. An adjustable stop IB is provided to determine the maximum depth of cut of the implement. The lever also has two inward projections 20 which can act as fulcrum means and the pivot i2 is provided on a rock rocable stirrup 2| pivotally attached to a composite rod 22 and sleeve 22a pivotaily attached ments of the lever II respectively open the port 8 or III and cause the implement to be raised or lowered to the correct depth and this correction, through the correspondin correction in the soil pressure on the implement, returns the pivot II to its normal balanced position with both ports 9 and Ill closed.

When the implement strikes an obstruction. such as a rock or root, the balance spring 24 is abnormally compressed and an excess movement beyond the normal range is imparted to the rod 22 and the associated draft-transmitting mechanism. The pivot I2 is moved to the left until the projections 20 engage the end of the cylinder 5a and the lever H is caused to rotate antilockwise. the projections 2|) acting as the fulcrum, until it engages stop 25 as shown in Fig. 4. It will also be noted that the top IQ of thelever H has left the crank I5. The oil then leaves the cylinder through the port I 0 and the weight of the implement is no longer borne by the tractor, that, is, by the oil in the to a duplex crank 23 which is pivoted on the tractor casing and has the compression link 3 universally attached thereto.

The arrangement so far described is known and the operation is as follows:

Fig. 2 shows the mechanism in a nos-tion corresponding to the implement having been raised. there being no compression in the link 3 and the valve 2 covering both pc-rts 9 andv In so that there is no movement of oil. To lower the implement to working pos tion the manual lever I1 is moved to engage the stop II which has been adjusted to a position corresponding to the depth of cut required. Thereupon the eccentric I5 rotates the lever ll anti-clockwise about the pivot 12 and moves the valve B to the right so that drop port III is uncovered and allows oil to The ram piston I then moves inwards and the implement sinks under its own weight until it reaches the required depth. When cylinder. Thus, as expla ned in prior Patent No. 2,118,181, the traction wheels 2 then spin harmlessly owing to the reduction of tractive grin. and damage, especially to the implement, is obviated or mitigated.

It has been found, however, that owing to the substantial reduction in traction consequent upon the aforesaid wheel spin there is a correspondingly substantial reduction in the compression of the spring 24, and thus the pivot l2 may move substantially back to the right (Fig. 2) so that. under the influence of spring II, the lever H may be rotated about the projections 2|! in clockwise d rection suiliciently to cause the valve I to close the release port 10 and open the suction port 9 so that the oil pressure in the cylinder will be re-established and tend to lift the implement However, if the implement is caught in an overhanging obstruction, .the lift ng effect will merely increase the tractive grip of the driv ing wheels and the overload release will again be operated. If this cycle is rapidly repeated the tractor and implement wll oscillate backwards and forwards or "shudder and may cause eases damage before the operator can disconnect the drive to the driving wheels.

In accordance with the invention a latch-carrier or lever 26 is pivoted on the pin l2a, that is, on the pivot I! of the lever II and is normally urged by the tension spring 21 so that the proiection II engages the edge of the top of the lever II and so maintainsthe levers II and 26 in predetermined relationship. The lever 26 carries a pivoted latch II having an arcuate face whose radius is struck about the latch pivot a and having a stop 28b above said fac 29a.

During normal operation when the top I! of the lever II is in contact with the eccentric II, the latch rests on top of the collar 30 and is inoperative as shown in Fig. 2. when an obstruction is encountered and the top It moves away from the eccentric It, as shown in Fig. 4, the latch 2! falls so that the face No comes into engagement with the collar 30 and the stop 29!) prevents further falling of the latch. Thus when the pivot I2 moves to the debt due to the decreased draft pressure on the balance spring 2!. the lever' ll does not rotate clockwise about the projections 2. as hitherto. but merely pivots about the abutment owing to the spring 21 overcoming the effect of the spring ll. During this return movement of the pivot I! to the right, which is in effect a lost motion between the stirrup 2i and the valve 8 or between the latch 29 and the stirrup 2i which frees the latch 29, the lever II and the associated parts from the considerable stress that would be set up if the balance spring were held in the compressed position by the latch when the draft is reduced by the wheel slip, the lever or latch carrier 26 is caused to rotate anti-clockwise with reference to the lever Ii and so stresses the spring 21 which allows the lost motion and helps it to overcome the ef fect of spring ll. At the same time, the latch 29 has an anti-clockwise movement about the collar 30. The valve 8 is thus held in the position shown in Fig. 4 and the shuddering effect is avoided. To release the latch the operator simply pulls the manual control lever ll up to the raised position and the clockwise rolling effect of the collar 3|) on the arcuate face 29a, which is frictionally engaged against the collar by spring pressure, rolls up and disengages the latch 28 which rides over the collar 30, being restored to the position shown in Fig. 2 by the spring 21,

Fig. 10 shows a modification of the latch wherein. the stop projection 29!) is omitted and the curved face 29a is so formed that from, at or near its lower edge upwards the radii from the latch pivot 25a to the surface 29a gradually increase. This prevents the latch falling down past the collar as there will be a wedging action which will also facilitate disengagement of the latch when control lever I1 is raised.

It will be seen from the above that the invention can be readily applied to existing tractors.

The modified form shown in Figs. 8 and 9 is the same as that above described except that the lever II is formed in two para Ila, llb hinged together at It! and normally held in alignment against the stop 3| by the spring I, the said hinge and spring providing a. yielding or lost motion connection. The lever is also further modified in that it is formed with a sidewards projection pin 32 at the top which projects towards the collar III. In this form the latch previously described is replaced by the latch 33 pivoted on a concentric portion of the shaft It on the left hand side of the collar 30 (Fig. 5).

The

latch has an arcuate latch recus 34 and a protation of a projection II on the shaft II.

During normal operation the latch 33 rests on the projection 32 in withdrawn or inoperative position as shown in full lines in Fig. 9.

When the lever Ila, lib is displaced to a position away from the cam or crank ll corresponding to excess draft pressure, as shown in full lines in Fig. 8, the latch 33 falls down so that the recess 3 engages the projection 32 on the lever part Na and is retained there and so maintains the top of the lever in the displaced position and keeps the oil control valve I in the release position. When the draft is correspondingly reduced owing to the wheel slip the lever Ha, llb "breaks about the pivot and assumes the position shown in chain dotted lines in Fig. 8 and the pivot l2 and stirrup 2| move load of the balance spring 24 which would set up considerable stress therein after the excess draft pressure has been removed. This condition as shown in the chain dotted lines on Fig. 815 maintained until the operator moves the manual control lever I! to raise the implement out of the groundwhen the projection 36 on the shaft it engages the projection 35 on the latch 33 and lifts it free of the lever ll so that the floating lever can return under the action of spring It to contact with and be controlled by the cam or crank l5.

As shown in Fig. 11 said lost motion hinge 40 and stop 3| may also be employed in the embodiment in Figs. 1 to 5 to allow a lost motion between the lower end of the lever II and the other parts thereof to prevent undue stresstherein under conditions where the lower end may tend to move further than allowed by the abutment 25. Both yieldable arrangements are provided as insurance against damage to the lever II by the failure of either of the yieldable means to function to permit the full range of moveent to the right of pivot l2.

In all the arrangements shown, before raising the implement, the operator will usually back the tractor slightly to cause the implement to free the obstruction.

What I claim is:

1. In a tractor having means for the attachment of a soil-working or agricultural implement, a power-operated control unit for movin said implement up and down with reference to the tractor and supporting it on the tractor, an operator-controlled member for controlling said unit to raise orlower the implement, and overload-release means adapted to put said control unit out. of effective operation when an excess of draft pressure on the implement occurs so that the latter is no longer supported or largely supported on the tractor and slipping of the traction wheels occurs; catch means for automatically maintaining said power unit out of operation during the consequent decrease of draft pressure consequent on said slipping and means on said member for rendering said catch means inoperative when said member is moved to implement-lifting position.

2. In a tractor havin means for the attachment of a soil-working or agricultural implement, a power-operated control unit for moving said implement up and down with reference to the 4 tractorandaappm'tingitmithetnctonandior operatingaaidunittomiseandlowertbeimpleaunt, and overload release means adapted to putsaidcmtroiunitcutofeilecflveoperatimwhen an'excmoldraftpremlnemtheimplementoccmssothatthelatterunolongersupportedor ingorag'ricultm-al'nnplemmflthetmctor'comm'lslngmeansiormovablyattachingtheimplementtheretm'apower-opemtedcmtrolunitfor.

moving the implement upand down with referencetothetractm'andsuppm'tingittherman implement draft-transmitting connection includii agdraft-balancmg-meansbetweenthehnpiementandacontrolmunberofsaidunihsald control member being movable-under the opporcdmfluencesofthebaiancemeamandofthe draft pressureon the implement to implement.

lif'ting,holdingorloweringpositlomandsaid connectionincludingapartmovabletoextreme posltionbythedraftagainsttheactionofsaid balancemeanstocauaetheemtrolmemberto movetosaidioweringpositiontocauseslipping ofthetractordrivingwheelswhenthereisan 'excesotdmftwesm-eontheimplementand check means amociated with said part so as automatimlly to come-into action when said'part retardtheremrnofsaidpazttromsaidpositim andtopa-eventorretardtheretirrnofsaidcontrolmember to implement-lifting position as a consequence of the reductionofdraftpressure duetosaidwheelslip.

4. In combination a tractor and a soil-workin; or agricultural implement, the tractor comprising meansi'or movabiy attaching the implement thereto. a power-operated control unit for moving the implement up and down with referencetothetractorandsimportingitthereman implement draft-transmitting connection including draft-balancing means between the imple-v eii'ective relationship with the implement when there is an excessof draft on the latter reduce the, draft; means associated means so as automatically to when the control means is position to prevent the control draftisreduced.

c.lnatractorhavlngmeansfortheattachable by pressure iiuidrfrom the pump for moving the implement up and down with reference to the tractor, valve means for the device, a drafttransmitting connection including resilient balance means between the implement and valve means and movable to an extreme position corresponding to presure-release position of the valve mean by the implement for relieving the fluid pressure on said device when there is an excess or draft on the implement, resistant means operatlvely engageable with said connection when it moves to said extreme position toprevent the connection means and the valve means being immcdiately, returned from said position due to the reduction in the draft consequent on the wheel 1 following the release of pressure.

I. In combination a tractor and a soil-engaging implement, the tractor comprising means for attaching the implement so as to be capable of up and down movement on the tractor, a power 40 unit comprising a pump and a device operable -ismovedtosaidextremepositiontopreventor ment and a control member 0! said unit, said control member being movable under the opposed influences of the balance means and 0f the draft pressure on the implement to implement lifting, holding or lowering positions and being movable bythedraftagainsttheactionoisaid balance means to said lowering position to cause slipping of the tractor driving wheels when there is an excess of draft pressure on the implement, a manually operable member for moving said control member and a latch member which is bypressureiluidfromthe pumpformovingthe implement upand down and supporting it -on the tractor, a control valve for said device movable into fluid-admitting, holding or release positions respectively to raise, hold or lower the implement on the tractor, an implement drafttransmitting connection between the implement and valve including balance means resistant to the draft on the implement and adapted on variations of the draft of the implement to move within a normal range to cause or allow movement of the valve to raise or lower the implement to correct said variations or maintain the implement at a constant depth of cut and adapted to move beyond said range to move the valve to fluid-release position when there is an excess of draft pressure on the implement to relieve the tractor of the implement weight and cause the tractor drivwheels to slip and resistant means automatically putinto operation by movement of the connection means beyond said range to prevent the immediate return oi said valve by the balance means for fluid-release position to fluid-admitautomatically movable on occurrence of excess ting position when the draft pressure is reduce by said wheel slip. x

8. In combination a tractor and a soil-engaging implement, the tractor comprising means for attaching the implement so as to be capable of up and down movement on the tractor, a power unit comprising a pump and a device operable by pressure fluid from the pump for moving the implement up and down and supporting it on the I tractor, a control valve for said device movable into fluid-admitting, holding or release positions wheels to slip; a latch member automaticallyenonthe tractor, a manual control means for moving said valve, an implement draft-transmitting connection between the implement and valve in cluding balance means resistant to the draft on the implement and adapted on variations of. the

draft of the implement to cause or allow movement of the valve to raise or lower the implement to correct said variations or maintain the implement at a constant depth of cut and adapted to move the valve to fluid-release position when there is an excess of draft pressure on the implement to relieve the tractor of the implement weight and cause the tractordriving wheels to slip, and latch means automatically movable into drawn from stop position by the movement of' said manual means to a position corresponding to fluid-admitting position of the valve member.

9. In the combination of a tractor and a soilworking or agricultural implement, means for movably attaching the implement to the tractor, a power-operated control unit for 'moving the implement up and down with reference to the tractor and supporting it thereon, an implement draft-transmitting connection including draftbalancing means between the implement and a.

control member of said unit, said'control member being movable under the opposed influences of the balance means and of the draft pressure on the implement to implement lifting, holding or lowering positions and being movable by the draft against the action of said balance means to said lowering position to cause slipping of the tractor driving wheels when there is an excess of draft pressure on the implement, said draft-transmitting connection comprising a part connected to the control member, a part connectedto the balance means and a resilient lost motion device between said two parts, and cheek means to engage said first part on excess of draft pressure to check return of said control member to implement lifting position as a consequence of the reduction of draft pressure, due to said wheel slip, said lost motion device allowing return of said second part and the balance means on the reduction of draft gageable on excess of draft pressure occurring with a part of said draft-transmitting connection to prevent the immediate return of said valve by the balance means from fluid-release position to fluid-admitting position when the draft pressure is reduced and a resilient lost motion connection between said valve and the balance means allowing the latter to return when the draft pressure is reduced from its excess draft position without altering the position of the valve.

11. In a tractor having means for connecting a soil-working implement thereto so as to be capable of up and down movement on the tractor,

a hydraulic power unit comprising a pump, a pressure operable device connected thereto for raising, lowering and supporting-the implement on the tractor, spaced admission and releaseports for said-device, a movable'contr'ol valve for said ports and means for controlling the position of said valve manually and by the opposed effects of resilient balance means-and the soil pressure or draft on the implement, said control means comprising manually movable means and a floating lever which is connected at spaced points to the valve and a pivot movable under the influence of the balance means and the draft and which lever is urged to bear normally at a further spaced point against said manually movable means but is adapted to move away from said means when there is an excess of draft pressure to move the valve to open the release port; a latch member adapted to interpose between said float 40 nection associated with said lever to allow return movement of said pivot and balance means from excess draft position relative to the latch memher without moving said valve.

without effect on the position of the control memv ber.

10. In the combination of a tractor and a soilengaging implement, means on the tractor for attaching the implement so as to be capable of up and down movement on the tractor, a power unit comprising a pump and a device operable by pressure fluid from the pump for moving the implement up and down and supporting it on the tractor, a control valve for said device movable into fluid-admitting, holding or release positions respectively to raise, hold or lower theimplement on the tractor, an implement draft-transmitting connection between the implement and valve including balance means resistant to the draft on .the implement and adapted on varia-' tions of the draft of the implement to cause or allow movement of the valve to raise or lower the implement to correct said variations or maintain the implement at a constantdepth of cut and adapted to move the valve to fluid-release position when there is an excess of draft pressure on the implement to relieve the tractor of the implement weight and cause the tractor driving 12. In the combination of a tractor and an implement, means on the tractor for movably attaching the implement thereto, a power-operated control unit for moving the implement up and down with reference to the tractor and supporting it thereon, an implement draft-transmitting connection including draft balancing means between the implement and a control member of said unit, said control member being movable under the opposed influences of the balance means and of the draft pressure on the imple ment to implement lifting, holding, or lowering positions and being movable by the draft against the action of said balance means to said lowering position to cause slipping of the tractor driving wheels when there is an excess of draft pressure on the implement, and a latch member which is automatically movable on occurrence of excess draft pressure to a check position in which it prevents the return of said control member to implement-lifting position.

iii. In the combination of a tractor and a soilworking or agricultural implement, means for movably attaching the implement to the tractor, a power-operated control unit for moving the implement up and down with reference to the tractor and supporting it thereon, an implement draft-transmitting connection including draftbalancing means between the implement and a control member of said unit, said control member being movable under the opposed influences of the balance means and of the draft pressure on the implement t implement lifting, holding, or lowering positions and being movable by the draft against the action of said balance means to said lowering position to cause slipping of the tractor driving wheels when there isan excess of draft pressure on the implement, a manually operable member for moving said control member and resistant means which is automatically'movable on occurrence of excess draft pressure to a check position in which it resists the a return of said control member to implementlifting position and which is withdrawable to an inoperative position by movement of said manually operable member to implement-lifting position.

14. In the combination of a tractor and a soilworking or agricultural implement, means on the tractor for movably attaching the implement thereto, a power-operated control unit for moving the implement up and down with reference to the tractor and supporting it thereon, an implement draft-transmitting connection including draft-balancing means between the implement and a control member of said unit, said control member being movable under the opposed influences of the balance means and of the draft pressure on" the implement to implement lifting, holding or lowering positions and being movable by the draft against the action of said balance means to said lowering position to'cause slipping of the tractor driving wheels when there is an excess of draft pressure on the implement,

said draft-transmitting connection comprising'a part connected to the control member, a part connected to the balance means and a resilient lost motion device between said two parts, and

means to prevent immediate return of said control member to implement-lifting position as a consequence of the reduction of draft pressure,

said device movable into fluid-admitting, hold-' ing or release positions respectively to raise, hold or lower the implement on the tractor, an implement draft-transmitting connection between the implement and valve including balance means resistant to the draft on the implement and adapted on variations of the draft of the implement to cause or allow movement of the valve to raise or lower the implement to correct said' variations or maintain the implement at a constant depth of cut and adapted to move the valve to fluid-release position when there is an excess of draft pressure on the implement to relieve the tractor of the implement weight and cause the tractor driving wheels to slip; resistant means operatively associable on excess of draft pressure occurring with .a part of said drafttransmitting connection to prevent the immediate return of saidvalve by the balance means from fluid-release position to fluid-admitting position when the draft pressure is reduced and a resilient lost motion connection between said part and the balance means allowing the latter to return-when the draft pressure is reduced such movement is ineffective on the control valve.

raising, lowering and supporting the implement on the tractor, spaced admission and release ports for said deviceflajmovable control valve for said ports and means for controlling the position of said valve manually and by the opposed effects of resilient balance means and the soil pressure or draft on the implement, said control means comprising manualhr movable means and a floating lever which is connected at spaced points to the valve and a pivot movable under the influence of the balance means and the draft and which lever is urged to bear normally at a further spaced point against said manually movable means but is adapted to move away from said means when there is an excess of draft pressure to move the valve to open the release port; a latch member adapted to interpose between said floating lever and said manual means, the latter and the; latch acting as abutment means to prevent the floating lever moving the valve to close the release port. and open the admission port under the influence of the balance means when the draft is reduced and additional means coordinated with the said floating lever, abutment and latch to shift the fulcrum of the lever from a point where movement of the lever by the action of the balance means is effective upon the control valve to a point where 1'1; In a Ferguson type of tractor-implement hookup, the combination of'a tractor, a hitch provided with an upper pressure link and a lower draft link, a hydraulic lift on the tractor, a manually-controlled actuator, a valve to control said lift adapted to be operated by said actuator, an automatic depth' control and overload release on the tractor including a thrust member adapted also to operate said valve and controlled by movement of the pressure link in accordance with reactions from the implement, and apparatus for connecting the thrust member to the valve and for preventing shuddering of the tractor and implement by the oscillation of the valve to repeat lifting and releasing the load of .the implement upon the tractor, said apparatus comprising a lever arranged to move the valve upon actuation by the said depth and overload-release, a latch thrown into operative position by the operation of the thrust member in the overload release and means operating with the latch in such operative position to condition the lever to be ineffectual to move the valve until the latch is reset to inoperative position.

18. The subject matter claimed in claim 17 but in which the means operating with the latch in operative position to-condition the lever to be ineffectual, etc., includes alternative ful-' crum points for the lever and means whereby the lever is shifted, when the latch is thrown into operative position, from a fulcrum pointon which the lever swings to move the valve to a.

second fulcrum point on which the lever swings without moving the valve.

19. The subject matter claimed in'claim 17 but in which the means operating with the latch in operative position to condition the lever to be ineifectual," etc.,' includes alternative fulcrum points for the lever and spring means whereby without altering inefiect the lever is shifted, when the latch is thrown into operative position, from a fulcrum point on which the lever swings to move the valve to a second fulcrum point on which the lever swings without moving the valve. 7

20. The subject matter claimed in claim 1'7 but in which the "means operating with the latch i operative position to condition the lever to be etc.,includes floating of the'lever and three fulcrum points for the lever; one near one end for connection with the manually controlled actuator; one atan intermediate point to make the lever effectual upon-the valve whenmoved by an excess of thrust; and one at the connection with the valve, which fulcrum point, when in use, makes the lever ineilectual to swing the valve in obedience to movement of the thrust member. Y

21. In a Ferguson type of tractor-implement hookup, the combination of a tractor, a hitch provided with an upper pressure link and a lower draft link and having a hydraulic lift on the tractor, .a manually-controlled actuator, a valve to control said lift and adapted to be operated by said actuator, an automatic depth control and overload release including a thrust' member adapted also to operate said valve and controlled by movement of the pressure link in accordance with reactions from the implement, apparatus connecting the thrust member to the valve and for preventing shuddering of the tractor and trailer by the oscillation of the valve to repeat lifting and releasing of the load of the implement upon the tractor, said apparatus comprising a connection between the thrust member and the valve which is alternately an actuating and a lost motion connection, and means actuated upon operation of the overload release to cause the connection between the thrust member and the valve to assume the lost motion phase until reset.

22. The combination claimed in claim 21 in which the alternate lost motion and actuating connection is afforded by a lever as to which the fulcrum is shifted from a point on which the lever movement moves the valve to a point on which the lever swings ineffectually so far as moving the valve.

23. The combination claimed in claim- 21 in which the alternate lost motion and actuating connection is afforded by a lever with shiftable fulcrum points, one effectual and the other ineffectual to communicate movement of the thrust member to the valve, and a member actuated by the overload release movement of the thrust member together with spring means for causing such shifting of fulcrum points.

24. In combination a tractor and a soil-working or agricultural implement, the tractor comprising means for movably attaching the implement thereto, a power-operated control unit for moving the implement up and down with reference to the tractor and supporting it thereon, an implement draft-transmitting connection including draft-balancing means between the implement and a control member of said unit and a pivoted lever movable alternatively about a fulcrum to cause movement of the control member and about a further fulcrum without causing movement of the control member, said control member being movable under the opposed influences of the balance means and of the draft pressure on the implement to implement lifting, holding or lowering positions and being movable by the draft against the action of said balance means to said lowering position to cause slipping of the tractor driving wheels when there is an excess of draft'pressure on the implement and resist-l ant means eil'ective on said lever to cause it to move about said further fulcrum so that the control member is not returned-to implement-lifting position as a result at the'reductlon of the draft pressure due to said wheel slip.

25. In a tractor comprising means for the attachment of an implement, a unit embodying power means for moving said implement up and.

down with reference to the tractor and control means movable by the draft pressure on the implement to raise and lower the implement in accordance with the draft pressure and to an extre'me position for putting said power means out is moved to said extreme position to prevent the control means being immediately returned from said position and consequently to prevent the power means immediately being restored into effective lifting relationship with the implement when the draft is reduced.

26. In a control unit for agricultural apparatus of the type. wherein an implement is moimted on a tractor for power operated movement between an inoperative position in which the implement is unsupported and free to rest upon the ground and an operative position in which the tractor supports at least a portion of the implements weight, said control unit having in combination means for controlling the movements of said implement between said positions including releasing means responsiveto an excessive implement draft load for eflecting movement of the implement to its inoperative grounded position, and restraining means acting on the releasing means to maintain the releasing means in such-condition and thereby disable the control unit.

2'7. In a control mechanism for automatically controlling the vertical position of a, tractor drawn implement with respect to the ground and the tractor and including a control unit embodying means responsive to the draft on the implement for maintaining a predetermined vertical position of the implement and responsive to an excess of draft on the implement for discontinuing the vertical support, thereof, said control means having in combination a member movable by such excess draft pressure on the implement to discontinue the operation of the control unit, means operable upon the movement of said member to such position to hold it against immediate return and thereby prevent re-establishment of the operation of the control unit, and means for releasing the holding means to enable re-establishment of operation of the control unit. I

28. In a tractor including means for attachment of an implement, aunit embodying power means for moving the implement up and down with respect to thetractor in response to changes in the draft, control means operated by the draft with such control means to keep the same in position to maintain release of the power' means and prevent raising of the implement and throw.-

in: its weight upon the tractor after the excess draft has been relieved by the tractor wheels slipping, whereby alternate release and re-engagement of the power lifting means with the,

implement is avoided, and "shuddering" prevented.

29. In a tractor including means for attach-' ment of an implement, a unit embodying power means for moving the implement up and down with respect to the tractor in response to changes in the draft, control means operated by the draft making the power mean effective and prevent raising of the implement and throwing its weight upon the tractor after the excess draft has been I eases relieved by shuddering" prevented. 4

30. In a tractor including means for attachment of an implement, a unit embodying power means for moving the implement 'up and down with respect to the tractor in response to changes in the draft, control means operated by the draft to control the power means in such up and down movement, and to also release the power means .and put the same out of effective lifting relationship with the implement to unload the tractor of the weight of the implement when there is an excess of draft due to unusual obstruction, and holding means tripped by movement of the control means, when the same is actuated by excess draft to release the power means, and operating to keep the control means from again making the power means effective and prevent raising of the implement and throwing its weight upon the tractor after the excess draft has been relieved by the tractor wheels slipping, whereby alternate'release and re-engagement of the power lifting means with the implement is avoided and "shuddering" prevented.

- HENRY GEORGE FERGUSON.

the tractor wheels slipping, whereby alternate release and re-engagement of the power lifting means with the implement is avoided and

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