NZ603439B - Improvements in and Relating to Load Transfer - Google Patents

Abstract

603439 Disclosed is a load sensing and lift cylinder adjusting system for a three-point linkage arrangement (1002) on a tractor (1000). The system includes a control system and load setting system, a load sensing system and a load adjusting system. The load setting system is configured to allow a desired load to be pre-set for lift cylinder(s) (1004) of the three point linkage (1002) when first connected to a towed implement (1001) and prior to commencing a work operation with the implement (1001). Once the load setting system has pre-set the load, the load sensing system is informed of a pre-set load being selected and then monitors the load on the lift cylinder(s) (1004). If the load drops from the pre-set load a signal is sent to the load adjusting system which diverts oil from a pressurised oil supply to the lift cylinder(s) (1004) to maintain the pre-set load. If the pre-set load is exceeded a signal is sent to the load adjusting system which diverts oil from the lift cylinder(s) (1004) back to the tractor hydraulic oil supply. desired load to be pre-set for lift cylinder(s) (1004) of the three point linkage (1002) when first connected to a towed implement (1001) and prior to commencing a work operation with the implement (1001). Once the load setting system has pre-set the load, the load sensing system is informed of a pre-set load being selected and then monitors the load on the lift cylinder(s) (1004). If the load drops from the pre-set load a signal is sent to the load adjusting system which diverts oil from a pressurised oil supply to the lift cylinder(s) (1004) to maintain the pre-set load. If the pre-set load is exceeded a signal is sent to the load adjusting system which diverts oil from the lift cylinder(s) (1004) back to the tractor hydraulic oil supply.

Description

James & Wells ref: 237957/14 PATENTS FORM NO. 5 Fee No. 4: 0 PATENTS ACT 1953 COMPLETE SPECIFICATION IMPROVEMENTS IN AND NG TO LOAD TRANSFER I, Kalvin Jit Singh, a New Zealand citizen of 105 Old Te Kuiti Road, RD 6, Otorohanga 3976, New Zealand 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: James & Wells ref: 237957/14 IMPROVEMENTS IN AND RELATING TO LOAD TRANSFER TECHNICAL FIELD The t invention relates to improvements in and relating to load transfer.

BACKGROUND ART The present invention has particular application to both tractors which tow implements via means of 3 point e (hitch) or simply via a tow bar.

A major problem faced by tractors when towing (pulling) a heavy load, is that the effective load being towed by the tractor, can vary considerably when traversing variable ground conditions, and traction can suffer as a result. Some non-limiting examples of such varying ground conditions can include: Soil and rocky or stony ground; Dry and muddy and/or wet ground; Flat and undulating ground; or Hills and flat ground.

Typically, difficulties are encountered at the interfaces between the different ground conditions.

The above discussed loss of traction experienced by a tractor towing an implement, has over the years, been sought to be addressed in a number of different ways, including: the addition of ballast to the tractor; draft control systems; and automatic performance management systems.

However, these systems still all have their cks as detailed below.

All conventional tractors available on the market today all still require the addition ballast which is “dead” weight (in the order of several tons or more depending on the size of the tractor and load to be towed) that is added to the tractor to se on. The requirement for ballast to be added to tractors remains despite tractors being fitted with draft control and tic management s to combat loss of traction. As will be understood the addition of dead weight to be moved by a tractor in addition to the load to be towed significantly reduces fuel Draft control The majority of new tractors today are fitted with a draft control system which es a sensor which senses increased draft forces arising from the towed implement pulling back on the hitch James & Wells ref: 237957/14 arms of a three point hitch, in situations of increased drag and indicating the potential for a loss in traction. When increased draft forces are encountered, the draft control system ds by lifting the hitch arms, in an attempt to reduce the drag, by lifting the implement a little further out of the . However, this response by the draft control system can eventually become a problem, when the draft control automatically engages several times, during a towing operation, as the repeated lifting se causes the implement to be totally lifted out of the ground - which is of course rable. A problem with the draft control system is that it cannot operate in reverse and lower the arms once reduced drag is encountered. It is a one way system.

Automatic management systems Automatic management systems sense wheel slippage by monitoring wheel speed and true ground speed. When there is a ence of 10-15% between the wheel speed and true ground speed, the system recognises this as a wheel slippage event, and operates the lifting arms to lift the implement out of the ground a fraction to reduce drag. However, these systems are notoriously unreliable in practice as: - by the time wheel slippage is detected (i.e. when there is a 10-15% speed differential) it is often too late as the drag forces being experienced are significant; - the system typically overcompensates due to the significant drag forces and ends up lifting the implement totally out of the ground; - the system is not geared to lower the implement after a wheel slippage event has occurred.

It is an object of the t ion to address the foregoing ms or at least to provide the public with a useful choice.

All references, including any s or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the ants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art ations are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

Throughout this ication, the word "comprise", or variations thereof such as "comprises" or "comprising", will be understood to imply the inclusion of a stated t, integer or step, or group of ts integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.

James & Wells ref: 237957/14 DEFINTIONS The term ‘drawbar’ as used herein refers to a beam on the front of a towed implement used for attaching to a tow bar on a tractor to enable towing.

The term ‘tow bar’ as used herein refers to a bar on the back of a tractor used for towing.

The term three-point linkage arrangement as used herein refers to: - a conventional three point e on the rear of a tractor as is well known in the art; - a tow bar only tractor which has been modified to also pull from the front of the tractor as disclosed in Figure 3 of this specification and as also detailed in .

DISCLOSURE OF THE INVENTION According to one aspect of the present invention there is provided a load sensing and lift cylinder adjusting system for a three-point linkage arrangement on a tractor, which - a hydraulic oil ; - a control system and load setting system; - a load sensing system in the form of a load g proportional valve in fluid connection with the lift cylinder; - a load adjusting system which includes a load sense pump connected to the load sensing proportional valve and the tractor’s hydraulic oil supply; wherein the load setting system is configured to allow a desired transfer load to be pre-set for lift cylinder(s) of the three point linkage, when first connected to a towed implement, prior to cing a work ion with said ent, and once the load setting system has pre- set the load, the load sensing system is informed of a pre-set load being selected and then monitors the load on the lift cylinder and: - if the load drops from the pre-set load this sends a signal to the load adjusting system which s oil from a pressurised oil supply to the lift cylinder to maintain the pre-set load; - if the pre-set load transfer pressure is exceeded a signal is sent to the load ing system which diverts oil from the lift cylinder back to the tractor’s hydraulic oil supply.

According to another aspect of the present invention there is provided a load sensing and lift cylinder adjusting system for a three-point e arrangement on a tractor, substantially as James & Wells ref: 237957/14 described above, wherein the system includes at least one shock ing device capable of absorbing a hydraulic shock wave.

According to another aspect of the present invention there is provided a method of controlling the lift cylinder(s) used on a three-point linkage arrangement on a tractor comprising the steps - setting a desired load on the lift er(s) once an implement has been connected to the three-point linkage arrangement; - monitoring the load on the lift cylinder(s) whilst towing the implement; - continually adjusting the lift cylinder(s) to maintain the pre-set load as is required.

According to a further aspect of the t invention there is provided a tractor which includes a load sensing and lift cylinder ing system for a three-point linkage ement substantially as described above.

BRIEF DESCRIPTION OF THE GS Further aspects of the present invention will become apparent from the ensuing description which is given by way of example only and with reference to the accompanying drawings in which: Figure 1 shows a tic view of a load sensing and lift cylinder adjusting system for a three point linkage on a tractor in accordance with one preferred embodiment of the present invention; Figure 2A shows a schematic view of a tractor towing a towed implement and going over a rise in the ground to illustrate operation of the system shown in Figure 1; Figure 28 shows a schematic view of a tractor towing a towed implement and going over a sion on the ground to illustrate operation of the system shown in Figure 1; Figure 3 shows a schematic view of a tractor sold with a tow bar only which has been modified to include a rear lift cylinder and to also pull from the front of the tractor which can utilise the present invention.

BEST MODES FOR NG OUT THE INVENTION The load sensing and lifting er adjusting system of the present invention is made up of the following systems: James & Wells ref: 237957/14 First, a control system which is in the form of a PLC and load setting system, which utilises a user interface (control panel) normally located in the cab of the tractor, to allow for input of d load transfer information into the control system.

Secondly, a load adjusting system which has a ional valve, cooperating with a load sensing proportional valve and load sense pump.

Thirdly, a load sensing system in the form of a load sensing proportional valve which detects changes in load and the magnitude of the change in the load.

These three s are now discussed in more detail in relation to the drawings.

With respect to Figure 1 there is provided a load sensing and lifting cylinder adjusting system (LAS) for a three-point linkage on a tractor lly indicated by arrow 1.

The LAS 1 integrates into the hydraulic system of a tractor’s three point linkage, via a spool type directional valve 2. The directional valve 2 which is ted to the hydraulic supply line (hose) 3 at an inlet port (not shown), which supplies hydraulic fluid from the tractor’s hydraulic fluid supply 100, via a load sense pump 101 to hydraulic lift arms (hydraulic rams or cylinders) 102 (of the three point linkage (not shown), at the rear of a tractor (not shown)). The directional valve 2 also has a first inlet/exit port (not shown) connected to a lift arm supply line 4, which in turn is effectively ted to the lift arms 102 via inlet/output line 5.

The directional valve 2 is operated by an associated solenoid 6.The solenoid 6 is connected to a control system PLC and user interface (not shown), in the tractor cab (not shown). The user interface enables a driver (not shown) to te the LAS 1, and set the desired weight to be transferred from the towed implement (not shown) to the tractor, at which point the control system PLC governs overall operation of the LAS 1.

The solenoid 6 operates the ional valve 5 to direct fluid either: - to the lift arm via an inlet/outlet port (not shown) and lift supply line 4, or - to a load sensing proportional (LSP) valve 8 via second inlet/output port (not , and a second inlet/output line 7, which is connected to a load sensing proportional (LSP) valve The LSP valve 8 is also operated by an ated solenoid 9 which is again connected to and actuated by the control system (not shown). A shock absorber in the form of a nitrogen accumulator 10 is connected to the lic line 7 by way of a hydraulic side branch line 11.

The nitrogen accumulator 10 s the LAS 1 to absorb any shocks experienced in the hydraulic fluid, due to rapid changes in the towed load.

The LSP valve 8 has a first inlet/outlet port (not shown) which connects the LSP valve to the directional valve as aforementioned via line 7. In addition the LSP valve 8 has an inlet line 12, James & Wells ref: 237957/14 which es hydraulic fluid to the LSP valve 8 from the load sense pump 101. Line 12 also has a branch line 13 coming off, which supplies high pressure hydraulic fluid to the tractor system via the load sense pump 101, when the LSP valve 8 shuts off inlet line 12. In addition, the LSP valve 8 also has an outlet port (not shown) and associated line 17, which can redirect hydraulic fluid received from the directional valve 2, in an over pressure situation in the lift cylinders 102, to the tractor's hydraulic fluid supply 100.

The load sense pump 101 also has an additional supply port (not shown) which conventionally can be used for providing hydraulic fluid to towed implements, which have hydraulic ent thereon. In the present invention, a load sense supply line 14 is connected to the onal supply port on pump 101, and this is connected to the LSP valve 8 via a priority valve in the form of a ball valve 15. The ball valve 15 has a port (not shown) which is connected to a tractor supply line 16. The ball valve 15 senses when the tractors essential es, such as brakes or steering, require pressurised hydraulic fluid, it s lic fluid to line 16 in such situations, as a matter of priority. Providing, that fluid to line 16 takes precedence over supplying rised hydraulic fluid to the LAS 1, until such time as hydraulic fluid is no longer required by ial es.

In practice, diversion of hydraulic fluid to essential services does not affect operation of the LAS 1, as the need for oil by essential services typically is only required for around 1-3 seconds, at maximum, in most normal situations. It being understood, if essential services require additional pressurised hydraulic fluid for a longer time period, then the tractor is in a serious situation - where the normal towing operation is most likely a low priority.

The following description details how the LAS of Figure 1 operates, in practice, in each of the two scenarios depicted in Figures 2A and 2B.

In s 2A and 2B there is provided a tractor 1000 which is towing a ground working implement 1001 via the three point linkage 1002. The three point linkage has an upper hitch arm 1003 which is connected to the towed implement 1001. A pair of hydraulic lift cylinders 1004 (of which only one is visible) are fixedly mounted to the rear of the tractor 1000 at their base. Each cylinder 1004 has the distal end of their piston rod pivotally connected to a lift arm 1010, which is pivotally ted to a lift rod 1011, to effectively connect the lift cylinders 1004 to the lower hitch arms 1005 as is known in the art.

When the tractor goes over a rise 1006, the lift cylinders 1004 experience a downward force X, this increases the pressure of the hydraulic fluid within the lift cylinders 1004. As the pressure in the cylinder 1004 now exceeds the pre- set load transfer re - that the user initially selected after attaching the implement to the tractor - this is sensed by the LSP valve 8. The control system (not shown) upon receiving this information from the LSP, operates the solenoids 6, 9 on the directional and LSP valves 2, 8 respectively, so as to direct hydraulic fluid James & Wells ref: 237957/14 from the cylinder back to the hydraulic fluid supply of the tractor 100 via line 17. To thereby reduce the re in the lift cylinders 1004 until it reaches the pre- set cylinder pressure.

When the tractor goes into a dip 1007 in the ground the lift cylinder 1004 experiences an upward force Y which decreases the pressure of the hydraulic fluid within the lift cylinders 1004. As the pressure in the cylinders 1004 is now below the pre- set load transfer pressure - that the user initially selected after ing the implement to the tractor - this is sensed by the LSP valve 8. The control system (not shown) upon receiving this information from the LSP valve 8 operates the solenoids 6, 9 on the directional and LSP valves 2, 8 to enable the load sense pump 101 to pump pressurised hydraulic fluid from the tractor’s lic fluid supply to the lift cylinders 1004. This occurs until the pressure in the lift cylinders 1004 reaches the pre- set cylinder pressure — as detected by the LSP valve 8.

In Figure 3 there is shown a tractor 2000 which does not have a three point linkage but instead utilises only a tow bar 2001 to pull an ltural implement 2002, via the implement’s drawbar 2003. This tractor has been modified to include a lift cylinder 2004 which is mounted at the base thereof to the rear of the tractor 2000. The tractor 2000 has also been modified to e a lift arm 2005 which is pivotally attached to the rear of the tractor 2002 and to which the piston rod of the cylinder 2004 is pivotally connected. This tractor 2000 has also been modified to: — include the LAS 1 of Figure 1 (not shown); and - include the load transfer ism of the applicant‘s earlier patent application WO 2011/25392 which has a chain 2006 transferring load from the towed implement to the front of the tractor 2000.

Example 1 In this example a user has hitched a plough to the three point hitch of a r. Once the implement is attached to the three point hitch the user can switch on the LAS 1 of Figure 1.

This energises the solenoids of the directional valve and LSP valve. Prior to the LAS being activated by the user, the directional valve acts a simple one way valve, and only allows hydraulic fluid to be supplied to the lift cylinders, via the tractor’s normal draft l .

However, once the LAS is activated the control system takes over control of the directional valve, and the one way valve is deactivated. The solenoid then actuates the valve in ance with instructions received from the control system.

Initially, the LAS instructs the directional valve and LSP valve to direct fluid to the lift cylinders, via the load sense pump, until the pressure selected by the user is reached. At this point the LSP valve shuts off the supply line from the load sense pump. As the directional valve and LSP valve are still in fluid communication, via line the LSP can r the lift cylinder pressure.

James & Wells ref: 237957/14 For example, if the user selects a pressure of 800psi for the lift cylinder, then the control system operated the solenoid on the LSP valve, so that the load sense pump, will pump hydraulic fluid to the lift cylinders, until this pressure is reached as aforementioned.

Then during the towing operation, if the LSP valve senses that the 800psi re is exceeded in the lift cylinders, the control system operates the id associated with the LSP valve to direct fluid back to the tractor's hydraulic fluid supply, until the target 800psi pressure within the cylinders is reached.

If however, during in a towing operation the LSP senses a decrease in the 800psi pressure, the control system operates the solenoid ated with the LSP valve, to allow the load sense pump to pump fluid to the cylinders until 800psi pressure within the ers, is once again attained.

DETAILED DISCUSSION OF ALTERNATE WAYS TO IMPLEMENT THE INVENTION The control system may be any suitable PLC and the load setting system may be any suitable user interface effectively connected to the PLC to allow a user to select load transfer settings.

The control system and load setting system may include a screen or other visual indicator device, for displaying the load to be transferred to the tractor from the towed implement and/or the pressure at which the lift cylinder, is to be maintained during the towing of the ent.

The load sensing system may include a load sensing proportional valve which is coupled to the lift cylinder of the three point linkage.

The load sensing proportional valve may come in a variety of different forms without departing from the scope of the present invention.

In one embodiment the load sensing proportional valve may include a solenoid which is controlled by the l system and used to operate the load sensing proportional valve.

The load adjusting system may e a directional valve coupled to (Le. in fluid communication with) a load g proportional valve which is in turn coupled to a load sense pump.

The directional valve may have a variety of different configurations for controlling the flow of hydraulic fluid, without departing from the scope of the t invention. For example the directional valve may be selected from: - Spool type directional valves; - Poppet type ional ; - Rotary type directional valves.

James & Wells ref: 237957/14 r this list should not be seen as limiting.

In one embodiment the directional valve may include a solenoid which is controlled by the control system and used to operate the ional valve.

The load sense pump may be the load sense pump which is present in the existing hydraulic system of a tractor.

The load sense pump may be connected to the load sense proportional valve so as to create a stand by pressurised oil t, which maintains hydraulic fluid flowing around the circuit at a constant pressure of 300psi. The load sense pump may be configured so that this rised fluid circuit is the default configuration of the valve. The pressurised fluid circuit is always operating unless : a pressure drop in the lift er is detected, or a ball priority valve which is included in the pressurised fluid circuit, detects that fluid needs to be redirected to the tractor’s brakes, or steering, or other essential hydraulic service, as an overriding priority.

Preferred embodiments, of the present invention may have a number of advantages over the prior art which can include, but should not be limited to: - The ability to sense within a on of a second any change in lift cylinder pressure from a pre-set pressure; - The ability to react to any change in lift cylinder pressure within a fraction of a second; - The ability to effectively lift or lower the lift cylinders to maintain a constant towed load.

Aspects of the present invention have been bed by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope f as defined in the appended claims.

James & Wells ref: 237957/14

Claims (8)

WHAT I CLAIM IS:

1. A load sensing and lift cylinder ing system for a three-point linkage arrangement on a tractor, which includes: - a hydraulic oil supply; - a control system and load setting system; - a load sensing system in the form of a load sensing proportional valve in fluid tion with the lift cylinder; - a load adjusting system which includes a load sense pump ted to the load sensing proportional valve and the tractor’s hydraulic oil supply; wherein the load setting system is configured to allow a desired load to be pre-set for lift cylinder(s) of the three point e, when first connected to a towed ent, prior to commencing a work operation with said implement, and once the load setting system has pre-set the load, the load sensing system is informed of a pre-set load being selected and then monitors the load on the lift cylinder via the oil pressure from within the lift cylinder and: - if the load drops from the pre-set load this sends a signal to the load adjusting system which s oil from a hydraulic oil supply to the lift cylinder to maintain the pre-set load; - if the pre-set load is exceeded a signal is sent to the load ing system which diverts oil from the lift cylinder back to the tractor’s hydraulic oil supply.

A load sensing and lift cylinder adjusting system for a three-point linkage arrangement on a tractor as claimed in claim 1 wherein the system includes at least one shock absorbing device e of absorbing a hydraulic shock wave.

A load sensing and lift cylinder adjusting system for a three-point linkage arrangement as claimed in claim 1 or claim 2 wherein the control system is in the form of PLC and load setting , which utilises a user interface located in the cab of the tractor, to allow for input of desired load transfer information into the control system.

A load sensing and lift cylinder adjusting system for a point e arrangement as claimed in claim 3 wherein it is the load adjusting system which has a directional valve, cooperating with a load sensing proportional valve and load sense pump. James & Wells ref: /14

5. A load sensing and lift er adjusting system for a three-point linkage arrangement as claimed in any one of the preceding claims wherein it is a load sensing proportional valve which detects changes in load and the magnitude of the change in the load.

6. A tractor which includes a load g and lift cylinder adjustment system for a three- point linkage arrangement as claimed in claim 1.

7. A load sensing and lift cylinder adjusting system for a three-point linkage arrangement on a tractor as substantially described herein with reference to any one of the s and/ or Examples.

8. A method of controlling the lift cylinder(s) used on a point linkage arrangement on a tractor as substantially described herein with reference to any one of the