Claims:WE CLAIM:
1. An improved hydraulic hitch valve system (100) for agricultural vehicles, comprising:
a hydraulic pump (101); a check valve (102) placed at the inlet port of the said hydraulic pump (101); a hydraulic reservoir (103a, 103b) filled with oil; a control valve (104), the said control valve (104) receiving oil from the hydraulic reservoir (103a) through the hydraulic pump (101) whose flow it regulates to and from a hydraulic cylinder (105), the said hydraulic cylinder (105) consisting of a piston (106) which facilitates the lifting/ lowering of the hitch through a valve actuator (107) based on the oil flow through the said hydraulic cylinder (105); a valve body (108) housing the said control valve (104), check valve (102), and valve actuator (107), the said valve body (108) on which a relief valve (109) is mounted; and a control system (110); characterised in that,

(i) the control valve (104) consisting of at least two dump ports (112a, 112b) connected with the hydraulic pump (101) through at least two dump stations (113a, 113b), the said control valve (104) having a single hydraulic spool construction integrated with three modes of operation comprising neutral mode, lifting mode and lowering mode, whereby:

during the neutral mode, the oil dumps into the hydraulic reservoir (103a) through the said two dump ports (112a, 112b) of the control valve (104) while simultaneously blocking the oil flow through the check valve (102);

during the lifting mode, the valve actuator (107) is moved so as to block the dump ports (112a, 112b) as a result of which the pressure raises in the system (100) and simultaneously the neutral section opens up to port of the hydraulic cylinder (105), enabling power stoke of the hydraulic cylinder (105);

during the lowering mode, the valve actuator (107) is moved so as to open the dump ports (112a, 112b) to the hydraulic reservoir (103a), enabling the flow of oil from the dump stations (113a, 113b) to the hydraulic reservoir (103a) while simultaneously at the least pressure, the cylinder oil is vented to the hydraulic reservoir (103b) through lowering notches (114a, 114b);

(ii) the valve actuator (107) is lever and link type and acts as an interface between the operator input and the control valve (104) for mode selection;

(iii) the control system (110) consists of a spring assembly (115) to ensure spool movement of the control valve (104) against the actuating lever and to always keep the control valve (104) in dynamic mode to avoid possible spool jam.

2. The improved hydraulic hitch valve system as claimed in claim 1, wherein the control valve (104) is a manually operable four way three position direction control valve.

3. The improved hydraulic hitch valve system as claimed in claim 1, the spool movement of the control valve (104) is kept in continuous oscillation through a cam (117) and follower (118) arrangement connected to a rotational member (116).

4. A method of operation of the improved hydraulic hitch valve system (100) as claimed in claim 1, the said method comprising the steps of:
(ii) the operator giving input to the control system (110) whereby:

if the input given is for neutral mode, the oil dumps into the hydraulic reservoir (103a) through the two dump ports (112a, 112b) of the control valve (104) while simultaneously blocking the oil flow through the check valve (102);

if the input given is for lifting mode, the valve actuator (107) is moved so as to block the dump ports (112a, 112b) as a result of which the pressure raises in the system and simultaneously the neutral section opens up to port of the hydraulic cylinder (105), enabling power stoke of said hydraulic cylinder (105), thereby resulting in the lifting of the implement connected to the hitch of the tractor;

if the input given is for lowering mode, the valve actuator (107) is moved so as to open the dump ports (112a, 112b) to the hydraulic reservoir (103a), enabling the flow of oil from the dump stations (113a, 113b) to the hydraulic reservoir (103a) while simultaneously at the least pressure, the cylinder oil is vented to the hydraulic reservoir (103b) through the lowering notches (114a, 114b), thereby resulting in the lowering of the implement connected to the hitch of the tractor

Dated this 29th day of October 2021

, Description:IMPROVED HITCH VALVE SYSTEM WITH INTEGRATED SPOOL AND DUMP CIRCUIT FOR AGRICULTURAL VEHICLES
FIELD OF INVENTION
The present invention relates to a hitch valve system of a gear pump driven hydraulics system employed in utility vehicles. The invention particularly relates to an improved hitch valve system with integrated spool and dump circuit for utility vehicles including agricultural vehicles such as tractors.
BACKGROUND OF INVENTION
Hydraulic systems are used generally in agricultural vehicles such as tractors to lower or hold an implement, mounted on the mechanical linkage at any chosen height. The principle applied in the said hydraulic systems is Pascal’s law where the pressure applied to an enclosed fluid is transmitted equally in all directions such that small force acting on a small area can produce a higher force on a surface of larger area. Tractor hitches are employed for attaching and operating agricultural implements. In tractors which employ hydraulic systems, particularly tractors with built-in lift systems, the mechanical linkages mostly involve 3-point linkages otherwise called as 3-point hitch systems for connecting with the implement. A typical 3-point linkage involves two bottom links and one top link in which the bottom links are connected to two lift arms through lift links. The top link is used for connecting the third hitch point of the implement and is adjustable for maintaining the implement level and suction angle. Further, 3-point hitch transfers weight and resistance of an implement to drive wheels on a tractor.
In conventional hydraulic hitch valve systems, the hitch valve is actuated by mechanically displacing a hydraulic spool through a set of mechanical linkages. The hydraulic spool connects the fluid passages to direct hydraulic oil from a pump into a ram cylinder for lifting the implement. The spool also relieves oil from the ram cylinder back to the oil sump during a lowering motion of the implement by connecting the passage when the implement shifts to its original position. The implement remains held up in the neutral position as the spool does not allow any flow of oil from or to the ram cylinder by closing/ opening the passage. During unloading, when the implement load is being held or lowered, the pump oil flow is required to dump in the sump at a very low pressure. For unloading of oil effectively at a low pressure, while holding or lowering the implement load, an unloading valve is provided. Additionally, the hydraulic systems generally known in the art employ an additional compensator valve to stabilize the changes in pressure and to adjust the volume/ flow rate. Therefore the design of conventional hydraulic hitch valve systems encompasses multiple components which make it complex and less efficient in terms of design. There is therefore a need for more efficiently designed hydraulic hitch valve systems with lesser components.
The Indian Patent Application 101/CHE/2012 discloses a system for operating a single acting hydraulic cylinder that includes a directional valve in which there is one extreme position where the workport is connected to a tank return conduit, another extreme position where the workport is connected to a pump supply conduit, and a closed intermediate position where the workport is disconnected from both the pump and the tank. The directional control valve is a three-position proportional spool valve that is pilot operated by pressure applied to a pilot port. The said directional valve is biased towards the one extreme position by a spring .The said system involves a pressure compensator that also provides self priming of the directional valve. However, the spool disclosed in the said invention is pilot operated and an Electro Hydraulic Hitch (EHH) system solenoid valve is utilized.
Patent document RU2232685 discloses a traction and transport vehicle where hitch is furnished with pivot lifting and lowering hydraulic cylinder. Power hydraulic cylinders of mounting are controlled by hydraulic unit including safety valve and three-position four-line distributor. Further, the said patent application discloses shoe brakes located on the rear wheels, equipped with wheel brake cylinders; a hydraulic linkage mechanism with a hitch in the form of a fork with a kingpin, the wheel brakes are equipped with separate control circuits, each of which consists of a master cylinder connected to the wheel brake cylinder, a servo cylinder and a control valve and the spool of which is kinematically connected to the brake pedal. Pivot lifting and lowering hydraulic cylinder is hydraulically coupled with two position four-line electrically-controlled distributor. In the neutral position of the three-position valve, its first and second lines are interconnected. In order to raise or lower the linkage mechanism with the hitch, the three-position valve of the valve body switches to one of the positions, for example the upper one, and communicates the rod cavity of the hydraulic cylinder with the outlet of the steering unit, and the piston cavity with the hydraulic tank. The rod of the hydraulic cylinder, moving under the action of fluid pressure, will raise the linkage mechanism. The first line is connected to the pressure line of the make-up pump, the second line is connected to the drain, third and fourth - with piston and rod cavities of hydraulic cylinder of lifting and lowering of kingpin. However, the invention disclosed by the said patent document comprises of various hydraulic circuits such as hydrostatic transmissions, hydraulic start-stop, breaks, hitch and auxiliary applications.
In US Patent Publication 2008/0093093 "passive" or "static" hydraulic system is disclosed wherein a main control valve on an agricultural tractor or the like is maintained in a neutral position during a time that the system is in the operating mode with hold-down pressure applied to the tools. A spool valve is provided in its neutral position particularly in a charging position for charging the system in, and in a lifting position for lifting tools off the ground in hold-down fluid line is connected at one end with spool valve. When the valve is in its neutral position, the pump and reservoir on a tractor are isolated from the rest of the system with hold-down pressure trapped in the circuit. This is contrasted to an "active" system wherein the tractor valve would normally be held open in the hold down mode so as to continuously circulate pressurized oil through the circuit and over a pressure relief valve as part of the system. However, the said invention pertains to implement cylinder control and is similar to a clamping circuit.
Indian Patent Application 3905/CHE/2013 discloses a hydraulic draft control system for a vehicle, said hydraulic draft control system having a control lever quadrant disposed in said vehicle and adapted for holding a position control lever and a draft control lever. Further, the said hydraulic draft control system disclosed by the said patent document comprises a position control linkage connected to the said position control lever, a draft control linkage connected to said draft control lever, a control valve connected to said position control linkage and said draft control linkage through a main spool. The said hydraulic draft control system also possesses a draft spring system adapted to sense a load exerted by a top link of the said hitch disposed in the said vehicle. In neutral position of the said system, the main spool is displaced such that the pilot port is closed. The closed position of the pilot port results in pressure build up which moves the regulator piston and unseats the ball-regulator valve allowing pump flow to a reservoir through the port. However, the hitch valve of the said invention possesses an unloader valve, thereby having separate lifting and lowering valve.
US Patent No. 7,434,392 discloses a configurable hydraulic system for agricultural tractor and implement combination in the form of an application circuit such that various hydraulic actuators on the implement are operated by connection to the hydraulic system on the tractor. The said system operates with a single electrically operated, three-way, three-position spool valve and has one position in which the supply line is connected to the connector port, another position in which the return line is connected to the connector port, and a closed position. However, the three-position spool valve is used for the application circuit – for the tractor and implement configurations, and does not provide for a single mechanism to carry out the functions of lifting, lowering and providing a compensator.
The Indian Patent Application 516/MUM/2011 discloses position control and draft control valves in four way three position type solenoid operated hydraulic valves wherein the said compensator valve is a pressure and / or flow regulating type hydraulic valve. The system comprises a valve block assembly, a microprocessor based controller, a double acting cylinder configured with a check valve and pilot piston valve, wherein said valve block assembly comprises of position control and draft control solenoid valve those are electronically configured with the said controller and hydraulically configured with a hitch pump and a steering pump. However, the spool is for the system for double acting cylinder and is solenoid operated.
The prior art references mentioned hereinabove disclose conventional 3-point hitch systems which are either pilot operated or solenoid operated hydraulic systems of utility vehicles including tractors. Also, the inventions disclosed by the cited prior art documents employ complex hydraulic circuits and none of the cited prior art documents addresses the elimination of pump loading. More importantly, none of the cited prior art documents provide for a mechanism to integrate the dump circuit with the spool circuit thereby eliminating the need for an additional compensator valve.
Therefore there is a need in the art to provide an integrated hitch valve system that eliminates pump loading and/ or the need for an additional compensator valve while integrating simultaneous dump and neutral, lift, fast and slow lowering. In order to overcome the above mentioned drawbacks in the existing art, the instant invention discloses a circuit which is designed with a 3 position spool valve with an integrated mechanism of lifting, lowering, neutral, and dump. The invention is very unique in its way that it is able to solve the problem solely based on the integrated valve system designed with less hydraulic elements for controlling agricultural implements and attachments.
OBJECTIVES OF THE INVENTION
The main objective of the present invention is to provide an improved hitch valve system for agricultural vehicles, that eliminates pump loading and/ or the need for an additional compensator valve while integrating simultaneous dump and neutral, lift, fast and slow lowering.
Another objective of the present invention is to provide an improved hitch valve system in which a single component replaces lifting spool, lowering spool and compensator, thereby providing a single integrated mechanism for lifting, lowering, neutral, and dump.
Another objective of the present invention is to provide a hydraulic hitch valve system with lesser components having lesser design complexity.
SUMMARY OF THE INVENTION
The present invention provides an improved hydraulic hitch valve system (100) for agricultural vehicles, said improved hydraulic hitch valve system (100) comprising a hydraulic pump (101); a check valve (102) placed at the inlet port of the said hydraulic pump (101); a hydraulic reservoir (103a, 103b) filled with oil; a control valve (104), the said control valve (104) receiving oil from the hydraulic reservoir (103a) through the hydraulic pump (101) whose flow it regulates to and from a hydraulic cylinder (105), the said hydraulic cylinder (105) consisting of a piston (106) which facilitates the lifting/ lowering of the hitch through a valve actuator (107) based on the oil flow through the said hydraulic cylinder (105); a valve body (108) housing the said control valve (104), check valve (102), and valve actuator (107), the said valve body (108) on which a relief valve (109) is mounted; and a control system (110); characterised in that,

(i) the control valve (104) consisting of at least two dump ports (112a, 112b) connected with the hydraulic pump (101) through at least two dump stations (113a, 113b), the said control valve (104) having a single hydraulic spool construction integrated with three modes of operation namely neutral mode, lifting mode and lowering mode, whereby:

during the neutral mode, the oil dumps into the hydraulic reservoir (103a) through said two dump ports (112a, 112b) of the control valve (104) while simultaneously blocking the oil flow through the check valve (102);

during the lifting mode, the valve actuator (107) is moved so as to block the dump ports (112a, 112b) as a result of which the pressure raises in the system and simultaneously the neutral section opens up to port of the hydraulic cylinder (105), enabling power stoke of said hydraulic cylinder (105);

during the lowering mode, the valve actuator (107) is moved so as to open the dump ports (112a, 112b) to the hydraulic reservoir (103a), enabling the flow of oil from the dump stations (113a, 113b) to the said hydraulic reservoir (103a) while simultaneously at the least pressure, the cylinder oil is vented to the hydraulic reservoir (103b) through lowering notches (114a. 114b);

(ii) the valve actuator (107) is lever and link type and acts as an interface between the operator input and the control valve (104) for mode selection;

(iii) the control system (110) consists of a spring assembly (115) to ensure spool movement of the control valve (104) against the actuating lever and to always keep the control valve (104) in dynamic mode to avoid possible spool jam.

In the preferred embodiment of the present invention, the control valve (104) is a manually operable four way three position direction control valve.

In the preferred embodiment of the present invention, the spool movement of the control valve (104) is kept in continuous oscillation through a cam (117) and follower (118) arrangement connected to a rotational member (116).

The present invention further provides a method of operation of the improved hydraulic hitch valve system (100) for agricultural tractors, the said method comprising the steps of:

(i) the operator giving input to the control system (110) whereby:

if the input given is for neutral mode, the oil dumps into the hydraulic reservoir (103) through the two dump ports (112a, 112b) of the control valve (104) while simultaneously blocking the oil flow through the check valve (102);

if the input given is for lifting mode, the valve actuator (107) is moved so as to block the dump ports (112a, 112b) as a result of which the pressure raises in the system and simultaneously the neutral section opens up to port of the hydraulic cylinder (105), enabling power stoke of said hydraulic cylinder (105), thereby resulting in the lifting of implement connected to the hitch of the tractor;

if the input given is for lowering mode, the valve actuator (107) is moved so as to open the dump ports (112a, 112b) to the hydraulic reservoir (103a), enabling the flow of oil from the dump stations (113a, 113b) to the said hydraulic reservoir (103a) while simultaneously at the least pressure, the cylinder oil is vented to the hydraulic reservoir (103b) through the lowering notches (114a, 114b), thereby resulting in the lowering of implement connected to the hitch of the tractor.

BRIEF DESCRIPTION OF DRAWINGS
Figure 1 represents the single integrated hydraulic spool circuit of the improved hydraulic hitch valve system (100) of the present invention.
Figure 2 illustrates the hydraulic mechanism of the improved hydraulic hitch valve system (100) of the present invention in neutral mode.
Figure 3 illustrates the hydraulic mechanism of the improved hydraulic hitch valve system (100) of the present invention in lifting mode.
Figure 4 illustrates the hydraulic mechanism of the improved hydraulic hitch valve system (100) of the present invention in the slow lowering mode.
Figure 5 illustrates the hydraulic mechanism of the improved hydraulic hitch valve system (100) of the present invention in the fast lowering mode.
Figure 6 illustrates the enlarged view of the spool movement of the control valve (104) in the improved hydraulic hitch valve system (100) of the present invention
DETAILED DESCRIPTION OF THE INVENTION
The present invention as embodied by an “Improved hitch valve system with integrated spool and dump circuit for agricultural vehicles” succinctly fulfills the above-mentioned need[s] in the art. The present invention has objective[s] arising as a result of the above-mentioned need[s], said objective[s] having been enumerated hereinabove.
The following description is directed to an improved hitch valve system with integrated spool and dump circuit for agricultural tractors. In as much as the objective(s) of the present invention are enumerated, it will be obvious to a person skilled in the art that, the enumerated objective(s) are not exhaustive of the present invention in its entirety, and are enclosed solely for the purpose of illustration. Further, the present invention encloses within its scope and purview, any structural alternative(s) and/or any functional equivalent(s) even though, such structural alternative(s) and/or any functional equivalent(s) are not mentioned explicitly herein or elsewhere, in the present disclosure. The present invention therefore encompasses also, any improvisation[s]/modification[s] applied to the structural alternative[s]/functional alternative[s] within its scope and purview. The present invention may be embodied in other specific form[s] without departing from the essential attributes thereof.
Furthermore, the terms and phrases used herein are not intended to be limiting, but rather are to provide an understandable description. Throughout this specification, the use of the word "comprise" and variations such as "comprises" and "comprising" may imply the inclusion of an element or elements not specifically recited.
The present invention provides an improved hydraulic hitch valve system (100) for agricultural vehicles, said improved hydraulic hitch valve system comprising a hydraulic pump (101); a check valve (102) placed at the inlet port of the said hydraulic pump (101); a hydraulic reservoir (103a, 103b) filled with oil; a control valve (104), the said control valve (104) receiving oil from the hydraulic reservoir (103a) through the hydraulic pump (101) whose flow it regulates to and from a hydraulic cylinder (105), the said hydraulic cylinder (105) consisting of a piston (106) which facilitates the lifting/ lowering of the hitch through a valve actuator (107) based on the oil flow through the said hydraulic cylinder (105); a valve body (108) housing the said control valve (104), check valve (102), and valve actuator (107), the said valve body (108) on which a relief valve (109) is mounted; and a control system (110); characterised in that,

(i) the control valve (104) consisting of at least two dump ports (112a, 112b) connected with the hydraulic pump (101) through at least two dump stations (113a, 113b), the said control valve (104) having a single hydraulic spool construction integrated with three modes of operation namely neutral mode, lifting mode and lowering mode, whereby:

during the neutral mode as shown in Figure 2, the oil dumps into the hydraulic reservoir (103a) through the said two dump ports (112a, 112b) of the control valve (104) while simultaneously blocking the oil flow through the check valve (102);

during the lifting mode as shown in Figure 3, the valve actuator (107) is moved so as to block the dump ports (112a, 112b) as a result of which the pressure raises in the system and simultaneously the neutral section opens up to port of the hydraulic cylinder (105), enabling power stoke of said hydraulic cylinder (105);

during the lowering mode as shown in Figures 4 and 5, the valve actuator (107) is moved so as to open the dump ports (112a, 112b) to the hydraulic reservoir (103a), enabling the flow of oil from the dump stations (113a, 113b) to said hydraulic reservoir (103a) while simultaneously at the least pressure, the cylinder oil is vented to the hydraulic reservoir (103b) through lowering notches (114a, 114b);

(ii) the valve actuator (107) is lever and link type and acts as an interface between the operator input and the control valve (104) for mode selection;

(iii) the control system (110) consists of a spring assembly (115) to ensure spool movement of the control valve (104) against the actuating lever and to always keep the control valve (104) in dynamic mode to avoid possible spool jam.

In the preferred embodiment of the present invention, the control valve (104) is a manually operable four way three position direction control valve.

In the preferred embodiment of the present invention, the spool movement of the control valve (104) is kept in continuous oscillation through a cam (117) and follower (118) arrangement connected to a rotational member (116) as shown in Figure 6. As the valve actuator (107) makes 360 degree rotation, the cam (117) and follower (118) will convert the rotational motion in to oscillatory motion, so that spool oscillate in line with the control system (110).

The present invention further provides a method of operation of the improved hydraulic hitch valve system (100) for agricultural vehicles, the said method comprising the steps of:
(i) the operator giving input to the control system (110) whereby:

if the input given is for neutral mode as shown in Figure 2, the oil dumps into the hydraulic reservoir (103a) through the two dump ports (112a, 112b) of the control valve (104) while simultaneously blocking the oil flow through the check valve (102);

if the input given is for lifting mode as shown in Figure 3, the valve actuator (107) is moved so as to block the dump ports (112a, 112b) as a result of which the pressure raises in the system and simultaneously the neutral section opens up to port of the hydraulic cylinder (105), enabling power stoke of the hydraulic cylinder (105), thereby resulting in the lifting of the implement connected to the hitch of the tractor;

if the input given is for lowering mode as shown in Figures 4 and 5, the valve actuator (107) is moved so as to open the dump ports (112a, 112b) to the hydraulic reservoir (103a), enabling the flow of oil from dump to the hydraulic reservoir (103a) while simultaneously at the least pressure, the cylinder oil is vented to the hydraulic reservoir (103b) through the lowering notches (114a, 114b), thereby resulting in the lowering of the implement connected to the hitch of the tractor.
The technical advancement provided by the present invention is that the hydraulic hitch control valve provided by this invention comprises of a single hydraulic spool construction in which simultaneous modes of operation namely dump and neutral, lifting, fast and slow lowering, are integrated into a single circuit. Such integration eliminates the necessity for an additional compensator valve while providing a less complex design.
In the preferred embodiment of the present invention, the hydraulic circuit is designed with a 4 way 3 position spool valve as the control valve (104), wherein at the neutral position, it not only blocks the oil to/from the working port, but also within this neutral band, a pair of dump stations (113a, 113b) will allow all the flow from pressure port to tank through the return port (111). During the operation of the improved hydraulic hitch valve system (100) in neutral mode, the oil is dumped into the hydraulic reservoir (103a) through the pair of dump ports (112a, 112b) provided in the control valve (104) with least pressure drop, and at the same time, the oil flow through the check valve (102) will be blocked in the neutral gallery. This is default spool position wherein there is a balance between the control system (110) and valve actuation. Further, during engine off condition, the check valve (102) closes and ensures no or very less leakage.
In the preferred embodiment of the present invention, to get to lifting mode, valve actuator (107) is moved, so that the spool moves to lift position. In this condition, the dump ports (112a, 112b) are blocked, and as a result pressure rises in the system (100). Simultaneously neutral section opens up to port of the hydraulic cylinder (105), enabling power stoke of the hydraulic cylinder (105).
In the preferred embodiment of the present invention, to allow the gravity down of the hydraulic cylinder (105), the valve actuator (107) is moved to the lowering position, either by slow lowering as shown in Figure 4 or fast lowering as shown in Figure 5 as required (which is determined by the position of the spool). In this condition, the dump ports (112a, 112b) are open to the hydraulic reservoir (103a) enabling pump flow from the dump stations (113a, 113b) to the reservoir (103a) at the least pressure while simultaneously, the oil from the hydraulic cylinder oil is vented to the hydraulic reservoir (103b) through appropriate slow or fast lowering notches (114a, 114b).
For illustration,
Example 1 – Refer Figure 2
In a specific example of the present invention, during neutral mode as shown in Figure 2, the oil is dumped to the hydraulic reservoir (103a) through the pair of dump ports (112a, 112b) provided in the control valve (104), with the least pressure drop, and at the same time, the oil flow through the check valve (102) will be blocked in the neutral gallery. This is the default spool position wherein there is a balance between the control system (110) and valve actuation. Further, during engine off condition, the check valve (102) closes and ensures that there is no or very less leakage.
Example 2 – Refer Figure 3
In another specific example of the present invention, to get to the lifting mode as shown in Figure 3, the valve actuator (107) is moved by the operator, so that the spool moves to the lifting position. In this condition, the dump ports (112a, 112b) are blocked and as a result, the pressure raises in the system. Simultaneously, the neutral section opens up to the port of the hydraulic cylinder (105), enabling power stoke of said hydraulic cylinder (105).
Example 3 – Refer Figures 4 and 5
In another specific example of the present invention, to allow the gravity down of the hydraulic cylinder (105), the valve actuator (107) is moved to the lowering position, either by slow lowering as shown in Figure 4 or fast lowering as shown in Figure 5 as required (which is determined by the position of the spool). In this condition, dump ports (112a, 112b) are open to the hydraulic reservoir (103) enabling pump flow from the dump stations (113a, 113b) to the said hydraulic reservoir (103) at the least pressure while simultaneously, the hydraulic cylinder oil is vented to the hydraulic reservoir (103) through appropriate slow or fast lowering notches (114a, 114b).
It will be apparent to a person skilled in the art that the above description is for illustrative purposes only and should not be considered as limiting. Various modifications, additions, alterations, and improvements without deviating from the scope of the invention may be made by a person skilled in the art.