PREVENTING LOST POWER GENERATION AND PROVIDING FUEL SAVING BY FLOW SHARING AND FLOW DIRECTION IN AN OPEN HYDRAULIC CIRCUIT HAVING MULTIPLE PUMPS

TECHNICAL FIELD

The present invention relates especially to hydraulic construction equipments where user-1 and user- 2 or multiple users that work under multiple and different pressures are grouped.

PRIOR ART In this study, the hydraulic cylinders, hydraulic motors, hydraulic angular movement elements will be named as "users" shortly, which are located on the equipment in the hydraulic construction equipments that have been produced in the current technology. The multiple users, on the other hand, will be named as the user group. In order for the users to complete the work in a more serial, faster and more efficient way, it is demanded that the users or user groups work together simultaneously. When the working durations of the construction equipments are analyzed, it can be observed that the users have simultaneous working durations up to 40-50%.

In any kind of construction equipments having a hydraulic system, it is required that the different pressure and flow needs of the users that are transferring movement should be met with the system pumps in the case that they need to work separately at different times and, simultaneously at the same time. While there is generally no problem experienced in the working environment of the users individually, in the case of simultaneous working, there emerges a loss of power which cannot be disregarded.

In the case that one pump is used for two Users that have been working at different flow rates and pressures on the same hydraulic circuit; more power is drawn from the engine than required. In the case that two users are worked in the same time on the same feeding source and one of the users is working under a higher pressure than the other, more power is drawn from the engine than required. While the amount of energy drawn from the engine should be as much as the work that is done; in the case that two different users working simultaneously and having different pressure necessity, as the pump should be worked depending on the high pressure demand of the pump in order to meet the pressure need of the user demanding high pressure, more power is drawn, which results in extra fuel consumption.

In order for the users to work simultaneously, currently hydraulic direction control valves are used with closed central load-sensing (flow sharing). In the hydraulic system applications conducted with other classical type valves, double pump and double-sided valves are used. Alternatively, it is provided that the flow-dividing valves and the users work together. Choosing this type of application with the standard valves brings about big mounting problems and costs because of the limited capacity of mounting location on the equipment and the difficulty of installation- assembly.

In the case that different users on the equipment in the hydraulic systems work at the same time, they need to share the flow. In their non-simultaneous working independently from each other, in other words in the case that they work at different time slots, maximum pump flow is needed.

When it is needed to share the flow depending on the need of the system from the feeding source with constant flow (as the users work under different pressures depending on the work that they do), the pump available in the hydraulic system generates pressure depending on the need of the user in need of high pressure. The pressure difference between the pump line and the user-1 line, and the pressure difference between the pump line and the user-2 line are named as 'ΔΡΙ ' and 'ΔΡ2', respectively; 'ΔΡΙ ' and 'ΔΡ2' create high pressure difference on the flow-dividing valve or valves. When it is considered that the need for high pressure is necessary for user-1 , the high pump pressure does not create any loss for user-1 which is in need of high pressure; while it creates a pressure difference 'AP2=Ppump-Puser2 ' for the user-2 which works with less pressure. The difference of pressure emerges as a loss of power in terms of the flow of the pump. As the loss of power that has been generated does not turn into a working energy, it comes about as heat energy. The hydraulic oil of the engine starts to get heated during the working duration .

As it is necessary to keep the oil temperature in hydraulic systems within a certain range (40-70°C) for the components working in the hydraulic system, it is needed to locate a cooler on the hydraulic system. As the coolers of big size cause a problem of capacity and location in the engine, mostly smaller size coolers are preferred which can provide closed-circuit cooling, work with a separate hydraulic pump and hydraulic motor, and have hydraulic-ventilator drives. When we consider the energy that these coolers consume, it is needed to include the extra cooling power losses into the system, as well.

The flow-dividing application types conducted in the hydraulic systems and the disadvantages are described in the following.

Method of dividing flow by using flow-dividing (working independently from pressure and temperature) valves: In the method of using the flow coming from one single pump by dividing it into two, the cylinders cannot use maximum pump flow in the case that the cylinders work at different times. The pump flow is used by always dividing it into two.

The method of dividing the flow by using special compensator valves (load-sensing valves) in front of each user (independent from pressure and temperature): each user can use maximum flow under single-working conditions from the pump line on one single pump, and in case of common usage, the flow is divided for each user, and it becomes possible to make different divisions. By means of the compensators located on the input or output of spool on the valves with load- sensing, it becomes possible to transmit desired amount of oil to the users. As the spool used inside of these valves are fully proportional spool and they use balance compensator before or after each spool, their cost of production is high, which is 3-5 times more expensive than the classic valves. As more than one spool passage is made in the pump passings from the pump to the user in the load- sensing valves, it generates more loss of pressure compared to the open-circuit semi-proportional classic valves.

In the prior art, two cylinders are worked by using double pumps at the same time. In the case that there are two users working simultaneously on the engine, the ideal solution is to use double pumps sending the flow separately, independently from each other for each user. Therefore, each pump works under a pressure as much as it needs, and only a flow pass power loss is generated on the valves. In the case that there is more than one user on the engines, it is needed to use double-sided valve for each user. This means that two-times more valves are used than the system requires. As the system needs maximum flaw in single workings, the double-sided valve will be activated at the same time, and the pumps will be worked with their own single valves in the case of simultaneous usage.

The most appropriate solution for preventing loss of pressure is activating two cylinders by using double pump, double-sided valve. Here, while the user-1 works alone, the two-sided valve can work with two pumps by being stimulated at the same time, one direction valve is stimulated when the user- 1 and user-2 work together, P1 and P2 pump flow is sent to different users seperately, and they can work under different pressures.

The biggest problem in this circuit is that the hydraulic circuit seems to be appropriate for two cylinders, however in the case that there are more than one user working simultaneously on the machine, it is disadvantageous to bind them together with two separate valve slice in terms of limited capacity of location. Moreover, it is not easy to control pilot lines with the installation materials to be used. The hydraulic circuit turns into a very complex structure. Such a way of mounting is not acceptable in the construction equipments. Therefore some companies produce special valves, and try to use line combinations. This solution is again not preferred by the producers as there is no standard type of valve production. When the condition emerged as a loss of energy has been analyzed in the case that the users work together;

The pump power source flow is Q=160 L/min, The working pressure for User-1 is P1 =250 bar;

The working pressure for User-2 is P2=50 bar, and the amount of lost power in the case that the users work together in a system that the users work together is calculated as follows. As the pressure in either flow-dividing or load-sensing systems under co-working conditions will be generated depending on the user pressure having a high pump pressure, the pump has to operate at P1 = 250 bar.

ΔΡ1 =0 Bar; ΔΡ2=Ρ2-Ρ1 =250-50=200 Bar. The energy loss for both methods (flow-dividing or load-sensing systems) under co-working conditions is calculated below by the formula N=(P ^* Q)/600.

Energy loss for User-1 (N1):

P1 :250 bar Working pressure

Q1 =80 L/min Working flow ΔΡ1 =0 bar The pressure difference between pump-user

N1 =(AP1 ^* Q1)/600→N=0*80/600=0 KW Lost Power.(The flow passage from directional valve and installation of pipe pressure losses have been ignored.)

Energy loss for User 2 (N2):

P2: 50 bar Working pressure Q2=80 L/min Working flow

ΔΡ2= 200 bar Pressure difference between pump-user

Ν2=(ΔΡ2*Ο2)/600→Ν=200*80/600=26.67 KW Lost Power Finally;

Consequently ;

N=N1+N2=26.67 KW energy loss emerges. In the lost power generation, the ΔΡ loss between the pump and the user should be calculated as the total lost power.

The total energy loss increases so long as the pump flow gets higher. The calculated energy is the wasted energy and causes unnecessary fuel consumption. Moreover, as the lost power comes up, the oil temperature used in the system increases as well. If a generalization is made depending on the above-mentioned calculation, in the case that the users are required to work simultaneously and separately in the open-circuit systems where there is more than one user;

-Generally a great energy loss does not come about in the case of individual working,

-If they work at different pressures in the case that they work together, loss of energy comes about. The main parametrical features that are requested while purchasing construction equipments:

• The condition that some of the users (cylinders and hydraulic motor) available on the machine can work simultaneously together and at different flow and pressure rates as much as the engine power allows. · The condition that the users do not affect the working conditions (speed, power, performance, etc.) of each other, the operator can easily control the machine while working with the machine.

The specification that while the users (cylinders and hydraulic motors) are working individually, they can work at maximum speed rates that the pump flow rate will determine. The movements are much more serial and faster as all the users on the machine use the whole flow.

• The condition that the fuel consumption of the construction equipment is low.

• The ability that machines with improved characteristics can be purchased in exchange for low prices. · Controllable load sensitivity: The ability that the operator can feel the load at the rate of increasing pressure when the digger of the construction equipment touches on a piece such as pipe or cable. (In the open-circuit hydraulic systems, it is possible to sense that load, whereas the possibility to sense that load in the load-sensing closed-circuit hydraulic systems is weak.) Based on the state of the art, the object of the present invention is to provide solutions to the above- mentioned problems and to fulfill the main parametrical values that are requested while making preference in purchasing construction equipments.

ADVANTAGES OF THE PRESENT INVENTION

By using valves which work with an algorithm logic that can provide the flow rate that the pumps have generated while the users are working simultaneously to be transferred to separate user groups without combining it, and that can combine the flow rates of the pumps when single user is working; the energy loss (N=N1 +N2) as heating that emerges because of pressure difference (ΔΡ), is totally minimized. The possible energy loss within the system is generally the loss resulting only from the resistance of the installation elements. By means of the flow redirecting and sharing valve, the pumps are united through the FLOW SHARING VALVE when user-1 and user-2 groups are activated individually, and the flow rate Q1 +Q2 that the pumps (P1 , P2) have generated is directed to the user which is going to work. When the user-1 and user-2 groups are activated at the same time, by warning is sent to the FLOW SHARING VALVE, and the flow rates that the pumps (P1 , P2) have generated are separated, and while the Q1 flow rate that P1 pump has generated is directed to user-1 group, the Q2 flow rate that the P2 pump has generated is directed to user-2 group, and therefore it becomes possible to use power without at loss.

In this case, by using one-way valve that is warned by the operator for each user, the working conditions are provided to be fulfilled. Therefore, in addition to the fuel saving, some other advantages are obtained as well, such as easy installation mounting of valve and warning lines, cost-efficiency, working at in small volumes (location-economy). The energy loss case in the system according to the present invention is analyzed as follows;

When the amount of lost power (N) is calculated in a system where;

Pump power source flow rate is Q=Q1 +0.2=80+80 L/min;

Working pressure for user-1 (10) is P1 =250 bar, and its flow rate is Q 1 =80 L/min;

Working pressure for user-2 (10') is P2=50 bar, and its flow rate is Q2=80 L/min; the energy loss is calculated as follows depending on the formula N=(P*Q)/600 for both methods at co-working conditions.

Energy loss for user-1 (10):

P1 :250 bar Working pressure

Q1 =80 L/min Working flow rate ΔΡ1 =0 bar Pressure difference between the pump-user

N1 =(AP1*Q1)/600→N=0*80/600=0 KW Lost power.

Energy loss for user-2 (10'):

P2: 50 bar Working pressure

Q2=80 L/min Working flow rate ΔΡ2= 0 bar Pressure difference between the pump-user

N2=(AP2 ^* Q2)/600→N=0*80/600=0 KW Lost power

The total lost power results in N=N1 +N2= 0 KW energy loss. (The flow rate passage and installation pressure losses are ignored.) In order to prevent the above-mentioned lost powers in the case of simultaneous working, the number of pumps is increased in the system, and a flow sharing and redirecting valve has been added which unites or divides the pump pressure lines. In the case that the users work together, they can work at different pressure rates, and the total system flow rate can be divided into two without causing any pressure difference. Therefore, even if a cylinder works at a low pressure, the other cylinder can easily increase up to the maximum pressure rate at the same time. For that, energy is drawn from the system as much as the work done. The lost powers are prevented as there remains no pressure difference (ΔΡ) on the valves.

As the lost power (N) is reduced, the capacity of chosen coolers on the machine is reduced as well. It is provided to supply the users with necessary amount of oil flow rate and pressure transfer (without causing pressure loss), and to draw energy from the engine as much as the work that is completed.

Thanks to said improvements, it is provided to use standard valves having low production cost and coolers of low capacity. When the power consumption is considered, the emerging lost is minimized. Moreover it is provided to reduce the fuel consumption to a great extent, caused by the power losses. As a result, a kind of machine has been created which does not cause any lost powers in the construction equipments having users that work simultaneously, and which has a lower production cost. It is provided to manufacture machines having controllable load sensitivity and much lower fuel consumption, which is the most important factor, (as much as the need of the work that is completed).

It can be applied to the Backhoe-Loader machine which is an open-system hydraulic circuit, having multiple pumps, providing flow-sharing and redirecting. Moreover, it also aimed to use it in other construction equipments comprising user-1 , user-2 or user groups replacing user-1 and user-2.

In order to reach this object, the present invention generally comprises;

• At least two pumps as the pump feeding source in order to provide said users with simultaneous working conditions at different pressures;

· Direction control valves conveying the flow rates (Q1 , Q2) that the pumps (P1 , P2) have generated when they are stimulated to work to the users by allowing them to pass on them;

• Flow sharing and redirecting valve which does not allow to pass on itself and separates the flow rates (Q1 , Q2) that the pumps (P1 , P2) have generated when the direction control valves are stimulated in order for said users to work at different time slots; and which combines and allows the flow rates (Q1 , Q2) that the pumps (P1 , P2) have generated when said direction control valves are stimulated in order for the users to work simultaneously at the same time slot. The pump, direction control valves and the flow sharing and redirecting valve are designed in such a way that;

• The flow rates Q1 +Q2 that the pumps P1 , P2 have generated are transferred to user-1 or user-2 through the flow rate-sharing and redirecting valve in the case that only user- 1 or user-2 is working;

• The Q1 and Q2 flow rates that the pumps P1 , P2 have generated are transferred to user-1 and user-2 separately without passing through the flow sharing and redirecting valve in the case that the user-1 and user-2 work simultaneously.

BRIEF DESCRIPTION OF THE FIGURES Figure 1. the diagram of an open-system hydraulic circuit where multiple pump (P1 , P2) having constant flow rate is used and which prevents lost power (N) by providing flow sharing and redirecting, and provides fuel saving.

Figure 2. the diagram of a circuit showing a case where multiple pump (P1 , P2) having constant flow rate is used, the flow sharing and redirecting valve (30) is normally in open (0) position, Q1 and Q2 flow rates that P1 +P2 pumps generate feed user-1 (10).

Figure 3. the diagram of a circuit showing a case where multiple pump (P1 , P2) having constant flow is used, the flow sharing and redirecting valve (30) is normally in open (0) position, Q 1 and Q2 flow rates that P1 +P2 pumps generate feed user-2 (10').

Figure 4. the drawing showing the circuit diagram when the user-1 (10) and user-2 (10') groups work at the same time where multiple pump (P1 , P2) having constant flow rate is used. The flow sharing and redirecting valve (30) should stay in closed (1 ) position. In this case, the Q1 flow rate that P1 pump generates feeds user-1 (10), and Q2 flow rate that P2 pump generates feeds user-2 (10'), separately.

Figure 5. is the diagram of an open-system hydraulic circuit where multiple pump (P1 , P2) having variable flow rate is used, and which prevents lost power (N) generation by providing flow sharing and redirecting, and which provides fuel saving.

Figure 6. is the circuit diagram showing the case where multiple pump (P1 , P2) having variable flow rate is used, the flow sharing and redirecting valve (30) is normally in open (0) position, Q1 +Q2 flow rates that P1 +P2 pumps generate feed user-1 (10). Figure 7. is the circuit diagram showing the case where multiple pump (P1 , P2) having variable flow rate is used, the flow sharing and redirecting valve (30) is normally in open (0) position, Q1 +Q2 flow rates that P1 +P2 pumps generate feed user-2 (10'). Figure 8. shows the circuit diagram when the user-1 (10) and user-2 (10') groups where multiple pump (P1 , P2) having varible flow rate is used, work at the same time. The flow sharing and redirecting valve (30) stays in closed (1) position. In this case, the Q1 flow rate that P1 pump generates feeds user-1 (10), and Q2 flow rate that P2 pump generates feeds user-2 (10'), separately. Figure 9. is the Backhoe-Loader application where multiple pump (P1 , P2) having constant flow rate is used.

Figure 10. is the Backhoe-Loader application where multiple pump (P1 , P2) having variable flow rate is used.

REFERENCE NUMBERS 10-10'. User-1 and user-2 P1-P2-P3. Pumps

30. Flow sharing and redirecting valve T1 -T2-T3. Tank

50-50'. Direction control valves stimulated by the operator 2.5.1 , 2.5.2. Orifices 2.6.1 , 2.6.2. Orifices

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be understood better when it is described with certain references to the above-mentioned figures and reference numbers. Figure 1 shows the diagram of an open-system hydraulic circuit where multiple pump (P1 , P2) is used, which prevents lost power (N) by providing flow sharing and redirecting, and which provides fuel saving. The users (10, 10') (cylinders, hydraulic motor, actuators) will desire to use the maximum flow rate (Qmax) in its individual workings, available on the machine in hydraulic systems; and they will need to share the present flow rate (Qmax) in the case that they work simultaneously. The users (10, 10') working most on the machine are known statistically and it should be considered that they are grouped (10, 10') by being divided into two.

In the case that the users of the divided groups (10, 10') work simultaneously;

It should be considered that double pump (P1 , P2) usage is preferred as the pump feeding source in order to provide a simultaneous working condition at different pressures for the two user groups (10, 10') at the same time. In the case that the flow rate (Q1 , Q2) that the pumps (P1 , P2) have generated when the users (10, 10') work at the same time is transferred to the user groups (10, 10') separately without being united, there will emerge no pressure difference. Likewise, in the case that single user (10 or 10') works, by using a flow sharing and redirecting valve (30) that can unite the flow rates (Q 1 , Q2) of the pumps (P1 , P2), the energy loss (N) is minimized, which is generated because of the pressure difference (ΔΡ) that is discharged when the flow rates (Q1 , Q2) is directed to the user or user group (10 or 10') that will work by uniting the flow rates. The possible energy loss (N) within the system will be the losses that will result from the resistance of the installation elements.

By using a two-position direction control valve which is normally open, the above-mentioned flow sharing and redirecting process can be conducted. What is important here is that said two-position direction control valve which is normally open can conduct the above-mentioned Logic Algorithm. In the case which is drawn in Figure 1 , the Q1 , Q2 and Q3 flow rates that all the pumps (P1 , P2, P3) generate while working are transferred to the tank (T1 , T2, T3).

In the following, the simultaneous and non-simultaneous workings of user-1 (10) and user-2 (10') will be explained in accordance with the figures.

With the logic algorithm that is formed; If only user-1 (10) is working, the flow sharing and redirecting valve (30) should always stay in normally open (0) position, (Q1 and Q2 flow rates that P1 +P2 pumps generate should feed user-1 (10).) (See Figure 2)

If only user-2 (10') is working, the flow sharing and redirecting valve (30) should always stay in normally open (0) position, (Q1 and Q2 flow rates that P1 +P2 pumps generate should feed user-2 (10').) (See Figure 3)

If the user-1 (10) and user-2 (10') groups work simultaneously; flow sharing and redirecting valve (30) should stay in closed (1) position. (Q1 flow rate that P1 pump generates should feed user-1 (10); while Q2 flow rate that P2 pum p generates should feed user-2 (10') separately.) (Figure-4).

The position-switching warnings of the valve (30) to be used for flow sharing and direction control (from 0 position to 1 position, from 1 position to 0 position) can be of any kind such as hydraulic pilot, pneumatic pilot, electrical and mechanical operated.

In the case that the operator wishes to use user-1 (10) or user-2 (10') or both of the users (10, 10') together, by using the direction control valves (50, 50') which are controlled by changing their positions, classical semi proportional valves, the pressure losses of which are lower, the pressure decrease on the valve (50, 50') may be decreased to a much lower level. By means of a special design to be applied on the direction control valve types, it is possible to use a fully proportional spool.

Figure 1 shows the diagram of an open-system hydraulic circuit where multiple constant flow pump (P1 , P2) is used, which prevents lost power (N) by providing flow sharing and redirecting, and which provides fuel saving. Q1 : P1 Main Pump Flow Rate P1 (User 1 Group movements)

Q2: P2 Main Pump Flow Rate P2 (User 2 Group movements)

Q3: P3 Pilot Pump Flow Rate P3 (Flow sharing pilot movement)

While the users (10 or 10') are working individually in a non-simultaneous manner, the flow rate (Q1 and Q2) that the P1 and P2 main pumps generate unites through the flow sharing and redirecting valve (30) and gets directed to the user (10, 10') by passing through the stimulated direction control valve (50, 50'). While the users (10 and 10') are working simultaneously together, the flow sharing and redirecting valve (30) switches its position, and the union of flow rates of the P1 and P2 pumps is prevented. The user 1 group is fed through the P1 main pump, while the user 2 group is fed through the P2 main pump.

P3 pump feeds the user-2 group (10') in the construction equipments, and at the same time provides pilot feeding for the flow sharing and redirecting valve (30) by making it to be stimulated.

Let us describe the working principle of an open-system hydraulic circuit diagram where multiple pump (P1 , P2, P3) is used representing user-1 (10) and user-2 (10') group, preventing lost power generation (N) by providing flow sharing and redirecting, and providing fuel saving.

When the pumps (P1 , P2, P3) are activated when all the circuit elements are in Figure 1 position, the direction control valves (50, 50') are in an open position to the tank (T1 , 12, 13). As long as the pilot line is open (valve numbered (50)) 20% of the flow rate (Q1 , Q2) of the P1.P2 pumps is discharged into the tank through the direction control valve numbered (50) through the orifices numbered ( 2.5.1 ) and (2.5.2); while the 80% is discharged into the tank through by-pass valves numbered (2.3.1 ) and (2.3.2) without any pressure. P3 pump is discharged into the tank (T3) through the direction control valve (50') without any pressure.

The flow sharing and redirecting valve (30) is in "0" position with spring effect in the first working. P1 and P2 pumps feed the system by getting united at this step (0) of the valve (30). The user-1 group (10) starts to work upon the stimulation of the direction control valve (50). The user-2 group (10'), on the other hand, starts to work upon the stimulation of the direction control valve (50'). When both of the valves (50, 50') are stimulated at the same time and switched to any of the positions in Figure 4 as differently than the positions in Figure 1, user-1 (50) and user-2 (50') groups start to work together. The individual and together working logic of the grouped users can be observed from the schematic diagrams given in figure-1 , figure-2, figure-3 and figure-4 for applications with constant flow rate.

The hydraulic circuit is given in Figure 5, where Q1 and Q2 flow rates generated by using P1 + P2 pumps having variable flow rate work by means of the flow sharing redirecting valve (30) in an open circuit hydraulic system, and where said valve (30) is normally at open (0) position.

Q1 : Main Pump Flow Rate P1 (User 1 Group movements) Q2: Main Pump Flow Rate P2 (User 2 Group movements)

Q3: Pilot Pump Flow Rate P3 (Flow sharing pilot movements)

While the users (10, 10') are working individually, the user-1 (10) and user-2 (10') groups are fed through P1 and P2 pumps with P1 + P2 pump flow rates (Q1 , Q2). While working together, user-1 (10) and user-2 (10') feed the system separately through the flow sharing and redirecting valve (30). While the users (10, 10') are working simultaneously, the flow -sharing and -redirecting valve (30) switches its position from (0) to (1), and therefore the union of P1 and P2 main pump flow rates (Q1 , Q2) is prevented. The user-1 (10) group and user-2 group are fed through P1 and P2 main pump, respectively. P3 pump feeds user-2 group (10') in construction equipments, and at the same time provides pilot feeding for the stimulation of flow sharing and redirecting valve (30).

Representing the user-1 (10) group and user-2 (10') group, the working principle of the flow sharing and redirecting valve (30) by locating two separate redirecting valves (50, 50') at the pilot output lines is as follows: When the pumps (P1 , P2) available in the circuit given in Figure 5 are worked, the direction control valves (50, 50') are in an open position to the tank. As long as the pilot line is open (valve (50)), the load-sensing line stimulation pilot lines of pumps (P1 , P2) are discharged into the tank without any pressure through the direction control valve (50) through 2.6 orifices. P1 and P2 pumps, the pressure line of which is closed and the load-sensing line is open to the tank (T1 , T2, T3), reset themselves at 14-15 bar. P3 pump is discharged into the tank (T3) without any pressure through the direction control valve (50'). (See Figure 5).

Flow sharing and redirecting valve (30) is in "0" position with spring effect in the first working. P1 and P2 pumps get united and feed the system. User-1 (10) group starts to work upon the stimulation of the direction control valve (50). (See Figure 6). User-2 (10') group starts to work upon the stimulation of direction control valve (50 ). (See Figure 7). In the case that both of the valves (50, 50') are stimulated, user-1 and user-2 (10, 10') start to work together (See Figure 8).

The together and separate working logics of the grouped users (10, 10') can be considered as the pump applications (P1 and P2 in figure-5, figure-6, figure-7, figure-8) having variable flow rates.

The individual workings of the users (10, 10') start with the position-switching of any of the valves (50 or 50') after getting stimulated. Working of user-1 (10) group: direction valve (50) is stimulated. Direction valve (50') is in starting position. (Figure 6). As the load-sensing line is blocked, P1 pump provides flow rate to the system. As the load-sensing line is blocked, P2 pump provides flow rate to the system. P3 pump is discharged into the tank (T3) through the valve (4) without any pressure. The flow sharing and redirecting valve (30) is kept at "0" position with the spring effect as Px=Py is available at the stimulation parts. There is a flow on the flow sharing and redirecting valve (30).

For user-1 group, P1 +P2 pumps start to provide flow rate as much as the Q1 +Q2 flow rates.

Working of user-2 group: (Figure 7) The direction control valve (50') is stimulated and takes the position at Figure 7. The direction control valve (50) is in a normal position without any stimulation. As the load-sensing line is blocked, P1 pump makes the Q1 flow rate reach to user-2. As the load sensing orifice line is blocked, P2 pump makes the Q2 flow rate reach to user-2 (10'). P3 pump makes its flow rate (Q3) reach to user-2 (10') through direction control valve (50'). As the flow sharing valve is Px=Py=user-2 (10') pressure, the spring effect is kept at position "0". For user-2 (10') group, P1 +P2+P3 pumps provide flow rate to the system as much as Q1 +Q2+Q3 flow rates.

In the case that the users (10, 10') work simultaneously together, both of the direction control valves (50 and 50 ) are required to turn into a stimulated position. (See Figure 8) Direction control valves (50 and 50') get activated together. As the P1 load sensing line is blocked,valves activate the P1 pump. As the P2 load sensing line is blocked, valves activate the P2 pump. P3 pump provides flow rate to the system through the valve numbered 4. As the flow sharing and redirecting valve (30) is Px=0; Py=User-2 pressure, it switches to position "1". P1 and P2 pumps start to provide Q1 flow rate to user-1 (10) line and Q2 flow rate to the user-2 line. As the flow sharing valve is in a closed position, even if the pumps directly work at different pressures, the user-1 (10) line uses the Q1 flow rate of P1 pump, while the user-2 line uses the Q2+Q3 flow rates of P2+P3 pumps.

The exemplary use of the above-mentioned hydraulic structure on the parts of the Backhoe-Loader construction equipment is provided. The loader part is used as the loading means. There are lift, shovel, , 4x 1 bucket cylinders on the loader. It has wide area of usage as pumps with either constant or variable flow rate.

Backhoe part is used for digging as excavator. There are boom, arm, bucket , rotation, telescopic arm cylinders thereon. In the user-1 (10) group, there are rotating, telescopic arm cylinders; and in user-2 (10') group there are boom, arm, bucket cylinders. The cylinders in user-1 (10) and user 2(10') groups can not only work individually, but also together as independently from each other. How the Backhoe- Loader application will be on the pumps with constant and variable flow rates can be observed on Figure 9 and Figure 10.