Patent Description:
<CIT> describes a hydraulic unit and a method for using the hydraulic unit. The hydraulic unit comprises a servo-motor driving two pumps, where in the servo-motor and the two pumps are connected via one shaft. Both pumps are fluidly connected to a tank.

<CIT> describes a hydraulic circuit comprising a hydraulic pump and a hydraulic motor driving the hydraulic pump, and a shutoff valve forming a shut-off circuit, allows pressure to build up between the hydraulic motor and the shut-off valve. A pressure intensifier is provided to compensate for pressure losses in the shut-off circuit. The hydraulic motor is mechanically coupled to the hydraulic pump and drives it.

<CIT> describes a hydraulic transformer controller and winch system of deep-water dynamic locating crude oil conveyor devices. The hydraulic transformer s a variable motor rigidly connected by two output shafts, specifically a traditional hydraulic transformer composed of a primary motor and a secondary motor.

<CIT> discloses another known hydraulic flow boost arrangement.

In many applications of hydraulic systems either the hydraulic consumer is far away from the tank and the power takeoff or the space for hydraulic supply or drive is limited but the system requires a working area having wide range of torque or fluid flow. In such cases, usually either expensive or space-consuming components or systems having a high number of components are used to cope with the above requirements. For example, many farm implements are installed at the front of the tractor, however in many cases the tractor power takeoff is only available at the rear. This forces the implements manufacturer to create two separate structures to avoid installing a long and winding suction pipe: a hydraulic power station structure with pump, tank, filters, cooler at the rear side; and a hydraulic operating system structure with control valves at the front side. In another example, on machines where the engine is mainly used to drive devices other than hydraulic pumps (e.g. generators or electric-machines (EM) for electric propel systems), there is no space to install hydraulic pumps, and, normally, only a small power takeoff with limited torque to drive a steering pump is available. When the system requires higher flow to move any hydraulic work functions, usually a pump through the generator / EM is mounted, which increases the cost of the electrical equipment and creates installation problems due to the high length of the assembly. In a third example, winch drives require high torque/low speed when lifting loads, and high speed/low torque when collecting the cable without load. In these cases, manufacturers often use variable piston motors or large displacement variable pumps thereby causing high installation costs.

An example of the latter system is disclosed in document <CIT> having two gerotor-type motors with similar displacement volumes. They may be operated in either a series or a parallel mode. When operated in parallel, the known arrangement produces the same torque as a single element equivalent type hydraulic motor but utilizes one half as much fluid flow and runs at a reduced speed. During operation of the motor elements in series, the motor runs at the same speed as a single element motor of equivalent size but at decreased torque. In either mode, the dual element motor utilizes one half the flow of a single element motor. However, the known hydraulic system does not provide enough variability to meet the above needs.

It shall be emphasized that assemblies containing two displacement-type ring gear machines are generally known, for example, from <CIT>. This document describes a transaxle differential which uses two identical facing rotary displacement mechanisms that better deals with loss of traction situation of two opposite wheels of a vehicle. This, however, is a fully different application and does not help to solve above problems.

Accordingly, the object underlying the invention is to provide a less costly and/or smaller but more universally usable system providing individual solutions or adaptions to the above special requirements.

This problem is solved by a hydraulic flow boost arrangement according to claim <NUM> having a first port, a second port and a tank for a working fluid and providing a flow boost, wherein the arrangement further comprises a first displacement-type ring gear machine having a first internal gear and a second displacement-type ring gear machine having a second internal gear, wherein an inlet port of the first ring gear machine is connected to the first port, an outlet port of the second ring gear machine is connected to the second port, wherein the first displacement-type ring gear machine is a motor and wherein second displacement-type ring gear machine is a pump, and a first shaft of the first internal gear and a second shaft of the second internal gear are connected such that the first shaft and the second shaft rotate with the same rotational speed. Further, the tank is in fluid communication to a first tank connection line for the working fluid, wherein a first displacement volume of the first ring gear machine is different from a second displacement volume of the second ring gear machine, wherein an inlet port of the second ring gear machine is connected to an outlet port of the first gear machine and the first tank connection line, wherein the tank is in fluid communication to the first tank connection line via a check valve means, wherein the check valve means is configured to prevent backflow of working fluid from the output port of the first ring gear machine into the tank.

In one embodiment, the first ring gear machine and the second ring gear machine is a gerotor or geroler motor.

The above arrangement consists of two displacement-type ring gear machines, e.g. gerotor motors, with different displacement volumes (short: displacements) and connected shafts rotating with the same rotational speed. This comprises that they rotate in the same rotational direction. In one embodiment, the first shaft and the second shaft are directly connected using the same shaft. Accordingly, if the first port is an inlet for hydraulic fluid and the second port is an outlet for the working fluid (the "normal" flow direction of flow boost arrangement operation), the first ring gear machine acts as a pure motor and the second ring gear machine acts as an internal gear pump and they are connected in series. As both rotate with the same rotational speed, the "flow out" of the second motor, i.e. the second port, is the "flow in" of the first motor, i.e. the first port, multiplied by the displacement difference of both gear machines, which is called multiplication ratio in the following. The multiplication ratio is calculated as the ratio of the second displacement volume and the first displacement volume if the working fluid flows from the first port to the second port. It is the reciprocal value if the arrangement is used in the opposite flowing direction, that means the working fluid flows in the opposite direction, i.e. from the second port to the first port. The necessary flow input to compensate the difference between the first and the second gear machine is sucked or fed back via the first tank connection line directly from or to the tank. A check valve means is provided between the tank and the first tank connection line to prevent backflow of working fluid from the output port of the first ring gear machine into the tank if the arrangement is used in the normal flowing direction. As a result of the above operation, the flow boost arrangement provides a fluid flow at the output port (second or first port) that is the fluid flow at the input port (first or second port) multiplied by the multiplication ratio. The multiplication ratio may be less than or greater than <NUM>. In one embodiment, this arrangement acts as a power converter, in such a way that a ratio less than <NUM> increases the flow rate and decreases the pressure, and in another embodiment with a ratio greater than <NUM> the arrangement increases the pressure and decreases the flow rate. It shall be emphasized that a ratio close to <NUM> produces a neutral effect, so that in one embodiment the difference in the ratio should at least compensate for the tolerances and efficiencies of the system, that may lead in one embodiment to a multiplication ratio less than <NUM> or in another embodiment to a multiplication ratio greater than <NUM>. Accordingly, the pressure provided at the output port is the pressure at the input port multiplied by the reciprocal of the multiplication ratio. The multiplication ratio may be adapted to the specific need of the respective system in which the arrangement is used by choosing the respective displacement volumes of the first ring gear machine and the second ring gear machine accordingly. In correspondence with the above explanation, flow "boost" is used with regard to this invention in a general way. It is used for an increase of the flow rate from the input port (first or second port) of the flow boost arrangement to the output port (i.e. the respective other port, second or first port) or for a decrease of the flow rate. This depends on the multiplication ratio observed for the respective flow direction of the working fluid through the flow boost arrangement. The invention may be used in any system or arrangement having an incompressible working fluid such as water, oil or similar.

The above object is further solved by a hydraulic system for providing a pre-defined pressure within a suction line of a pump supplying a hydraulic consumer using a pressure line, wherein the hydraulic system comprises a pump with a suction line, a pressure line and a hydraulic consumer with a return line, the pump supplying the hydraulic consumer using the pressure line, wherein the system comprises the hydraulic flow boost arrangement as described above, wherein in a first state the return line of the hydraulic consumer is connected to the first port of the hydraulic flow boost arrangement and the second port of the flow boost arrangement is in fluid communication with the suction line of the pump, wherein the system further comprises a second tank connection line which branches off the suction line and is in fluid communication with the tank of the working fluid of the flow boost arrangement via a check valve means, wherein the check valve means opens if the pressure at the output port of the flow boost arrangement is above a pre-defined pressure threshold value.

In the above system the flow boost arrangement allows the suction line of the pump to remain pressurized regardless of the flow difference between the pump outflow (i.e. the pressure line) and the return line of the hydraulic consumer. Therein the pressure line is in fluid connection with the inlet of the hydraulic consumer, e.g. a differential cylinder, and the return line is connected to the output of the hydraulic consumer. This allows to provide the tank (of the flow boost arrangement and the system) to be installed remote from the pump, for example in an application where the pump is at the rear and the hydraulic consumer with the tank is at the front of a vehicle, e.g. a tractor. This avoids the need to manufacture two structures (e.g. in the front and in the rear) for a single implement. In this embodiment, the second tank connection line connected to the tank with the second check valve means ensures a constant pressure (corresponding to the pre-defined pressure threshold value) in the suction line by compensating for the pressure losses due to the pipe length and the unevenness between pump and tank and balances the inlet pump flow in the suction line to the outlet pump flow in the pressure line. In one embodiment, the multiplication ratio of the flow boost arrangement is greater than <NUM>, for example greater than <NUM>.

In one embodiment of the above system, the hydraulic consumer is a differential cylinder, wherein the multiplication ratio of the flow boost arrangement is greater than a sections ratio of the differential cylinder, for example by <NUM> or by <NUM>. This may compensate for pressure losses along the suction line of the pump.

In one embodiment of the above system, the system further comprises a selector valve within the return line, wherein in a first position of the selector valve the system adopts the first state and in a second position of the selector valve the system adopts a second state in which the flow boost arrangement is bypassed. Bypassing the flow boost arrangement means in this embodiment, that the return line is in fluid connection with the suction line without passing the flow boost arrangement. This embodiment has the advantage that the flow boost function may be overridden when the return flow is greater than the flow in the pressure line (pump flow). This may be the case in a back movement the hydraulic consumer, e.g. the differential cylinder.

In one embodiment, the system may provide another check valve means in the suction line between the branching off of the second tank connection line and the inlet port of the pump. Alternatively or additionally, the system may provide a fourth check valve means parallel to the second check valve means but acting in the opposite direction. The third and fourth check valve means prevent cavitation during the pump start-up, wherein the third check valve means maintains flow in the suction line when the pump is stopped and the fourth check valve means allows direct suction from the tank while the flow boost arrangement is starting.

In one embodiment, in the return line, the system may comprise a filter means and/or a cooling means. Additionally or alternatively, the system may comprise a <NUM>/<NUM> way valve or a <NUM>/<NUM> way valve within the return line and the pressure line, thereby realizing a first moving direction, an opposite second moving direction of the hydraulic consumer (e.g. a differential cylinder) and/or a stop or idle position of the system.

The above object is further solved by a hydraulic system for providing a pre-defined flow range at an inlet port of a hydraulic consumer which is supplied with a pressurized working fluid by a pump, wherein the hydraulic system comprises a pump and a hydraulic consumer with an inlet port, wherein the system comprises the flow boost arrangement as described above, wherein in a first state a supply port of the pump is connected to the to the first port of the flow boost arrangement and the second port of the flow boost arrangement is connected to the inlet port of the hydraulic consumer, wherein in the first state the flow boost arrangement is used in the normal flowing direction. This allows, for example, a steering pump to be used to move work functions at the hydraulic consumer that require higher flow at lower pressure. Accordingly, in one embodiment, the pump may be connected to the first port of the flow boost arrangement via a known steering unit. This avoids to mount a pump through a generator or electric machine if there is no space to install hydraulic pumps and thereby the cost of the electrical equipment. Additionally, such system reduces the total length and facilitates the design of the structure since the flow boost arrangement can be installed anywhere. In one embodiment the multiplication ratio of the flow boost arrangement is greater than <NUM>, for example greater than <NUM>.

In one embodiment of the above system, the system further comprises a selector valve having at least a first position and a second position, wherein in the first position the system adopts the first state and the second position of the selector valve the system adopts a second state in which the flow boost arrangement is bypassed. Bypassing the flow boost arrangement means in this embodiment, that the support port of the pump is in fluid connection with the inlet port of the hydraulic consumer without passing the flow boost arrangement. This embodiment has the advantage that the flow boost function may be overridden when the greater flow provided by the flow boost arrangement is not needed by the hydraulic consumer. The hydraulic consumer may be, for example a differential cylinder or a hydraulic motor. The outlet port of the hydraulic consumer may be in fluid connection with the tank.

In one embodiment of the above system, further the selector valve comprises a third position, wherein in the third position of the selector valve the system adopts the third state in which the supply port of the pump is connected to the second port of the flow boost arrangement and the first port of the flow boost arrangement is connected to the inlet port of the hydraulic consumer, and wherein the rotation direction of the first shaft and the second shaft is reversed compared with the rotation direction of the state in which the selector valve is in the second position. In the third state the fluid flow in the flow boost arrangement is reversed with regard to the first state. This means that the multiplication ratio of the flow boost arrangement in this state corresponds to the reciprocal value of the multiplication ratio used in the first state. Such embodiment may be used if on the one hand high speed / low torque and on the other hand low speed / high torque is needed. For example, winch drives require high torque/low speed when lifting loads, and high speed/low torque when collecting the cable without load, i.e. the winch drive motor is an example of a hydraulic consumer. In this embodiment of the invention, however, the selector valve, e.g. a solenoid valve, may control input flow to the flow boost arrangement in such a way that three states are realized. In the first state the flow boost arrangement is activated such that the multiplication ratio is greater than <NUM> so that the input flow to the winch drive motor inlet port increases and, proportionally, the maximum available pressure at the winch drive motor inlet port decreases. In the second state, where the flow boost arrangement is bypassed the flow boost arrangement is deactivated and the system works without any flow or pressure boost. In the third state the flow boost arrangement operates in a "negative" flow boost mode which means that the maximum available pressure at the winch drive motor inlet port increases and, proportionally, the input flow to the winch drive motor inlet port decreases.

In one embodiment, the system may comprise a <NUM>/<NUM> way valve or a <NUM>/<NUM> way valve within the fluid connection line prior the inlet port of the hydraulic consumer and after the outlet port of the hydraulic consumer, thereby realizing a first moving direction, an opposite second moving direction of the hydraulic consumer (e.g. a differential cylinder) and/or a stop or idle position of the system.

The above object is further solved by a hydraulic system for increasing cooling efficiency comprising a pump, a hydraulic consumer, a working fluid tank, a cooling means and the flow boost arrangement as described above, wherein the tank of the flow boost arrangement is in fluid connection with the working fluid tank or forms the working fluid tank, wherein the pump provides the hydraulic consumer with cooled working fluid from the working fluid tank, wherein in a first state an outlet port of the hydraulic motor is in fluid connection with the first port of the flow boost arrangement and the second port of the flow boost arrangement is in fluid connection with an input port of the cooling means and an output port of the cooling means is in fluid connection with the working fluid tank such that the cooled working fluid is lead back to the working fluid tank. In one embodiment of this system, a multiplication ratio of the flow boost arrangement is greater than <NUM>, for example greater than <NUM>. Since the working fluid tank is in fluid connection with the tank of the flow boost arrangement or the tank of the flow boost arrangement forms the working fluid tank, in this embodiment a closed loop cooling system is created comprising the working fluid tank and, if applicable, the tank of the flow boost arrangement, the first tank connection line, the second displacement-type ring gear machine, the second port of the flow boost arrangement, the line connecting this port to the cooling means, the cooling means and the tank connection line connecting the output port of the cooling means with the working fluid tank. Within the flow boost arrangement, the working fluid from the tank provided by the first tank connection line mixes with the working fluid being at an elevated temperature from the hydraulic consumer thereby providing a first cooling step. Additionally, the flow boost arrangement provides an increase in the inlet flow so that the cooling means may be used at a higher flow rate thereby increasing heat dissipation.

In one embodiment, the above system further comprises a filter means located in the working fluid connection line connecting the second port of the flow boost arrangement and to the cooling means.

In one embodiment of the above system, the system further comprises a selector valve, e.g. a solenoid valve, having at least a first position and a second position, wherein in the first position the system adopts the first state and the second position of the selector valve the system adopts a second state in which the flow boost arrangement is bypassed. Bypassing the flow boost arrangement means in this embodiment, that the outlet port of the hydraulic consumer is in fluid connection with the inlet port of the cooling means without passing the flow boost arrangement. This embodiment has the advantage that the flow boost function may be overridden when the greater cooling efficiency provided by the flow boost arrangement is not needed in the system. The hydraulic consumer may be, for example, a differential cylinder or a hydraulic motor.

In one embodiment of above systems, the first tank connection line may be in fluid communication with the tank via a filter means to filter the working fluid when leaving the tank.

Embodiments of the invention will now be described with reference to the drawing, in which schematically and exemplarily.

<FIG> shows an embodiment of a hydraulic flow boost arrangement <NUM> comprising a first gerotor motor <NUM> and a second gerotor motor <NUM> wherein a first shaft <NUM> of the first gerotor motor <NUM> is directly connected to a second shaft <NUM> of the second gerotor motor <NUM> such that the first shaft <NUM> and the second shaft <NUM> rotate with the same rotational speed in the same direction. As shown in <FIG> the first shaft <NUM> and the second shaft <NUM> form a common shaft. The flow boost arrangement <NUM> further comprises a first port <NUM> connected to the inlet port 11a of the first gerotor motor <NUM> and a second port <NUM> connected to the outlet port 12b of the second gerotor motor <NUM>. An outlet port 11b of the first gerotor motor <NUM> is in fluid communication with the inlet port 12a of the second gerotor motor <NUM> via conduits <NUM> and <NUM>. Further, a working fluid tank <NUM> is provided which is in fluid communication with the inlet port 12a of the second gerotor motor via the first tank connection line <NUM> and conduit <NUM>, wherein in the first tank connection line <NUM> a check valve <NUM> is provided to avoid backflow of the working fluid into the tank <NUM>.

In the embodiment shown in <FIG> working fluid flows from the first port <NUM> to the input port 11a of the first gerotor motor <NUM> that operates as a motor driving by its first shaft <NUM> the second shaft <NUM> of the second gerotor motor <NUM> that operates as a pump. The working fluid is communicated from the output port 11b of the first gerotor motor <NUM> to the input port 12a of the second gerotor motor <NUM>. The second gerotor motor <NUM> pumps the working fluid to its output port 12b and further to the second port of the flow boost arrangement. In this embodiment, the first displacement volume V1 of the first gerotor motor <NUM> is, e.g., V1 = <NUM><NUM> and the second displacement volume V2 of the second gerotor motor <NUM> is, e.g. V2 = <NUM><NUM>. Accordingly, the multiplication ratio of the flow boost arrangement in the shown operation mode is V2/V1 = <NUM>. Accordingly, if, for example, a flow rate of <NUM>/min is provided at the first port <NUM>, the second gerotor motor <NUM> pumps a flow rate of <NUM>/min working fluid and provides this flow rate at its second port <NUM>. The second gerotor motor <NUM> receives <NUM>/min from the first gerotor motor <NUM> and sucks another <NUM>/min from the working fluid tank <NUM>. Hence, the flow boost arrangement doubles the input flow rate received at its first port <NUM> in accordance with its multiplication ratio and provides it at its second port <NUM>. Correspondingly, the pressure at the second port drops approximately by a factor equal to the multiplication ratio compared with the pressure at the first port.

<FIG> and <FIG> show a first application of a flow boost arrangement <NUM> which is, for example, an application for use in a large vehicle like a tractor <NUM>. The tractor <NUM> comprises a manifold of different hydraulic consumers, containing, e.g. a differential cylinder <NUM> in the front as well as the tank <NUM> for a working fluid, a cooling means <NUM>, a filter means <NUM> and the flow boost arrangement <NUM> as shown in more detail in <FIG>. The flow boost arrangement <NUM> with tank <NUM>, the cooling means (cooler) <NUM>, the filter means (filter) <NUM>, a selector valve <NUM> as well as a second tank connection line <NUM> forming an assembly <NUM> which is shown in <FIG>, wherein <FIG> symbolizes the local set-up of the system's components.

In the first state of the system shown in <FIG> the pressurized output flow of a pump <NUM> is connected via a pressure line <NUM> to an inlet port <NUM> of the differential cylinder <NUM>. The second (output) port <NUM> of the differential cylinder <NUM> is in fluid connection with the first port <NUM> of the flow boost arrangement <NUM> via a return line <NUM>, a <NUM>/<NUM> way valve <NUM>, the filter means <NUM>, the cooler means <NUM> and a solenoid selector valve <NUM> having a first position as shown in <FIG>. The second port <NUM> of the flow boost arrangement <NUM> is connected via a suction line <NUM> to the input port of the pump <NUM>. The flow boost arrangement <NUM> may be constructed similar to the flow boost arrangement <NUM> shown in <FIG> but having a multiplication ratio of <NUM>, wherein, for example, the first gerotor <NUM> has a displacement volume of <NUM> cm3 and the second gerotor <NUM> a displacement volume of <NUM> cm3 producing a magnification ratio of <NUM>. The input flow rate at the first port <NUM> of the flow boost arrangement <NUM> is, for example, <NUM>/min revealing an output flow rate at the second port <NUM> of the flow boost arrangement <NUM> of <NUM>/min. The tank <NUM> of the working fluid is further in fluid communication via a second tank connecting line <NUM> with the suction line <NUM>. In the second tank connecting line <NUM>, a check valve <NUM> is provided. Further, parallel to the check valve <NUM> second check valve <NUM> is accommodated, wherein the second check valve <NUM> is provided which opens if the pressure above the check valve <NUM> is higher than a pre-defined threshold value, e.g. <NUM> bar. The <NUM> bar check valve <NUM> ensures a constant pressure in the suction line <NUM> thereby compensating for the pressure losses due to the pipe length and the unevenness between pump and tank. It further balances the inlet pump flow to the outlet pump flow at, e.g., <NUM>/min. Accordingly, the working fluid flows into the tank <NUM> via the second tank connecting line <NUM> if the flow rate at the inlet of check valve <NUM> is greater than or equal to <NUM>/min and the pressure at the check valve <NUM> is greater than <NUM> bar.

It shall be indicated, that according to the embodiment present at <FIG> and <FIG> the differential cylinder <NUM> may have a sections ratio of <NUM>:<NUM>. For such sections rate the above dimensions of the elements having the above flow boost arrangement <NUM> as indicated above may be used.

In a second position of the selector valve <NUM> the system provides a second state, in which the flow boost arrangement <NUM> is bypassed by connecting the return line <NUM> to the suction line <NUM>. This state is used if there is a higher pressure in the return line <NUM>.

Further, the system comprises a <NUM>/<NUM> way valve <NUM> realizes a first and a second movement direction (left and right position) of the differential cylinder <NUM> as well as a stop/idle state (middle position).

The system shown in <FIG> and <FIG> allows the suction line <NUM> to remain pressurized regardless of the flow difference between the pressure line <NUM> and the suction line <NUM>.

Another application of the flow boost arrangement is shown in the embodiments of <FIG> in which systems are described realizing states proving different flow rates / torque to a hydraulic consumer (e.g. a motor <NUM> or a differential cylinder <NUM>).

The embodiment shown in <FIG> allows a steering pump to be used to move work functions that requires higher flow at lower pressure (first state) and lower flow at higher pressure (second state). A pump <NUM> is connected via a steering unit <NUM> to a conduit <NUM>. The conduit <NUM> may be connected with an overpressure relief element <NUM> which provides in the second state of a solenoid selector valve <NUM> as shown in <FIG> the working fluid flowing in conduit <NUM> bypasses the flow boost arrangement <NUM> similar to the one depicted in <FIG> and is in fluid communication with the inlet port <NUM> of a manifold <NUM> comprising several hydraulic consumers such as a differential cylinder or a motor (e.g. motor <NUM>). The outlet port <NUM> of the manifold <NUM> is connected to a tank <NUM>. In the second state, the flow rate is rather small. If the solenoid selector valve <NUM> is in the second position the system adopts a first state providing a higher flow rate at the manifold inlet port <NUM> than in the second state. In this case, the conduit <NUM> is connected to the first port <NUM> of the flow boost arrangement <NUM>, wherein the second port <NUM> of the flow boost arrangement <NUM> is connected to the inlet port <NUM> of the manifold <NUM>. In the first state the flow rate at the second port <NUM> of the flow boost arrangement <NUM> is the flow rate at the first port <NUM> of the flow boost arrangement <NUM> multiplied by the multiplication ratio. Accordingly, if the multiplication ratio is greater than <NUM> the flow rate at the inlet port <NUM> will be greater in the first state compared with the second state of the system and the torque provided at the inlet port <NUM> is calculated from the pressure at the first port <NUM> of the flow boost arrangement <NUM> by applying a factor that is the reciprocal of the multiplication ratio.

The embodiment of a system depicted in <FIG> comprises a winch <NUM> that is driven by the hydraulic motor <NUM> forming a hydraulic consumer. The system realizes three states that are shown in <FIG>. In the first state depicted in <FIG>, a high flow and low torque is needed at the input port of the hydraulic motor <NUM> to rotate the winch <NUM> fast with low load (to collect the cable <NUM>). <FIG> shows the situation (third state) in which a medium flow and torque is needed at the input port of the hydraulic motor <NUM> to lift a medium-sized load <NUM>. In the second state illustrated in <FIG> the hydraulic motor <NUM> lifts a high load <NUM> so that a low flow rate and a high torque is needed at the input port of the hydraulic motor <NUM>.

Analogous to the embodiment shown in <FIG> the system comprises the pump <NUM>, the conduit <NUM>, the flow boost arrangement <NUM> (the check valve <NUM> is not shown), a first <NUM>/<NUM> way selector valve <NUM>, a second <NUM>/<NUM> way selector valve <NUM>, the hydraulic motor <NUM> and the tank <NUM> as depicted in <FIG> showing different states of the system. The pump pressurizes the input port of the hydraulic motor <NUM> for the winch <NUM> via the first selector valve <NUM> and the second selector valve <NUM>. The first selector valve <NUM> is used to select one of three different states of the system dependent on the position of the valve <NUM>. By the second selector valve <NUM> the user chooses the rotation direction of the winch (first direction if the left position is taken and second, opposite direction if the right position is taken). If the second selector valve <NUM> uses the center position as indicated in <FIG> the system is in a stop or idle position.

The second state depicted in <FIG> is realized by the system by taking the center position of the selector valve <NUM> as shown in <FIG>. The pump, for example, provides the working fluid with a flow rate of <NUM>/min and a pressure of <NUM> bar. A medium rotation speed of the hydraulic motor <NUM> is provided.

The first state shown in <FIG> is adopted by using the selector valve <NUM> such that it accommodates the left position (see <FIG>). The working fluid passes the flow boost arrangement <NUM> thereby increasing the flow rate from <NUM>/min to <NUM>/min and reducing the pressure from <NUM> bar to <NUM> bar. Accordingly, the winch <NUM> may be moved with high rotation speed but lifts only a small load due to its low torque provided.

In the latter position of the first selector valve <NUM> (right position) shown in <FIG> the direction of the fluid flow through the flow boost arrangement <NUM> is reversed so that the inlet flow is provided at the second port <NUM> and the outlet flow at the first port <NUM>. Accordingly, the multiplication ratio is the reverse value compared to the multiplication factor used in the first state of the system (see <FIG> and <FIG>).

<FIG> depict an embodiment of the system similar to the one illustrated in <FIG> and <FIG>, wherein the hydraulic consumer is a differential cylinder <NUM>, that works similar to the embodiment shown in <FIG>. The system further comprises additionally a <NUM>/<NUM> way selector valve <NUM> for selecting the moving direction of the hydraulic cylinder <NUM> (left and right position) and for providing a stop or idle position. Additionally or alternatively, the system may comprise a counterbalance valve <NUM> accommodated in the conduit between the hydraulic cylinder <NUM> and the selector valve <NUM>. The system realizes a first state shown in <FIG> where a low load <NUM> may be moved with high speed due to flow boost provided by the flow boost arrangement <NUM> (the check valve <NUM> is not shown).

In the second state the flow boost arrangement <NUM> is bypassed so that a higher load <NUM> may be moved by the differential cylinder <NUM> at lower speed (low flow, high pressure)
<FIG> shows a diagram in which on the left-hand side the heat dissipation at ΔT = <NUM> is drawn for different cooler types (OK-ELH <NUM>, <NUM>, <NUM>, <NUM> and <NUM>) used at different rotational speed (<NUM>, <NUM>, <NUM>, <NUM> rpm) over the flow rate of the coolant oil in l/min. On the right-hand side the respective specific heat dissipation [kW/K] is provided. Both marked points <NUM> and <NUM> illustrate, for example, that for the cooler OK-ELH <NUM> by using a coolant flow rate of <NUM>/min a heat dissipation of <NUM> kW is provided whereas with the same cooler type and a double flow rate of <NUM> kW a heat dissipation of <NUM> kW may be provided. This is <NUM>% more than when using the flow rate of <NUM>/min. Accordingly, the heat dissipation may be considerably increased by increasing the flow rate. Hence, usually designers of cooling systems select the size of the cooler based on the flow available for cooling which may be expensive for larger flow rates.

Accordingly, the embodiment shown in <FIG> provides a system having an increased cooling rate. This is realized by using the flow boost arrangement as depicted in <FIG> and creating a closed loop system component that decreases the temperature faster thereby increasing cooling efficiency.

This system comprises a tank <NUM> which supplies the flow boost arrangement <NUM> with the working fluid but also a hydraulic consumer in form of a motor <NUM>. Particularly, the tank comprises cooled working fluid to the motor <NUM> driven by a pump <NUM> and a filter <NUM>. The rotational direction of the motor <NUM> as well as the stop/idle position of the system is controlled by a <NUM>/<NUM> way selector valve <NUM>. An output port <NUM> of the motor <NUM> is in fluid communication with the first port <NUM> of the flow boost arrangement <NUM> via a second solenoid selector valve <NUM>. The second selector valve <NUM> has two positions. If the second selector valve <NUM> is in the first position shown in <FIG>, a first state will be adopted in which increased cooling will be provided by the flow boost arrangement <NUM>. In the second position of the second selector valve <NUM> the flow boost arrangement <NUM> is bypassed thereby providing lower heat dissipation as indicated below (second state).

Referring to the first state shown in <FIG> the second port <NUM> is in fluid communication with the tank <NUM> via a filter means <NUM> and a cooling means <NUM>. Accordingly, the working fluid cooled by the cooling means <NUM> flows back into tank <NUM>. Because the flow boost arrangement <NUM> comprises the tank <NUM>, as well, as a source for additional flow for provision to the second gerotor <NUM>, the cooled working fluid is mixed with the working fluid received from the motor <NUM> at the inlet port of the second gerotor <NUM>. Accordingly, a closed loop is created comprising the second gerotor <NUM>, the filter means <NUM>, the cooling means <NUM> and the tank <NUM>.

Claim 1:
A hydraulic flow boost arrangement (<NUM>) comprising a first port (<NUM>), a second port (<NUM>) and a tank (<NUM>) for a working fluid, further comprising a first displacement-type ring gear machine (<NUM>) having a first internal gear and a second displacement-type ring gear machine (<NUM>) having a second internal gear, wherein an inlet port (11a) of the first ring gear machine (<NUM>) is connected to the first port (<NUM>) and an outlet port (12b) of the second ring gear machine (<NUM>) is connected to the second port (<NUM>), wherein the first displacement-type ring gear machine (<NUM>) is a motor and wherein second displacement-type ring gear machine (<NUM>) is a pump, wherein the tank (<NUM>) is in fluid communication to a first tank connection line (<NUM>) for the working fluid, wherein a first shaft (<NUM>) of the first internal gear and a second shaft (<NUM>) of the second internal gear are connected such that the first shaft (<NUM>) and the second shaft (<NUM>) rotate with the same rotational speed, wherein a first displacement volume (V1) of the first ring gear machine (<NUM>) is different from a second displacement volume (V2) of the second ring gear machine (<NUM>), wherein an inlet port (12a) of the second ring gear machine (<NUM>) is connected to an outlet port (11b) of the first gear machine (<NUM>) and the first tank connection line (<NUM>), wherein the tank (<NUM>) is in fluid communication to the first tank connection line (<NUM>) via a check valve means (<NUM>), wherein the check valve means (<NUM>) is configured to prevent backflow of working fluid from the output port (11b) of the first ring gear machine (<NUM>) into the tank (<NUM>).