The invention refers to a hydraulic circuit of a mobile hydraulic crane, namely of a crane, which is either during transporting thereof in its folded i.e. inactive position, or also during its operation, mounted onto a motor vehicle chassis. Such crane is generally powered by hydraulic driving means, which are energized via a hydraulic powering system of a belonging motor vehicle. Pursuant to the International Patent Classification (IPC ), such invention belongs to transporting and hoisting, namely to foldable hydraulic jib cranes in the class B 66 C 23/86.

The purpose of the invention is to assure that in a hydraulic circuit, which is intended for energizing of hydraulic driving means which are disposable on a crane, on the one hand each one of said hydraulic driving means should be, independently on status of the residual hydraulic driving means on the same crane, all the time supplied with a sufficient quantity of properly compressed hydraulic media, while on the other hand, supplying of excessive quantity of said compressed hydraulic media towards each particular hydraulic means, or also towards various control valves, which serve for regulating the flow of said hydraulic media towards each particular driving unit, should be excluded.

A mobile hydraulic crane as such is mounted onto a chassis of a motor vehicle and is to this aim furnished with a base frame, which is as such firmly connected with said vehicle chassis and on which a crane column is mounted rotatably around a vertical geometric axis, so that said column is, like a cantilever, embedded within said base frame in such reliable manner that the crane is able to lift and displace a load. A primary crane arm is attached to a free terminal area of said column pivotally around a horizontal geometric axis, while a secondary crane arm is attached to a free terminal area of said primary arm, also pivotally around a horizontal geometric axis, wherein said secondary arm can optionally be telescopically conceived and is in such case furnished with a hydraulic driving assembly, which is intended for translatory displacement of each into another inserted bearing tubes or profiles of such telescopic secondary arm to and fro with regard to each other. A grabber, which is suitable for manipulating each load, is pivotally, either directly or indirectly via a suitable hydraulic rotating unit, connected to the free terminal area of said secondary arm. Said hydraulic rotating unit includes a hydraulic motor, which is suitable for controlled rotation of the grabber around a vertical geometric axis. Said primary arm is supported on said column by means of a hydraulic cylinder, which is on the one hand pivotally attached to the column and on the other hand also pivotally to the primary arm. Quite analogously, Said secondary arm is supported on said primary arm by means of a hydraulic cylinder, which is on the one hand pivotally attached to the primary arm and on the other hand also pivotally to the secondary arm. Said hydraulic cylinders are together with each belonging control components integrated within a hydraulic circuit of the crane, which is hydraulically connectable with a hydraulic powering unit on a motor vehicle, on which said crane is mounted.

As mentioned, said column is rotatably around the vertical geometric axis embedded within the base frame. To this aim, the base frame is in its central area furnished with a substantially cylindrical passage, within which a substantially cylindrical section of the column is inserted, wherein at least two roller bearings, which are spaced apart from each other in a vertical direction, are mounted between the inner wall of said passage and the external surface of said cylindrical section of the column and are suitably spaced apart from each other in a vertical direction. Such arrangement allows on the one hand a stable anchoring of a cantilevered column into the base frame, and on the other hand also a required rotation of the column around the vertical geometric axis. In order to enable said rotation of the column, the column is, either on its circumference or on its front surface, furnished with a gear, which is arranged in a horizontal plane and is adjusted for cooperation with a pair of gear racks, which are arranged in parallel with each other and are simultaneously displaceable in a horizontal plane and in opposite directions with regard to each other, wherein each of said gear racks is each per se displaceable by means of a hydraulic cylinder, so that two hydraulic cylinders are arranged within the area of said base frame, which extend parallel with each other and which are adjusted for simultaneously acting in opposite directions.

Said base frame for attachment of the crane onto a motor vehicle chassis among others comprises a tubular bearing member, in which supporting legs are inserted, which are intended for supporting and maintenance of stability of the crane during the operation thereof. Each of said supporting legs comprises a horizontal bearing member, which is insertable into said tubular bearing member on the base frame, as well as a vertically towards the ground extending telescopic supporting leg. By transporting of the crane in a folded state thereof. Said horizontal bearing member of each supporting leg is pushed into the interior of said tubular horizontal bearing member of the base frame and is properly secured against any further undesired displacement. Prior to activation of the crane, each horizontal bearing member of the belonging supporting leg is extracted at certain extent and secured against further displacing, upon which by means of extension of telescopic supporting legs due to reliable resting thereof onto the ground, the crane is in a stable manner supported on the ground, which is usually assured in at least two points located outside of the horizontal silhouette of the vehicle. Also said displacement and vertical expansion of the supporting legs is performed by means of suitable hydraulic driving means, i.e. hydraulic cylinders.

Therefore, various hydraulic driving means are mounted on a mobile hydraulic crane, depending on type and configuration thereof, in particular hydraulic cylinders serving for displacement of supporting legs in horizontal and vertical direction, said pair of hydraulic cylinders as required for rotating the column, said cylinder for supporting and pivoting of said primary arm, said cylinder for supporting and pivoting of said secondary arm, said hydraulic driving means for displacement of telescopic bearing sections of the secondary arm, said hydraulic motor for rotating said grabber as well as hydraulic driving means for manipulating said grabber as such. In fact, there is a plurality of different hydraulic driving means, which may essentially differ from each other with regard to quantity of the hydraulic media, which needs to be supplied to each of them during their operation, wherein these driving means may generally be activated or deactivated either in correlation with each other, or also quite independently on each other, with the sole purpose, that the operator could be able to control all these crane components precisely, accurately and synchronously.

All the hydraulic driving means, which stay at the disposal on each particular crane, are hydraulically integrated either into a single hydraulic circuit, or optionally also into several hydraulic circuit. In general, a reservoir with the hydraulic media and a pump for compressing and distributing the hydraulic media from said reservoir towards each particular hydraulic components are foreseen to this aim, wherein said distribution of the hydraulic media is generally performed via hydraulic conduits either directly or in most cases indirectly via various hydraulic control units, e.g. control valves or proportional valves, which enable proper and controlled distribution of the hydraulic media towards the each particular hydraulic driving means in order to assure a precise and accurate operation of each of said hydraulic driving means per se.

Said hydraulic media reservoir is usually mounted, or can be mounted, on a vehicle, on which the crane is mounted, and the same also applies for the hydraulic pump, which is moreover also driven by means of a vehicle engine, therefore in most cases by an internal combustion engine. By trucks, which are suitable for mounting of a crane thereon, the engine is usually positioned in the front area of the vehicle, wherein the torque transmission towards the rear wheels of the vehicle is established by means of a shaft, which extends in a longitudinal direction of the vehicle. Said shaft is, similarly like on tractors or similar construction machines, furnished with an additional connecting nipple, by which a pump can be, either directly or indirectly via a suitable transmission gearbox, mechanically interconnected just in order to become rotatable by means of said vehicle engine. The pump is therefore driven by means of a shaft, which is rotated by a predetermined revolution rate and may eventually be varied within a pre-determined area, although in general said revolution rate should preferably be at least approximately constant. Namely, each increasing of the revolution rate would lead to increasing of fuel consumption together with substantial increasing of emission of exhaustion gases and noise. As said, during operation of the crane the truck is stabilized in a desired position, and all these consequences are generally undesired. On the other hand, as mentioned, there are numerous hydraulic components mounted on the crane, which during their operation require different quantities of the hydraulic media, so that during operation of the crane as a whole, the complete required quantity of the hydraulic media, which needs to be forwarded to each active hydraulic components during the time may also essentially vary. Consequently, whenever a pump is used, which is driven by a shaft with approximately constant turning rate, it should be a pump with a variable flow rate, which means that despite to constant turning rate of the driving shaft of the pump, the flow rate of the hydraulic media exiting the pump can be regulated either manually or by means of a suitable electronic control unit. However, such pumps, including the belonging control appliances, are much more complicated than just simple pumps with constant flow rate, and are moreover also much more risky in view of potential irregularities and defects. In such pumps also the yield is usually lower than in pumps with constant flow rate, wherein the losses among others result in generation of heat, which leads to overheating, and an additional hydraulic media cooler must often be used in a hydraulic circuit, furnished with such a pump. In addition to that, each changing of the flow rate in such pumps is performed slowly, so that is difficult to accommodate it to each particular requirements and quick changes, which occur by controlling of different hydraulic components. As a consequence, in the field of cranes the pumps should generally be simple and reliable pumps with a constant flow rate, which are by a predetermined and at least approximately constant rotation speed capable to provide at least approximately constant outflow rate of the hydraulic media from the pump towards the hydraulic circuit, wherein the pressure can then also be adjusted in a suitable manner and in accordance with each particular needs. When using a pump with a constant flow rate, one should bear in mind that the pump must be selected with regard to a maximal estimated flow rate within each particular hydraulic circuit, which might occur, if all hydraulic components integrated within the circuit would be simultaneously activated, wherein each one of disposable hydraulic component would have to be supplied with a required quantity of properly compressed hydraulic media. On the contrary, certain irregularities might occur during operation of certain control valves, which could lead to proportional effects and various interactions between these components. In general, hydraulic components might also be arranged within several separate hydraulic circuits, wherein each one of such circuits could be furnished with its own pump, but in such case the complete hydraulic system would be much more expensive and also much more complicated, since several pumps would have to be driven simultaneously by the same shaft, wherein the pumps would also have to be controlled and accommodated depending on actual needs of each corresponding hydraulic components including each belonging control means.

In the practice, two types of hydraulic circuits are used for the purpose of energizing and controlling of hydraulic driving means on cranes, namely i) hydraulic circuits with integrated pump with a constant flow rate in combination with open center directional control valves, which are at present commercially available as type DX6 manufactured by Hydac, or type Hl 70 manufactured by Parker; or ii) hydraulic circuits with integrated pump with variable flow rate in combination with closed center load sensing directional control valves, which are at present commercially available as type LX6 manufactured by Hydac, or type L90LS manufactured by Parker; or also as type PVG32, type PVG16 or type PVG100 manufactured by Danfoss. Hydraulic circuits from the first group i) are typically reliable and economic, and are able to react quickly to each change or shifting of control valves. In such case, the pump must permanently assure maximal required quantity of the hydraulic media, which is needed by simultaneous operation of all hydraulic components, while each activation of each particular hydraulic component is performed by means of a corresponding control valve. In the area of each active hydraulic component, the hydraulic media is re-directed back to the reservoir. Consequently, the whole required quantity of the hydraulic media permanently circulates within the hydraulic circuit, and is in the area of each active hydraulic component guided through the component, while in each inactive hydraulic components the hydraulic media is by-passed back to reservoir. Such concept therefore leads to the need on flowing a huge quantity of the hydraulic media through different control valves, although an essential part thereof is not used at all, which sometimes makes difficult controlling by simultaneous activation/deactivation of several hydraulic components, and which in particular also leads to essential energy losses, which results in excessive fuel consumption and emissions by powering the pump, and also in essential heating or even overheating of the hydraulic media, which leads to negative impact in view of reliability of hydraulic components and sometimes also to generation of unpleasant noise.

In hydraulic circuits from the second group ii) the quantity of the hydraulic media, which is each time circulated within the hydraulic circuit, is typically adjusted to each actual needs of the hydraulic components, but for such purpose a pump with variable flow rate must be integrated within such a hydraulic circuit, and such pump must be combined with proportional valves, which are controlled on the basis of signals, which are received either from an electronic control unit or from sensors, which are suitable for detecting of operational activity of each particular hydraulic component. This means that in each particular circumstances a proportional valve, which belongs to each hydraulic components, is activated either on the basis of a command, or on the basis of a signal as received from the corresponding sensor, upon which a signal is generated as an information about the required quantity of the hydraulic media, which is then transmitted to the hydraulic pump, which on the basis of said signal starts supplying a required quantity of the hydraulic media. Such concept can be supported by modem electronic hardware and software, but is very complex and requires much more constituent parts, and is therefore also quite risky and exposed to wide range of potential irregularities.

Within the context of the aspects, which refer to the first group i), there are several known hydraulic circuits which are suitable for application on cranes, and which are disclosed in the prior art. For example, a pretty complex hydraulic circuit is disclosed in RU 2087408 Cl, in which each particular hydraulic component is integrated within its own hydraulic circuit, which includes a hydraulic pump and all required control valves. This means that, on a crane, each hydraulic cylinder or each hydraulic rotating unit needs to be furnished with its own hydraulic pump, which results in enormous manufacturing expenses and in addition to that, just mounting of a plurality of pumps together with each belonging driving means also requires a lot of space.

On the other hand, also within the context of the aspects, which refer to the second group ii), there are several known hydraulic circuits which are suitable for application on cranes, and which are disclosed in the prior art. For example, a crane is disclosed in WO 2008/143584 Al, which is furnished with substantially all previously mentioned hydraulic components. The aim of said known solution is adjusting the pressure of the hydraulic media to each particular loadings on the primary crane arm, by which on the one hand each potential overloading of the crane could be a priori excluded, while on the other hand, inefficient operation of unloaded crane under excessive pressure of the hydraulic media supplied by the pump could also be avoided. To this aim, a control valve is integrated between the pump and each hydraulic driving means, and is controlled by means of an electronic control unit on the basis of parameters, which depend on the one hand on position of crane arms and on the other hand on signals, which are received from sensors, which are arranged on surfaces on pistons in cylinders, which are exposed to pressure of the hydraulic media. Said control unit is pretty complicated and must also be supported by a pretty complex software, which should take care on the one hand about maintaining of maximal pressure within the cylinder between the crane column and the primary crane arm, and on the other hand for monitoring of pressure differences i.e. differential pressure in other hydraulic driving units in order to assure supplying of a sufficient amount of the hydraulic media to all hydraulic driving units. The main problem of such controlling is a quite complicated concept, which in practice during operation of the crane in different conditions leads to essential differences between pre-determined ideal parameters, which are determined on the basis of a mathematical model, and real parameters, on the basis of which in each particular circumstances operation of the crane would actually have to be controlled. In addition to that, each type of the crane requires development of a special software version.

The present invention refers to a hydraulic circuit of a mobile hydraulic crane, wherein such circuit comprises at least

- a reservoir, which is suitable for collecting and storage of each required quantity of a hydraulic media; - a hydraulic pump, which is suitable for pumping said hydraulic media at a predetermined flow rate as well as for compressing said hydraulic media to a predetermined pressure, as well as

- each required hydraulic driving units, which are suitable for displacing and positioning of mechanical constituent parts of the crane.

In this, each of said hydraulic driving units is equipped with a control valve, which is either hand-operated or is operated in any other manner, and which is suitable for directing of said hydraulic media to flow either into each belonging hydraulic driving unit, or via a reverse hydraulic conduit back to said reservoir. Moreover, said hydraulic pump is on the one hand by means of a sucking conduit hydraulically interconnected with said reservoir and is on the other hand by means of a compression conduit hydraulically interconnected with at least one group of said control valves, which are each per se hand-operated or otherwise actuated. Each one of said control valves is hydraulically interconnected on the one hand with each belonging hydraulic driving unit and on the other hand, either per se or jointly within the belonging group, also with the reservoir.

The invention proposes that said hydraulic pump is a hydraulic pump with a constant flow rate, namely a hydraulic pump, which by a pre-determined constant rotation speed thereof provides a constant flow rate of the hydraulic media, which is supplied to it from the reservoir, and that each one of said groups of control valves intended for controlling of hydraulic driving units suitable for displacing and positioning of mechanical constituent parts the crane is a hand-operated closed center proportional valve, which is capable to generate an electric signal as soon as at least one of said control valves within the group is activated, as well as that a hydro-logic valve is integrated within said compression conduit between the hydraulic pump and each disposable group of said control valves for controlling said hydraulic driving units on the crane, and is suitable for adjusting of a flow rate of the hydraulic media on the basis of a signal transmitted to it. Said hydro-logic valve is on the one hand via hydraulic conduits hydraulically interconnected with each of said groups of control valves for controlling said hydraulic driving units on the crane, and on the other hand via said reverse hydraulic conduit with the reservoir. In addition to that, said hydro-logic valve is in the view of a required signal transmission electrically interconnected with each of said groups of control valves for controlling said hydraulic driving units on the crane and is adjusted, on the one hand, to permit just a partial quantity of the hydraulic media to flow therethrough, which is currently required on the basis of a received signal about currently activated control valves which are required for operation of just those hydraulic driving units, which are hydraulically interconnected with currently activated control valves, and on the other hand, instead of directing of the complete amount of the hydraulic media supplied by said pump with a constant flow rate towards the groups of control valves for controlling of hydraulic driving units on the crane, said hydro-logic valve is also capable to re-direct the excessive hydraulic media flow via the reverse conduit back to the reservoir.

A further embodiment of the invention provides that said hydraulic circuit is equipped with at least two hydraulic pumps with constant flow rate, which are on the one hand, each per se, via suction conduits hydraulically connected with a single common reservoir, while on the other hand each of said hydraulic pumps is via a compression conduit hydraulically connected with at least one of said groups of control valves for controlling of hydraulic driving units on the crane, wherein a hydro-logic valve is integrated in the area of each of said compression conduits of each one of said pumps, namely in the area between each pump and each group of control valves for controlling of hydraulic driving units on the crane, which is connected therewith. Said hydro-logic valve is in the view of a required signal transmission electrically interconnected with each one of said groups of control valves for controlling said hydraulic driving units on the crane and is adjusted, on the one hand, to permit just a partial quantity of the hydraulic media to flow therethrough, which is currently required on the basis of a received signal about currently activated control valves which are required for operation of just those hydraulic driving units, which are hydraulically interconnected with currently activated control valves, and on the other hand, instead of directing of the complete amount of the hydraulic media supplied by said pump with a constant flow rate towards the groups of control valves for controlling of hydraulic driving units on the crane, said hydro-logic valve is also capable to re-direct the excessive hydraulic media flow via the reverse conduit back to the reservoir.

Said groups of control valves for controlling of hydraulic driving units on the crane are configured on the basis of estimated functional interactions among the hydraulic driving units and also on the basis of estimated partial flow rates required for reliable operation of said hydraulic driving units either by solely operation of each one of them or by their simultaneous operation.

In one of the embodiments of the invention, said control valves in the first group are hydraulically connected with the driving units, which serve for displacing of supporting legs on the crane in a direction apart from each other and also for extraction thereof, while the hydraulic driving units for displacing and positioning of the residual constituent parts of the crane are hydraulically connected to form at least two further groups of control valves, which are each per se via hydraulic conduits connected with said hydro-logic valve. The invention will be described in more detail on the basis of embodiments and with reference to the attached drawings, in which

Fig. 1 is a schematically presented embodiment of a hydraulic circuit of a mobile hydraulic crane;

Fig. 2 is a schematically presented further embodiment of a hydraulic circuit of a mobile hydraulic crane; and

Fig. 3 presents a mobile hydraulic crane in front view, which is furnished with hydraulic driving units, which are powered by hydraulic media and integrated in the hydraulic circuits according to Figs. 1 and 2.

Hydraulic circuit 1 of a mobile hydraulic crane 9, an embodiment of which is presented in Fig. 1, comprises at least a reservoir 2, which is suitable for collecting and storage of each required quantity of a hydraulic media, a hydraulic pump 3, which is suitable for pumping said hydraulic media at a pre-determined flow rate as well as for compressing said hydraulic media to a pre-determined pressure, as well as each required hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79, which are suitable for displacing and positioning of mechanical constituent parts 81, 82, 83, 84, 85, 86, 87, 88 of the crane 8, wherein each of said hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79 is equipped with a hand-operated or otherwise actuated control valve 41, 42, 43; 51, 52, 53; 62, 62, 63, which is suitable for directing of said hydraulic media to flow either into each belonging hydraulic driving unit 71, 71', 72, 73, 74, 75, 76, 77, 78, 79, or via a reverse hydraulic conduit 456 back to said reservoir 2.

Said hydraulic circuit 1 is in Fig. 1 presented in an embodiment, which includes a single hydraulic pump 3, while in the hydraulic circuit according to Fig. 2 two hydraulic pumps 3, 3’ are foreseen. But in each case each disposable hydraulic pump 3, 3’ is on the one hand by means of a sucking conduit 31 hydraulically interconnected with said reservoir 2, while on the other hand it is by means of a compression conduit 32; 324, 325, 326 hydraulically interconnected with at least one group 4, 5, 6 of control valves 41, 42, 43; 51, 52, 53; 62, 62, 63, which are each per se hand-operated and adapted for controlling of said hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79.

In the shown embodiments (Figs. 1 or 2 in connection with Fig. 3) said hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79 are foreseen for displacing and positioning of mechanical constituent parts 81, 82, 83, 84, 85, 86, 87, 88 of the crane 8, namely

- hydraulic droving units 71, 71 ’ are hydraulic cylinders within a bearing frame of a column 81 of the crane 8, which are acting in opposite directions and are in combination with a gear on said column 81 and gear racks on piston rods of said hydraulic cylinders capable for performing of controlled rotation of the column around the vertical geometric axis thereof;

- a hydraulic driving unit 72 is either a sole cylinder, or a pair of oppositely acting hydraulic cylinders, which is/are intended for displacing of hydraulic supporting legs 86, 86 arranged on each side of the crane in a direction apart from each other;

- hydraulic driving units 73, 74 are hydraulic cylinders in supporting legs, which are directed towards the ground and enable supporting and stabilizing of the crane 8 on the ground;

- a hydraulic driving unit 75 is a hydraulic cylinder, by means of which a primary crane arm 82 is pivotally around the horizontal geometric axis supported on the column 81 of the crane 8; - a hydraulic driving unit 76 is a hydraulic cylinder, by means of which secondary crane arm 82, which is optionally telescopic extendable, is pivotally around the horizontal geometric axis supported on said primary crane arm 82;

- a hydraulic driving unit 77 is a hydraulic cylinder, by means of which an extractable section 84 of the telescopic extendable secondary crane arm 83 is driven;

- a hydraulic driving unit 78 is a hydraulic motor of a rotating unit 88, by means of which a grabber 85 is attached to the secondary arm 83 of the crane 8; while

- a hydraulic driving unit 79 is system of hydraulic cylinders, by which the arms of said grabber 85 fir manipulating each load are displaceable.

In the shown embodiment, said hydraulic pump 3, 3' is a hydraulic pump with a constant flow rate, namely a hydraulic pump, which at a pre-determined constant rotation speed thereof provides a constant flow rate of the hydraulic media, which is supplied to it from the reservoir 2. Each of said groups 4, 5, 6) of said control valves 41, 42, 43; 51, 52, 53; 62, 62, 63, which are intended for controlling of said hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79, which are suitable for displacing and positioning of mechanical constituent parts said 81, 82, 83, 84, 85, 86, 87, 88 of the crane 8, is a hand-operated closed center proportional valve, which is capable to generate an electric signal, which is marked with dotted line in Fig. 1, as soon as at least one of said control valves 41, 42, 43; 51, 52, 53; 62, 62, 63 within the belonging group 4, 5, 6 is activated. In addition to that, a hydro-logic valve 9, 9' is integrated within said compression conduit 32 between the hydraulic pump 3, 3' and each disposable group 4, 5, 6 of said control valves 41, 42, 43; 51, 52, 53; 62, 62, 63 for controlling said hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79 on the crane 8, wherein said hydro-logic valve 9, 9' is suitable for adjusting of a flow rate of the hydraulic media on the basis of a signal transmited to it. Moreover, said hydro-logic valve 9, 9' is on the one hand via hydraulic conduits 324, 325, 326 hydraulically interconnected with each of said groups 4, 5, 6 of control valves 41, 42, 43; 51, 52, 53; 62, 62, 63 for controlling said hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79 on the crane 8, and on the other hand via said reverse hydraulic conduit 91 with the reservoir 2. In this said hydro-logic valve 9, 9' is in the view of a required signal transmission electrically interconnected with each of said groups 4, 5, 6 of control valves 41, 42, 43; 51, 52, 53; 62, 62, 63 for controlling said hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79 on the crane 8 and is adjusted, on the one hand, to permit just a partial quantity of the hydraulic media to flow there-through, which is currently required on the basis of a received signal about control valves 41, 42, 43; 51, 52, 53; 62, 62, 63 which are activated at that time and are required for operation of just those hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79, which are hydraulically interconnected with currently activated control valves 41, 42, 43; 51, 52, 53; 62, 62, 63, and on the other hand, instead of directing of the complete amount of the hydraulic media supplied by said pump 3, 3' with a constant flow rate towards the groups 4, 5, 6 of control valves 41, 42, 43; 51, 52, 53; 62, 62, 63 for controlling of hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79 on the crane 8, said hydro-logic valve 9, 9' is capable to re-direct the excessive hydraulic media flow via the reverse conduit 91 back to the reservoir 2.

In a further embodiment according to Fig. 2, two hydraulic pumps 3, 3' with a constant flow rate are integrated in said hydraulic circuit 1. Mounting of two pumps 3, 3’ onto the same driving shaft, which is connectable to, is usually feasible without any serious problems, which may however be different, if more pumps 3, 3’ would have to be applied in such manner. Use of an additional pump 3’ may lead to certain benefits, in particular in the view of quicker supplying of more hydraulic media to each desired groups 4, 5, 6 of control valves 41, 42, 43; 51, 52, 53; 62, 62, 63 of hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79 on the crane 8. To this aim, said pumps 3, 3’ are on the one hand, each per se, via suction conduits 31, 31' hydraulically connected with a single common reservoir 2, while on the other hand each of said hydraulic pumps 3, 3' is via a compression conduit 32, 32' hydraulically connected with at least one of said groups 4, 5, 6 of control valves 41, 42, 43; 51, 52, 53; 62, 62, 63 for controlling of hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79 on the crane 8. In the shown embodiment according to Fig. 2, the first pump 9 is hydraulically connected with the first group 6 of control valves 61, 62, 63, while second pump 9’ is hydraulically connected with residual groups 4, 5 of control valves 51, 52, 53; 62, 62, 63. Just as an example and as just one of numerous potential possibilities selections among various possible combinations, the control valve 61 in the group 6 can be connected with the hydraulic driving unit between the column 81 and the primary arm 82 of the crane 8 (Fig. 3), the control valve 51 in the other group 5 is hydraulically connected with the hydraulic driving unit 75 between the primary crane arm 82 and the secondary arm 83 of the crane 8, the driving units 72, 73, 74 for displacement of supporting legs 86, 87 can be connected with the group 4 of control valves 41, 42, 43, and the residual driving units can be hydraulically connected with the residual control valves in said groups 5, 6. Interconnections between the control valves 41, 42, 43; 51, 52, 53; 62, 62, 63 and hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79 on the crane 8 are generally determined by taking into consideration a sustainable distribution of the hydraulic media flow in the view of functional correlations among the components on various types of cranes, and also a logical arrangement of handles for manually actuating said control valves 41, 42, 43; 51, 52, 53; 62, 62, 63, which makes managing the crane 8 easier. Also in a hydraulic circuit 1 according to Fig. 2, a hydro-logic valve 9, 9’ is integrated in the area of each of said compression conduits 32, 32’ of each one of said pumps 3, 3’, namely in the area between each pump 3, 3’ and each group 4, 5, 6 of control valves 41, 42, 43; 51, 52, 53; 62, 62, 63 for controlling of hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79 on the crane 8, which is connected therewith. Said hydro-logic valve 9, 9’ is in the view of a required signal transmission, as marked by a dotted line in Fig. 2, electrically interconnected with each one of said groups 4, 5, 6 of control valves 41, 42, 43; 51, 52, 53; 62, 62, 63 for controlling said hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79 on the crane 8 and is adjusted, on the one hand, to permit just a partial quantity of the hydraulic media to flow there-through, which is currently required on the basis of a received signal about control valves 41, 42, 43; 51, 52, 53; 62, 62, 63 which are currently activated and are required for operation of just those hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79, which are hydraulically interconnected with control valves 41, 42, 43; 51, 52, 53; 62, 62, 63 activated at that time, and on the other hand, instead of directing of the complete amount of the hydraulic media supplied by each relevant pump 3, 3' with a constant flow rate towards the groups 4, 5, 6 of control valves 41, 42, 43; 51, 52, 53; 62, 62, 63 for controlling of hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79 on the crane 8, said hydro-logic valve 9, 9' is capable to re-direct the excessive hydraulic media flow via the reverse conduit 91 back to the reservoir 2.

Groups 4, 5, 6 of control valves 41, 42, 43; 51, 52, 53; 62, 62, 63 for controlling of hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79 on the crane 8 are configured on the basis of estimated functional interactions among the hydraulic driving units 71, 71', 72, 73, 74, 75, 76, 77, 78, 79 and also on the basis of estimated partial flow rates required for reliable operation of said hydraulic driving units (71, 71', 72, 73, 74, 75, 76, 77, 78, 79 either by solely operation of each one of them or by their simultaneous operation.

In the shown embodiment, the control valves 41, 42, 43 of the first group 4 are hydraulically connected with the driving units 72, 73, 74, which serve for displacing of supporting legs 86, 87 on the crane 8 in a direction apart from each other, as well as for extraction thereof. The other hydraulic driving units 71, 71', 75, 76, 77, 78, 79 for displacing and positioning of the residual constituent parts 81, 82, 83, 84, 85, 88 of the crane 8 are hydraulically connected to form at least two further groups 5, 6 of control valves 51, 52, 53; 62, 62, 63, which are each per se via hydraulic conduits 325, 326 connected with said hydro-logic valve 9, 9'. In the embodiments according to Fig. 1 and 2, said first group 4 is together with the second group 5 supplied by the hydraulic media by means of the same pump 9, or 9’ respectively. However, even in a situation, when e.g. supporting legs 86, 87 on the crane are used just for the purpose of stabilization of the crane 8 and the belonging vehicle, by activation of at least one of control valves 41, 42, 43 of the first group 4, the hydro-logic valve 9, 9’ would permit flowing just a such quantity of the hydraulic media through the hydraulic conduit 324, which is required for reliable operation of just that hydraulic driving unit, which is connected with the activated control valve of said group 4, while the excessive quantity of the hydraulic media would be forwarded directly through the reverse conduit 91 back to the reservoir 2 without any need on circulating through the conduits 324 and 325 and both groups 4, 5 prior to be returned back to the reservoir 2.