Abstract:
Disclosed is a control system for a hydraulic work machine, comprising a plurality of hydraulic work circuits for supplying actuators and/or drive units of movable machine parts with hydraulic fluid, and an emergency stop circuit for the work circuits for avoiding danger caused by the machine parts. According to this disclosure, the emergency stop circuit comprises a single safety valve which is connected in parallel to the work circuits via at least one branch line each at the inlet and to a pressure relief point at the outlet.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of PCT/EP2015/058852, filed Apr. 23, 2015, which claims priority to DE 10 2014 207 669.2, filed Apr. 23, 2014, both of which are hereby incorporated herein by reference in their entireties. 
     
    
     BACKGROUND 
       [0002]    The invention relates to a control system for a hydraulic work machine, in particular for a movable or stationary thick matter pump, a truck mixer, an excavator or a mobile crane, having a plurality of hydraulic operating circuits which can preferably be controlled by means of a central control unit and which are configured in order to supply pressure oil to actuation members and/or drive units of movable machine components, and having an emergency stop circuitry for the operating circuits which can be activated to stop a machine movement in order to prevent danger resulting from the machine components. The invention further relates to a hydraulic work machine having such a control system. 
         [0003]    Automatic concrete pumps contain a large number of hydraulically movable machine components, in particular the mast arms of the concrete distribution mast which are connected to each other by means of articulated axles in order to prepare the concrete which is required at the building site and to convey it to the processing location. Uncontrolled disruptions in complex systems of this type could lead to serious damage in the operating environment or to the machine. Therefore, there is required a safety or emergency stop circuitry which, where applicable, enables intervention safely in the functional sequence and enables undesirable consequences of failures and damage to be avoided. 
       SUMMARY 
       [0004]    Based on the above discussion, this disclosure further improves the control systems known in the prior art and using the simplest means possible achieves a reliable emergency stop function which stops machine movements in a plurality of hydraulic operating circuits which are operated at the same time. 
         [0005]    This disclosure is based on the notion of connecting all the hydraulic operating circuits via a common safety valve in a pressure-free state and consequently stopping the movements of machine components by switching off the hydraulic drive energy. Accordingly, it is proposed according to this disclosure that the emergency stop circuitry have a single safety valve which is connected in parallel at the inlet thereof to the operating circuits or the pressure oil branches thereof by means of at least one branch line each and which is connected at the outlet side to a pressure relief point. Consequently, it is possible to shut down actuation members or drive units of consumers with little switching complexity without each individual actuation member/consumer having to be considered separately. Consequently, dangerous movements of large machine components, such as mast arms, can also be stopped with a short reaction time. Such an emergency stop also interrupts machine movements in the event of an emergency, in contrast to an emergency operation which is not relevant in this instance and in which such movements are still possible where applicable with reduced drive energy or auxiliary energy. 
         [0006]    Advantageously, the safety valve can be switched as a directional valve between a blocking position which is assumed during normal operation and a throughflow position which transmits the emergency stop function and which is preferably resiliently centered as a rest position. Consequently, even in the event of a failure of the (electrical) control, an independent assumption of the safe position is ensured. 
         [0007]    In order to afford an operator a possibility of intervention, it is advantageous for the safety valve to be able to be actuated manually by means of an emergency stop button. In parallel, it is also possible to implement in the central control unit an automatic safety shutdown, or to activate the valve by means of a suitable safety module. 
         [0008]    Advantageously, the safety valve can be actuated as an electrohydraulic directional valve by means of an electrical control line. This is preferably carried out in such a manner that the emergency stop is ensured even in the event of a power failure. 
         [0009]    Depending on the drive in the open or closed operating circuit, it is advantageous for the pressure relief point to be formed by means of a tank or a suction return filter of a pressure oil source. 
         [0010]    In order to prevent a short-circuit between the different consumers, it is advantageous for a non-return valve which is permeable in the direction of the safety valve to be arranged in each branch line. 
         [0011]    Another structural simplification can be achieved by the non-return valves being arranged in a common valve block. 
         [0012]    An advantageous intervention possibility, in particular for thick matter pumps, is produced by at least one actuation member being formed by means of an actuation cylinder which acts on a variable displacement pump. In order to switch both adjustment chambers at the same time to the same pressure, it is advantageous for the actuation cylinder to be connected to the inlet of the safety valve by means of a branch line at each of the two sides thereof (in particular at the base and rod side in a differential cylinder). 
         [0013]    As long as at least one drive unit is acted on with pressure oil in an open drive circuit by means of a pump, it may also be advantageous for the branch line to branch between the pump and drive unit in the main oil flow of the pump or alternatively at a pump controller. 
         [0014]    In order to further comply with the safety requirements, it is advantageous for the safety valve to be provided with a position monitoring system. 
         [0015]    For particularly advantageous use, there is provision for the operating circuit to be configured to operate at least one element from the group thick matter pump, distributor mast, stirrer, hydraulic accumulator, support leg. 
         [0016]    In order to carry out control or drive functions, the hydraulic operating circuits each contain a hydraulic pressure source for supplying pressure oil to the actuation members and/or drive units of movable machine components. In this instance, there is provision for the branch lines to each lead from a pressure side of the hydraulic pressure source or a pressure oil branch of the operating circuits to the inlet of the safety valve. 
         [0017]    The subject-matter of this disclosure is also a hydraulic work machine having a control system according to this disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: 
           [0019]    The single FIGURE shows a hydraulic circuit diagram of a control system for a truck-mounted concrete pump with an emergency stop circuitry. 
       
    
    
     DESCRIPTION 
       [0020]    The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure. 
         [0021]    The truck-mounted concrete pump  10  which is indicated only schematically in the circuit diagram comprises as a hydraulic work machine a plurality of movable machine components which are driven by means of hydraulic operating circuits  12 , in particular a concrete distributor mast  14  with hydraulically actuatable articulated joints  16 , a two-cylinder concrete pump  18  with hydraulically driven conveyor pistons and pipe diverter, a concrete feed container  20  which is arranged upstream of the pump  18  and which has a hydraulic stirrer and support arms  22  which can be laterally deployed and which have support legs which can be hydraulically extended. In the event of an emergency, in order to enable a stoppage or shutdown of all hydraulically produced movements—in particular those involving danger—by means of the simplest control construction possible, there is provided an emergency stop circuitry  24  which comprises a single electrohydraulic safety valve  26 . 
         [0022]    All the hydraulic operating circuits  12  can be controlled by means of a central control unit  28 . In this instance, electric lines  30  enable an electric valve reversal. 
         [0023]    In order to supply pressure oil to the hydraulic drive of the concrete pump  18 , there are provided two hydraulic reversing pumps  32  which are constructed as swash plate axial piston pumps and whose swash plate angle can be adjusted by means of actuation cylinders  34 . The actuation cylinders  34  can be actuated in each case by means of an associated control valve  36  in accordance with the desired conveying quantity. In the switching position I, a base-side action of pressure and, in the switching position II, a rod-side action of pressure on the actuation cylinders  34  by means of a respective operating circuit  12  is enabled. This leads in this instance from a hydraulic pressure source  37  (hydraulic pump) to the tank  38  and contains the control valve  36  and the actuation cylinder  34 . Further details of such a pump control system can also be derived from WO 97/18395 to which reference is made in this context. 
         [0024]    The supply of pressure oil to the distributor mast  14  is carried out in an additional open operating circuit  12 ,  40  in which a variable displacement pump  42  provides as a pressure source a considerably smaller quantity of oil in comparison with the hydraulic reversing pumps  32 . An additional pump  44  supplies the motor  46  of the stirrer in the concrete feed container  20  with hydraulic drive energy via the operating circuit  12 ,  48 . Furthermore, a hydraulic accumulator  47  is provided as a pressure source which can be loaded by a variable displacement pump  57  in order to support the switching of the pipe diverter of a two-cylinder concrete pump  18 . 
         [0025]    The safety valve  26  can be switched as a 2/2 directional valve between a passage position I which transmits the emergency stop function and a blocking position II. The blocking position II is electrically controlled during normal operation by means of an actuation element  50  (by means of the control unit  28  or/and a separate emergency stop monitoring unit), whilst the passage position I is resiliently centered in a powerless state as a rest position. A manual activation of the actuation element  50  is possible via an emergency off switch  51 . In this instance, a position monitoring of the safety valve  26  should also be configured in order to comply with the requirements of DIN EN ISO 13849. 
         [0026]    In order to bring about the emergency stop via a pressure relief of all the hydraulic operating circuits  12 , they are connected to the inlet of the safety valve  26  parallel with each other by means of at least one branch line  52  each. The outlet thereof leads to a pressure relief point  54  which in the example shown is formed by means of a tank  38 . During driving in a closed circuit, pressure relief at a suction return filter is also conceivable (not shown). 
         [0027]    The safety valve  26  is of a sufficient size so that even with the maximum quantity of oil and the lowest permissible operating temperature, the dynamic pressure is sufficiently low to be able to maintain the pressure relief. 
         [0028]    In order to prevent a short-circuit between the individual consumers, non-return valves  56  are arranged in the branch lines  52 . These may either be arranged in a common valve block or in a decentralized manner. 
         [0029]    As a result of the large delivery quantity of the hydraulic reversing pumps  32 , they are not intended to have the pressure relieved directly via the safety valve  26 . Instead, the actuation cylinders  34  are switched to the same pressure at the rod side and base side by means of a branch path so that the swash plate angle of the reversing pumps is adjusted to “zero conveying quantity.” At the necessary minimum pressure, a throttle may be provided. 
         [0030]    When driving in an open circuit, in an emergency stop situation a main oil flow may be diverted directly via the electrohydraulic safety valve  26 , as shown for the variable displacement pump  42 . Alternatively, the pump controller thereof may also have the pressure relieved by means of the branch line  52 ′. 
         [0031]    While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.