Patent Publication Number: US-2015071791-A1

Title: Method for operating a hydraulic pump arrangement, and hydraulic pump arrangement

Description:
The present invention relates to a method for operating a hydraulic pump arrangement according to the preamble of claim  1  and a hydraulic pump arrangement according to the preamble of claim  15 . 
     TECHNICAL BACKGROUND 
     Hydraulic pump arrangements of the type described above are used for different applications. They are generally portable and are therefore equipped with an independent energy source, for example an accumulator or the like. On the one hand, they serve as a component of hydraulically driven rescue tools such as, for example, so-called jaws or cutting tools which are used by emergency service personnel for rescuing persons who are trapped or buried in vehicle wrecks. On the other hand, they are also used in machine tool engineering, for example for comminuting pieces of ballast etc. As a rule, the switching valves for operating the hydraulically driven tools are located directly on the tool, with the result that the operator can control the tool directly by means of the switching valve according to requirements. The hydraulic pump arrangements which are necessary for the drive are therefore usually connected to the individual tools via flexible hydraulic hoses. Hydraulic hoses can have different lengths here depending on use situation, and therefore bring about different pressure relationships. In addition, for different use situations there are different rescue tools which, under certain circumstances, have to be changed in situ if the situation requires it. Different rescue tools in turn give rise to different energy levels, for example different idling pressures. In order to lengthen the use times of the tools, efforts are made to lengthen the use times of the energy source as far as possible. For this reason, in the past there has been a changeover to the provision of energy saving modes. Such an energy saving mode takes place, for example, by switching over from a load state into a non-load state (switching over the operating state) if the vehicle no longer has to perform any work. 
     DOCUMENTED PRIOR ART 
     U.S. Pat. No. 5,678,982 discloses a portable hydraulic system according to the preamble of claim  1 . This hydraulic system already has a control system for the operation in a load state or non-load state with the aid of a switch which switches over between the load state and the non-load state as a function of a pressure threshold value. This pressure threshold value becomes an absolute pressure and is defined by a pressure sensor which taps the pressure at the outlet of the pump and actuates a changeover switch. The changeover switch is activated at the outlet of the pump as a function of the absolute pressure defined by the pressure sensor, and said changeover switch switches the system from a non-load state into a load state, or vice-versa. This known hydraulic system functions well as long as the components thereof, specifically the hydraulic pump arrangement, the hose line and the tool are adjusted to one another. However, when tools with different idling pressures are exchanged and/or when different hose lengths are used, malfunctions occur. In order to supply energy, two batteries are used which are arranged in the interior of the pump housing, closed off with a lid. The energy consumption is to be reduced by switching over from the load state into the non-load state, and as a result the operating time of the batteries is to be lengthened. However, even with such energy-saving measures the batteries are quickly used up if they are operated at full load owing to a considerable work to be performed. 
     OBJECT OF THE PRESENT INVENTION 
     The object of the present invention is to make available a new method for operating a hydraulic pump arrangement and a new hydraulic pump arrangement which ensures increased flexibility of use, safety of use and operating convenience. 
     MEANS OF ACHIEVING THE OBJECT 
     The present object is achieved with respect to the method of the generic type by the features of the characterizing part of claim  1  and with respect to the hydraulic pump arrangement of the generic type by means of the features of the characterizing part of claim  15 . Expedient configurations of the method according to the invention and of the hydraulic pump arrangement according to the invention are claimed in the dependent claims. 
     The invention has the advantage that the hydraulic pump arrangement can optionally also be supplied with electrical energy by a generator which is located on a vehicle, for example rescue vehicle. This results in the advantage that although the battery or the accumulator can become flat in an energy-saving drive concept, an energy supply can still remain effective and be maintained without wasting time. The connection of the power supply to the generator is made via an electrical cable which can have a considerable length and can be stored by means of a cable drum. If the operator has to enlarge his radius of action, for example in order to continue the work at another location in the case of a building which has collapsed due to an earthquake or on a vehicle involved in an accident, even with considerable cable lengths it may become necessary for the position of the vehicle carrying the generator to be changed. The energy supply gaps which result from this can be advantageously closed quickly and without wasting time by the battery or the accumulator. 
     As a result of the fact that the alternating current which is generated by the generator is only rectified, that is to say converted into direct current, in the power supply or at least in the region of the power supply, considerable cable lengths can be used without large losses. 
     The hydraulic pump arrangement according to the invention is expediently operated at a power of at least 800 watts, preferably of at least 900 watts, particularly preferably of at least 1000 watts. 
     As a result of the fact that at least one input variable for the control system which is dependent on the work to be performed by the motor of the hydraulic pump arrangement is defined as the control variable S, malfunctions because of interchanging pressure conditions when the hose length varies, when the tools are changed, in the case of temperature fluctuations etc. are effectively excluded because the relevant control variable is directly dependent on the work to be performed by the motor. First and second threshold values W1 and W2 are different. In particular, the first threshold value W1 is lower than the second threshold value W2. The control system makes it possible to switch over from the load state into the non-load state even when the movement of the tool stops under a load effect, for example when an emergency doctor in a vehicle requires somewhat more space to attend to the trapped person and therefore the rescue tool (for example a jaw cutter) has to be used once more, and to perform subsequent switching over from the non-load state into the load state during a further movement of the tool under a load effect. 
     In particular, two control variables S1 and S2, for example the motor current and the pressure, which both, as input variables dependent on the work which is to be performed by the motor of the hydraulic pump arrangement, can expediently be defined for the load-dependent control of the hydraulic pump arrangement, wherein the first control variable S1 (motor current) is assigned a first threshold value W1 at which switching over from the non-load state into the load state takes place, and the control variable S2 is assigned a second threshold value W2 at which switching over from the load state into the non-load state takes place. As a result, in the event of signal resolution problems of the one control variable the other control variable can be used as an auxiliary variable, and vice-versa. This permits more precise switching. 
     As a result of the fact that the second threshold value is preferably a variable value which is continuously updated during the operation of the hydraulic pump arrangement, i.e. is overwritten in a memory, the operation of the hydraulic pump arrangement adapts itself to a variety of operating situations. 
     According to one expedient embodiment of the method according to the invention, the control variable S is preferably also assigned a third threshold value W3, wherein switching over from the load state into the non-load state takes place as a function both of the second threshold value W2 and of the third threshold value W3. As a result, excessively rapid switching over from the load state into the non-load state is avoided. 
     The third threshold value W3 is preferably a fixedly predefined valve of the control variable S. 
     The motor current, i.e. the current consumption of the motor of the hydraulic pump which, is a measure of the work to be performed by the motor of the hydraulic pump arrangement, is expediently used as a control variable S. The motor current can be determined in different ways. 
     Alternatively, the pressure or the motor torque can also be used as a control variable S. 
     In all cases, this preferably involves time-related values, that is to say values which constitute changing the control variable S over a predefined time interval. 
     The hydraulic pump device according to the invention expediently detects the motor current by measuring a voltage drop across a resistance, on the basis of which the value of the motor current can be concluded. 
     Alternatively, the current measuring device such as, for example, an ammeter or the like can be provided for measuring the current in the motor line. 
     A rewritable memory of the RAM or EEPROM type expediently serves as a memory. 
     In the case of a load drop, the rotational speed of the motor is reduced by changing the motor voltage in terms of its rotational speed. For this purpose, a voltage with a preferably constant pulse level, i.e. intensity, but a different pulse width, is applied to the motor as voltage pulse. The voltage is therefore modulated. The current adjusts on the basis of the external load. 
     As a result of the fact that the shape of the housing of the power supply and the shape of the housing of the battery are identical at least over part of the housing, preferably over the entire housing, on the one hand the manufacturing costs of the battery or of the power supply can be reduced and on the other hand a uniform receptacle can be provided in the hydraulic pump arrangement. 
     The receptacle is expediently located on the rear of the hydraulic pump arrangement, as a result of which on the one hand in the case of restricted conditions a rapid changeover of the power supply by the battery or vice-versa can take place. In addition, the cable which is located on the power supply does not as a result have a disruptive effect during the handling of the hydraulic pump arrangement. 
     The flexibility of use and ease of handling is increased further as a result of the fact that in the state of use at least half of the depth of the respective housing, preferably at least two thirds, are located inside the rear contour line of the hydraulic pump arrangement in the receptacle on the rear of the hydraulic pump arrangement. The plug projection is not included here in the calculation of the depth. 
     The operating convenience of a corresponding hydraulic pump arrangement can be increased further as a result of the fact that a tank window is provided on the housing of the hydraulic pump arrangement and the interior of the transparent tank is illuminated. The operator can therefore consequently check the tank content of the hydraulic pump arrangement at any time even when in use at night or in use in dark spaces without having to use additional aids such as pocket lamps or the like. The operating convenience of the hydraulic pump arrangement is further increased as a result. 
    
    
     
       DESCRIPTION OF THE INVENTION ON THE BASIS OF EXEMPLARY EMBODIMENTS 
       Expedient configurations of the invention are explained below in more detail on the basis of figures in the drawings, in which: 
         FIG. 1  shows a schematic illustration of a first configuration of the present invention; 
         FIG. 2  shows a flowchart of the control system of the hydraulic pump arrangement according to the configuration in  FIG. 1 ; 
         FIG. 3  shows a diagrammatic illustration of the profile of the motor current of the hydraulic pump arrangement according to  FIG. 1 ; 
         FIG. 4  shows a further diagrammatic illustration of the profile of the motor current of the hydraulic pump arrangement according to  FIG. 1  with a working pause; 
         FIG. 5  shows a schematic illustration of a further configuration of the present invention; 
         FIG. 6  shows a schematic illustration of the use of the hydraulic pump arrangement according to the invention with various hose lengths; 
         FIG. 7  shows a schematic illustration of the use of the hydraulic pump arrangement according to the invention for various types of hydraulic tools; 
         FIG. 8  shows an illustration of an operator during use ( FIG. 8   a ), a highly simplified schematic illustration of the supply of a hydraulic pump arrangement for a tool which is connected via flexible hose lines, via a power supply and a generator ( FIG. 8   c ), an illustration of a typical use situation ( FIG. 8   b ), 
         FIG. 9  shows a perspective illustration of the accommodation facility of a battery or of a power supply on the rear of the hydraulic pump arrangement, and 
         FIG. 10  shows a side view of a hydraulic pump arrangement with an illuminated tank space. 
     
    
    
     The reference number  1  characterizes the inventive hydraulic pump arrangement in its entirety. It is portable and is connected via preferably flexible hose lines  15  to an exchangeable hydraulic tool  18 . Couplings  14  or  16  can be provided on the outlet of the hydraulic pump arrangement  1  and on the inlet of the hydraulic tool  18  for rapid coupling or uncoupling of the hydraulic pump arrangement. 
     The hydraulic pump arrangement  1  comprises a pump  2  and an electric motor  4  which drives the pump  2 . The electric motor  4  is supplied with electrical energy by an accumulator  19 , or rather by a power supply. The pump  2  has a tank  3  for the hydraulic fluid. A pressure line leads from the pump  2 , and the tank line leads from the tank  3  out of the hydraulic pump arrangement  1  to the respective coupling  14 . 
     A control device for sequence control of the hydraulic pump arrangement  1  is characterized by the reference number  10 . Said control device comprises, in particular, a microcontroller  6 , a memory  7 , a generator  8  for pulse-width modulation and an analog/digital converter  9 . The abovementioned components are accommodated on a circuit board. The microcontroller  6  is preferably connected to a main switch  5 . The latter is used to close or interrupt the circuit from the battery  19  to the microcontroller  6 . The electric motor  4  can be directly connected to the main switch  5  so that the former is supplied with electrical energy from the battery  19  when the main switch  5  is switched on. 
     According to the present invention, in particular the motor current, i.e. the current which the electric motor  4  consumes during operation of the hydraulic pump arrangement, is measured as a control variable S for the switching over of the load (switching over of the operating state). In the case of the configuration illustrated in  FIG. 1 , this expediently took place with the aid of a resistor  13 . The resistor  13  is connected by a signal line  23  to the analog/digital converter  9 . The latter converts the analog signals into digital signals for further signal evaluation. 
     The determination of the current is preferably carried out here indirectly over the voltage drop at the resistor  13 . This voltage drop is amplified by the subsequent amplifier  21  and passes as an input into the analog/digital converter  9  via the signal line  23 . The digital data is processed by the microcontroller  6  and reconciled with the data in the memory  7  (threshold values from the control logic). The corresponding pulse width is output from this in the generator  8  for the pulse-width modulation, and the power transistor  11  (for example a MOSFET transistor) is correspondingly switched. If the power transistor  11  is switched off, the current flows across the free-wheeling diode  12  which is connected in parallel with the motor  4 . The negative pole of the motor  4  is, as it were, clocked. However, it is also possible for the positive pole to be clocked. 
     The configuration of the present invention described above has two operating states, specifically a load operating mode and a non-load operating mode. In the case of the load operating mode, the full electrical power (for example 24 V) is fed to the electric motor  4 , and in the case of the non-load operating mode a reduced electrical power (for example 2 V) is fed to the electric motor  4 . The switching over is carried out by the control unit  10  by means of the generator  8  for the pulse-width modulation which interacts with the power transistor  11  as described. The generator  8  for the pulse-width modulation preferably forms, together with the power transistor  11 , continuous, periodic current signals which differ as a function of the respective load state only in their pulse width. In the case of the load state, the pulse width is greater with respect to a time unit, and in the case of the non-load state the pulse width is smaller. 
     The respective hydraulic tool  18  comprises a hydraulic cylinder  20  which is connected via a switching valve  17  to the hose lines  15 . The switching valve  17  is preferably what is referred to as a 4/3-way switching valve with which it is possible to define the two directions of movement (forward and back) of the hydraulic cylinder  20  as well as an idling position (central position of the switching valve  17 ). The switching valve  17  is preferably provided for example in the form of what is referred to as a star handle directly on the tool  18 . 
     The functional sequence of the hydraulic pump arrangement  1  according to the invention is explained in more detail below with reference to  FIG. 2 . If the hydraulic pump arrangement  1  according to the invention is put into operation by switching on the main switch  5 , the electric motor  4  is supplied with electrical energy (in this case for example with 2 V) in the non-load range. At the same time, in the manner described at the beginning the current which is consumed by the electric motor  4  is continuously determined. A difference current, that is to say difference in current is determined here over a permanently defined time period. A first threshold value W1 is stored in the control device  10 . In the logic of the microcontroller  6 , the determined value of the current consumption of the electric motor  4  is compared with the first threshold value W1. If the determined value of the current consumption is lower than the first threshold value W1, the hydraulic pump arrangement remains in the non-load range. If the determined value of the current consumption is larger than the first threshold value W1, the hydraulic pump arrangement switches into the load range. In the load range, the electric motor  4  is supplied with a voltage of, for example, 24 V. 
     Immediately after the switching up into the load range, the current is determined and is stored as a threshold value W2 in the memory  7 . In this context, the last value relating to this is overwritten in the memory. Therefore, an individual threshold value W2, which is dependent on the current conditions (temperature, connected hose length; type of rescue equipment) is stored in the load range invariably after the switching over. 
     In addition, a third threshold value W3 is predefined in the control system, which threshold value W3 constitutes a fixed value. If the continuously measured, consumed current of the electric motor  4  remains larger than the second threshold value W2 or third threshold value W3, the control system remains in the load operating mode. If the continuously measured consumed current of the electric motor  4  becomes smaller than the second threshold value W2 and even smaller than the third threshold value W3, the control system switches over to the non-load operating mode (2 V). 
     In  FIG. 3 , the control system of the motor drive is represented plotted against the time axis t by means of a current curve I. When the main switch  5  is activated, the electric motor is firstly supplied with a voltage of 2 V. After a certain time period, the control valve  17  is activated by the operator, on the basis of which the hydraulic cylinder  20  of the tool  18  is moved forward without an external load effect. In this context, the measured current I exceeds the first threshold value W1, with the result that the control device  10  switches over the operation from 2 V to 24 V. As long as no external load effect on the movement of the tool is present, the electric motor  4  merely requires (after a certain transient response) a substantially constant current. As soon as an external load acts on the tool movement, the current which is required by the electric motor  4  increases strongly until a release of tension occurs owing to the end of the deformation or the cutting of an object or component or the like. After the control valve  17  has been placed in the neutral position (open-circuit position), the current required by the electric motor  4  drops again strongly. As soon as the current becomes smaller than the third threshold value W3, and even smaller than the second threshold value W2, the control system switches over to the non-load operating mode (2 V). 
     The illustration according to  FIG. 4  differs from that according to  FIG. 3  in that a working pause is inserted during operation. The working pause as in  FIG. 4  can occur, for example, when the operator becomes uncertain and briefly releases the star handle before then nevertheless continuing. In this context, the control valve  17  is placed by the operator into the neutral position (open-circuit position). The current required by the electric motor  4  drops quickly. As soon as current consumption has undershot both the third threshold value W3 and the second threshold value W2, the control system switches over from the load operating mode into the non-load state. As soon as the working cycle is resumed again, the operator activates the control valve  17  again, with the result that current is drawn from the electric motor  4  again. Owing to the working pause, switching from the non-load state into the load operating mode occurs again, as a result of which a new threshold value W2 is determined and stored in the memory  7 . Since the working pause took place in the vicinity of the apex of the current curve, a very high threshold value W2 is stored. In order to avoid immediate switching over, the third threshold value W3 is provided. The control system switches from the load operating mode to the non-load state only if the determined motor current has also dropped below the third threshold value W3. 
     An alternative configuration of the present invention is known from  FIG. 5 . In contrast to the configuration according to  FIG. 1 , this embodiment of the invention has, instead of an electric resistor, a current-measuring device  22 , for example in the form of an ammeter. This current-measuring device measures the current in the motor line. The current-measuring device  22  is also connected to the analog/digital converter  9  via a signal line  23 . In the configuration according to  FIG. 5 , two further terminals T and P are also provided. 
     In addition, during the control of the load the pressure and/or the temperature can also be used as additional control variables, for example the pressure as a reference variable and the current as an auxiliary variable for ensuring more precise switching through a relatively high signal resolution. The detection of the temperature permits the use of an additional decision criterion in order to evaluate the main variable. In  FIG. 5 , this is characterized by the inputs T (temperature) and P (pressure) at the analog/digital converter  9 . 
     As illustrated in  FIG. 6 , the hydraulic pump arrangement  1  can be connected, depending on the purpose of use, to the same tool  18  via the couplings  14  and  16  and the variable hose lengths  15   a  and  15   b . The pressure conditions present in the system change as a result of the use of different hose lengths. This change in the pressure conditions leads, however, to no malfunction since according to the invention the control of the operation of the hydraulic pump arrangement  1  is provided by means of the motor current as a control variable S, and this variable is directly dependent on the work to be performed by the motor of the hydraulic pump arrangement  1 . 
     If the pressure conditions change owing to a comparatively long hose line  15 , the motor current also changes. This motor current is, however, compared with at least partially variable current thresholds (control system which is capable of learning). 
     The same also applies to the exchanging of the tools  18   a  to  18   c , as illustrated in  FIG. 7 . The operating pressure conditions also change here. For example, a tool  18   a  in the form of a cutter has a different current consumption in the open circuit than a jaw cutter (tool  1   b ). These differences are therefore also included in the control system of the hydraulic pump arrangement  1 . 
     The same applies to a change in the length of the hose lines with a simultaneous change in the type of tool  1   a  to  1   c.    
     Alternatively, instead of the motor current, the pressure and/or the torque can also be used as a control variable S, i.e. control parameter. 
     An operator, for example a firefighter or member of the rescue personnel providing technical assistance during deployment is illustrated in  FIG. 8   a . The tool  18 , the hydraulic pump arrangement  1  and the hose line  15  for the hydraulic fluid are portable and are located directly on the object of the deployment. 
     The illustration according to  FIG. 8   b  shows a typical accident situation of a vehicle which has left the carriageway and in which occupants are typically trapped and have to be freed as quickly as possible from the vehicle wreck by the emergency services. In many cases, and as is also illustrated in  FIG. 8   b , the emergency vehicle  28  can only be positioned at a certain distance from the vehicle wreck. 
       FIG. 8   c  shows a configuration of the hydraulic pump arrangement according to the invention which is connected via a flexible hose line  15  to a tool  18 , for example a cutting tool and/or jaw cutter. The hydraulic pump arrangement  1  is supplied with electrical energy here via an electric cable line  27  from a generator  29  located on the rescue vehicle  28 . Since the generator  29  generates alternating current, usually, for example, with a voltage of 220 volts or 230 volts, a rectifier  36 , which converts the alternating current (AC) into direct current (DC) is provided in the end region of the cable line  27 , that is to say in the region of the hydraulic pump arrangement  1 . 
     The arrangement which is illustrated in  FIG. 8   c  can therefore be used in a chronologically unlimited fashion, but the mobility of the tool  18  is restricted owing to the defined maximum length of the cable line. It is therefore possible, for example, for the vehicle wreck which is illustrated in  FIG. 8   b  to be further away from the generator  29  for the supply of the hydraulic pump arrangement  1  with electrical energy, with the result that the rescue vehicle  28  must firstly attempt to come closer to the accident point via detours, for example a freeway exit. In order to increase the flexibility of the deployment of the arrangement of the hydraulic pump arrangement  1 , hose line  15  and tool  18 , an electrical interface, in particular electrical plug-in interface  30 , is provided according to the invention on the hydraulic pump arrangement  1 . This electrical interface is provided for carrying out a rapid changeover with respect to the energy supply. 
     The illustration according to  FIG. 9  shows further details in this context. The cable line  27  comprises a plug  38  for connecting to the generator  29  ( FIG. 8   c ). Furthermore, cable line  27  is connected to a power supply  25 . For this purpose, a detachable plug-in connection  37  can be provided between the power supply  25  and the cable line  27 . In the configuration illustrated in  FIG. 9 , the power supply comprises a power supply housing  31  within which, for example, the electrical components such as, for example, the rectifier  36  ( FIG. 8   c ) and a transformer (not illustrated) are located together. On the side of the housing  31  facing away from the cable line  37  there is a plug-in projection  34  for making contact with the electrical plug-in interface  30  ( FIG. 8   c ). Alternatively, the rectifier  36 , can, however, also be accommodated in its own housing which is connected to the housing of the power supply via a comparatively short piece of cable. 
     The battery is provided with the reference number  24  and comprises both an identical plug-in projection  33  and a substantially identical housing  32 . In addition, a receptacle shaft  26  is provided for the respective housing  31  or  32 , preferably on the rear of the hydraulic pump arrangement  1  which is represented merely as a partial illustration in  FIG. 9 . In the interior of the receptacle shaft  26  there is a further receptacle shaft  35  for the respective plug-in projection  33 ,  34  of the battery  24  or of the power supply  25 . The receptacle shaft  26  and the respective housing  31 ,  32  of the power supply  25  or of the battery  24  are adjusted to one another in such a way that in the state of use of the power supply  25  or of the battery  24  at least half of the housing thereof, and preferably at least two thirds, disappears in the receptacle shaft  26 , that is to say dips therein, as a result of which the operating convenience and carrying comfort of the hydraulic pump arrangement is not adversely affected by the possibility of replacing the battery  24  by the power supply  25 . A further receptacle shaft  35  for the respective plug-in projection  33  or battery  24  or power supply  25  is located on the end side of the receptacle shaft  26 . 
     The hydraulic pump arrangement  1  according to the invention is operated at a power of at least 800 watts, preferably at least 900 watts, and preferably at least 1000 watts. The hydraulic pump arrangement can be particularly preferably operated in a power range from 950 watts to 1050 watts. The receptacle shaft  26  is provided with a latching coupling (not illustrated) which permits manually detachable latching securement of the battery  24  or of the power supply  25  in the receptacle shaft  26  to be ensured. 
       FIG. 10  shows a further expedient configuration of the present invention which provides a quite particular level of operating convenience even independently of the type of drive of the pump arrangement or the supply with electrical energy. The reference number  3  denotes a tank  3  in which hydraulic fluid for operating the tool, not illustrated in  FIG. 10 , is located. The housing of the hydraulic pump arrangement  1  comprises an, in particular, elongated tank window  39  which extends virtually over the entire depth of the tank  3  and which permits the user to view the filling level from the outside. In addition, in the interior an illumination  40 , for example in the form of an LED or a plurality of LEDs, is provided. As a result of the illumination  40 , the operator can always satisfactorily monitor the filling level of the tank  3  even under difficult visibility conditions, for example when in use at night or in dark rooms, without being dependent on additional aids such as pocket lamps or the like in this context. In addition, owing to the possibility of clearly detecting the tank contents, the tank contents can as such be dimensioned more tightly, as a result of which a reduced weight of the hydraulic pump arrangement  1  and therefore improved handling capability can be achieved in turn. 
     Furthermore, from  FIG. 10  it is also apparent that the housing of the power supply  25  or of battery  24  protrudes merely by a small amount over the external envelope curve of the housing of the hydraulic pump arrangement  1 . As a result, the handling capability of the hydraulic pump arrangement  1  is not worsened compared to a purely battery-operated solution. 
     LIST OF REFERENCE NUMBERS 
     
         
           1  Hydraulic pump arrangement 
           2  Pump 
           3  Tank 
           4  Motor 
           5  Main switch 
           6  Microcontroller 
           7  Memory 
           8  Generator for pulse-width modulation 
           9  Analog/digital converter 
           10  Control device 
           11  Power transistor 
           12  Free-wheeling diode 
           13  Resistor 
           14  Coupling 
           15  Hose line 
           16  Coupling 
           17  Switching valve 
           18  Tool 
           19  Accumulator or power supply 
           20  Hydraulic cylinder 
           21  Amplifier 
           22  Current-measuring device 
           23  Signal line 
           24  Battery 
           25  Power supply 
           26  Receptacle shaft 
           27  Cable line 
           28  Rescue vehicle 
           29  Generator 
           30  Electrical plug-in interface 
           31  Housing for power supply 
           32  Housing for battery 
           33  Plug-in projection for battery 
           34  Plug-in projection for power supply 
           35  Receptacle shaft for plug-in projection 
           36  Rectifier 
           37  Plug-in connection 
           38  Plug for generator 
           39  Tank window 
           40  Illumination