Abstract:
A hydraulic system ( 1 ) is disclosed comprising a pressure source ( 2 ), at least a hydraulic consumer ( 12, 13 ), and a pressure booster ( 16 ) arranged between the pressure source ( 2 ) and the hydraulic consumer ( 12, 13 ), wherein inactivating means ( 17 ) are provided inactivating or activating said pressure booster ( 16 ), said pressure booster ( 16 ) and said inactivating means ( 17 ) being part of a booster module ( 11 ). The operational possibilities of such a hydraulic system ( 1 ) should be extended. To this end the booster module ( 11 ) is part of a valve block ( 3 ), said valve block ( 3 ) comprising said booster module ( 11 ) and at least one valve module ( 9, 10 ) controlling said hydraulic consumer ( 12, 13 ).

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    Applicant hereby claims foreign priority benefits under U.S.C. §119 from European Patent Application No. EP 14186984 filed on Sep. 30, 2014, the contents of which are incorporated by reference herein. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to a hydraulic system comprising a pressure source, at least a hydraulic consumer and a pressure booster arranged between the pressure source and the hydraulic consumer, wherein inactivating means are provided inactivating or activating said pressure booster, said pressure booster and said inactivating means being parts of a booster module. 
       BACKGROUND 
       [0003]    Such a hydraulic system is known, for example, from EP 2 784 331 A1 (prior art according to article 54(3) EPC). 
         [0004]    The pressure source, e.g. a hydraulic pump, supplies hydraulic fluid under an elevated pressure. The hydraulic consumer can be operated by means of this elevated hydraulic pressure. 
         [0005]    In some applications the pressure supplied by the pressure source is not sufficient to operate the hydraulic consumer so that a pressure booster is used to permanently amplify the pressure supplied by the pressure source. The pressure booster is a pressure amplifier increasing the pressure supplied to the consumer. 
       SUMMARY 
       [0006]    The object underlying the invention is to extent the operational possibilities of a hydraulic system. 
         [0007]    This object is solved with a hydraulic system as described at the outset in that said booster module is part of a valve block, said valve block comprising said booster module and at least one valve module controlling said hydraulic consumer. 
         [0008]    When the booster module is part of the valve block, there is no need for additional piping connecting the valve module and the booster module. The combination of the valve module and the booster module allows for a simple construction. The valve block can be dimensioned with sufficient strength to withstand the higher pressure delivered by the booster module. Since the pressure booster can be activated or inactivated, the system can be operated with the pressure supplied by the pressure source alone, if this pressure is sufficient to operate the hydraulic consumer, or it can be operated using the pressure booster, i.e. the pressure intensifier, to supply an elevated pressure to the consumer. In such a system the pressure booster or pressure intensifier is activated only when required, i.e. the pressure booster is not “active” during normal operations. In this way it is possible to select a lower pressure or a higher pressure simply by using the inactivating means. In other words, the system is able to supply “pressure on demand”. 
         [0009]    In a preferred embodiment said valve block comprises an inlet module and an end module, said booster module being arranged between said inlet module and said end module, wherein a pressure line connecting said inlet module and said end module runs through said booster module. In this way it is possible to use the pressure line for two purposes. One purpose is to be a pressure source for the inlet of the pressure booster. The other purpose is to receive the elevated pressure from the high pressure output of the pressure booster. The only requirement is that in this case a check valve (or any other means for controlling pressure differences) is arranged within the pressure line in the booster module. Such a check valve is allowed since the closing direction in the pressure line is clearly defined. 
         [0010]    In a preferred embodiment said booster module is positioned between two valve modules. In this case the valve module located upstream the booster module with respect to the pressure source is supplied with pressure from the pressure source only. The valve module (or the valve modules) located downstream the booster module with respect to the pressure source can be supplied with higher pressure from the pressure booster, if necessary. Usually the pressure demand of the hydraulic consumers connected to the respective valve modules is known. By arranging the valve modules and the booster module a preselection can be made so that only part of the valve modules and consequently part of the hydraulic consumers can be supplied with the higher pressure of the pressure booster. This is an energy saving construction since higher pressure is delivered only to part of the system. 
         [0011]    Preferably said pressure booster is a hydraulic pressure booster. In a simple embodiment such a hydraulic pressure booster can be realized by using a differential piston having a larger face which is loaded by the pressure of the pressure source and an opposite smaller face generating the higher pressure. The ratio between the two faces basically determines the application factor of the hydraulic pressure booster. 
         [0012]    Preferably said inactivating means are hydraulic means. This is a rather simple way to realize the inactivating means, since in a hydraulic system it is possible to use hydraulic means without increasing dramatically the construction or maintenance costs. 
         [0013]    In a preferred embodiment said inactivating means are at least in part arranged in series with said pressure booster. In this way, supply of hydraulic fluid to said pressure booster can be interrupted. 
         [0014]    Preferably said inactivating means are hydraulically operated. In a hydraulic system hydraulic pressures are available which can be controlled to operate the inactivating means. 
         [0015]    Preferably said inactivating means comprise an inactivating valve located between said pressure line and said pressure booster, said inactivating valve interrupting, in a closed state, a connection between said pressure line and said pressure booster. When the inactivating valve is closed, there is no supply of hydraulic fluid from the pressure line to the pressure booster so that the pressure booster is not able to output any hydraulic fluid and consequently is not able to output any hydraulic fluid under a higher pressure. On the other hand, when the inactivating valve is opened, hydraulic fluid from the pressure line can reach the low pressure inlet of the pressure booster which can in turn operate to increase the pressure of the hydraulic fluid over the pressure in the pressure line. 
         [0016]    In a preferred embodiment said inactivating valve is loaded in opening direction by a pressure in said pressure line and in closing direction by a force of spring means. In this case the inactivating valve is opened, when the pressure in the pressure line increases. This can be, for example the case when the pressure source increases the pressure as response of a pressure demand signal by a LS pressure, i.e. a load sensing pressure. In this case the inactivating valve is opened so that the pressure booster receives with hydraulic fluid the pressure of which can be further increased. In this way the output pressure of the pressure source can be reduced. 
         [0017]    In another preferred embodiment said inactivating valve is loaded in opening direction by a pressure depending on a pressure in a load sensing line and in closing direction by a force of spring means. The load sensing line usually signals a pressure demand of a consumer. In this case the pressure booster can be activated depending on the pressure required, for example a load sensing pressure. When the pressure at the load dependent position signals that a higher pressure is required to operate the hydraulic consumer, for example to lift a heavy load, this pressure demand can automatically be transmitted to said inactivating valve, said inactivating valve is opening and activating said pressure booster. In this case no action of the operator is required. However, the hydraulic system can be used in an energy saving manner when the pressure booster is inactive, or in a powerful operation, when the pressure booster is used to generate a higher pressure. However, the last named operation is performed only when necessary. 
         [0018]    In a third preferred embodiment said inactivating valve is loaded in opening direction by a pressure in a pilot pressure line and in closing direction by a force of spring means. The pilot pressure line has a pressure which is sufficient to operate some valves. In this case the spring means can be designed with a lower spring force. 
         [0019]    Preferably an electrically operated valve is arranged between said pilot pressure line and said inactivating means. In some cases it is easier to use an electric signal line. The inactivating means are operated via an electrically operated valve which could be a magnetic or a solenoid valve which is operated by an electric current. There are some possibilities to operate the inactivating means. A first possibility is to use an electric switch, which can, for example, be positioned at a joystick with which the operator controls the function of a hydraulic consumer downstream said booster module. Another possibility would be to connect the signal line to a sensor sensing a pressure demand at the hydraulic consumer. 
         [0020]    In a preferred embodiment said inactivating valve is loaded in closing direction by a pressure in an auxiliary line connected to a tank line via throttling means, wherein a pressure relief valve is connected to said auxiliary line between said inactivating valve and said throttling means, an inlet of said pressure relief valve being connected to a high pressure output of said pressure booster. In this way the inactivating valve can be closed as soon as the pressure at the high pressure output of the pressure booster together with the force of the spring means exceeds the force on the opposite site of the inactivating valve. The inactivating valve is automatically closed as soon as the pressure delivered by the pressure booster exceeds a pre-determined threshold value defined by the relief valve. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    Preferred embodiments of the invention now are described in more detail with reference to the drawing, wherein: 
           [0022]      FIG. 1  shows a schematic illustration of a valve block, 
           [0023]      FIG. 2  shows a first embodiment of a pressure booster module, 
           [0024]      FIG. 3  shows a second embodiment of a pressure booster module, and 
           [0025]      FIG. 4  shows a third embodiment of a pressure booster module. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    In all figures the same elements are designated with the same reference numerals. 
         [0027]      FIG. 1  schematically shows a hydraulic system  1  having a pressure source  2 , for example a pump, and a valve block  3 . The pressure source  2  supplies hydraulic fluid with an elevated pressure to a pressure line  4  of the valve block  3 . The hydraulic fluid is taken from a tank  5 . A tank line  6  of the valve block  3  returns hydraulic fluid to the tank  5 . 
         [0028]    The valve block  3  comprises an inlet module  7  and an end module  8 . Two valve modules  9 ,  10  are arranged between the inlet module  7  and the end module  8 . Furthermore, a booster module  11  is arranged between the two valve modules  9 ,  10 . The booster module  11  will be described below with more details. 
         [0029]    The pressure line  4  and the tank line  6  each connect the inlet module  7  and the end module  8 , as it is known in the art. The pressure line  4  and the tank line  6  extend through the valve modules  9 ,  10  and through the booster module  11 . 
         [0030]    A hydraulic consumer  12  is connected to the valve module  9  and a hydraulic consumer  13  is connected to a valve module  10 . The hydraulic consumers  12 ,  13  can be, for example, a hydraulic cylinder or a hydraulic rotational motor. 
         [0031]    As it is known, all modules  7 - 11  together form a stack of modules, i.e. they contact each other and can be held together by clamping means, such as bolts or the like. 
         [0032]    Furthermore, a load sensing line  14  is guided through the valve block  3  and signals a load sensing pressure to the pressure source  2 . 
         [0033]    A pilot pressure line  15  is guided through the valve block  3  as well. However, this pilot pressure line  15  is not shown in  FIG. 1 , but in  FIGS. 2 to 4  only. 
         [0034]      FIGS. 2 to 4  show different embodiments of the booster module  11 . The booster module  11  comprises a hydraulic pressure booster  16  or pressure amplifier. The pressure booster  16  has a low pressure input IN, a high pressure output H, and a return port R. Such a pressure booster is disclosed, for example, in U.S. Pat. No. 7,726,950 B2. The disclosure of this document is incorporated by reference. 
         [0035]    The pressure booster  16  in the booster module  11  is provided with inactivating means  17 . The inactivating means  17  comprise an inactivating valve  18  arranged in a line  19  connecting the pressure line  4  and the input IN of the pressure booster  16 , i.e. it is connected in series with the pressure booster  16 . 
         [0036]    The inactivating valve  18  is usually held in the closed state shown in  FIG. 2  by the force of a spring  20 . The inactivating valve  18  furthermore comprises a first control port  21 . In the embodiment shown in  FIG. 2  the first control port  21  is connected to the tank line  4  as well. When the force at the first control port  21  generated by the pressure in the pressure line  4  exceeds the force of the spring  20  the inactivating valve is opened. In this case the input IN of the pressure booster  16  is supplied with hydraulic fluid having the pressure of the pressure line  4 . The pressure booster  16  increases this pressure and delivers hydraulic fluid under an elevated pressure to the pressure line  4 . 
         [0037]    A check valve  22  is located in the pressure line  4  between a point  23  connected to the inactivating valve  18  and a point  24  connected to the high pressure output H of the pressure booster  16 . 
         [0038]    A further check valve  25  is arranged in a line  26  between the high pressure output H of the pressure booster  16  and point  24  in the pressure line  4 . 
         [0039]    The return port R of the pressure booster  16  is connected to the tank line  6  via a check valve  27  opening in a direction towards the tank line  6 . 
         [0040]    The inactivating valve  18  may have a second control port  28  connected to the return port R of the pressure booster  16  via throttling means  29 . The pressure at the second control port  28  acts in the same direction as spring  20 . 
         [0041]    A pressure relief valve  30  is connected between a point in line  26  downstream the check valve  25  and the second control port  28 . The pressure relief valve  30  has a first pressure relief valve control port  31 , a second pressure relief valve control port  32  and a closing spring  33 . A pressure at the first pressure relief valve control port  31  generates a force on the pressure relief valve  30  acting in opening direction of the pressure relief valve  30 . This first pressure relief valve control part  31  is connected to the line  26  downstream the check valve  25 . The pressure at the second pressure relief valve control port  32  generates a force on the pressure relief valve  30  acting in closing direction. The closing spring  33  generates a force acting in closing direction as well. The second pressure relief valve control port  32  is connected to the second control port  28  of the inactivating valve  18 . 
         [0042]    When at the pressure relief valve  30  a force generated by the pressure at the high pressure output H of the pressure booster  16  exceeds the force of the closing spring  33  the pressure relief valve  30  opens and supplies the high pressure to the second control port  28  of the inactivating valve  18  thereby closing the inactivating valve  18  so that the supply of hydraulic fluid to the pressure booster  16  is interrupted. 
         [0043]    Inactivating means  17  comprising the inactivating valve  18  and the pressure relief valve  30  form a closed loop control adjusting the increased pressure just to the level needed. 
         [0044]      FIG. 3  shows a second embodiment of a booster module  11 . Same elements as in  FIG. 2  are designated with the same reference numerals. 
         [0045]    The booster module  11  shown in  FIG. 3  differs from that shown in  FIG. 2  in that the inactivating valve  18  is differently controlled. 
         [0046]    The inactivating valve  18  is located in the same line  19  between point  23  of the pressure line  4  and the input IN of the pressure booster  16 . 
         [0047]    However, the first control port  21  of the inactivating valve  18  is connected to the load sensing line  14  via a LS relief valve  34 . A first control port  35  of the LS relief valve  34  is connected to the LS line  14  as well. The pressure at the first control port  35  acts in opening direction of the LS relief valve  34 . A second control port  36  is connected to a line  37  connecting said LS relief valve  34  and the first control port  21  of the inactivating valve  18 . A pressure at the second control port  36  acts in closing direction on the LS relief valve  34 . Furthermore, a closing spring  38  acts in closing direction as well. Line  37  is connected to the tank line  6  via throttling means  39 . 
         [0048]    LS relief valve  34  opens when the pressure in the LS line  14  exceeds the force of closing spring  38 . As soon as LS relief valve  34  is open, inactivating valve  18  is opened as well and the pressure booster  16  is supplied with hydraulic fluid the pressure of which is to be amplified. 
         [0049]    The pressure relief valve  30  has the same function as in the embodiment shown in  FIG. 2 . 
         [0050]      FIG. 4  shows a third embodiment of the booster module  11 . Same elements as in  FIGS. 3 and 4  are designated with the same numerals. 
         [0051]    Activating of the inactivating valve  18  is made by operating an electrically operated valve  40  arranged between the first control port  21  of the inactivating valve  18  and the pilot pressure line  15 . When the electrically operated valve  40  is open, the pressure in the pilot pressure line  15  acts in opening direction on the inactivating valve  18 , thereby opening the inactivating valve  18 . 
         [0052]    The function of the pressure relief valve  30  is the same as in  FIGS. 2 and 3 . 
         [0053]    The electrically operated valve  40  can be remotely controlled, for example by means of an electrical switch located in a driver&#39;s cabin of a vehicle. When the switch is closed the electrically operated valve  40  is supplied with current thereby opening. When the current is switched off, a closing spring  41  closes the electrically operated valve  40 . 
         [0054]    Since in the embodiments in  FIGS. 2 to 4  different pressures are used to open the inactivating valve  18 , the spring  20  in all embodiments may have different characteristics. For example, the spring  20  in the embodiment shown in  FIG. 3  has to act against the pressure in the pressure line  4  whereas the spring in the embodiment shown in  FIG. 3  has to act against a pressure at the outlet of the LS relief valve  34  and the spring  20  in the embodiment shown in  FIG. 4  has to act against the pressure in the pilot pressure line  15  only. However, the dimensioning of the spring  20  belongs to the normal skill of an expert. 
         [0055]    When the booster module  11  is positioned between two valve modules  9 ,  10 , only the valve module  10  downstream the booster module  11  with respect to the pressure line  4  receives hydraulic fluid with a pressure higher than that delivered by the pressure source  2 . 
         [0056]    While the present disclosure has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this disclosure may be made without departing from the spirit and scope of the present disclosure.