HYDRAULIC FORMING MACHINE FOR PRESSING WORKPIECES, IN PARTICULAR FORGING HAMMERS, AND METHOD FOR OPERATING A HYDRAULIC FORMING MACHINE, IN PARTICULAR A FORGING HAMMER

Description

[0001] The underlying invention relates to a forging hammer and a method for operating a forging hammer.

[0002] Various forming machines are known for pressing workpieces during cold forming, particularly sheet metal forming, or during hot forming, particularly during the forging of metallic, malleable materials (see, for example, the VDI Lexicon volume "Production Technology Process Engineering," published by Hiersig, VDI-Verlag, 1995, pages 1107 to 1113). At least one ram or ram with a first forming tool of the forming machine is driven by a drive and moved relative to a second forming tool of the forming machine, so that the workpiece can be formed between the forming tools using forming forces.

[0003] Known hydraulic forming machines utilize a hydraulic drive via a hydraulic medium or hydraulic fluid, such as oil or water. The pressure energy of the hydraulic medium or fluid is initially converted into kinetic energy by pistons running in hydraulic cylinders, particularly in forging hammers, and finally, during the forming process, into mechanical forming work. The hydraulic drive of the piston can be a pump drive with a pump and an electrically controllable pump motor (see, for example, DE 196 80 008 C1) or a hydraulic accumulator drive with a pressure accumulator and a motor-driven pump for generating pressure in the pressure accumulator (see, for example, WO 2013 / 167610 A1).

[0004] DE 10 2015 105 400 A1 discloses a forging hammer with a striking tool coupled to a hydraulic differential cylinder for performing a working stroke and a return stroke. A hydraulic pump is provided to drive the differential cylinder, which is connected to the cylinder chambers of the differential cylinder via a simple directional control valve.

[0005] A hydraulic forging hammer with manual impact release is known from RU 2 327 542 C2. US 5,499,525 describes a hydraulic press for pressing sheet metal.

[0006] CA 3 111 771 A1 describes a device for shaping and / or cutting material, comprising a tool and a drive unit which moves the tool and supplies it with kinetic energy for shaping or cutting the material. To carry out a shaping or cutting process, the tool is accelerated by the drive unit, wherein the device is configured such that the tool is in contact with the drive unit at least during a large part of the acceleration, or such that the tool is stationary before kinetic energy is supplied to the tool by the movement of the drive unit. The device is further configured such that the tool is operatively separated from the drive unit before the tool impacts the material.

[0007] However, in known forming machines, especially forging hammers, there is still potential for improving the motion sequences of the ram and the associated tools, for example, to improve the achievement of a precise forming speed and / or its reproducibility. Furthermore, it would be desirable to improve forming machines of the type mentioned so that the occurrence of cavitation in the hydraulic circuit, particularly in the hydraulic working chambers of the hydraulic cylinder, the valves, and the lines of the control block, can be at least reduced during operation, and advantageously even substantially or completely avoided.

[0008] The object of the invention is to provide a new or improved forging hammer. In particular, a forging hammer is to be provided that enables improved motion control and regulation of the ram with the coupled impact tool for forming and / or that enables motion control with reduced or minimized cavitation formation in the hydraulic medium or hydraulic fluid, particularly in the hydraulic working chambers of the hydraulic cylinder, the valves, and the lines of the control block. Furthermore, a corresponding method for operating a forging hammer is to be provided.

[0009] This object is achieved by the features of independent claims 1 and 9. Embodiments emerge in particular from the dependent claims and from the following description of embodiments and embodiments.

[0010] According to a device-side embodiment of the invention, a forging hammer is provided for workpiece forming.

[0011] The forging hammer comprises a hydraulic cylinder which is designed and configured to drive a ram or ram configured for workpiece forming.

[0012] In operation, specific tools for the respective forming task are usually coupled to the ram or ram, which, when acting on a workpiece to be formed at the end of a working stroke or press stroke, form the workpiece.

[0013] The working stroke is followed by a return stroke or retraction of the hydraulic cylinder, which brings the ram or ram into a position to carry out a subsequent working stroke.

[0014] According to claims 1 and 9, the hydraulic cylinder is a differential cylinder which has an annular surface and a piston surface.

[0015] The hydraulic cylinder, for example a double-acting hydraulic cylinder, can comprise, as is usually the case, a piston that can be moved back and forth within a cylinder chamber. The piston is coupled to one end of a piston rod, and the other end of the piston rod is coupled to the ram. The movement of the piston moves the ram accordingly. Cyclical movement of the piston allows repeated forming operations to be performed.

[0016] To execute a working stroke, which in this application is understood to mean a movement of the hydraulic cylinder, in particular of the ram, which results in a forming operation, a first hydraulic working chamber of the hydraulic cylinder is pressurized with hydraulic fluid. At the same time, hydraulic fluid is displaced from a second hydraulic working chamber located on the opposite side of the piston. In a forging hammer with a differential cylinder, the second working chamber can be continuously pressurized during operation to execute work cycles (working stroke and return stroke). During the execution of a working stroke, the first hydraulic working chamber can be pressurized with the same pressure (system pressure) as the second hydraulic working chamber.The hydraulic fluid supplied to the first hydraulic working chamber acts on the piston surface, and the pressure of the hydraulic fluid in the second hydraulic working chamber acts on the annular surface of the piston, which is correspondingly smaller than the piston surface due to the coupled piston rod. The hydraulic fluid supplied to the first hydraulic working chamber therefore creates a force acting on the piston that is greater than the force acting on the piston from the second hydraulic working chamber via the annular surface of the annular chamber (product of pressure and area). This creates a resultant force that accelerates the piston and thus generates the working stroke. The return stroke orWhen the piston is retracted, accompanied by a corresponding movement of the ram, the pressure in the first hydraulic working chamber ends and the pressure constantly acting on the annular surface of the second hydraulic working chamber creates a force opposite to the force acting during the working stroke, which causes the return stroke or retraction. In a forging hammer, the pressure in the first hydraulic working chamber, which leads to an accelerating force on the piston during the working stroke, is usually ended before the forming process begins. This means that the force acting on the piston via the annular surface in the second working chamber once the pressure accelerating the piston has ended initially has a negative accelerating effect on the movement of the piston, before the forming process and the subsequent return stroke take place.In order for the return stroke to take place, it is necessary for the hydraulic fluid to be able to escape from the first hydraulic working chamber, in particular while the return stroke movement is taking place. The hydraulic fluid escaping from the first hydraulic working chamber is usually led into a tank. In the phase of the working stroke between the end of the pressurization in the first hydraulic working chamber leading to acceleration of the piston and the start of the return stroke, it is necessary for hydraulic fluid to be able to continue to flow into the first hydraulic working chamber, in particular to avoid negative pressures and the resulting cavitation. According to embodiments of the invention, the inflow into the first hydraulic working chamber in this phase is made possible by an actuator, in particular a controllable actuator.

[0017] The hydraulic working chambers are also referred to herein as the working chamber. Thus, a first working chamber refers to the first hydraulic working chamber, and a second working chamber refers to the second hydraulic working chamber.

[0018] The forging hammer further comprises a hydraulic circuit configured to operate the hydraulic cylinder. The term "hydraulic circuit" as used herein is to be understood in a particularly general sense. In particular, the term "hydraulic circuit" is intended to encompass not only hydraulic lines but, depending on the context, also additional components such as control units, regulating units, valves, pumps, etc., that are present or required for the hydraulic operation of the hydraulic cylinder.

[0019] In one embodiment, the hydraulic circuit comprises a valve with an adjustable, variable volume flow. The term “adjustable, variable” should be understood to mean that the volume flow of the valve is adjustable and at the same time allows variable, in particular time-variable, for example controllable, settings of the volume flow. Such a valve differs from a conventional on-off valve with only two selectable switching positions in that several or a multitude of switching positions can be specifically set. In particular, such valves can be designed such that the volume flow is essentially continuously or continuously adjustable, and that the opening state of the valve, in particular the opening width and opening time, can be specifically adjusted, in particular controllable, e.g. over time according to a function of time or as a function of other variables.Particularly suitable are controllable valves that allow for the control-based adjustment of the flow rate or the opening width and / or opening time. Examples of such valves are listed below, although a control valve is already mentioned as an example here, in which the opening width can be changed by voltage or current and can be opened or closed continuously depending on the applied voltage, for example, according to a time function, e.g., a ramp.

[0020] The valve is installed in the hydraulic circuit in such a way that the first hydraulic working chamber of the hydraulic cylinder, which is used to accelerate the ram during the working stroke for workpiece forming, can be pressurised with hydraulic fluid. The valve can, for example, connect the first working chamber via hydraulic lines to a hydraulic accumulator, in particular a pressure accumulator and / or a pump unit. If the valve is opened, the first working chamber is pressurised with the hydraulic fluid coming from the accumulator and / or the pump unit. The hydraulic pressure prevailing in the hydraulic fluid acts on the pressing surface of the hydraulic cylinder and generates a force to execute the working stroke. Since a differential cylinder is used, the side of the piston facing away from the piston rod, i.e. the piston surface, is usually used as the pressing surface, and the annular surface on the piston rod side is used as the return surface. For the return stroke orFor retraction, the annular surface in the second working chamber can be connected to a pressure accumulator and / or a pump unit, e.g. while simultaneously connecting the first working chamber to a tank to reduce the pressure applied to the piston surface, so that the pressure force generated via the annular surface is sufficient to move the components to be moved, e.g. ram, tool, piston rod, piston, hydraulic fluid of the first working chamber, etc., and to retract the hydraulic cylinder or piston.

[0021] The hydraulic circuit of the present embodiment, specifically a control or regulating unit, is particularly designed to adjust and vary, in particular to regulate, the volume flow of the valve as a function of a target speed of the ram to be achieved during an acceleration phase of the working stroke. For example, the control or regulating unit can be designed to adjust the volume flow, for example the opening width of the valve, over time such that the target speed is achieved within a predetermined or predeterminable stroke range of the piston. To adjust and vary the volume flow, a corresponding control or regulating unit can, for example, use data stored in a value table that is specific to the respective operating conditions and operating parameters, such as the forming machine, ram type, ram weight, tool height, tool weight, type of forming, type of material, etc., indicate volume flows to be set over time to achieve the desired target speed, or from which the control or regulating unit can determine the volume flows to be set. Alternatively or additionally, the forging hammer can have one or more pressure, position, speed and / or acceleration sensors, and the control or regulating unit can use measurement data from such sensors when setting the volume flows to achieve the target speed. In embodiments, the control or regulating unit can be designed to set the volume flow at least over time or partially on the basis of measured values from the said sensors, in particular dynamically, for example in order to maintain the target speed within a predetermined stroke range during a working stroke.After the required target speed has been reached, the acceleration of the piston in the direction of the working stroke is stopped by adjusting the flow of hydraulic fluid into the first working chamber.

[0022] The movement phase of the working stroke can in particular be a braking phase in which the ram is no longer hydraulically accelerated and the desired or set speed or speed required for forming, reached at the beginning of the movement, is essentially maintained. A braking phase can be said to occur if, during the movement phase, further accelerating forces, such as gravity, act on the ram, which would lead to a further increase in the set speed. If, for example, the forming machine is set up in such a way that, during the acceleration phase, gravity or a component of gravity acts in the direction of movement of the ram and the components moved with it, such as the ram, tool, etc., then gravity or the component of gravity acts as an accelerating force. This is the case, for example, if the forming machine is set up in such a way that the ram or ram moves parallel to gravity oris moved perpendicular to the machine base or machine foundation, and the movement in the acceleration phase is directed in the direction of gravity or towards the machine base. If the target speed is reached in the acceleration phase by pressurising the first working chamber with hydraulic fluid, gravity continues to act as an accelerating force in the machine design mentioned. In order to maintain the achieved target speed, a braking force counteracting the force of gravity is required, i.e. the movement phase forms a braking phase. With other designs, for example if the ram moves upwards against gravity in the acceleration phase, the movement phase can have different force effects. Overall, the movement phase is set up in such a way that the target speed reached in the acceleration phase is essentially maintained.

[0023] A constant pressure in the annular space of the cylinder can generate braking forces, i.e. negatively accelerating forces, in the movement phase of the working stroke following the acceleration phase. During the braking phase, the pressure applied to the first hydraulic working chamber, which leads to acceleration in the direction of the working stroke, ends. Since the piston continues to move in the direction of the working stroke during the movement phase, it is necessary that hydraulic fluid can flow into the first working chamber after the pressure applied to the first working chamber, which leads to acceleration, has ended. This is because the volume in the first working chamber of the cylinder, which continues to increase during the working stroke and also in the movement phase, would otherwise lead to a reduction in pressure and thus to cavitation, i.e. outgassing of the air dissolved in the hydraulic fluid, with resulting cavitation damage and a break in the hydraulic fluid column.

[0024] In the embodiments proposed herein, the hydraulic circuit and the control or regulating unit can be configured such that the pressure prevailing in the first working chamber during the movement phase, which is a braking phase, is, for example, above 1 bar, but in any case above the cavitation pressure of the hydraulic fluid. This allows cavitation in the first working chamber caused by outgassing of the hydraulic fluid to be avoided.

[0025] To prevent cavitation in the first working chamber during the braking phase, the volume flow of hydraulic fluid into the first working chamber can, for example, be adjusted or regulated in such a way that the pressure in the first working chamber can be kept substantially above the cavitation pressure. This counteracts a further drop in pressure in the first working chamber, with the aim of avoiding or substantially preventing a drop in pressure below the cavitation pressure. The volume flow into the first working chamber required during the braking phase can be provided by an actuator intended to execute the working stroke, e.g., a control directional valve.

[0026] In embodiments, the valve can, as already indicated, be designed as a controllable valve. Suitable valves include, for example, continuous directional control valves, proportional directional control valves, servo directional control valves, and / or control directional control valves. To control such a valve, the hydraulic circuit can comprise a corresponding control unit. The control unit can be configured to position the valve, and thus the volume flow, such that, depending on the target speed to be achieved and the available stroke of the hydraulic cylinder, the target speed can be achieved with a simultaneous short, in particular minimal or optimal, movement phase. The respective actual position and / or actual speed or variables characterizing the position or speed can be determined, for example, by one or more sensors of the forming machine.In a closed-loop control system, for example, the actual speed can be used as the controlled variable and the setpoint speed as the reference variable, and the closed-loop control can cause the volume flow to be adjusted and varied accordingly. The stroke range traveled to reach the setpoint speed (ratio of acceleration phase to movement phase) and other variables can also be used in the controlled system. Depending on the deviation between the actual and setpoint speed determined by the closed-loop control system, the closed-loop control can position the valve, i.e. the volume flow, accordingly, for example in such a way that the setpoint speed can be achieved with a specified stroke of the hydraulic cylinder. Alternatively, the valve, i.e. the volume flow, can be set or controlled, for example, based on values from a value table. Such a value table can be obtained, for example, from test runs or simulations.

[0027] In certain embodiments, the forging hammer comprises a hydraulic cylinder for driving a ram configured for workpiece forming, and a hydraulic circuit configured to operate the hydraulic cylinder, with an actuator for setting a volume flow of hydraulic fluid to fill a first hydraulic working chamber of the hydraulic cylinder during the execution of a working stroke immediately preceding the workpiece forming. The working stroke comprises an acceleration phase for accelerating the ram to a desired speed and a movement phase following the acceleration phase, in particular immediately following it.In this embodiment, the hydraulic circuit, the actuator, and the control or regulating unit are configured to adjust and vary, in particular to regulate, the volume flow into the first working chamber during the acceleration phase of the working stroke for accelerating the ram to the target speed as a function of the target speed such that the target speed is reached. Furthermore, the hydraulic circuit, the actuator, and the control or regulating unit are configured to reduce, in particular to reduce in a controlled manner, the volume flow in the subsequent movement phase of the working stroke to a post-flow volume flow, or to adjust and vary or regulate the volume flow such that the hydraulic pressure prevailing in the first hydraulic working chamber during the movement phase is substantially above the cavitation pressure of the hydraulic fluid.The movement phase can, as discussed above, be a braking phase. The cavitation pressure in this case is related to the hydraulic fluid in the first hydraulic working chamber. The forming machine can include a control unit for adjusting and varying, in particular regulating, the flow rate.

[0028] The hydraulic forming machine does not require a suction valve or suction tank. The volume flow required to avoid cavitation-critical pressure is supplied to the first working chamber during the movement phase via the actuator, also called a percussion valve in forging hammers.

[0029] In the following, the phase in which hydraulic fluid is supplied into the first working chamber via the actuator in order to avoid cavitation will be referred to as the post-flow phase or post-flow.

[0030] To ensure afterflow, the control valve can be pressure-controlled from the end of the acceleration phase of the working stroke, i.e. when the target speed is reached. This means that the opening cross-section and the associated volumetric flow can be changed in real time depending on the conditions in the piston chamber. In particular, it is possible for the actuator to be closed continuously rather than suddenly after the acceleration phase has ended, until control of the actuator begins, which then regulates the pressure in the first working chamber to a value above the cavitation pressure. The parameters required to control the actuator can be determined or fed back by sensors (control loop). For example, when controlling the pressure in the first working chamber to a value above the cavitation pressure, the pressure in the first working chamber can be determined or fed back by one or more pressure sensors installed in the first hydraulic working chamber.A break-off of the hydraulic fluid column or cavitation and the resulting damage can thus be largely or completely prevented.

[0031] An advantage of the embodiment according to claim 1 lies in the fact that a suction valve can be omitted. Instead, the filling of the first working chamber with hydraulic fluid during the movement phase or afterflow phase or afterflow, particularly during the braking phase, is achieved by appropriate positioning, particularly by control, of the actuator.

[0032] In particular, the actuator can be adjusted and varied, in particular controlled or regulated, such that sufficient hydraulic fluid can flow into the first working chamber via the actuator during the movement phase, in particular the braking phase. For example, in such a way that cavitation is avoided. In particular, the flow of hydraulic fluid can be adjusted and varied, in particular regulated, such that the pressure in the first working chamber is kept above the cavitation pressure, and that the target speed reached or set in the acceleration phase of the working stroke is kept or maintained substantially constant during the movement phase of the working stroke.

[0033] A position, in particular a control, of the volume flow of the actuator can be determined, for example, based on a measured actual position, a measured actual speed, and / or an actual pressure measured in the first working chamber. To measure the respective actual values, the forming machine can comprise corresponding sensors, i.e., one or more position, speed, and / or pressure sensors.

[0034] When using the actual pressure of the first working chamber, the position of the actuator can, for example, be based additionally or exclusively on the measured actual pressure from the moment the target speed is reached. However, the position of the actuator can also be based on the measured actual pressure during the acceleration phase. For example, the actual pressure measured during the acceleration phase can be used to suitably adjust the length of the acceleration phase and / or the movement profile or movement sequence of the ram. In particular, it is possible to describe the temporal and / or spatial movement sequence of the ram using a target value table or target value function for the pressure in the first working chamber, and to set the actual pressure using the target value table or the target value function by positioning the actuator. The same applies to the position and speed of the ram.It is also possible for the volume flow to be set and varied, in particular regulated, according to a predefined value table and / or (setpoint) function.

[0035] Setpoint tables or (setpoint) functions can be determined through test runs and / or simulation under given boundary conditions, including, for example, the mass of the ram and the components moving with it, the stroke of the hydraulic cylinder, and the type of hydraulic fluid (viscosity, etc.). The setpoint tables or (setpoint) functions can be stored, for example, in an electronic memory of the forming machine and made available to an actuator or control unit, in particular a closed-loop control system, for positioning the actuator.

[0036] With the forging hammer according to the invention comprising the actuator with adjustable, variable volume flow, it can advantageously be achieved that the acceleration phase can be extended relative to the movement phase or braking phase. By shortening or optimizing the movement phase, in particular the braking phase, cavitations in the first working chamber in particular can be reduced or even completely avoided, since, as mentioned, such cavitations can occur in this phase. With the proposed option of positioning the actuator based on the actual pressure in the first working chamber, it is also possible to counteract the formation of cavitations based on a direct pressure measurement. For example, the pressure in the movement phase can be regulated by appropriate control of the actuator in such a way that a drop in the actual pressure below the cavitation pressure is avoided.With the described pressure-based position of the actuator in the post-flow phase, a post-cavitation valve and a post-cavitation tank are no longer required. One advantage from a hydraulic operation perspective is that actuators typically have shorter response times than post-cavitation valves, so that cavitation can be avoided with greater reliability. For example, with post-cavitation valves, which are similar in design and function to a check valve, it can happen that they do not open or do not open completely during comparatively short post-cavitation phases and / or do not open quickly enough at high target speeds due to the longer response times. These disadvantages can be avoided with pressure-based control of the actuator in the post-flow phase, in which hydraulic fluid flows into the first working chamber.

[0037] In certain embodiments, the actuator can comprise a controllable valve and / or a controllable pump. The valve can comprise, for example, a continuous directional control valve, a proportional directional control valve, a servo directional control valve, and / or a control directional control valve. The pump can comprise, for example, a servo pump. The use of the aforementioned valves or pumps enables the implementation of advantageous, in particular relatively short, actuation times for positioning and varying the volume flows, and in particular a comparatively precise and / or repeatable execution of a movement cycle for workpiece forming. With such actuators, comparatively short actuation times and comparatively fast reaction and response times can be achieved, whereby cavitation, in particular even during short braking phases or post-flow phases, can be at least largely or even completely avoided.

[0038] According to embodiments, the forging hammer can further comprise at least one pressure sensor. The pressure sensor is configured at least to measure the hydraulic pressure prevailing in the first and / or second hydraulic working chamber during the working stroke and / or return stroke. The pressure sensor can, for example, be integrated into or connected to a hydraulic line connected to the first or second working chamber.

[0039] The hydraulic circuit or the actuating unit, in particular the control or regulating unit or a monitoring or regulating unit, can be configured to adjust and vary, in particular to regulate, the volume flow during a working cycle of the ram, at least in the movement phase, preferably also during the return stroke, depending on the hydraulic pressure measured by the at least one pressure sensor.

[0040] A control system can be based on a specified or specifiable hydraulic pressure, hydraulic pressure interval, and / or a specified or specifiable temporal or spatial hydraulic pressure profile as a reference variable. For example, the hydraulic pressure or its profile can be specified or specifiable for the duration of a working stroke or return stroke, or for the position of the ram or the piston of the hydraulic cylinder during a working stroke or return stroke.

[0041] Corresponding hydraulic pressures and / or curves can be obtained, for example, from a test operation of the forming machine and / or from simulations.

[0042] The above formulation, according to which the volume flow can be adjusted and varied depending on the hydraulic pressure, at least during the movement phase, is intended to mean in particular that the adjustment or variation of the volume flow based on the hydraulic pressure measured in the first working chamber (i.e., the actual hydraulic pressure) is not limited to the movement phase, but can also be carried out during the acceleration phase. Furthermore, it is possible to take into account a hydraulic pressure measured in the second working chamber during the working and / or return stroke.

[0043] According to embodiments, the hydraulic circuit or the actuating unit or the control or regulating unit, in particular a monitoring unit, for example a control unit, can be configured to adjust and vary the volume flow such that the hydraulic pressure in the first hydraulic working chamber during the movement phase corresponds to a predetermined or predeterminable pressure or is within a predetermined or predeterminable pressure range. For example, the predetermined or predeterminable pressure or pressure range can be between 2 and 6 bar, in particular 3 to 4 bar. Preferably, the predetermined pressure or pressure range is predetermined such that during the movement phase, in particular the braking phase, the hydraulic pressure in the first working chamber is above the cavitation pressure of the hydraulic fluid. Thus, cavitation can be at least largely avoided.

[0044] According to embodiments, the hydraulic circuit, in particular a control unit or the control or regulating unit, is configured to adjust and vary the volume flow depending on the respective target speed to be achieved. For example, the hydraulic circuit, in particular the control unit or the control or regulating unit, can be configured to adjust the volume flow based on a value table for target speeds and / or to dynamically adjust, in particular to regulate, it based on measured location and / or speed data of the ram or piston and / or measured hydraulic pressures. For this purpose, the forging hammer can, for example, comprise at least one sensor unit for measuring and / or storing location and / or speed data of the ram or piston and / or the hydraulic pressures.

[0045] According to embodiments proposed herein, the hydraulic circuit, in particular the control or regulating unit, can be configured to close the valve or the actuator essentially completely, at least temporarily, in the movement phase of the working stroke following the acceleration phase, in particular shortly before or exactly at the beginning of the forming process in order to avoid possible hydraulic backlashes into the system.

[0046] According to embodiments, the hydraulic circuit, in particular the control or regulating unit, is configured to adjust and vary the volume flow, in particular to regulate it, such that the acceleration phase is maximized while simultaneously minimizing or optimizing the movement phase. It is provided that the volume flow in the acceleration phase is adjusted such that the post-flow phase corresponds to the stroke of the hydraulic cylinder in the range of 10% to 30%, in particular 10% to 20%. In particular, the volume flow for accelerating the ram can be adjusted and varied such that the time remaining after the acceleration phase until immediately before the forming process is greater than the actuating, response, and / or switching times of the actuator.By adjusting and varying the volume flow in the acceleration phase, the length of the acceleration phase and the corresponding length of the movement or braking phase or their ratio can be adjusted, for example, depending on the respective target speed to be achieved.

[0047] For example, at low target speeds, the flow rate can be increased or adjusted more slowly and with a smaller increase or rate of change so that the target speed is reached in a late phase of the working stroke, e.g., in the last third of the working stroke. At high target speeds, the flow rate can be increased correspondingly faster, for example, so that the target speed is also reached in a late phase of the working stroke.

[0048] In some embodiments, it is possible for only a portion of the total stroke of the hydraulic cylinder to be used for a working stroke to accelerate the ram, starting from a reversal point in the ram's movement sequence with zero ram speed, up to the target speed. Accordingly, the return stroke can be shortened, in particular such that the target speed can be reliably, and in particular reproducibly, achieved in the partial stroke available starting from the return stroke position and up to the forming position. The return stroke positions suitable for given target speeds can be obtained, for example, from test or trial runs and / or by simulation, and provided, for example, in the form of a value table in a database of a control unit or regulating unit of the forming machine or the hydraulic circuit.

[0049] By shortening the return stroke, for example at comparatively low target speeds, it is possible to increase the frequency of forming operations on the forming machine and / or to save energy by shortening the return stroke.

[0050] According to method-related embodiments of the invention, a method for operating a forging hammer for workpiece forming is provided. For example, a forging hammer designed or configured according to one of the embodiments described herein can be used to carry out the method.

[0051] According to one embodiment of the method, during a working stroke performed for workpiece forming, a ram intended or configured for workpiece forming is accelerated by a hydraulic cylinder coupled to the ram in an acceleration phase. During the acceleration phase, a first hydraulic working chamber of the hydraulic cylinder is supplied with hydraulic fluid through a hydraulic circuit via a valve with an adjustable, variable volume flow. In particular, the method comprises supplying the first working chamber via the valve with an adjustable, variable volume flow.

[0052] In the proposed method, it is provided that the hydraulic circuit, in particular the control or regulating unit, adjusts and varies, in particular regulates, the volume flow of the valve in the acceleration phase depending on a target speed of the ram to be achieved in the acceleration phase.

[0053] The advantages described in connection with the forging hammer proposed herein can be achieved accordingly with the method.

[0054] By adjusting and varying the volume flow, it is particularly possible to adjust the volume of hydraulic fluid flowing into the first working chamber per unit of time and also the time interval in which hydraulic fluid flows into the first working chamber, in particular based on a control system or a control loop. This makes it possible, for example, to specifically and variably adjust the opening width of the valve and the opening duration, in particular the filling time. The volume flow can, for example, be set and / or varied as a function of time. This makes it possible, for example, to adjust the duration of the acceleration phase, in particular as a function of the target speed. For low target speeds, for example, a small opening width combined with a correspondingly longer filling time compared to large opening widths can be implemented by a control system.For high target speeds, the opening width can be selected to be larger. This makes it possible, especially for both low and high target speeds, to extend the acceleration phase, for example, until shortly before the forming process, so that the movement or braking phase can be reduced to a minimum.

[0055] According to process-related embodiments, the valve can be designed as a controllable valve. The valve can comprise a continuous directional control valve, a proportional directional control valve, a servo directional control valve, and / or a control directional control valve. The method can include controlling the volume flow, in particular, the opening width and opening duration of the valve can be controlled.

[0056] According to one embodiment, a method for operating a forging hammer for workpiece forming is provided, in which, during a working stroke performed for workpiece forming, a ram intended for workpiece forming is accelerated by a hydraulic cylinder coupled thereto in an acceleration phase. The forming machine can be designed according to an embodiment described herein according to the invention.

[0057] According to the method of the embodiment, during the working stroke a first hydraulic working chamber of the hydraulic cylinder is supplied with hydraulic fluid via an actuator with an adjustable, variable volume flow through a hydraulic circuit. During the acceleration phase, the volume flow is set and varied, in particular regulated, by the actuator as a function of the target speed by the hydraulic circuit, in particular the control or regulating unit, such that the target speed is reached. In the movement phase immediately following the acceleration phase, the hydraulic circuit, in particular the control or regulating unit, reduces the volume flow by appropriately setting the actuator to a post-flow volume flow such that the hydraulic pressure prevailing in the first hydraulic working chamber during the movement phase (braking phase) is substantially above the cavitation pressure of the hydraulic fluid.Adjusting and varying the actuator may in particular comprise regulating the actuator.

[0058] Analogous to the above, the proposed actuator enables adaptation of the acceleration phase, particularly the length of the acceleration phase, to the target speed. In particular, it is possible to adjust the acceleration phase in such a way that the subsequent movement or braking phase is shortened to a minimum or optimized.

[0059] Furthermore, the actuator or valve with adjustable, variable volume flow makes it possible to influence the opening and closing behavior. Compared to a sudden opening and closing of the hydraulic supply to the first working chamber, as in a forming machine with a prior art on-off valve, the proposed invention makes it possible to specifically influence, adjust, and vary the opening and closing behavior, in particular to regulate and adapt the switching on and off of the hydraulic fluid flows, e.g., oil flows, to the inertia of actual components (ramps) in order to counteract or prevent a disruption of the hydraulic fluid flows.

[0060] According to one embodiment, the actuator can comprise a controllable valve and / or a controllable pump. Such actuators make it possible to adjust, in particular to control or regulate, the volume flow over time, for example, according to a predetermined or predeterminable time function. The associated advantages have already been mentioned above.

[0061] The valve can, for example, comprise a continuous directional control valve, a proportional directional control valve, a servo directional control valve, and / or a control directional control valve. The pump can, for example, comprise a servo pump.

[0062] In this method, the volume flow can be controlled depending on the target speed when using the actuators mentioned.

[0063] According to one embodiment of the method, the volume flow is adjusted by the control or regulating unit during the working stroke, in particular during the movement phase, such that a predetermined or predeterminable hydraulic pressure or hydraulic pressure curve is essentially achieved in the first hydraulic working chamber. The volume flow can, for example, be dynamically adjusted and varied, in particular regulated, based on a hydraulic pressure measured in the first hydraulic working chamber by means of a pressure sensor. In the method, the hydraulic pressure in the first working chamber can be measured accordingly. The hydraulic pressure or hydraulic pressure curve can be read from a value table or database and used to adjust the volume flow, in particular to regulate or control it.It is also possible that the hydraulic pressure prevailing in the second working chamber is measured during a working cycle and used to control the working stroke and / or return stroke.

[0064] According to one embodiment, the volume flow is adjusted and varied, in particular regulated, by the control or regulating unit such that the hydraulic pressure in the first hydraulic working chamber during the movement phase corresponds to a predetermined or predeterminable pressure or is within a predetermined pressure range. The predetermined pressure or pressure range can be between 2 and 6 bar, preferably between 3 and 4 bar. In particular, the volume flow can be adjusted and varied, in particular controlled, such that the hydraulic pressure in the first working chamber is above the cavitation pressure of the hydraulic fluid.

[0065] According to one embodiment of the method, the volume flow is set and varied, in particular controlled or regulated, by the control or regulating unit depending on the respective target speed to be achieved. The volume flow is preferably set and varied, in particular dynamically adjusted, based on a value table for target speeds and / or based on measured location and / or speed data of the ram. The value table can be determined, for example, from test runs or by simulation. In the method, it is further possible for location and / or speed data of the ram or of a component of the forming machine moved thereby and / or the measured hydraulic pressures to be measured and / or stored, in particular temporarily stored, by at least one sensor unit. The measured and / or stored data can be used for setting and varying, in particular regulating, the volume flow.

[0066] According to one process-related embodiment, the volume flow is adjusted and varied, in particular regulated, by the control or regulating unit in such a way that the duration of the acceleration phase is maximized or optimized while simultaneously minimizing the duration of the movement phase. For example, the acceleration phase can be adjusted such that the target speed is reached shortly before the forming operation, so that in some embodiments the post-suction phase, and in other embodiments the post-flow phase, is shortened or optimized, and associated disadvantages, e.g., disruption of the hydraulic fluid flow, the formation of cavitations, etc., can be at least largely avoided.

[0067] Embodiments of the invention are described in more detail below with reference to the attached figures. They show: FIG. 1 schematically shows an exemplary structure of a forging hammer embodiment; FIG. 2 schematically shows, by way of example and diagrammatically, a voltage applied to a control valve used as a strike valve of the forging hammer of the embodiment as a function of time for a working cycle; FIG. 3 an opening diagram of a return stroke valve during operation of the forging hammer of the first embodiment; and FIG. 4 an exemplary schematic position and speed diagram of a ram during a working cycle.

[0068] FIG. 1 schematically shows an exemplary structure of a hydraulically operated forging hammer 1 according to an embodiment. The forging hammer 1 represents an example of a forming machine.

[0069] The forging hammer 1 comprises a ram 2 with a tool 3 attached thereto for forming a workpiece (not shown).

[0070] The ram 2 is coupled to a hydraulic cylinder 4. More precisely, the ram is mechanically coupled via a piston rod 5 to a piston 7 movable in a cylinder tube 6.

[0071] The hydraulic cylinder 4 is controlled via a hydraulic circuit 8. A first working chamber 9 of the hydraulic cylinder 4 and a second working chamber 10 are connected to the hydraulic circuit 8 via hydraulic lines. A pressing surface of the piston 7, also called the piston surface, faces the first working chamber 9, and a retraction surface of the piston 7, also called the annular surface, facing away from the pressing surface, faces the second working chamber 10.

[0072] The hydraulic circuit 8 comprises a pump unit 11 with a motor-driven pump and control valves, wherein the pump unit 11 is configured to generate a predetermined system pressure.

[0073] Downstream of the pump unit 11 is a control valve or control directional control valve 12 with a safety stage, which, in a first directional switching position, separates the pump unit 11, the second working chamber 10, and the storage unit 19 from the first working chamber 9, and, in a second directional switching position, connects the first working chamber 9 with the pump unit 11, the second working chamber 10, and the storage unit 19. The control directional control valve 12 forms a strike valve for regulating a working stroke or a forging stroke.

[0074] A brake valve 14 and a first pressure sensor 15 are provided between the control directional valve 12 and the first working chamber 9. The control directional valve 12, the brake valve 14, and the first pressure sensor 15 are connected to the first working chamber 9 via a first connection 16 located at an upper end of the cylinder tube 6.

[0075] The pump unit 11 is connected to a second port 17 located at a lower end of the cylinder tube 6. A second pressure sensor 18, a pressure accumulator 19, and a safety valve 20 are connected to the hydraulic line running between the pump unit 11 and the second port 17.

[0076] A third port 21 on cylinder 6, located between the first port 16 and the second port 17, leads to a valve 27, which can optionally block the line leading to the third port or switch it to a hydraulic tank 13. The line further comprises a third pressure sensor 22 and a throttle 28, by means of which a connection from the first port 16 to the valve 27 is realized. The third port 21 is located closer to the first port 16, for example, in an upper third of the cylinder tube 6 surrounding the first port 16.

[0077] The hydraulic circuit 8 further comprises a control unit 23, in particular a control or regulating unit 23, which is connected via data, control and regulating lines (not shown) to the components of the forging hammer 1 to be controlled or regulated, for example the pump unit 11, the control directional control valve 12, the pressure sensors 15, 18, 22 and a distance measuring unit 24. The distance measuring unit 24 is designed to detect the position or the distance traveled by the ram 2 and / or to determine the speed of the ram 2, e.g. from a distance measurement.

[0078] At the blacksmith hammer 1 after FIG. 1 the control unit 23, in particular the hydraulic circuit 8, is designed to adjust the impact energy generated for the workpiece forming of a workpiece by kinetic energy of the ram 2, in particular a target speed corresponding to the impact energy, which will be described in more detail below.

[0079] Based on the FIG. 1 In the situation shown, in which the ram 2 and correspondingly the piston 7 are at an upper reversal point, the ram 2 with tool 3 is accelerated by the first working chamber 9 being pressurized with hydraulic fluid, in particular hydraulic oil, via the control valve 12. Accordingly, the first working chamber 9 fills, causing the piston 7 and correspondingly the ram 2 to move downwards in a working stroke A, i.e., towards the workpiece to be formed. When the first working chamber 9 is pressurized, the ram 2 coupled to the piston 7 is accelerated.

[0080] The hydraulic circuit 8, in particular the control or regulating unit 23, is configured such that the ram 2 is accelerated to a predetermined or predeterminable target speed, corresponding to a predetermined or predeterminable impact energy.

[0081] When the lower reversal point of the piston 7 located in the area of the second connection 17 is reached, a workpiece is deformed at the forming point, with the ram 2 transferring the impact energy resulting from the desired speed to the workpiece.

[0082] After the workpiece has been formed, a return stroke R occurs. The hydraulic pressure constantly present in the second working chamber 10 accelerates the piston 7 and, accordingly, the ram 2 in the return stroke direction. During the return stroke, the fluid in the first hydraulic chamber 9 can flow via the third port 21 to the valve 27. This opens the way to the hydraulic tank 13, at least during the return stroke, so that the hydraulic fluid can flow there.

[0083] If the piston 7 overruns or closes the third port 21 at the end of the return stroke phase or in the upper third of the cylinder 6, the hydraulic fluid flows from the first port 16 via the throttle 28 to the valve 27, which is still connected to the hydraulic tank 13, until the piston 7 and, accordingly, the ram 2 with tool 3 finally stop. The control directional control valve 12 is completely or at least essentially closed during the entire return stroke phase.

[0084] Working stroke A and return stroke R form a working cycle of the forging hammer 1 which can be repeated.

[0085] The control or regulation of the working stroke A and return stroke R, e.g. by the control or regulation unit 23, is described in more detail below.

[0086] The control directional control valve 12 represents an example of a valve with an adjustable, variable volume flow. Depending on the voltage or current, in particular control or regulating signals, applied to the control directional control valve 12, the valve can be continuously opened and closed. In particular, the control directional control valve 12 can be controlled in a targeted manner, e.g., in the form of a ramp, by corresponding control or regulating signals determined or generated by the control unit 23. Furthermore, the control unit 23 and the control directional control valve 12 are configured, for example, but not limited to, via a cam control unit, so that the opening time can be controlled for a predetermined time, e.g., with an accuracy of 0.5 ms. Thus, the volume flow of the control directional control valve 12 can be adjusted and varied, with a total of several control variables being available for controlling the control directional control valve 12, i.e.the valve opening as such, and the opening time and the temporal course of the valve opening.

[0087] The hydraulic circuit 8 and the control unit 23 are configured such that the volume flow of the control directional valve 12 is controlled as a function of a target speed of the ram 2 to be achieved in an acceleration phase of a working stroke A.

[0088] At this point it should also be mentioned that in the design of the blacksmith's hammer shown, the bear is moved up and down parallel to the direction of gravity S.

[0089] The forging hammer 1 does not have a suction valve and, accordingly, no suction tank. To ensure that hydraulic fluid can flow into the first working chamber 9 of the forging hammer 1 after the target speed has been reached during the braking phase, the control unit 23 is configured such that it does not completely close the control directional control valve 12 after the target speed has been reached. The control unit 23 regulates the control directional control valve 12 such that sufficient hydraulic fluid can flow in and the pressure prevailing in the first working chamber 9 remains above the cavitation pressure of the hydraulic fluid. The braking effect is achieved by the system pressure present in the annular space of the second working chamber 10.

[0090] In particular, the control directional valve 12 can be controlled such that the pressure in the first working chamber 9 is significantly lower than the system pressure, but above the cavitation pressure. With such control of the control directional valve 12 during the movement phase, essentially the same braking effect can be achieved as when using a suction valve, wherein the braking, as mentioned, is effected by the system pressure present in the annular space of the second working chamber 10. The volume flow of the control directional valve 12 can, for example, be controlled such that the pressure in the first working chamber 9 is between 2 and 6 bar, above the cavitation pressure of the hydraulic fluid.

[0091] The control of the control directional valve 12 in the movement phase can, for example, be based on the pressure detected by the first and / or third pressure sensor 15 or 22.

[0092] The use of the control directional valve 12 has the advantage that control directional valves generally have shorter response times than anti-cavitation valves, so that cavitation can be avoided with greater reliability. Particularly in the transition phase from the acceleration phase to the movement phase of the working stroke, the short response times of control directional valves offer an advantage over comparatively sluggishly reacting anti-cavitation valves. A particular advantage against the formation of cavitation, however, is that the control directional valve 12 can be continuously adjusted from the acceleration volume flow to the afterflow volume flow, e.g. according to a linear or other non-linear function, without it having to be completely closed in the meantime. The hydraulic fluid flow cannot therefore be interrupted, and cavitation is essentially or completely avoided.

[0093] FIG. 2shows, by way of example and schematically, a voltage applied to the impact valve 12 of the forging hammer 1 as a function of time t for a working stroke A and return stroke R. As can be seen from FIG. 2 As can be seen, the control directional control valve 12 can be controlled in the acceleration phase of the working stroke A until the target speed is reached at time ts.

[0094] Based on the FIG. 1In the situation shown at the beginning of the working stroke A at the first time t1, the control directional valve 12 is actuated with a first voltage U1. Via the control directional valve 12, the first working chamber 9 is pressurized with hydraulic fluid in accordance with the opening width of the control directional valve 12 corresponding to the first voltage U1, with the system pressure applied to the inlet of the control directional valve 12. The ram 2 is accelerated by the hydraulic fluid entering the first working chamber 9 and the force of gravity S acting on the ram 2. Subsequently, the voltage U applied to the control directional valve 12 is increased according to a ramp up to a second voltage U2.

[0095] The initial first voltage U1, the ramp, and the second voltage U2 are regulated or adjusted by the control unit 23 such that the required or desired target speed, i.e., the desired impact energy, for the respective forming process is reached at a time ts. The voltages U1 and U2 and the ramp can be taken, for example, from a table of values for target speeds or impact energies, in particular specifically for a given work cycle, or can be adjusted accordingly.

[0096] Corresponding value tables can be created, for example, through simulation and / or test operation of the impact hammer. A simulation can use parameters such as the weight of the ram 2 and the components moved by the ram 2 (e.g., piston rod 5, piston 7, tool 3), the technical data of the hydraulic cylinder 4 (e.g., total stroke, pressing area), and the operating parameters of the hydraulic circuit 8 (e.g., system pressure, hydraulic fluid properties, temperature).

[0097] Apart from a ramp, i.e. a linear function of time, other, especially non-linear, functions can also be considered.

[0098] When the target speed is reached, the control valve 12 is not completely closed, but is controlled, e.g., according to a linear function, such that hydraulic fluid can continue to flow into the first working chamber 9. As already mentioned, the control is configured such that the pressure in the first hydraulic chamber 9 is above the cavitation pressure of the hydraulic fluid. Furthermore, since the control directional control valve 12 is not completely closed after the target speed is reached during the braking phase of the working stroke A, interruption of the hydraulic fluid flows can be avoided.

[0099] FIG. 3shows an opening diagram of the valve 27 (return stroke valve) during a working cycle (R, A) of the forging hammer 1. The valve 27 is closed during the working stroke A and is opened after forming (time t2), whereby the first working chamber 9 is connected to the hydraulic tank 13. As a result, the hydraulic fluid can flow from the first working chamber 9 during the return stroke R via the third port 21 and, after the piston 7 has passed the third port 21, via the throttle 28 into the hydraulic tank 13.

[0100] FIG. 4 shows a position and speed diagram of the ram 2 during a working cycle of the forging hammer 1. More precisely, FIG. 4 the course of the position X of the bear 2 and the speed V of the bear 2 as a function of time t.

[0101] Starting at the first time t1, the ram 2 is accelerated by appropriately controlling the volume flow of the control valve 12. In the present example, the control is carried out in such a way that the speed V increases linearly until the target speed Vsoll is reached. However, the proposed invention also allows for the implementation of other speed-time curves, i.e., not only linear curves.

[0102] Once the target speed Vsoll is reached, the hydraulic circuit 8 is controlled according to one of the operating modes described above, whereby the movement phase of the working stroke A, in which the ram 2 moves at a substantially constant target speed Vsoll, is FIG. 4 is not shown in a temporally resolved manner.

[0103] In the present example, the control in the movement phase (braking phase) is carried out in such a way that the target speed Vsoll is only reached shortly before the forming point, so the post-flow phase is advantageously shortened.

[0104] The position X of the ram 2 changes according to the linear speed change according to a parabolic function from the initial position 0 over the stroke H performed in the working cycle.

[0105] During the forming process at the second time t2, the ram 2 is braked and moves back to the starting position 0 due to the rebound energy and the return stroke control of the hydraulic circuit 8 as described above.

[0106] For the return stroke R, the hydraulic circuit 8 is controlled as described above, whereby in the present example the ram 2 experiences a linear change in speed V during the return stroke. At the upper reversal point at the third time t3, the ram 2 has zero speed.

[0107] Since the return surface of the piston 7 is an annular surface and thus smaller than the pressing surface of the piston 7, the acceleration of the ram 2 during the return stroke R is lower than during the working stroke A. In FIG. 6 the braking process in the area of the upper reversal point is not shown in time resolution.

[0108] Instead of the control valve 12, a controllable pump, such as a servo pump, can also be used. With such a pump, the volume flow can be adjusted and varied, in particular controlled, as described above, in accordance with the control valve 12.

[0109] The described embodiments of a forging hammer 1, generally a correspondingly configured forming machine with corresponding control, have in particular the following advantages.

[0110] By using valves or pumps with adjustable, variable flow rates, it is possible to change the hydraulic fluid supply relatively smoothly, avoiding sudden changes. This offers the particular advantage of avoiding cavitation, which can be caused by sudden changes in the flow rate, for example, due to a disruption of the hydraulic fluid flow due to the inertia of the hydraulic fluid.

[0111] The control or regulation of the hydraulic circuit possible with the proposed forming machine makes it possible, at a specified target speed, impact energy, or energy pre-selection, to extend the acceleration phase until shortly before the ram 2 or tool 3 impacts the workpiece, or to specifically accelerate the ram 2 until shortly before it impacts the workpiece, so that the post-flow phase can be shortened to a minimum or optimized. For example, the hydraulic circuit can control the forging hammer and regulate the volume flow such that, at low target speeds or low forming energies, a lower acceleration of the ram 2 is set over the entire stroke than at high target speeds or high forming energies.

[0112] When using a position measuring unit 24 in combination with comparatively quickly controllable control valves 12 or pumps and due to the comparatively short reaction times of such actuating units or control or regulating units, the working stroke can be carried out in a targeted and controlled manner.

[0113] The proposed forming machine also allows for advantages regarding the design of the hydraulic circuit 8. In particular, the comparatively complex impact valves used in prior art forging hammers 1 can be dispensed with. Compared to forming machines with a suction valve, structural simplifications can be achieved in that a suction valve and an associated reservoir, as well as associated hydraulic lines and components, can be eliminated.

[0114] A hydraulic forming machine 1 in the form of a forging hammer 1 for workpiece forming is provided, comprising a hydraulic cylinder 4 for driving a ram 2 configured for workpiece forming, and a hydraulic circuit configured to operate the hydraulic cylinder 4, wherein the hydraulic circuit 8 has a valve 12 and / or actuator with an adjustable, variable volume flow, via which a first hydraulic working chamber 9 of the hydraulic cylinder 4, used to accelerate the ram 2 during the execution of a working stroke A for workpiece forming, can be pressurized with hydraulic fluid. The hydraulic circuit 8, in particular of the control or regulating unit 23, is configured to adjust and vary the volume flow of the valve 12 or actuator as a function of a target speed Vsoll of the ram 2 to be achieved in an acceleration phase of a working stroke A, and to optimize the subsequent movement phase of the working stroke A.

[0115] The operating mode of the forging hammer 1 has the particular advantage that cavitation in the hydraulic fluid can be avoided after the target speed has been reached. This is achieved, in particular, by the controlled acceleration of the ram, so that the movement phase following the acceleration phase, i.e., the braking phase, of the working stroke is optimized, particularly with regard to the occurrence of cavitation.

[0116] In prior art forging hammers, the hydraulic circuit comprises a hydraulic fluid reservoir, the suction tank, connected to the first working chamber via a suction valve. In these designs, the suction valve, which is designed as a check valve, opens at a certain pressure ratio between the suction tank and the piston chamber, allowing hydraulic fluid to flow in. In prior art forging hammers, the acceleration phase of the working stroke is always at maximum pressure and flow rate. This results in long acceleration phases and short braking or suction phases for high target speeds. In contrast, shorter acceleration phases and longer braking or suction phases result for low target speeds.Since the re-suction is generally critical with regard to cavitation, especially during comparatively long re-suction phases, and the re-suction phase depends on many factors that are difficult or impossible to influence, such as manufacturing tolerances of the components of the re-suction valve (spring stiffness, friction of the running surface, mass, etc.), temperature of the hydraulic medium, properties of the fluid itself, fill level in the re-suction tank or container (geodetic pressure), etc., the known forging hammers are to be viewed rather critically with regard to functional reliability (e.g. cavitation).

[0117] Based on this, it is a finding of the underlying invention that re-suction can be completely eliminated by appropriate control / regulation of the acceleration phase. The latter enables, for example, a cavitation-free drive.

[0118] According to the invention, the after-suction can be eliminated or a cavitation-free drive can be implemented. In this case, the hydraulic fluid is supplied via the impact valve during the braking phase, so that an after-suction valve and after-suction tank are not required. The volume flow required to avoid cavitation-critical pressure is supplied to the first working chamber via the impact valve. For this purpose, the impact valve is preferably pressure-controlled from the end of the acceleration phase, i.e. the opening cross-section and the associated volume flow are changed in real time depending on the conditions in the piston chamber. In particular, it can be avoided that the impact valve is closed suddenly after the end of the acceleration phase. Instead, the impact valve can be closed continuously until the (pressure) control of the impact valve begins. The parameters required to control the impact valve can, for example,by a pressure sensor installed in the first hydraulic working chamber. This essentially or completely prevents the hydraulic fluid column from breaking off, resulting in cavitation and associated damage.

[0119] Overall, it can be seen that the problem underlying the invention is solved. List of reference symbols

[0120] 1 Blacksmith hammer 2 Bear 3 Tool 4 Hydraulic cylinder 5 Piston rod 6 Cylinder tube 7 Piston 8 Hydraulic circuit 9 First working chamber 10 Second working chamber 11 Pump unit 12 Control valve (beating) 13 Hydraulic tank 14 Brake valve 15 First pressure sensor 16 First connection 17 Second connection 18 Second pressure sensor 19 Pressure accumulator 20 Safety valve 21 Third connection 22 Third pressure sensor 23 Control unit 24 Position measuring unit 27 Valve (rising) 28 Throttle AWorking stroke RReturn stroke SGravity UVoltage tTime GSpeed XPosition HHub OOpen position

Claims

1. Forging hammer (1) for workpiece forming, comprising a differential cylinder (4) having an annular surface and a piston surface for driving a bear (2) set up for workpiece forming and mechanically coupled to the differential cylinder and a hydraulic circuit (8), which is set up for operating the differential cylinder (4) and has an actuator (12) with an adjustable variable volume flow for adjusting a volume flow of hydraulic fluid for filling a first hydraulic working room (9) of the differential cylinder (4) during the execution of a working stroke (A) immediately preceding the workpiece forming with an acceleration phase for accelerating the bear (2) to a set speed (Vsoll) and a movement phase following the acceleration phase, in which the set speed (Vsoll) reached is essentially maintained, the piston surface facing the first hydraulic working room (9), a control or regulating unit (23) of the hydraulic circuit (8) being set up to adjust and vary the volume flow as a function of the set speed (Vsoll) to be reached in each case, the control or regulating unit (23) being set up: - to adjust and vary the volume flow in the acceleration phase as a function of the set speed (Vsoll) so that the set speed (Vsoll) is reached, and - to reduce the volume flow in the subsequent movement phase to an after-flow volume flow in such a way that the hydraulic pressure prevailing in the first hydraulic working room (9) in the movement phase is essentially above the cavitation pressure of the hydraulic fluid, wherein the control or regulating unit (23) is set up to adjust and vary the volume flow in the acceleration phase in such a way that the movement phase corresponds to between 10% and 30% of the stroke of the differential cylinder (4).

2. Forging hammer (1) according to claim 1, wherein the actuator (12) comprises a controllable or adjustable valve and / or a controllable or adjustable pump, wherein the valve preferably comprises a continuous directional control valve, a proportional directional control valve, a servo directional control valve and / or a control directional control valve (12), and wherein the pump preferably comprises a servo pump.

3. Forging hammer (1) according to claim 1 or 2, further comprising at least one pressure sensor (15, 18, 22) set up to measure the hydraulic pressure prevailing in the first and / or second hydraulic working room (9, 10) during the working stroke and / or return stroke, and wherein the control or regulating unit (23) is set up to adjust and vary, in particular to regulate, the volume flow during a working cycle of the bear (2), but at least in the movement phase, as a function of the measured hydraulic pressure.

4. Forging hammer (1) according to any of claims 1 to 3, wherein the control or regulating unit (23) is set up to adjust and vary the volume flow in such a way that the hydraulic pressure in the first hydraulic working room (9) in the movement phase corresponds to a predetermined or predeterminable pressure or is in a predetermined or predeterminable pressure range, wherein the predetermined or predeterminable pressure or pressure range is preferably between 2 to 6 bar, more preferably between 3 to 4 bar, and / or wherein the volume flow in the acceleration phase is set such that the movement phase corresponds to between 10% and 20% of the stroke of the differential cylinder (4), and / or wherein the volume flow in the acceleration phase is set or varied such that the length of the acceleration phase and correspondingly the length of the movement phase and / or their ratio is set as a function of the set speed (Vsoll) to be achieved in each case.

5. Forging hammer (1) according to any of claims 1 to 4, wherein the control or regulating unit (23) is set up to adjust the volume flow based on a table of values for set speeds and / or is set up to dynamically adjust the volume flow based on measured location and / or speed data (X or V) of the bear (2), wherein the forming machine (1) further preferably comprises at least one sensor unit (24) for measuring and / or storing location and / or speed data of the bear (2).

6. Forging hammer (1) according to any of claims 1 to 5, wherein the control or regulating unit (23) is set up to substantially completely close the valve (12) or the actuator at least temporarily in the movement phase following the acceleration phase.

7. Forging hammer (1) according to any of claims 1 to 6, wherein the control or regulating unit (23) is set up to adjust and vary, in particular to regulate, the volume flow such that the movement phase is optimised, in particular shortened, preferably such that the acceleration phase is maximised while simultaneously minimising the movement phase, further preferably such that the movement phase corresponds in the range of 10% to 30%, in particular 10% to 20% of the stroke of the differential cylinder (4).

8. Forging hammer (1) according to any of claims 1 to 7, wherein the control or regulating unit (23) is set up to use only a part of the entire stroke (H) of the differential cylinder (4) for a working stroke (A), starting from a reversal point located in the movement sequence of the bear (2) with zero bear speed towards the set speed, to use only a part of the entire stroke (H) of the differential cylinder (4) and to shorten the return stroke (R) in such a way that the set speed (Vsoll) is reliably reached in a partial stroke starting from the return stroke position and available up to the forming position.

9. Method for operating a forging hammer (1) for workpiece forming according to any of claims 1 to 8, wherein the control or regulating unit (23) controls or regulates the hydraulic circuit (8) in such a way that, in a working stroke (A) executed for workpiece forming, a bear (2) provided for workpiece forming is accelerated in an acceleration phase by a differential cylinder (4) coupled thereto, wherein in the working stroke a first hydraulic working room (9) of the differential cylinder (4) is fed with hydraulic fluid by a hydraulic circuit (8) via an actuator (12) with an adjustable variable volume flow, wherein the control or regulating unit (23) adjusts and varies the volume flow by the actuator (12) in the acceleration phase as a function of the set speed (Vsoll) in such a way that the set speed (Vsoll) is reached, and in a movement phase immediately following the acceleration phase, in which the set speed (Vsoll) reached is essentially maintained, reduces the volumetric flow to an after-flow volumetric flow, in particular regulates it, such that the hydraulic pressure prevailing in the first hydraulic working room (9) in the movement phase is essentially above the cavitation pressure of the hydraulic fluid, wherein the control or regulating unit (23) adjusts and varies the volume flow in the acceleration phase in such a way that the movement phase corresponds in the range of 10% to 30% of the stroke of the differential cylinder (4).

10. Method according to claim 9, wherein the volume flow is dynamically adjusted and changed, in particular regulated, by the control or regulating unit (23) based on a hydraulic pressure measured in the first and / or second hydraulic working room (9, 10) by means of a pressure sensor (15, 18, 22).

11. Method according to claim 10, wherein the volume flow is set and varied by the control or regulating unit (23) such that the hydraulic pressure in the first hydraulic working room (9) in the movement phase, which is a braking phase, corresponds to a predetermined or predeterminable pressure or is in a predetermined pressure range, wherein the predetermined pressure or pressure range is between 2 to 6 bar, preferably 3 to 4 bar.

12. Method according to any of claims 9 to 11, wherein the volume flow is set by the control or regulating unit (23) based on a table of values for set speeds and / or is set, in particular dynamically set, based on measured location and / or speed data of the bear (2), wherein preferably location and / or speed data (X or V) of the bear (2) are measured and / or stored by at least one sensor unit (24) and are used in the setting of the volume flow.

13. Method according to any of claims 9 to 12, wherein the volume flow is set and varied, in particular regulated, by the control or regulating unit (23) in such a way that the time duration of the acceleration phase is maximised while simultaneously minimising the time duration of the movement phase, wherein, optionally, the time duration of the movement phase is 10% of the time duration of the acceleration phase.

14. The method according to any of claims 9 to 13, wherein the control or regulating unit (23) adjusts and varies the volume flow such that the movement phase corresponds in the range of 10% to 20% of the stroke of the differential cylinder (4).

15. Method according to any of claims 9 to 14, wherein the control or regulating unit (23) adjusts the volume flow over time so that the set speed is reached within a predeterminable stroke range of the differential cylinder (4), and / or for a working stroke (A), starting from a reversal point located in the movement sequence of the bear (2) with zero bear speed up to the set speed, uses only a part of the entire stroke (H) of the differential cylinder (4) and shortens the return stroke (R) in such a way that the set speed (Vsoll) is reliably reached in a partial stroke starting from the return stroke position and available up to the forming position.