Hydraulically operated handheld device

Abstract

Hydraulically operated hand-held device (1), wherein the hand-held device (1) comprises a hydraulic pump, a moving part (4), a fixed part (5) and a return valve (8) with an associated valve seat, wherein the moving part (4) can be moved into a working position by building up a hydraulic pressure which results from filling a hydraulic chamber (6) with hydraulic fluid from a storage chamber (3) using the hydraulic pump, wherein it can be achieved that the moving part (4) can be automatically moved back from the working position to an end position by opening the return valve (8) upon reaching a predetermined working pressure, characterized in that a pressure sensor (29) is further provided, wherein a return of the moving part (4) can take place as a function of a pressure value measured by the pressure sensor (29) by a triggerable opening of the return valve (8), and the working pressure,in which the opening of the return valve (8) is triggered, can be selected deviating from the predetermined working pressure, that an adjustment device (27) for different working pressures, which can be preset by the user, is provided on the handset, designed as an adjusting wheel, adjusting slide, an arrangement of a plurality of buttons, each button being assigned a predetermined working pressure, or as a keyboard with an associated display, the actually selected working pressure being shown on the display, that an evaluation / control electronics evaluates pressure measurements from the pressure sensor (29) during the movement of the moving part (4) towards the working position and compares these with the pressure setpoint predetermined via a button (28), that the working pressure can also be adjusted from outside the handset via a non-mechanical interface, in particular a radio and / or optical interface to the device.

Description

The invention relates first to a hydraulically operated hand-held device, for example. Pressing device or piercing or punching device, wherein the hand-held device has a hydraulic pump, a moving part, a fixed part and a return valve with an associated valve seat, wherein furthermore the moving part can be moved into an operating position by building up a hydraulic pressure which results from filling a hydraulic chamber with hydraulic medium from a storage chamber using the hydraulic pump, wherein it can be achieved that the moving part can be automatically moved back from the operating position into an end position by opening the return valve when a predefined operating pressure is reached.The invention also relates to a hydraulically operated hand-held device, for example a pressing device or a punch or punch device, wherein the hand-held device has a hydraulic pump, a moving part, a fixed part and a return valve with an associated valve seat, wherein the moving part can be moved into a working position by building up a hydraulic pressure which results from filling a hydraulic chamber with hydraulic medium from a storage chamber using the hydraulic pump, wherein it can be achieved that the moving part can be automatically moved back from the working position into an end position by opening the return valve when a predetermined working pressure is reached, wherein in any case the return valve only closes in this case after a specific hydraulic pressure acting on the return valve is undershot.The invention also relates to a hydraulically operated hand-held device of the type described above, wherein a pressure sensor is also provided.The invention also relates to a hydraulically operated hand-held device of the type described above, wherein a work sequence can also be triggered by a hand of a user acting on a switch.Such hand-held devices are known, for example, from DE 10 2008 028 957 A1, EP 0 944 937 B1 (U.S. Pat. No. 6,276,186 B1, U.S. Pat. No. 6,401,515 B2), WO 2014 / 108361 A1 and WO 2012 / 055901 A1.Such hand-held devices are used, for example, as pressing devices, preferably for pressing or crimping cable shoes with inserted cable or for pressing tubular or tubular workpieces. Such hand-held devices can also be used for punching or punching, in particular, metal components. Furthermore, such hand-held devices can also be designed as riveting devices or other cutting devices.A hydraulically operated hand-held device in the form of a pressing device is described, for example, in EP 0 944 937 B1 (U.S. Pat. No. 6,276,186 B1, U.S. Pat. No. 6,401,515 B2). This hand-held device has a return valve which, when a predetermined hydraulic pressure is reached, is displaced into a valve open position and is held in this position. This leads to a return flow of the hydraulic medium which displaces the movement part into the working position. The moving part moves back into the basic or end position due to the absence or reduced pressurization. At the latest when this end position is reached, the hydraulic pressure acting on the return valve is lowered in such a way that the return valve closes again automatically.DE 37 10 863 A1 discloses a check valve for a hydraulically operated hand-held device, which permits a controlled opening and closing of the flow in a hydraulic system. The check valve operates pilot-controlled and can be hydraulically unlocked if necessary. A stable, sensitive control is achieved by several throttle points and damping elements.US 2005 / 0 016 375 A1 discloses a hydraulically operated hand-held device which can be operated both with a constant volume flow and with a constant pressure. An integrated adjusting unit enables simple and tool-free changeover between the two operating modes without having to disassemble the device.US 2005 / 0 235 730 A1 discloses a hand-held device having a closed hydraulic system of compact design, which operates without an external supply of pressurized medium and generates linear forces, for example for cutting, crimping or lifting.Proceeding from the state of the art shown, the invention is concerned with the object of specifying a hydraulically operated hand-held device which, with a simple design of the device, enables the machining of workpieces which differ in particular with regard to size and / or material, or simplifies handling and increases operating reliability.To achieve the object, a hand-held device is proposed, in which it is also provided that a pressure sensor (29) is predetermined, wherein a return of the movement part (4) can take place as a function of a pressure value measured by the pressure sensor (29) by triggering the return valve (8) to open, and the working pressure at which the opening of the return valve (8) is triggered can be selected deviating from the predetermined working pressure, that an adjusting device (27) for different working pressures preset by the user is provided on the hand-held device, designed as a control wheel, control slide, an arrangement of a plurality of keys, wherein each key is occupied by a predetermined working pressure, or as a keyboard with an associated display, wherein the actually selected working pressure is reproduced on the display, an evaluation / control electronics in the course of the movement of the movement part (4) in the direction of the working position evaluates pressure measurement values of the pressure sensor (29) and compares these with the pressure setpoint value specified via a button (28), and in that the working pressure can additionally also be adjusted from outside the hand-held device via a non-mechanical interface, in particular a radio and / or optical interface to the device.With regard to the hydraulically operated hand-held device, it is in this respect considered that a hydraulic pressure acting on the return valve can be increased, independently of reaching the predefined working pressure, to a pressure value which causes the return valve to open.The predetermined working pressure is the hydraulic pressure which is established in the hydraulic medium by a working process, at which the return valve moves into the open position on account of its structural design. This hydraulic pressure is established in the hydraulic chamber, when the return valve is closed, which hydraulic chamber extends from the movement part as far as a closing surface of the return valve. The structural design is preferably provided in that a partial piston surface of a valve piston is seated in the valve seat in the closed state, i.e. forms the said closing surface. A certain hydraulic pressure is then required in order to lift the return valve out of the valve seat by acting on this partial piston surface, so that hydraulic medium can drain through the valve seat, for example into a hydraulic medium storage space. The return valve is further preferably designed as a valve piston in such a way that it has a total piston surface on which the hydraulic medium acts when the return valve is raised from the valve seat, that is to say is in the open position. Due to the size ratio between the total piston surface and the partial piston surface, a comparatively very low pressure can be sufficient in the open position of the return valve relative to the partial piston surface to hold the return valve in its open position. The surface that complements the partial piston surface to form the total piston surface can also be acted upon by hydraulic medium in the closed state of the return valve. However, not due to the hydraulic medium, which is contained in the hydraulic chamber terminating at the named closing surface. In a practical design, for example, a pressure of 300 to 600 bar, further for example 400 or 500 bar, may be required with respect to the partial piston surface in order to lift the return valve out of the valve surface, while the total piston surface only requires a pressure of a few, for example, 5.4 or less bar, for example, up to 0.5 bar, for example, in order to remain in the open position. In a specific embodiment, this pressure acting on the entire piston surface can be generated, for example, by a restoring spring acting on the movement part.With regard to an embodiment of the hand-held device as a punching or punching device, the predetermined working pressure is generally selected to be higher than the pressure required for carrying out the punching or punching operation. In this respect, the predetermined working pressure can also be set so high that the return valve only still works in the sense of a pressure relief valve without further measures. The same applies in principle, for example, to a configuration of the hand-held device as a riveting device. Alternatively, however, the embodiment of the hand-held device, in particular in the variants specified by way of example, can also be provided such that, when the return valve is triggered on the basis of the predefined working pressure, the movement part, insofar as no further intervention takes place, returns to its predefined starting position.According to the invention described here, however, a hydraulic pressure at which the return valve is moved into the open position can be achieved in that a pressure increase in hydraulic medium acting on the return valve is carried out with an action means which is independent of a working process which is carried out with the hand-held device. This increase in pressure is carried out in the hydraulic medium which acts on the surface of the return valve which, when the return valve is open, supplements the partial piston surface to form the total piston surface. When the return valve is closed, this hydraulic medium is separated in terms of flow from the hydraulic medium acting on the moving part. The pressure can be applied for a short time, if necessary. The pressure increase is selected such that the return valve is thereby moved into the open position. The pressure prevailing in the hydraulic medium acting on the moving part with respect to the moving part for carrying out the working process has regularly not yet reached the predefined working pressure. It is thus provided that the return valve can be hydraulically opened before the working pressure which is predetermined in accordance with the release pressure at the return valve is present at the movement part.The return valve can be hydraulically displaced into the open position independently of the prevailing working pressure at the movement part.The return valve preferably closes only after a specific hydraulic pressure acting on the return valve has dropped to such an extent that the pressure load required for holding the return valve in the open position due to the structural design of the return valve is no longer present.The return valve is automatically opened at a changeable, i.e. preselected working pressure modified with respect to the predetermined working pressure, preferably as a result of a corresponding pressurization of the return valve.The working pressure which is only reached during a working operation can also be set as a modified working pressure. Thus, for example, a working pressure can be specified by the user as a modified working pressure via a control wheel or via buttons on the device, which working pressure is less than the maximum permissible working pressure, that is to say the aforementioned specified working pressure at which the return valve preferably also opens automatically, or also corresponds to this maximum working pressure. The latter may be useful, for example, if the aforementioned maximum working pressure is actually to be reached, but also only to be reached, with higher accuracy. Thus, at an exemplary predetermined or maximum working pressure of 600 bar, working pressures of 50 to 600 bar can be adjusted continuously or stepwise. Thus, a load-related adaptation to the machining of workpieces to be carried out by means of the device can be carried out, while maintaining an automatic return of the moving part into the end position after reaching the operating pressure which is optionally set.It is additionally provided that the setting of the modified working pressure can be carried out from outside the hand-held device, for example via a radio interface or optical interface.The pressure increase preferably only acts briefly. In terms of time, the pressure increase in the range of a few tenths of a second can only be effective, for example over a period of 1 / 10 to 5 / 10 seconds.The pressure increase is carried out in particular by feeding hydraulic medium into the space provided downstream of the valve seat with regard to a direction of outflow of the hydraulic medium. This space, which is also referred to below as valve space, is provided before opening of the return valve on the one hand by the total piston surface minus the partial piston surface and on the other hand by the surface of the valve seat facing the total piston surface, including a delimiting surface of the pressure increasing piston and optionally a surface of a line section provided in this context. The latter is in any case arranged as far as the pressure-increasing piston is arranged directly as part of the valve chamber. It can also be separated from it, for example, by a check valve. Preferably, there is also no actual feeding of additional hydraulic medium into the valve chamber. Merely reducing the valve space by a movement of the pressure-increasing piston may be sufficient. This can also result in the required increase in pressure.Due to the additional pressure load behind the valve seat, an initial pressure increase for the displacement of the return valve into the open position acts on the one hand on the total piston surface of the return valve (minus the partial piston surface of a valve tip which is not yet effective at the moment of the pressure increase). It also acts essentially decoupled from the movement part because it is still exposed-only-at the moment of the pressure increase-to the hydraulic pressure "in front of" the valve seat (viewed with regard to the flow direction of the hydraulic medium through the open return valve). As a result, only a substantially smaller increase in pressure is required than in front of the valve seat (viewed with regard to the direction of flow of the hydraulic medium through the open return valve). Behind the valve seat there is a substantially larger surface area which acts on the return valve (see also in this respect the EP 0 944 937 B1 mentioned in detail (U.S. Pat. No. 6,276,186 B1, U.S. Pat. No. 6,401,515 B2)). The difference can mean, in particular, a factor of 100 or more. If, therefore, 400 or 600 bar are required upstream of the valve seat for opening the valve, a pressure of 6 bar or less, 4 or 2 bar, for example, may already be sufficient downstream of the valve seat for opening the return valve.The initial pressure increase preferably moves a piston of the return valve out of the valve seat, after which, as is known from the prior art, a return opening for the hydraulic medium is opened and the returning hydraulic medium acts on the piston surface of the return valve, which surface is enlarged with respect to the valve seat surface, i.e. the partial piston surface, and thus also holds the return valve in the open position at reduced pressure or decreasing pressure. The increase in pressure for reaching the triggering pressure therefore preferably takes place only over a region which is narrowly limited (with the initially mentioned) and which requires only such a time duration that the piston of the return valve is raised out of the sealing position.The pressure increase can be carried out by a method of a pressure increase piston. This is preferably a movable pressure-increasing piston which acts on the hydraulic medium.In order to achieve an initial pressure increase, the pressure increase piston is to be moved abruptly. This can be done manually by the user, for example via a correspondingly provided lever arrangement. In this regard, an electromechanical displacement of the pressure-increasing piston is preferred.The pressure-increasing piston can be moved in a hydraulic medium cylinder which is hydraulically continuously connected to a return line of the hydraulic medium. Thus, the hydraulic medium flowing back after opening the return valve preferably acts against the pressure-increasing piston counter to the direction of travel of the pressure-increasing piston upon pressure increase. The returning hydraulic medium can support or bring about a return displacement of the pressure-increasing piston into a basic position. However, this is preferably only when a force application to the pressure-increasing piston is omitted. In the case of electromechanical displacement by an electromagnet, this is the case, for example, when the magnetic force has dropped. The magnetic force falls off in the case of conventional setting and preferably only when the return valve is again in its closed position.A negative pressure can also be generated by the rearward displacement of the pressure increasing piston in order to thus assist or actively trigger a closing process of the return valve. For such support or active triggering of a closing process of the return valve, the aforementioned drop in the magnetic force, in the case of the described electromechanical design, may already be sufficient. This can also help to provide a restoring spring acting on the pressure-increasing piston. If necessary, it is also possible to carry out a further displacement of the pressure-increasing piston beyond the starting position out of a basic position counter to the direction of the pressure increase, in order to thus generate a vacuum, if necessary an additional vacuum, and to trigger or assist the closing process of the return valve. In this regard, reference is made to the aforementioned DE 10 2008 028 957 A1 and the corresponding inclusion of the disclosure content in the present application. Thus, by means of the pressure increase described here by means of a pressure increase piston for the targeted opening of the return valve, a means can also be provided at the same time which enables a targeted closing of the return valve.The pressure-increasing piston can be moved via a drive separate from a drive of the hydraulic pump. Both drives can be electromechanical drives. Preferably, both drives are operated via a common power supply.The pressure-increasing piston can be moved linearly via an actuating magnet. In this respect, a spindle drive, for example, can also be provided for the linear displacement of the pressure-increasing piston.In a further development, it is provided that the valve chamber is connected to the hydraulic medium storage chamber via a separate check valve. This check valve opens when the pressure in the valve chamber falls. For example, this check valve opens when the return valve is closed or closed, in order to thus allow the pressure-increasing piston to move back into its starting position comparatively quickly. When the return valve is open and the pressure of the returning hydraulic medium is present, this check valve is thereby closed. The discharge of the hydraulic medium into the hydraulic medium storage space takes place via a discharge opening released by the return valve.In a further solution to the object, it is aimed at a return of the movement part being carried out or triggered as a function of a pressure value measured by the pressure sensor by automatic opening of the return valve taking place thereon, at which the opening of the return valve is triggered, can be adjusted.With regard to the hand-held device, it is aimed at a return of the movement part being able to take place as a function of a pressure value measured by the pressure sensor by triggering opening of the return valve, and that the working pressure at which the opening of the return valve is triggered is adjustable.The adjustability of the hydraulic or working pressure with which a workpiece or the like is acted upon via the movement part enables adaptation, for example to the workpiece conditions, which can be effected in particular in the simplest manner by the user. Thus, for example, softer, correspondingly more easily deformable materials can be subjected to a lower working pressure or hydraulic pressure than, in contrast, harder materials. Workpieces with different parameters can thus be machined with only one hand-held device.With the adjustable working pressure, a working pressure can be selected which differs from the pressure in the hydraulic medium at which the return valve, due to its design, would be moved into its open position anyway. In this regard, reference is also made to the above explanations. This pressure at which the return valve is moved into the open position on account of its structural design is referred to as the predefined working pressure. The selected, set working pressure can, however, also be selected to correspond to the specified working pressure. Regardless of the selected working pressure, however, the predefined working pressure is maintained unchanged. It only plays no role as long as a selected working pressure is provided below the predetermined working pressure or in accordance with it.An adjusting device for different, selectable working pressures is provided. This can be a control wheel or a control slide, alternatively an arrangement of a plurality of keys, each key being occupied by a predetermined working pressure. A keyboard with an associated display can also be provided. An adjustment of the selectable working pressure can optionally also be carried out alternatively or additionally via a non-mechanical interface, in particular a radio and / or optical interface to the device.Also, with regard to the display, a display can be provided which reproduces the actually selected working pressure.If, as preferably provided, the return of the moving part is triggered by the release of the load, it can furthermore also be provided that termination of the return of the moving part is achieved by renewed actuation. This can be achieved in particular in that, upon renewed actuation, the electrical voltage on the actuating magnet which acts on the pressure-increasing piston falls. This is in any case the opening and / or closing of the return valve is carried out as described above. By the return displacement of the pressure increasing piston which then occurs, the closing of the return valve can be effected. This rearward displacement, which is also only or substantially effected by the pressure of the hydraulic medium flowing in the valve chamber when the return valve is open or flowing through the valve chamber into the hydraulic medium storage chamber, then simultaneously ensures a pressure drop in the valve chamber such that the return valve closes. A spring acting on the pressure-increasing piston in the direction of its starting position, in which, for example, no magnetic force acts, can be provided in a supporting manner.Independently of a repeated actuation of the manually actuatable switch, a drop in the force acting on the pressure-increasing piston usually results when a predetermined end position of the moving part is reached. This corresponds to the mode of operation of the previously known return valve according to EP 0 944 937 B1 mentioned at the beginning.By cancelling the action of the switch, in particular releasing the switch which is usually designed as a button, it is therefore preferred not only to stop the forward movement of the movement part, but rather to return the latter in the direction of a basic position.The return can be achieved by the return valve, which also opens when a predetermined working pressure is reached, being moved into an open position by one of the measures already described above, which leads to a return of the hydraulic medium acting on the moving part.On the other hand, the opening of the return valve can also be effected mechanically, for example electromechanically, for example as a function of the detection of a cancellation of the switch action. Here, the return valve is acted upon directly, for example via a linkage, when the return valve is designed as a valve piston, for example via a piston rod in this respect.The switch actuation can be detected by sensors. The motor current of a drive driving the hydraulic pump can also be monitored, for example. This is particularly the case in which the operation of the hydraulic pump is directly dependent on the switch actuation. A omission of the motor current in this regard is evaluated as a cancellation of the switch actuation.A signal for opening the return valve can be generated.Opening of the return valve can furthermore, as is also preferred, be achieved by increasing the hydraulic pressure acting on the return valve. In this regard, reference is made to the explanations described above.It can also be provided, for example, that the return of the moving part takes place only by a corresponding switch actuation, i.e. in particular a cancellation of the actuation of the manually actuated switch, if a first workpiece contact has been detected beforehand on the device side.A corresponding touch or proximity sensor can be provided for this purpose. For this purpose, the motor current of the pump drive can also be monitored. Alternatively or additionally, the signal of a pressure sensor detecting the pressure in the hydraulic medium can be evaluated for this purpose.With regard to the motor current or the pressure in the hydraulic medium, a detected significant increase can be evaluated as the workpiece contact. The significant increase is distinguished in particular in that a previously given approximately linear pressure increase is left when the movement part is moved forward. The contact with the workpiece can be assumed, for example, when, based on a unit of time, the motor current or the stated pressure is 2 or more percent above a linear increase calculated from a preceding unit of time. Such an increase by up to 10 percent or more, for example up to 20 percent, can also be evaluated as a contact with a workpiece. This is true both with regard to an actually measured pressure and with regard to the motor current of the pump drive, since the pump must run with a correspondingly increased force when the resistance against the moving part, as is given by a workpiece contact, is increased.The pressure sensor, not only in connection with the last-described embodiment, is in particular preferably an electrical or electronic pressure sensor, further in particular a pressure sensor which, when the device is switched on, continuously undertakes a pressure measurement at specific time intervals. The time intervals can be in the range of a few seconds up to a few tenths of a second. The time intervals are preferably given in the range of one or a few milliseconds, for example in the range between 1 and 200 ms.If, in the course of carrying out a pressing, cutting or punching operation, for example, a return movement is desired for certain reasons, for example in an emergency, the actuation switch is released alone. The moving part is not only stationary after this, but also returns at the same time.The return valve can also be moved into the open position, for example, via a piston rod, as indicated, which is directly connected to a valve piston, or a similar linkage, on which piston rod or linkage a servomotor acts, in order to trigger the return movement of the movement part.Furthermore, it can be provided that a complete return of the movement part is first allowed to wait before a next actuation is enabled. For example, a predetermined fixed time period of 5 or 10 seconds may be predetermined. Alternatively, it can also be established via the pressure sensor whether the return has taken place (completely).A possible (additional) hydraulic pressurization of the return valve for triggering a movement of the movement part back into the end position enables an energy-saving operation. Since the device does not necessarily have to operate until the release pressure of the return valve is reached, but rather the return can be initiated in a targeted manner when the intended machining has taken place, in the case of a battery-operated hand-held device with a charged battery, significantly more machining operations can be carried out than in the case of solutions in which the fixed release pressure always has to be reached during each working operation.In the known solutions, the deactivation cannot always take place at the desired pressure despite a pressure sensor provided. If, for example, a pressure of 230 bar is desired, then a pressure of, for example, 300 bar can still develop with corresponding inertia. A disconnection at a specific pressure, such as the 230 bar mentioned, is essential in particular in connection with self-piercing rivets, since otherwise the rivet can be over-pressed depending on the material. The brief increase in pressure acting on the return valve results in a rapid pressure drop at the movement part as a result of the opening of the return valve. The reaction, i.e. the opening of the return valve, takes place in a time range of one or a few tenths of a second, at least up to one second. It can also be a time range of a few milliseconds, for example two, four or ten milliseconds.The invention is explained below with reference to the attached drawing, which however represents only one exemplary embodiment. The drawing shows: FIG. 1 is an overall view of a hydraulically operated hand-held device in the form of a pressing device; FIG. 2 is an enlarged sectional view taken along the line II--II in FIG. 1; FIG. 3 shows the enlargement of the region III in FIG. 2; FIG. 4 is a view corresponding to FIG. 2 when a moving part of the hand-held device is moved into an operating position; FIG. 5 is a view corresponding to FIG. 4, with a return valve opened and the pressure-increasing piston actuated; FIG. 6 shows the enlargement of the region VI in FIG. 5 ; FIG. 7 is a bottom view against the hand-held device according to arrow VII in FIG. 1.First of all, with reference to FIG. 1, a hydraulically operated hand-held device 1 in the form of a pressing device is shown and described, comprising an electric motor 2, a hydraulic pump, not shown in detail, a hydraulic medium storage space 3 and a movement part 4 designed as a hydraulic piston.The movement part 4 is movable relative to a fixed part 5 formed by the device housing or, for example, the cylinder in which the hydraulic piston moves. The moving part 4 is now, for example, the tool holder illustrated in FIG. 1. It can also be, for example, the hydraulic piston (see, for example, FIG. 2 ).In particular, the components hydraulic medium storage space 3, return valve 8, adjusting device 27 and optionally also further ones are accommodated in an appliance body K, which is not shown here in further detail.The hydraulic chamber 6 comprises the chamber into which hydraulic medium is pumped. This starts at the delivery side of the hydraulic pump. As shown in FIG. 2, for example, the hydraulic chamber 6 has a return line 7, via which the hydraulic medium can flow back into the hydraulic medium storage chamber 3 via a return valve 8.As can be seen in particular from FIGS. 4 and 5, the hydraulic chamber 6 changes with the working state of the hand-held device 1. After opening the return valve 8 (FIG. 5 ), the hydraulic piston or the moving part 4 moves back in the direction of its rest position according to FIG. 2 The space upstream of the hydraulic piston in this respect is incorporated into the hydraulic space 6, but at the same time also when the return valve is open the passage through the valve seat and the space directly upstream of the return valve 8.The electric motor 2 for operating the hydraulic pump and thus for moving the moving part 4 in the direction of the working position is activated via a switch 9, which is preferably designed as a manually actuatable button. The electric power supply of the electric motor 2, as in addition preferably also of switching / control electronics, takes place via a battery, not shown, on the device side or via an electrical line.In the valve closure position, the return valve 8 is pressed into the valve seat by means of a compression spring 10. The valve seat preferably consists in detail of a screw-in part 12 which is screwed into the housing of the hand-held device 1 via a thread 11.In the valve seat, optionally in the screw-in part 12, a through bore 13 is provided. This is in flow communication with the return line 7.Due to the narrow cross section of the through-flow bore 13 in the valve seat in cooperation with the prestress applied by the compression spring 10, the return valve 8 opens only when a specific release pressure is exceeded. This is the specified working pressure mentioned at the beginning. This release pressure can be, for example, 600 or 700 bar.After the return valve 8 has opened, the pressure of the hydraulic medium no longer prevails only on the surface corresponding to the cross-sectional surface of the throughflow bore 13, a partial piston surface, for example given by a valve needle 14, but rather on the entire surface facing the hydraulic chamber (lower surface 17) of the return valve piston 15 of the return valve 8 having the valve needle 14. The valve needle 14 does not have to be ideally formed tapering to a point. Preferably, it is at least formed conically.This pressure is preferably generated during the return of the moving part 4 by a spring 16 acting on the moving part 4 and urging the moving part 4 into the end position.In the outflow flow direction downstream of the through-flow bore 13, the pressure is once again significantly lower. For example, the pressure, in particular at the beginning of the return of the movement part, is only 3 / 4 or less of the pressure upstream of the throughflow bore 13 or the valve seat, in practice for example approximately half. This pressure difference is, however, substantially equalised thereafter and is as a rule only comparatively small soon after the beginning of the return of the movement part.After opening the return valve 8, the chamber 26 adjoining the through-flow bore 13 up to the lower surface 17 of the return valve piston 15 is incorporated into the hydraulic chamber. The hydraulic medium then flows via a discharge opening 18 into the storage chamber 3.An axial bore 19 passing through the lower surface 17 and preferably secured against rebound enables hydraulic medium to flow from the hydraulic medium storage space into the valve space 26 in the closed state of the return valve 8 according to FIGS. 2 and 3 in particular to facilitate a return of the pressure-increasing piston 22 (see also further below in this regard).Without further measures, in particular without an intervention from the outside, for example by the user, the hydraulic or triggering pressure lifting the valve needle 14 out of the valve seat corresponds to the specified working pressure on the moving part 4.However, a possibility is created of displacing the return valve 8 into its open position without the hydraulic pressure necessary for raising the return valve 8 being present at the movement part 4. Accordingly, work, for example pressings with the hand-held device 1, is possible which requires lower work pressures on the moving part 4 than the release pressure for the return valve 8.For this purpose, a further line 20 filled with hydraulic fluid is preferably provided associated with the hydraulic chamber adjoining the through-flow bore 13 in the outflow direction. This line 20 continues into a hydraulic medium cylinder 21, in which the aforementioned pressure-increasing piston 22 is preferably linearly displaceable. The line 20 could also be shorter than shown or could also be omitted.By means of an electrically controllable actuating magnet 23, a linear movement of the pressure increasing piston 22 in the hydraulic medium cylinder 21 or in the line 20 can be achieved. The movement of the pressure-increasing piston 22 brought about when the actuating magnet 23 is activated is preferably carried out counter to the force of a restoring spring 24 acting on the pressure-increasing piston 22.Via bores 25 provided in the screw-in part 12, for example, and preferably aligned in the displacement direction of the return valve 8, the line 20 hydraulically forms part of the space 26.In the installed state, the screw-in part 12 does not bear directly against the facing housing wall, so that hydraulic medium moved by the pressure-increasing piston 22 can easily flow out of the line 20 via the bore 25 into the part of the space 26 which is provided downstream of the valve seat in the outflow direction of the hydraulic medium.The hand-held device 1 preferably has an adjusting device 27 by means of which the maximum working pressure applied to the moving part 4 can be preset by the user. In the exemplary embodiment shown, a plurality of keys 28 are provided for this purpose, for which keys 28 predetermined pressure values are stored. The setting device can be used to set the selected working pressure described above which is modified from the predetermined working pressure (or in individual cases also in accordance therewith). Reference is also made at this point to the further, possibly alternative possibilities of the initially mentioned radio connection etc.Thus, for example, a working pressure of 200 bar or 300 bar leading to the triggering of the return valve can be preselected.An evaluation / control electronics evaluates pressure measurement values of a pressure sensor 29 during the movement of the movement part 4 in the direction of the working position and compares these with the pressure setpoint value predefined via a button 28.When the pressure setpoint value is reached, a corresponding signal is generated, which leads to activation of the actuating magnet 23.The pressure-increasing piston 22 moves abruptly, as a result of the activation of the actuating magnet 23, counter to the force of the preferably provided restoring spring 24, into the feed position according to the representations in FIGS. 5 and 6, As a result, the pressure-increasing piston 22 moves into a tight, virtually circumferentially sealed interaction with the hydraulic medium cylinder 21 of the line 20, hydraulic medium located upstream of the pressure-increasing piston 22 is displaced in a direction of displacement of the pressure-increasing piston 22 in the direction of the return valve 8, and therefore in the exemplary embodiment shown is displaced into the space "downstream" of the throughflow bore 13. This is the space 26 already mentioned, the valve space. This valve chamber is hereby acted upon in the sense of a reduction in size. This leads to a brief increase in pressure in the chamber 26 for acting on the undersurface 17 of the return valve 8, and due to the action of the diameter surface of the undersurface 17 which is substantially enlarged compared to the cross-sectional surface of the throughflow bore 13 in the valve seat, the lifting of the return valve 8 can already be achieved by building up a pressure of a few bar, for example 2 to 5 bar. This pressure is (first) achieved solely by the piston-like displacement of the pressure-increasing piston 22.The valve needle 14 is then lifted from the valve seat, so that the return of the hydraulic medium from the hydraulic chamber 6 back into the hydraulic medium storage chamber 3 can take place, wherein the return valve 8 is held in the lifted position until the moving part 4 reaches the end position according to FIG. 2 and thus falls below the opening holding pressure for the return valve 8.The pressure increase at the return valve 8 by the pressure increase piston 22 acts initially. As the return valve 8 is raised and the space 26 is connected to the outlet opening 18 with the flow bore 13 simultaneously opened, the pressure prevailing as a result of the return of the movement part 4 acts on the return valve 8.The electrical application of the actuating magnet 23 can also take place initially in the manner of pulses, so that after the complete forward stroke of the pressure-increasing piston 22, the latter is almost suddenly in the advanced position according to FIG. 6. When a working cycle is regularly performed, i.e. when it is in particular not desired to prematurely end the return of the moving part, the pressure-increasing piston 22 remains in this position preferably as a result of the given loading of the actuating magnet 23.By means of a substantially premature, prior to complete return movement of the moving part, the actuation of the actuating magnet 23 is canceled, the pressure-increasing piston 22 can correspondingly move prematurely back into its starting position. The enlargement of the valve chamber 26 connected therewith can ensure such a pressure drop that a desired closing of the return valve 8 is achieved as a result.With a return movement of the pressure-increasing piston 22, a flow path from the hydraulic medium storage chamber 3 into the valve chamber 26 preferably also opens simultaneously in order to supply the valve chamber 26 with the required hydraulic medium, which permits the mentioned return movement of the pressure-increasing piston 22. As soon as the return valve 8 is closed again, hydraulic medium can no longer flow into the space 26 via the valve seat. This flow path can be provided by a check valve arranged in the valve piston and / or a connecting path from the hydraulic medium storage space 3 to the line 20. Also, with a return movement of the pressure increasing piston 22, a (further) discharge path for hydraulic medium into the hydraulic medium storage space 3 can simultaneously first be formed via a line section 31 which is released by the return pressure increasing piston 22. Furthermore, however, additionally or alternatively, hydraulic medium can (also) drain directly into the hydraulic medium storage space 3.In the actuated state, see FIG. 5 and in particular FIG. 6, it is also important that a front surface of the actuating piston 34, which is formed here conically, bears directly against the associated wall. On the other hand, the actuating piston 34 rearward thereof does not completely fill the expanded space 33. Due to a flattened portion or the like on one of its sides, a free space 35 remains in the expanded space 33 even in the state advanced upon actuation according to FIG. 6.The advancement of the moving part 4 into the working position is preferably maintained only as long as the user actuates the switch 9. In one embodiment, a signal is generated when the switch 9 is released (even before a working process is completed), which leads to an activation of the actuating magnet 23 and thus to a pressure increase in the space 26 via the pressure increase piston 22. Accordingly, when the switch 9 is released, the return valve 8 is moved into the open position, which leads to an automatic return of the movement part 4 into the end position.The pressure-increasing piston 22 can be arranged transversely to the return valve 8. This supports a desired compact construction.In addition, as also shown in the exemplary embodiment, it can be provided that the adjusting magnet 23 or the relevant construction section is surrounded by the hydraulic medium by projecting into the hydraulic medium storage space 3.The above explanations serve to explain the inventions which are covered overall by the application and which develop the prior art in each case also independently, at least by the following combinations of features, namely:Hydraulically operated hand-held device, which is characterized in that a pressure sensor 29 is furthermore predetermined, wherein a return of the movement part 4 can take place as a function of a pressure value measured by the pressure sensor 29 by triggering the return valve 8 to open, and the working pressure at which the opening of the return valve 8 is triggered can be selected deviating from the predetermined working pressure, in that an adjusting device 27 for different working pressures which can be preset by the user is provided on the hand-held device, designed as a control wheel, control slide, an arrangement of a plurality of keys, wherein each key is occupied by a predetermined working pressure, or as a keyboard with an associated display, wherein the actually selected working pressure is reproduced on the display, an evaluation / control electronics in the course of the movement of the movement part 4 in the direction of the working position evaluates pressure measurement values of the pressure sensor 29 and compares these with the pressure setpoint value specified by a button 28 so that the working pressure can additionally also be adjusted from outside the hand-held device via a non-mechanical interface, in particular a radio and / or optical interface to the device.A hand-held device, which is characterized in that the pressure sensor continuously performs a pressure measurement at specific time intervals when the device is switched on.A hand-held device, characterized in that the time intervals are given in the range of one or less milliseconds, for example in the range between 1 and 200 ms. A hand-held device, which is characterized in that the hydraulic pressure acting on the return valve 8 can be increased, independently of reaching the predetermined working pressure, to a pressure value which brings about an opening of the return valve 8.A hand-held device, which is characterized in that a movable pressure-increasing piston 22 is provided for increasing the pressure.A hand-held device, which is characterized in that the pressure-increasing piston 22 is movable in a hydraulic medium cylinder 21, which is hydraulically continuously connected to a return line 7 of the hydraulic medium.A hand-held device, which is characterized in that the pressure-increasing piston 22 is movable via a drive separate from a drive of the hydraulic pump.A hand-held device, which is characterized in that the pressure-increasing piston 22 is movable via an adjusting magnet 23.A hand-held device, which is characterized in that the hydraulic volume usable for increasing the pressure value on the return valve 8 is connected to the hydraulic medium storage space 3 via a check valve 30.A hand-held device, which is characterized in that a workflow can furthermore be triggered by a hand of a user acting on a switch 9, wherein a return of the movement part 4 can be triggered by cancelling the action.

Claims

Hydraulically operated hand-held device (1), wherein the hand-held device (1) has a hydraulic pump, a moving part (4), a fixed part (5) and a return valve (8) with an associated valve seat, wherein the moving part (4) can be moved into an operating position by building up a hydraulic pressure which results from filling a hydraulic chamber (6) with hydraulic medium from a storage chamber (3) using the hydraulic pump, wherein it can be achieved that the moving part (4) can be automatically moved back from the operating position into an end position by opening the return valve (8) when a predefined operating pressure is reached, characterized in that a pressure sensor (29) is furthermore predefined, wherein a return of the moving part (4) can take place by triggering opening of the return valve (8) as a function of a pressure value measured by the pressure sensor (29), and the operating pressure, in which the opening of the return valve (8) is triggered, it is selectable deviating from the predetermined working pressure, that an adjusting device (27) for different working pressures which can be preset by the user is provided on the hand-held device, designed as a control wheel, control slide, an arrangement of a plurality of keys, each key being occupied by a predetermined working pressure, or as a keyboard with an associated display, the actually selected working pressure being reproduced on the display, that evaluation / control electronics evaluates pressure measurement values of the pressure sensor (29) during the movement of the movement part (4) in the direction of the working position and compares these with the pressure target value predetermined via a key (28), that the working pressure can additionally also be adjusted from outside the hand-held device via a non-mechanical interface, in particular a radio and / or optical interface to the device.Hand-held device according to claim 1, characterised in that the pressure sensor continuously undertakes a pressure measurement at specific time intervals when the device is switched on.Hand-held device according to claim 2, characterised in that the time intervals are given in the range between 1 and 200 ms.Hand-held device according to one of the preceding claims, characterized in that the hydraulic pressure acting on the return valve (8) can be raised, independently of the predetermined working pressure being reached, to a pressure value which brings about an opening of the return valve (8).Hand-held device according to claim 1, characterised in that a movable pressure-increasing piston (22) is provided for increasing the pressure.Hand-held device according to either of Claims 4 and 5, characterized in that the pressure-increasing piston (22) is movable in a hydraulic medium cylinder (21) which is connected hydraulically constantly to a return line (7) for the hydraulic medium.Hand-held device according to one of Claims 4 to 6, characterized in that the pressure-increasing piston (22) can be moved via a drive which is separate from a drive of the hydraulic pump.Hand-held device according to one of Claims 4 to 6, characterized in that the pressure-increasing piston (22) is movable via an actuating magnet (23).Hand-held device according to one of Claims 4 to 7, characterized in that the hydraulic volume which can be used to increase the pressure value on the return valve (8) is connected to the hydraulic medium storage space (3) via a nonreturn valve (30).Hand-held device according to one of the preceding claims, characterized in that a workflow can furthermore be triggered by a hand of a user acting on a switch (9), wherein a return of the movement part (4) can be triggered by cancelling the action.

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