EP3261804B1 - Method for operating a hydraulically operated handheld apparatus and hydraulically operated handheld apparatus - Google Patents

Description

The invention initially relates to a method according to the features of the preamble of claim 1.

In addition, the invention relates to a hydraulically operated hand-held device according to the features of the preamble of claim 9.

Such methods and hand-held devices are, for example, from DE 10 2008 028 957 A1 , EP 0 944 937 B1 ( U.S. 6,276,186 B1 , U.S. 6,401,515 B2 ) and WO 2014/108361 A1 known.

Such hand-held devices are used, for example, as pressing devices, preferably for pressing or crimping cable lugs with an inserted cable or for pressing tubular or hose-shaped workpieces. Such hand-held devices can also be used for perforating or punching metal components in particular. 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, for example, in EP 0 944 937 B1 ( U.S. 6,276,186 B1 , U.S. 6,401,515 B2 ) described. This manual device has a return valve, which is shifted into a valve open position when a predetermined hydraulic pressure is reached and is held in this position. This leads to a return flow of the hydraulic medium that shifts the moving part into the working position. Due to the lack of or reduced pressurization, the moving part moves back to the basic or end position. 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.

From the WO 2012/055901 A1 a hydraulic hand-held device is known which has a pressure sensor which opens a solenoid valve when a limit pressure is reached. The limit pressure is specified by a memory chip to be used.

Proceeding from the prior art presented, the invention is concerned with the task of specifying a method for operating a hydraulically operated hand-held device or a hydraulically operated hand-held device which, with a simple structure of the device, enables or facilitates the processing of workpieces that are particularly different in terms of size and/or material .handling simplified.

This object is achieved with the subject matter of claim 1, whereby it is based on the fact that the hydraulic pressure acting on the return valve to trigger a movement of the moving part into the end position is increased independently of the predetermined working pressure being reached, with an initial pressure increase triggering a piston of the return valve a valve seat, after which a return opening for the hydraulic medium is released and the returning hydraulic medium acts on a total piston area of the return valve that is larger than a partial piston area and thus holds the return valve in the open position even with reduced pressure or decreasing pressure.

With regard to the hydraulically operated handheld device, claim 9 is based on the fact that the hydraulic pressure acting on the return valve can be increased to a pressure value that causes the return valve to open, regardless of whether the predetermined working pressure is reached, the pressure increase being initial-type and having a piston the return valve is moved out of a valve seat to release a return opening for the hydraulic medium, wherein the returning hydraulic medium can also act on a total piston area of the return valve that is larger than a partial piston area and can thus hold the return valve in the open position even with reduced pressure or decreasing pressure.

The predetermined working pressure is the hydraulic pressure that occurs in the hydraulic medium as a result of a working process and at which the return valve moves into the open position due to its structural design. When the return valve is closed, this hydraulic pressure is established in the hydraulic chamber, which extends from the moving part to 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, ie forms the said closure surface. A specific 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 flow through the valve seat, for example into a hydraulic medium reservoir. The return valve is further preferably designed as a valve piston in such a way that it has a total piston area on which the hydraulic medium acts when the return valve is lifted out of the valve seat, ie is in the open position. Due to the size ratio between the total piston area and the partial piston area, in the open position of the return valve compared to the partial piston area, a comparatively very low pressure can be sufficient to hold the return valve in its open position. The area that supplements the partial piston area to form the total piston area can also be acted upon by hydraulic means when the return valve is in the closed state. However, not by the hydraulic medium contained in the hydraulic space ending at the said closure surface. In a practical interpretation, a pressure of 300 to 600 bar, further for example 400 or 500 bar, may be required, for example with respect to the partial piston area, in order to remove the return valve from the Lift valve area, while the total piston area only requires a pressure of a few, for example 5, 4 or less bar, about up to 0.5 bar, for example, to remain in the open position. In a specific embodiment, this pressure acting on the entire piston area can be generated, for example, by a restoring spring acting on the moving part.

With regard to the design of the hand-held device as a perforating or punching device, the specified working pressure is generally selected to be higher than the pressure required to carry out the perforating or punching process. In this respect, the specified working pressure can also be set so high that the return valve only works in the sense of a pressure relief valve without further measures. The same applies in principle, for example, to an embodiment of the hand-held device as a riveting device. As an alternative to this, however, the design of the hand-held device, in particular in the variants given by way of example, can be provided such that when the return valve is triggered due to the specified working pressure, the moving part moves back to its specified starting position, provided no further intervention takes place.

According to the innovation 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 the hydraulic medium acting on the return valve is carried out with a means of action that is independent of a work process that is carried out with the hand-held device . This pressure increase is carried out in the hydraulic medium, which acts on the area of the return valve, which, when the return valve is open, supplements the partial piston area to form the total piston area. 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 optionally be given for a short time. The pressure increase is selected so that the return valve is shifted to the open position. The pressure prevailing with regard to the moving part for carrying out the work process in the hydraulic medium acting on the moving part has regularly not yet reached the predetermined working pressure. It is thus given that the return valve can be opened hydraulically before the working pressure corresponding to the triggering pressure at the return valve is applied to the moving part.

The return valve can be moved hydraulically into the open position independently of the prevailing working pressure on the moving part.

The return valve preferably only closes after a specific hydraulic pressure acting on the return valve has dropped so far that the pressure load required due to the structural design of the return valve to hold the return valve in the open position is no longer present.

The return valve can be opened automatically at a changeable, i.e. preselected working pressure that is different from the specified working pressure, preferably as a result of corresponding pressurization of the return valve.

Also, the working pressure that is achieved during a work process—only—can thereby be adjusted as a modified working pressure. For example, the user can specify a working pressure as a modified working pressure using a setting wheel or buttons on the device, which is lower than the maximum permissible working pressure, i.e. the above-mentioned specified working pressure, at which the return valve preferably also opens automatically, or also corresponds to this maximum working pressure.

The latter can be useful, for example, if the stated maximum working pressure is actually, but only, to be achieved with greater accuracy. For example, with an exemplary specified or maximum working pressure of 600 bar, working pressures of 50 to 600 bar can be adjusted steplessly or step by step. It is thus possible to adapt the load to the machining of workpieces to be carried out by means of the device, while maintaining an automatic return of the moving part to the end position after the possibly set working pressure has been reached.

It can also be provided that the modified working pressure can be set from outside the hand-held device, for example via a radio interface or optical interface.

The increase in pressure preferably acts only briefly. In terms of time, the pressure increase can only be effective in the range of a few tenths of a second, for example over a period of 1/10 to 5/10 of a second.

The pressure increase is carried out in particular by feeding hydraulic medium into the space provided with regard to an outflow direction of the hydraulic medium after the valve seat. This space, which is also referred to below as the valve space, is in front of an opening of the return valve on the one hand by the total piston area minus the partial piston area and on the other hand by the surface of the valve seat facing the total piston area including a delimiting surface of the pressure-increasing piston and possibly a surface of a given in this context Line section given. The latter in any case insofar as the pressure-increasing piston is arranged directly as part of the valve chamber. It can also be separated from this, for example, by a non-return valve. There is also preferably no actual feeding of additional hydraulic medium into the valve space. Merely reducing the size of the valve chamber by moving the pressure-increasing piston can 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 to move the return valve into the open position acts on the one hand on the total piston area of the return valve (minus the partial piston area of a valve tip that is not yet effective at the moment of the pressure increase). It also acts essentially decoupled from the moving part because at the moment of the pressure increase it is still - only - exposed to the hydraulic pressure "before" the valve seat (considered with regard to the direction of flow of the hydraulic medium through the open return valve). As a result, only a significantly lower pressure increase is required than in front of the valve seat (considered with regard to the direction of flow of the hydraulic medium through the open return valve). There is a significantly larger area behind the valve seat, which acts on the return valve (see also the details given here EP 0 944 937 B1 ( U.S. 6,276,186 B1 , U.S. 6,401,515 B2 )). In particular, the difference can mean a factor of 100 or more. So if 400 or 600 bar is required before the valve seat to open the valve, after the valve seat a pressure of 6 bar or less, for example 4 or 2 bar, can be sufficient to open the return valve.

According to the invention, the initial pressure increase 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 released and the returning hydraulic medium acts on the piston surface of the return valve, which is larger than the valve seat surface, i.e. the partial piston surface, and so on keeps the return valve in the open position even with reduced pressure or decreasing pressure. The pressure increase to reach the Accordingly, the triggering pressure takes place only over a narrowly limited time range (as initially mentioned), which only requires such a period of time that the piston of the return valve is lifted out of the sealing position.

The pressure increase can be performed by a process of a pressure-increasing 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-increasing piston must be moved abruptly. This can be done manually by the user, for example using a correspondingly provided lever arrangement. In this respect, 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 constantly connected to a return line of the hydraulic medium. The hydraulic medium flowing back after the opening of the return valve thus preferably acts on the pressure-increasing piston in the opposite direction to the displacement direction of the pressure-increasing piston when the pressure increases. The returning hydraulic medium can support or bring about a return displacement of the pressure-increasing piston into a basic position. However, this is preferred only when a force has been applied to the pressure-increasing piston. In the case of an electromechanical displacement by an electromagnet, this is the case, for example, when the magnetic force has dropped. With the usual setting, the magnetic force falls and preferably only falls when the return valve is again in its closed position.

A negative pressure can also be generated by moving the pressure-increasing piston backwards, in order to support or actively trigger a closing process of the return valve. In the case of the described electromechanical design, the said drop in the magnetic force can already be sufficient for such a support or active triggering of a closing process of the return valve. The fact that a restoring spring acting on the pressure-increasing piston is provided can also contribute to this. If necessary, a further displacement of the pressure-increasing piston from a basic position against the direction of the pressure increase can also be carried out beyond the initial position in order to generate an additional negative pressure and trigger or support the closing process of the return valve. In this regard, reference is made to the initially mentioned DE 10 2008 028 957 A1 , as well as the corresponding inclusion of the disclosure content in the present application, referenced or referred to. Thus, by means of the pressure increase described here by means of a pressure-increasing 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 that is separate from a drive of the hydraulic pump. Both drives can be electromechanical drives. Both drives are preferably operated via a common power supply.

The pressure-increasing piston can be moved linearly via an actuating magnet. In this respect, for example, a spindle drive 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 reservoir via a separate non-return valve stands. This check valve opens when the pressure in the valve chamber drops. For example, this check valve opens when the return valve closes or is closed, in order to enable the pressure-increasing piston to move back to its starting position comparatively quickly. If the return valve is open and the pressure of the returning hydraulic medium is present, this check valve is thereby closed. The hydraulic fluid drains into the hydraulic fluid reservoir via a drain opening released by the return valve.

A setting device for different working pressures that can be preset by the user can be provided on the hand-held device, designed as an adjusting wheel, adjusting slide, an arrangement of a plurality of keys, with each key being assigned a predetermined working pressure, or as a keyboard with an associated display, with the The actually selected working pressure is shown on the display.

The adjustability of the hydraulic or working pressure, with which the moving part acts on a workpiece or the like, enables an adjustment, for example to the workpiece conditions, which can be brought about in the simplest way by the user. For example, softer, correspondingly more easily deformable materials can be subjected to a lower working or hydraulic pressure than, in contrast, harder materials. Workpieces with different parameters can thus be machined with just one handheld device.

With the adjustable working pressure, a working pressure can be selected that deviates from the pressure in the hydraulic medium at which the return valve would be brought into its open position anyway due to its structural design. In this regard, reference is also made to the above statements. This pressure, at which the return valve is brought into the open position due to its structural design, is referred to as the specified working pressure. However, the selected, set working pressure can also, as already explained above, be chosen to match the specified working pressure. Regardless of the selected working pressure, the specified working pressure remains unchanged. It only plays no role as long as a selected working pressure is provided below the predetermined working pressure or in accordance with this.

The setting of the selectable working pressure can optionally also be carried out via a non-mechanical interface, in particular a radio and/or optical interface to the device.

The return movement of the moving part can also only take place by removing the loading if a first contact with the workpiece has been detected beforehand by the device.

With regard to the cancellation of the actuation of the manually operated switch for triggering the return movement of the moving part, provision can also be made for the return movement of the moving part to be terminated by repeated actuation. This can be achieved in particular by the electrical voltage on the actuating magnet, which acts on the pressure-increasing piston, dropping when it is actuated again. In any case, this is the case when the opening and/or closing of the return valve is carried out as described above. The closing of the return valve can be brought about by the return displacement of the pressure-increasing piston that then occurs. This rearward displacement, which is also only or largely due to the pressure of the pressure flowing in the valve chamber when the return valve is open or through the valve chamber into the hydraulic medium reservoir flowing hydraulic medium is effected, then at the same time ensures such a pressure drop in the valve chamber that the return valve closes. A spring acting on the pressure-increasing piston in the direction of its initial position, in which, for example, no magnetic force acts, can be provided in a supporting manner.

Irrespective of a repeated actuation of the hand-operated switch, there is generally a drop in the loading force acting on the pressure-increasing piston when a predetermined end position of the moving part has been reached. This corresponds to the mode of operation of the previously known return valve according to the one mentioned at the outset EP 0 944 937 B1 .

By canceling the actuation of the switch, not only is the forward movement of the moving part aborted, but rather a return of the same in the direction of a basic position.

The return can be achieved in that the return valve, which also opens when a predetermined working pressure is reached, is shifted into an open position with 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 take place mechanically, for example electromechanically, for example depending on the detection of a cancellation of the actuation of the switch. In this case, 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 relevant piston rod.

The actuation of the switch can be detected by sensors. For example, the motor current of a drive that drives the hydraulic pump can also be monitored. This is particularly the case when the operation of the hydraulic pump is directly dependent on the actuation of the switch. A cessation of the relevant motor current is evaluated as a cancellation of the switch loading.

A signal to open the return valve can be generated.

Furthermore, as is also preferred, the return valve can be opened by increasing the hydraulic pressure acting on the return valve. In this regard, reference is made to the explanations described above.

With regard to the first contact with the workpiece, a corresponding contact or proximity sensor can be provided. The motor current of the pump drive can also be monitored for this purpose. Alternatively or additionally, the signal of a pressure sensor that detects 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 a workpiece contact. The significant increase is characterized in particular by the fact that a previously given approximately linear increase in pressure is left when the moving part is advanced. Workpiece contact can be assumed, for example, if, based on a unit of time, the motor current or the pressure mentioned is 2 or more percent above a linear increase extrapolated from a previous unit of time. Such an increase of up to 10 or more, say up to 20 percent, can also be counted as contact with a workpiece. This applies both to an actually measured pressure and to the specified motor current of the pump drive, since the pump has to run with a correspondingly increased force when the resistance against the moving part increases, as is the case when the workpiece comes into contact.

The pressure sensor, not only in connection with the last-described embodiment, is particularly preferably an electrical or electronic pressure sensor, more particularly a pressure sensor that constantly carries out a pressure measurement at specific time intervals when the device is switched on. 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 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 process, for example, a return is desired for certain reasons, for example in an emergency, simply releasing the actuating switch is sufficient. After this, the moving part not only stands still, but moves back at the same time.

The return valve can also be shifted into the open position, for example via a piston rod directly connected to a valve piston, as indicated, or a similar linkage, on which piston rod or linkage a servomotor acts, in order to trigger the return movement of the moving part.

Furthermore, it can be provided that a complete return of the moving part is first awaited before the next actuation is released. For example, a predetermined fixed period of time of 5 or 10 seconds can be specified. Alternatively, the pressure sensor can also be used to determine whether the return (complete) has taken place.

A possible (additional) hydraulic pressurization of the return valve to trigger a movement of the moving part back into the end position enables energy-efficient work. Since the device as a whole does not necessarily have to work until the release pressure of the return valve is reached, but the return can be initiated specifically when the intended processing has been carried out, significantly more processing can be carried out with an accumulator-operated hand-held device with a charged accumulator than with solutions in which the fixed release pressure must always be achieved for each work process.

In the case of the known solutions, in spite of a pressure sensor being provided, the switch-off cannot always take place at the desired pressure. If, for example, a pressure of 230 bar is desired, a pressure of, for example, 300 bar can still develop with the appropriate inertia. Switching off at a certain pressure, such as the 230 bar mentioned, is particularly important in connection with punch riveting, since the rivets can otherwise be over-pressed depending on the material. Due to the short-term pressure increase acting on the return valve, there is a rapid pressure drop given on the moving part due to opening of the return valve. The reaction, ie the opening of the return valve, takes place in a time range of one or a few tenths of a second, in any case up to one second. It can also be a time range of a few milliseconds, for example two, four or ten milliseconds.

Fig. 1

eine Gesamtansicht eines hydraulisch betriebenen Handgerätes in Form eines Pressgerätes;

Fig. 2

den vergrößerten Schnitt gemäß der Linie II-II in Figur 1;

Fig. 3

die Herausvergrößerung des Bereiches III in Figur 2;

Fig. 4

eine der Figur 2 entsprechende Darstellung, bei Bewegung eines Bewegungsteiles des Handgerätes in eine Arbeitsstellung;

Fig. 5

eine der Figur 4 entsprechende Darstellung, bei einem geöffneten Rücklaufventil und betätigtem Druckerhöhungskolben;

Fig. 6

die Herausvergrößerung des Bereiches VI in Figur 5;

Fig. 7

die Unteransicht gegen das Handgerät gemäß Pfeil VII in Figur 1.

The invention is explained below with reference to the attached drawing, which, however, merely represents an exemplary embodiment. On the drawing shows:

1

an overall view of a hydraulically operated hand tool in the form of a pressing device;

2

the enlarged section according to the line II-II in figure 1 ;

3

the enlargement of area III in figure 2 ;

4

one of the figure 2 Corresponding representation when moving a moving part of the hand-held device into a working position;

figure 5

one of the figure 4 Corresponding representation, with an open return valve and actuated pressure booster piston;

6

the enlargement of area VI in figure 5 ;

7

the bottom view against the handset according to arrow VII in figure 1 .

Shown and described, first with reference to figure 1 , A hydraulically operated hand-held device 1 in the form of a pressing device with an electric motor 2, a hydraulic pump (not shown in detail), a hydraulic medium reservoir 3 and a moving part 4 designed as a hydraulic piston.

The moving part 4 can be moved 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 in figure 1 shown tool holder. It can also be the hydraulic piston, for example (see e.g figure 2 ).

In particular, the components of the hydraulic fluid reservoir 3, the return valve 8, the adjustment device 27 and possibly others as well are accommodated in a device body K, which is not shown here in further detail.

The hydraulic chamber 6 includes the space into which hydraulic medium is pumped. This begins on the pressure side of the hydraulic pump. As for example in figure 2 shown, the hydraulic chamber 6 has a return line 7 via which the hydraulic medium can flow back into the hydraulic medium reservoir 3 via a return valve 8 .

As can be seen in particular from the figures 4 and 5 results, the hydraulic chamber 6 changes with the working state of the hand-held device 1. In the representation according to FIG figure 4 is the moving part 4 in a opposite figure 2 changed position. After the return valve 8 ( figure 5 ) moves the hydraulic piston or the moving part 4 back towards its rest position according to figure 2 . The space upstream of the hydraulic piston is included in the hydraulic space 6, but at the same time the passage through the valve seat and the space directly in front of the return valve 8 when the return valve is open.

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 operable button. The electrical supply of the electric motor 2, as well as preferably also switching/control electronics, takes place via an accumulator, not shown, on the device or via an electrical line.

In the closed valve position, the return valve 8 is pressed into the valve seat by means of a pressure spring 10 . In detail, the valve seat preferably consists of a screw-in part 12 which is screwed into the housing of the hand-held device 1 via a thread 11 .

A through-flow bore 13 is provided in the valve seat, optionally in the screw-in part 12 . In terms of flow, this is connected to the return line 7.

Due to the narrow cross-section of the through-flow bore 13 in the valve seat in conjunction with the preload applied by the pressure spring 10, the return valve 8 only opens when a certain triggering pressure is exceeded. This is the specified working pressure mentioned at the beginning. This triggering pressure can be 600 or 700 bar, for example.

After the return valve 8 has opened, the pressure of the hydraulic medium is no longer only present on the area corresponding to the cross-sectional area of the flow bore 13, a partial piston area, for example given by a valve needle 14, but on the entire area facing the hydraulic chamber (bottom area 17 ) of the return valve piston 15 of the return valve 8 having the valve needle 14. The open return valve 8 is therefore already held in the open position by a very low pressure in the return line 7, for example a pressure of 2 to 5 bar.

The valve needle 14 does not have to be formed so that it tapers to an ideal point. In any case, it is preferably formed in the shape of a cone.

This pressure is generated when the moving part 4 moves back, preferably by a spring 16 acting on the moving part 4 and loading the moving part 4 into the end position.

In the outflow direction of flow downstream of the through-flow bore 13, the pressure is again significantly lower. For example, the pressure, especially at the beginning of the return movement of the moving part, is only 3/4 or less of the pressure in front of the flow bore 13 or the valve seat, in practice, for example, about half. However, this pressure difference then essentially balances out and is usually only comparatively small soon after the beginning of the return movement of the moving part.

After the return valve 8 has been opened, the space 26 adjoining the flow bore 13 is included in the hydraulic space up to the lower surface 17 of the return valve piston 15 . The hydraulic medium then flows into the reservoir 3 via a discharge opening 18. The space 26 is also referred to above and below as the valve space.

An axial bore 19 which penetrates the lower surface 17 and is preferably non-return-proof enables the return valve 8 in the closed state according to FIG figures 2 and 3 a subsequent flow of hydraulic medium from the hydraulic medium reservoir into the valve chamber 26, in particular to facilitate a return movement of the pressure-increasing piston 22 (see also further below).

Without further action, in particular without intervention from the outside, for example by the user, the valve needle 14 comes out of the valve seat lifting hydraulic or release pressure the specified working pressure at the moving part 4.

However, it is possible to move the return valve 8 into its open position without the hydraulic pressure required to lift the return valve 8 being applied to the moving part 4 . Correspondingly, work, for example pressing with the hand-held device 1, is possible which requires lower working pressures on the moving part 4 than the triggering pressure for the return valve 8.

For this purpose, a further line 20 filled with hydraulic fluid is preferably provided in association with the hydraulic chamber adjoining the flow bore 13 in the outflow direction. This line 20 continues in a hydraulic fluid cylinder 21, in which the aforementioned pressure-increasing piston 22 is preferably linearly displaceable. The line 20 could also be shorter than shown or omitted.

A linear movement of the pressure-increasing piston 22 in the hydraulic medium cylinder 21 or in the line 20 can be achieved by means of an electrically controllable actuating magnet 23 . The movement of the pressure-increasing piston 22 brought about when the actuating magnet 23 is activated preferably takes place against the force of a return spring 24 acting on the pressure-increasing piston 22.

The line 20 hydraulically forms part of the chamber 26 via bores 25 provided in the screw-in part 12, for example, and preferably aligned in the displacement direction of the return valve 8.

In the installed state, the screw-in part 12 is not in direct contact with 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 can flow into the part of the space 26 which is in the outflow direction of the hydraulic medium after the valve seat.

The hand-held device 1 preferably has an adjustment 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 adjust the above-described selected working pressure, which is modified (or, in individual cases, also corresponds to this) with respect to the specified working pressure. Reference is also made at this point to the other, possibly alternative, options for the radio connection etc. mentioned at the outset.

For example, a working pressure of 200 bar or 300 bar that triggers the return valve can be preselected.

During the movement of the moving part 4 in the direction of the working position, evaluation/control electronics evaluate measured pressure values from a pressure sensor 29 and compare them with the desired pressure value specified via a button 28 .

When the desired pressure value is reached, a corresponding signal is generated, which leads to the actuating magnet 23 being activated.

As a result of the activation of the actuating magnet 23, the pressure-increasing piston 22 moves abruptly into the advance position according to the representations in FIGS figures 5 and 6 . As a result, the pressure-increasing piston 22 moves into a close, practically circumferentially sealed interaction with the Hydraulic fluid cylinder 21 of the line 20. Hydraulic fluid located in front of the pressure-increasing piston 22 is displaced in a direction of travel of the pressure-increasing piston 22 in the direction of the return valve 8, and thus in the illustrated embodiment into the space "after" the flow bore 13. It is therefore related to displaces the closed state of the return valve 8 into the space formed by the lower surface 17 and the associated side of the screw-in part 12 and a part of the cylinder in which the return valve 8 is housed. It is the already mentioned space 26, the valve space. This has an effect on this valve chamber in the sense of a reduction. This leads to a brief increase in pressure in the space 26 to act on the lower surface 17 of the return valve 8. As a result of the pressure being applied to the diameter area of the lower surface 17, which is significantly larger than the cross-sectional area of the flow bore 13 in the valve seat, the return valve 8 is raised by building up a pressure of a few bar, for example 2 to 5 bar, already achievable. This pressure is (initially) 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 hydraulic fluid can flow back from the hydraulic chamber 6 back into the hydraulic fluid reservoir 3, with the return valve 8 being held in the raised position until the moving part 4 reaches the end position according to figure 2 reached and thus the opening holding pressure for the return valve 8 is fallen below.

The pressure increase at the return valve 8 by the pressure-increasing piston 22 has an initial effect. With the lifting of the return valve 8 and the associated connection of the space 26 with the drain opening 18 with simultaneous opening of the flow bore 13, the pressure prevailing due to the return movement of the moving part 4 acts on the return valve 8.

The electrical loading of the actuating magnet 23 can also initially take place in a pulsed manner, so that after the pressure-increasing piston 22 has been fully advanced, it is almost suddenly in the advanced position according to FIG figure 6 located. If a working cycle runs regularly, i.e. if in particular no premature termination of the return movement of the moving part is desired, the pressure-increasing piston 22 preferably remains in this position as long as the actuating magnet 23 is also acted upon.

The pressure-increasing piston 22 can correspondingly move back prematurely into its initial position as a result of an almost premature cancellation of the action on the actuating magnet 23, which took place before the moving part has moved back completely. The enlargement of the valve space 26 associated with this can ensure such a pressure drop that a desired closure of the return valve 8 is thereby achieved.

When the pressure-increasing piston 22 moves back, a flow path from the hydraulic medium reservoir 3 into the valve chamber 26 preferably opens at the same time, in order to supply the valve chamber 26 with the required hydraulic medium, which enables the pressure-increasing piston 22 to move back. 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 reservoir 3 to the line 20 . A return movement of the pressure-increasing piston 22 can also simultaneously open up a (further) discharge path for hydraulic fluid into the hydraulic fluid reservoir 3, initially via a line section 31 which is released by the pressure-increasing piston 22 moving back. Next but also additionally or alternatively via a receptacle 32 for a piston shaft 33 of the pressure booster piston 22. Here and The preferably adjoining expanded space 33, in which an actuating piston 34 of the pressure-increasing piston 22 is located, hydraulic fluid can (also) run directly into the hydraulic fluid reservoir 3.

When actuated, see figure 5 and particularly figure 6 , It is also important that a front surface of the actuating piston 34, which is cone-shaped here, rests directly against the associated wall. On the other hand, the actuating piston 34 does not completely fill the expanded space 33 at the rear. As a result of a flattening or the like on one of its sides, it also remains in the advanced state according to FIG figure 6 a free space 35 in the extended space 33.

The forward movement 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 work process is completed), which leads to an activation of the actuating magnet 23 and thus to an increase in pressure in the chamber 26 via the pressure-increasing piston 22 . Accordingly, when the switch 9 is released, the return valve 8 is shifted into the open position, which leads to an automatic return of the moving part 4 into the end position.

The pressure-increasing piston 22 can be arranged transversely to the return valve 8. The longitudinal axes of the pressure-increasing piston 22 and the return valve 8 intersect outside of the respective extension areas. This supports a desired compact design.

In addition, it can be provided, as also shown in the exemplary embodiment, that the actuating magnet 23 or the relevant structural section is surrounded by hydraulic medium by protruding into the hydraulic medium reservoir 3 . <b>List of reference characters:</b> 1 handset 25 drilling 2 electric motor 26 space 3 Hydraulic fluid storage room 27 adjustment device 4 moving part 28 button 5 fixed part 29 pressure sensor 6 hydraulic room 30 check valve 7 return line 31 line section 8th return valve 32 admission 9 counter 33 space 10 pressure spring 34 actuating piston 11 thread 35 free space 12 screw-in part 13 flow hole 14 valve needle 15 return valve piston 16 feather 17 undersurface 18 drain hole 19 axial bore 20 management 21 hydraulic fluid cylinder 22 booster piston K device body 23 control magnet 24 return spring

Claims (15)

1. A method for operating a hydraulically operated hand-held device (1), for example a pressing device and/or a hole-punching or punching device, 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 furthermore the moving part (4) is displaced into a working position by build-up of hydraulic pressure which is produced by filling a hydraulic chamber (6) with hydraulic medium from a storage chamber (3) using the hydraulic pump, and the moving part (4) is automatically moved back from the working position into an end position by an opening of the return valve (8) when a predefined working pressure is reached, characterized in that the hydraulic pressure acting on the return valve (8) is increased to trigger a movement of the moving part (4) into the end position independently of reaching the predefined working pressure, wherein an initial type of pressure increase moves a piston of the return valve from a valve seat, whereafter a return opening for the hydraulic medium is released and the returning hydraulic medium acts upon an enlarged total piston surface of the return valve compared with a partial piston surface and thus holds the return valve in the open position even with reduced pressure or decreasing pressure.
2. The method according to claim 1, characterized in that the area which the partial piston surface adds to the total piston surface can also be acted upon by hydraulic medium in the closure state of the return valve, wherein, preferably, the pressure increase is accomplished in the hydraulic medium which acts on the surface.
3. The method according to any one of the preceding claims, characterized in that the return valve (8) is opened automatically at a modified working pressure compared with the predefined working pressure, wherein, preferably, the modified working pressure can be set.
4. The method according to any one of the preceding claims, characterized in that the increase in the hydraulic pressure is accomplished by supplying hydraulic medium into a given chamber (26) downstream of the valve seat with a view to the drain direction of the hydraulic medium.
5. The method according to claim 4, characterized in that the pressure increase is carried out by reducing the space (26) given after the valve seat, wherein, preferably, the space (26) given after the valve seat before an opening of the return valve is given 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 minus the partial piston surface including a delimiting surface of the pressure-increasing piston and optionally a surface of a line section given in this connection.
6. The method according to any one of the preceding claims, characterized in that the increase in the hydraulic pressure is accomplished by a movement of a pressure-increasing piston (22), wherein, preferably, the pressure-increasing piston (22) is moved into a hydraulic medium cylinder (21).
7. The method according to claim 6, characterized in that the hydraulic medium cylinder (21) is continuously connected to a return line (7) of the hydraulic medium and/or the hydraulic medium cylinder (21) is only hydraulically in communication with the return line (7) of the hydraulic medium when the return valve is open.
8. The method according to any one of claims 6 or 7, characterized in that the pressure-increasing piston (22) is moved via a separate drive from a drive of the hydraulic pump and/or that the pressure-increasing piston (22) is moved by means of an adjusting magnet (23).
9. A hydraulically operated hand-held device (1), for example a pressing device and/or a hole-punching or punching device, 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 furthermore the moving part (4) can be displaced into a working position by build-up of hydraulic pressure which is produced by 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) is automatically moved back from the working position into an end position by an opening of the return valve (8) when a predefined working pressure is reached, characterized in that the hydraulic pressure acting on the return valve (8) can be increased independently of reaching the predefined working pressure to a pressure value which brings about an opening of the return valve (8), wherein the pressure increase is of an initial type and moves a piston of the return valve from a valve seat for release of a return opening for the hydraulic medium, wherein further the returning hydraulic medium can act upon an enlarged total piston surface of the return valve compared with a partial piston surface and thus can keep the return valve in the open position even with reduced pressure or decreasing pressure.
10. The hand-held device according to claim 9, characterized in that a movable pressure-increasing piston (22) is provided to increase the pressure.
11. The hand-held device according to claim 10, characterized in that the pressure-increasing piston (22) is movable in a hydraulic cylinder (21), wherein, preferably, the hydraulic medium cylinder (21) is continuously hydraulically in communication with a return line (7) of the hydraulic medium, or is only hydraulically in communication with the return line (7) of the hydraulic medium when the return valve is open.
12. The hand-held device according to any one of claims 10 or 11, characterized in that the pressure-increasing piston (22) is movable by means of a drive separate from a drive of the hydraulic pump, wherein, preferably, the pressure-increasing piston (22) is movable by means of an adjusting magnet (23).
13. The hand-held device according to any one of claims 9 to 12, characterized in that a hydraulic volume which can be used to increase the pressure value on the return valve (8) is in communication with the hydraulic storage chamber (3) via a check valve (30).
14. The hand-held device according to any one of claims 9 to 13, characterized in that the area which the partial piston surface adds to the total piston surface can also be acted upon by hydraulic medium in the closure state of the return valve, and/or that the pressure is increased in the hydraulic medium which acts upon the area of the return valve which, when the return valve is open, the partial piston surface adds to the total piston surface.
15. The hand-held device according to any one of claims 9 to 13, characterized in that the pressure increase can be accomplished by means of a reduction in the size of the space (26) given downstream of the valve seat, wherein, preferably, the space (26) given downstream of the valve seat upstream of an opening of the return valve is given on the one hand by the total piston surface minus the partial piston surface and on the other hand by the area of the valve seat facing the total piston surface minus the partial piston surface including a delimiting surface of the pressure-increasing piston and optionally a surface of a line section given in this connection.

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