Method for operating a hydraulically operated handheld device, and hydraulically operated handheld device

Abstract

A hydraulically operated handheld device and a method of operating same are provided. The device includes a hydraulic pump, a moving part, a fixed part and a return valve with an associated valve seat. The moving part is moved into a working position due to the buildup of a hydraulic pressure by filling a hydraulic chamber with hydraulic medium from a reservoir with the aid of the hydraulic pump. The moving part can be automatically moved back from the working position into an end position upon reaching a predefined working pressure by opening the return valve. The hydraulic pressure acting upon the return valve is increased by a separately triggerable pressure increase, which results in opening of the return valve, in a hydraulic medium volume located upstream of the return valve in a flow direction of the hydraulic medium during the movement into the end position.

Claims

1. A method comprising: providing a hydraulically operated handheld device including a reservoir, a hydraulic pump for pumping hydraulic medium from the reservoir, a moving part, a hydraulic chamber, a fixed part and a return valve with an associated valve seat, the moving part being movable relative to the fixed part; pumping hydraulic medium from the reservoir into the hydraulic chamber thereby causing a build-up of hydraulic pressure in the hydraulic chamber and causing the moving part to move into a working position; and causing an increase of hydraulic pressure acting to open the return valve at a hydraulic pressure in the hydraulic chamber below a predetermined working pressure which would cause the return valve to automatically open and automatically moving the moving part from the working position into an end position, and wherein the hydraulic pressure acting upon the return valve for causing movement of the moving part into the end position is in a hydraulic medium volume located upstream of the return valve in a flow direction of the hydraulic medium flowing during the movement of the moving part into the end position.

2. The method according to claim 1, further comprising decreasing the hydraulic pressure acting upon the return valve thereby closing the return valve.

3. The method according to claim 2, wherein the hydraulic pressure decrease is affected by opening a line section upstream of the return valve.

4. The method according to claim 1, wherein the hydraulic pressure increase acting on the return valve is partially affected by blocking or restricting a line section upstream of the return valve.

5. The method according to claim 4, wherein the hydraulic pressure increase acting on the return valve is further affected by pumping hydraulic medium into a line section between the pump and the return valve.

6. A hydraulically operated handheld device comprising: a hydraulic pump; a reservoir; a moving part; a hydraulic chamber; a fixed part; and a return valve with an associated valve seat, wherein the moving part can be moved into a working position due to a build-up of a hydraulic pressure by filling the hydraulic chamber with hydraulic medium from the reservoir using the hydraulic pump, wherein the moving part can be automatically moved back from the working position into an end position upon reaching a predefined working pressure by opening the return valve, and wherein the hydraulic pressure acting upon the return valve for triggering a movement of the moving part into the end position can be increased by a separately triggerable pressure increase, which results in opening of the return valve, in a hydraulic medium volume located upstream of the return valve in a flow direction of the hydraulic medium flowing during the movement of the moving part into the end position.

7. The handheld device according to claim 6, wherein the hydraulic pressure acting upon the return valve can be decreased by a separately triggerable pressure decrease, which results in closing of the return valve, in the hydraulic medium volume located upstream of the return valve in a flow direction of the hydraulic medium during the movement into the end position.

8. The handheld device according to claim 7, further comprising a line section upstream of the return valve in the flow direction, wherein the line section can be blocked or restricted in order to achieve the pressure decrease.

9. The handheld device according to claim 6, further comprising a line section upstream of the return valve in the flow direction, wherein the line section can be blocked or restricted and hydraulic medium can be introduced into the blocked or restricted line section to achieve a pressure increase.

10. The handheld device according to claim 6, further comprising a second line section, wherein the hydraulic pump pumps hydraulic medium into the second line section when the return valve is in an open position of the return valve.

11. The handheld device according to claim 10, wherein the separately triggerable pressure increase is affected by blocking the second line section.

12. The handheld device according to claim 6, wherein a blocking means which affects the separately triggerable pressure increase is prestressed into an open position.

13. The handheld device according to claim 12, wherein the blocking means comprises a magnet-actuated piston.

14. A hydraulically operated handheld device comprising: a body; a reservoir within the body and configured to hold hydraulic medium, the reservoir including a first return valve which only allows fluid to flow out of the reservoir; a moving part comprising a hydraulic piston movably mounted in a cylinder, the cylinder being mounted to the body, wherein the piston and the cylinder define a hydraulic chamber into which hydraulic medium can flow into or out of; a first fluid line between the first return valve and the hydraulic chamber which allows for flow of hydraulic medium from the reservoir to the hydraulic chamber; a displaceable piston within the body, the displaceable piston being movable into the first fluid line, wherein the first fluid line is blocked or restricted when the displaceable piston is displaced into a closed position to prevent fluid flow along the first fluid line and to separate the first fluid line into a first line section and a second line section, the second line section always being flow connected to the first return valve, and the first fluid line is open when the displaceable piston is displaced into an open position to allow fluid flow along the first fluid line; a second fluid line between the second line section and the reservoir, the second fluid line always being flow connected to the second line section; a second return valve within the body, the second return valve being movable into the second fluid line, wherein the second fluid line is blocked when the second return valve is displaced into a closed position to prevent fluid flow along the second fluid line, and the second fluid line is open when the second return valve is displaced into an open position to allow fluid flow along the second fluid line; and a hydraulic pump for pumping hydraulic medium from the reservoir to the first and second fluid lines.

15. The handheld device according to claim 14, further comprising an electrically actuatable magnet which is activatable to cause displacement of the displaceable piston into the closed position.

16. The handheld device according to claim 15, further comprising a pressure sensor which measures pressure in the hydraulic chamber.

17. The handheld device according to claim 16, further comprising a second pressure sensor which measures pressure in in the second fluid line.

18. The handheld device according to claim 15, further comprising a pressure spring which acts on the displaceable piston to bias the displaceable piston into the open position.

19. The handheld device according to claim 14, wherein the second return valve includes a piston which can be seated within a valve seat of the body, wherein the piston of the second return valve is biased into engagement with the valve seat by a pressure spring.

20. The handheld device according to claim 14, further comprising a spring which acts on the hydraulic piston of the moving part against a pressure build-up in the hydraulic chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is described in greater detail below with reference to the attached drawings, which merely show an exemplary embodiment. In the drawings:

(2) FIG. 1 shows a general view of a hydraulically operated handheld device in the form of a pressing device concerning a first embodiment;

(3) FIG. 2 shows a top view of the handheld device;

(4) FIG. 3 shows an illustration corresponding to FIG. 1, however, in a partially exposed manner;

(5) FIG. 4 shows an enlarged detail of the region IV in FIG. 3;

(6) FIG. 5 shows an illustration corresponding to FIG. 4 upon reaching a pressure threshold during the course of a movement of a moving part of the handheld device into a working position;

(7) FIG. 6 shows an illustration corresponding to FIG. 4 with opened blocking means and opened return valve;

(8) FIG. 7 shows a follow-up illustration to FIG. 6 after stopping a return movement of the moving part into a home position by closing the blocking means;

(9) FIG. 8 shows an illustration corresponding to FIG. 2 and concerning a second embodiment;

(10) FIG. 9 shows an illustration of the second embodiment corresponding to FIG. 4,

(11) FIG. 10 shows the second embodiment in the form of an illustration according to FIG. 5; and

(12) FIG. 11 shows a follow-up illustration to FIG. 10 according to FIG. 6.

DESCRIPTION OF THE EMBODIMENTS

(13) A hydraulically operated handheld device 1 in the form of a pressing device with an electric motor, 2, a not-shown hydraulic pump, a hydraulic medium reservoir 3 and a moving part 4 in the form of a hydraulic piston is initially described with reference to FIG. 1.

(14) The moving part 4 can be moved relative to a fixed part 5, which is respectively formed by the device housing or, for example, the cylinder, in which the hydraulic piston moves. For example, the moving part 4 forms the tool receptacle illustrated in FIG. 1. It may also be realized, for example, in the form of a hydraulic piston (see for example FIG. 3).

(15) Particularly the hydraulic medium reservoir 3, the return valve 8, the blocking means 19, the adjusting device 27 and, if applicable, other components are accommodated in a device body K that is not illustrated in greater detail in the figure.

(16) The hydraulic chamber 6 comprises the space, into which hydraulic medium is pumped. This space begins on the pressure side of the hydraulic pump. According to FIG. 3, for example, the hydraulic chamber 6 comprises a return line 7, through which the hydraulic medium can flow back into the hydraulic medium reservoir 3 via a return valve 8.

(17) According to FIGS. 4 and 7, in particular, the hydraulic chamber 6 changes with the operating state of the handheld device 1. In the illustration according to FIG. 4, the moving part 4 is in a different position than in FIG. 3. After the return valve 8 opens (FIG. 6), the hydraulic piston or the moving part 4 respectively moves back in the direction of its idle position. The hydraulic chamber 6 includes the space, which is insofar arranged upstream of the hydraulic piston, as well as the passage through the valve seat and the space directly upstream of the return valve 8 when the return valve is open.

(18) The electric motor 2 for operating the hydraulic pump and therefore for displacing the moving part 4 in the direction of the working position is activated by means of a switch 9 that is preferably realized in the form of a hand-actuated push button. The power supply for the electric motor 2 and preferably also for switching/control electronics is realized by means of a not-shown accumulator of the device 1 or an electric line.

(19) In the closed valve position, the return valve 8 is pressed into the valve seat by means of a pressure spring 10. The valve seat preferably consists of a screw-in part 12, which is screwed into the housing of the handheld device 1 by means of a thread 11.

(20) A flow-through bore 13 is provided in the valve seat, if applicable in the screw-in part 12. This bore is fluidically connected to the return line 7.

(21) Due to the narrow cross section of the flow-through bore 13 in the valve seat and the prestress generated by the pressure spring 10, the return valve 8 only opens when a defined triggering pressure is exceeded. This concerns the initially cited predefined working pressure. This triggering pressure may lie, for example, at 600 or 700 bar.

(22) After the return valve 8 has opened, the pressure of the hydraulic medium no longer is applied to only the area corresponding to the cross-sectional area of the flow-through bore 13, namely a partial piston area that is formed, for example, by a valve needle 14, but also to the entire area (lower surface 17) of the return valve piston 15 of the return valve 8, which faces the hydraulic chamber and comprises the valve needle 14. Consequently, the opened return valve 8 is 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 realized in an ideally pointed manner. In any case, it is preferably realized conically.

(23) During the return movement of the moving part 4, this pressure is preferably generated by a spring that acts upon the moving part 4 and presses the moving part 4 into the end position.

(24) The pressure is once again significantly lower downstream of the flow-through bore 13 in the outflow direction. At the beginning of the return movement of the moving part, in particular, this pressure only amounts, for example, to ¾ or less of the pressure upstream of the flow-through bore 13 or the valve seat, namely to about half of this pressure in practical applications. However, this pressure difference is then essentially equalized and typically only very small soon after the return movement of the moving part begins.

(25) After the return valve 8 opens, the hydraulic chamber includes the space that is located adjacent to the flow-through bore 13 and extends up to the lower surface 17 of the return valve piston 15. The hydraulic medium then flows into the reservoir 3 through an outflow opening 18. The space is also referred to as valve chamber above and below.

(26) Without additional measures, particularly without an external intervention, e.g., by the user, the hydraulic pressure or triggering pressure lifting the valve needle 14 off the valve seat corresponds to the aforementioned predefined working pressure on the moving part 4.

(27) However, an option is provided for displacing the return valve 8 into its open position without applying the hydraulic pressure required for lifting the return valve 8 to the moving part 4. Accordingly, the handheld device 1 is capable of performing tasks, for example compression processes, which require lower working pressures on the moving part 4 than the triggering pressure for the return valve 8.

(28) To this end, a blocking means 19 is provided and assigned to the hydraulic chamber arranged upstream of the return valve 8. In preferred embodiments, this blocking means 19 is realized in the form of an electrically actuatable magnetic valve.

(29) In the illustrated exemplary embodiment, the blocking means 19 is essentially composed of a linearly displaceable blocking piston 20 with a conical blocking surface and an electrically activatable operating magnet 21.

(30) The blocking means 19, particularly the blocking piston 20, is arranged so as to protrude into the return line 7. In its blocking position, the blocking piston 20 is suitable for dividing the return line 7 into a first line section 22 between the moving part 4 and the blocking means 19 and a second line section 23 between the blocking means 19 and the return valve 8 viewed in the backflow direction of the hydraulic medium.

(31) In another preferred embodiment, the blocking piston 20 is prestressed from its valve seat position, in which the first line section 22 and the second line section 23 are separated, into an open position. To this end, a return spring 24, particularly in the form of a pressure spring, may be provided as shown in order to generate the corresponding prestress.

(32) The introduction of hydraulic medium for displacing the moving part 4 forward in the direction of the working position takes place in the region of the second line section 23 while the blocking means 19 is opened. A return valve 25 is provided at this location.

(33) The handheld device 1 preferably comprises an adjusting device 27, by means of which the maximum working pressure applied to the moving part 4 can be pre-adjusted by the user. In the illustrated exemplary embodiment, a multitude of buttons 28 are provided for this purpose, wherein predefined pressure values are respectively assigned to said buttons 28. Accordingly, the above-described selected working pressure, which is modified in comparison with the predefined working pressure (or in individual instances also corresponds thereto), can be adjusted with the adjusting device. At this point, we also refer to the other, if applicable, alternative options of the initially mentioned radio link, etc.

(34) For example, a working pressure of 200 bar or 300 bar can be preselected for triggering the return valve.

(35) During the course of the movement of the moving part in the direction of the working position, evaluation/control electronics evaluate pressure values measured by a pressure sensor 29, 29′ and compare these pressure values with the nominal pressure value predefined by means of a button 28. The pressure sensor 29′ may obviously be a pressure sensor that is directly assigned to the hydraulic chamber 6. A pressure sensor 29 may alternatively or additionally also be arranged in the return line 7 and, if applicable, in the second line section 23 as illustrated, e.g., in FIG. 4. However, since the blocking piston 20 preferably moves back into the open position automatically as described in greater detail further below and a pressure measurement is not absolutely necessary for this purpose, but the pressure sensor 29 can no longer measure the pressure in the hydraulic chamber 6 when the blocking piston 20 is in the closed position, it is preferred to provide the pressure sensor 29′ that is directly assigned to the hydraulic chamber 6 in any case, particularly to provide only this pressure sensor 29′.

(36) Once the nominal pressure value is reached, a corresponding signal is generated and leads to an activation of the operating magnet 21 of the blocking means 19.

(37) As a result of the activation of the operating magnet 21, the blocking piston 20 abruptly moves into the forward position according to FIG. 5 against the force of the preferably provided return spring 24. In this way, the preferably conical sealing surface of the blocking piston 20 moves against the facing opening edge of the first line section 22 in a sealing manner.

(38) The hydraulic medium, which subsequently continues to be pumped from the reservoir 3 into the second line section 23, leads to a corresponding pressure increase beyond the nominal pressure value predominating in the first line section 22. Due to the very small receiving volume for hydraulic medium, which is essentially formed by only the second line section 23, the triggering pressure for displacing the return valve 8 into the open position is particularly reached within a fraction of a second, e.g. within 2 to 5 ms (see FIGS. 5 and 6).

(39) The operating magnet 21 of the blocking means 19 drops after the pressure-induced displacement of the return valve piston 15 into the open position. The blocking piston 20 is displaced into the open position, particularly in a spring-loaded manner, and therefore lifted off the valve seat such that the backflow of the hydraulic medium from the hydraulic chamber 6 into the hydraulic medium reservoir 3 can take place, wherein the return valve 8 is held in the raised position until the moving part 4 has reached the end position according to FIG. 3 and/or the pressure falls short of the pressure for holding open the return valve 8.

(40) The displacement of the blocking piston 20 into the open position can be realized in different ways. The operating magnet 21 is preferably designed for acting upon the blocking piston 20 with such a low force that it is pressed into the open position due to the pressure difference between the hydraulic chamber 6 and the second line section 23, which is generated by the blocking piston 20, after the return valve 8 has opened regardless of whether the blocking piston 20 is still acted upon by the operating magnet 21. For example, this can already be realized with a pressure difference of 1 bar or more. This displacement into the open position is also desirable and required because an excessively long closed state could once again lead to the pressure falling short of the pressure, at which the return valve 8 closes, due to the outflow of the hydraulic medium in the second line section 23. It would furthermore be conceivable that the actuation of the operating magnet 21 is time-controlled. When closing of the blocking means, in this case particularly the blocking piston 20, is triggered, it would therefore be conceivable that the required actuation of the operating magnet 21 lasts for a predefined time period, which in this case preferably also lies in the range of milliseconds to tenths of a second. If the aforementioned force acting upon the blocking piston 20 is adjusted correspondingly low as it is the case in preferred embodiments, the blocking piston can already be moved back into an open position due to the aforementioned pressure difference regardless of whether it is still acted upon by the operating magnet. The opening force acting upon the blocking piston is naturally also dependent on the area, which the blocking piston blocks at the transition from the first to the second line section 22 and 23. This is accordingly also chosen such that the aforementioned opening preferably takes place automatically regardless of an actuation of the operating magnet.

(41) The pressure increase on the return valve 8, which is realized by blocking the return line 7 with the aid of the blocking means 19, may act initially. As the return valve 8 is raised and the blocking means 19 is subsequently displaced into the open valve position, the pressure predominating due to the return movement of the moving part 4 acts upon the return valve 8.

(42) The blocking means 19 initially may also be electrically acted upon in a pulsed manner such that the blocking piston 20 is after a complete forward stroke located in the extended position according to FIG. 5 in a virtually abrupt manner. During a regular working cycle, i.e. if the return movement of the moving part should not be prematurely terminated, the blocking piston 20 remains in the raised position, in which it respectively releases the return line 7 and connects the line sections 22 and 23.

(43) The return line can be closed and the first and second line sections 22, 23 can thereby be separated by electrically acting upon the blocking means 20 prematurely, namely before the return movement of the moving part is completed, wherein this leads to such a pressure drop upstream of the return valve 8 in the flow direction and accordingly in the second line section 23 that the return valve 8 is thereby closed in the desired manner.

(44) The forward movement of the moving part 4 into the working position preferably only continues as long as the user actuates the switch 9. In an embodiment, a signal is generated when the switch 9 is released (also prior to the completion of a working process) and leads to an activation of the blocking means 19 and therefore to a pressure increase in the second line section 23 upstream of the return valve 8 in the backflow direction. Accordingly, the return valve 8 is displaced into the open position when the switch 9 is released, wherein this in turn leads to an automatic return movement of the moving part 4 into the end position.

(45) In order to reliably achieve this result although only inertial forces acting upon a pump component such as a pump piston may suffice, it is proposed that releasing the switch preferably does not lead to a standstill of the pump at exactly the same time, but the pump or a motor acting upon the pump is rather deactivated with a delay. This delay is chosen such that the required pressure increase can be achieved, i.e. in the range of a few milliseconds to tenths of a second.

(46) The blocking piston 20 may be arranged parallel to the return valve 8. The longitudinal axes of the blocking piston 20 and the return valve 8 may therefore extend parallel to one another.

(47) FIGS. 8 to 11 show a second embodiment of a handheld device 1. With respect to its functionality, this embodiment is to a substantial degree realized identical to the above-described first exemplary embodiment.

(48) In this case, the handheld device 1 also comprises a return valve 8 that can be activated with a triggering pressure in order to connect the return line 7 to the hydraulic medium reservoir 3.

(49) Furthermore, an electromagnetically actuatable blocking means 19 for acting upon the hydraulic medium volume located upstream of the return valve 8 in the backflow direction of the hydraulic medium is also provided in this case.

(50) The blocking means 19 functions and acts as in the above-described exemplary embodiment.

(51) The return valve 8 essentially also acts as in the above-described exemplary embodiment, particularly with respect to the triggering of the return valve S and the associated lifting of the return valve piston 15 into a position, in which it connects the return line 7 to the outflow opening 18 of the reservoir 3.

(52) In this exemplary embodiment, it is possible to lock the raised return valve position, in which the return valve piston 15 is displaced out of the valve seat in order to release the backflow path to the reservoir 3. For this purpose, the return valve piston 15 may comprise a circumferential waist-like constriction 26 opposite of the end comprising the valve needle 14. A locking finger 30, which is spring-loaded in the locking direction, engages into the thusly formed engagement region in the raised position of the return valve piston according to FIGS. 10 and 11. In the illustrated exemplary embodiment, the locking finger 30 acts transverse to the longitudinal direction and to the displacement direction of the return valve piston 15.

(53) The locking finger 30 is mounted in a housing section 31 in a linearly displaceable manner. In this housing section 31, a pressure spring 32 acts upon the locking finger 30, particularly such that it presses the locking finger 30 in the direction of the return valve piston 15.

(54) An actuating section 33, which freely protrudes over the housing section 31, is integrally formed on the locking finger 30 opposite of its end that cooperates with the return valve piston 15, wherein said actuating section makes it possible to move the locking finger 30 back as a result of a pulling movement against the effect of the pressure spring 32 in order to thereby release the return valve piston 15. Due to the effect of the pressure spring 10, the return valve piston drops back into the valve seat position, in which the backflow path is blocked.

(55) In this embodiment, the return valve piston 15 preferably also can only drop back into the valve seat position once the hydraulic pressure acting upon the overall piston area has dropped to a level that allows this displacement of the piston into the valve seat position. This can be realized upon completion of the return movement of the moving part 4 into a home position or by activating the blocking means 19 during the course of the return movement of the moving part 4, wherein a pressure reduction, which allows the displacement of the return valve piston 15 back into the valve seat position, is in the latter case also adjusted in the second line section 23 if the return movement of the moving part 4 has not been completed as a result of blocking the return line 7.

(56) The preceding explanations serve for elucidating all inventions that are included in this application and respectively enhance the prior art independently with at least the following combinations of characteristics, namely:

(57) A method, which is characterized in that the hydraulic pressure acting upon the return valve 8 for triggering a movement of the moving part 4 into the end position is increased by means of a separately triggerable pressure increase, which results in opening of the return valve 8, in a hydraulic medium volume located upstream of the return valve 8 in a flow direction of the hydraulic medium during the movement into the end position.

(58) A method, which is characterized in that the hydraulic pressure acting upon the return valve 8 is decreased by means of a separately triggerable pressure decrease, which results in closing of the return valve 8, in a hydraulic medium volume located upstream of the return valve 8 in a flow direction of the hydraulic medium during the movement into the end position.

(59) A method, which is characterized in that a line section upstream of the return valve 8 in the aforementioned flow direction is blocked or restricted in order to achieve the pressure decrease.

(60) A method, which is characterized in that a line section upstream of the return valve 8 in the aforementioned flow direction is blocked or restricted and hydraulic medium is introduced into the thusly blocked or restricted line section in order to achieve a pressure increase.

(61) A method, which is characterized in that the hydraulic medium pump delivers into a second line section 23, through which the hydraulic medium flowing in the open state of the return valve 8 also flows.

(62) A method, which is characterized in that the second line section 23 is blocked in order to achieve the pressure increase.

(63) A handheld device, which is characterized in that the hydraulic pressure acting upon the return valve 8 for triggering a movement of the moving part 4 into the end position can be increased by means of a separately triggerable pressure increase, which results in opening of the return valve 8, in a hydraulic medium volume located upstream of the return valve 8 in a flow direction of the hydraulic medium during the movement into the end position.

(64) A handheld device, which is characterized in that the hydraulic pressure acting upon the return valve 8 can be decreased by means of a separately triggerable pressure decrease, which results in closing of the return valve 8, in a hydraulic medium volume located upstream of the return valve 8 in a flow direction of the hydraulic medium during the movement into the end position.

(65) A handheld device, which is characterized in that a line section upstream of the return valve 8 in the aforementioned flow direction can be blocked or restricted in order to achieve the pressure decrease.

(66) A handheld device, which is characterized in that a line section upstream of the return valve 8 in the aforementioned flow direction can be blocked or restricted and hydraulic medium can be introduced into the thusly blocked or restricted line section in order to achieve a pressure increase.

(67) A handheld device, which is characterized in that the hydraulic medium pump delivers into a second line section 23, through which the hydraulic medium flowing in the open state of the return valve 8 can also flow.

(68) A handheld device, which is characterized in that the second line section 23 can be blocked in order to achieve the pressure increase.

(69) A handheld device, which is characterized in that the blocking means 19 is prestressed into an open position.

(70) A handheld device, which is characterized in that the blocking means 19 consists of a magnet-actuated closing means.

(71) All disclosed characteristics are essential to the invention (individually, but also in combination with one another). The disclosure content of the associated/attached priority documents (copy of the priority application) is hereby fully incorporated into the disclosure of this application, namely also for the purpose of integrating characteristics of these documents into claims of the present application. The characteristic features of the dependent claims characterize independent inventive enhancements of the prior art, particularly for submitting divisional applications on the basis of these claims.

LIST OF REFERENCE SYMBOLS

(72) 1 Handheld device 2 Electric motor 3 Hydraulic medium reservoir 4 Moving part 5 Fixed part 6 Hydraulic chamber 7 Return line 8 Return valve 9 Switch 10 Pressure spring 11 Thread 12 Screw-in part 13 Flow-through bore 14 Valve needle 15 Return valve piston 16 Spring 17 Lower surface 18 Outflow opening 19 Blocking means 20 Blocking piston 21 Operating magnet 22 First line section 23 Second line section 24 Return spring 25 Return valve 26 Constriction 27 Adjusting device 28 Button 29 Pressure sensor 29′ Pressure sensor 30 Locking finger 31 Housing section 32 Pressure spring 33 Actuating section K Device body