阅读说明：本技术 高压清洗机 (High pressure cleaning machine ) 是由 维尔纳·施瓦布 安德烈·内德莱亚 加布里埃尔·埃尔泰特 于 2017-08-16 设计创作，主要内容包括：本发明涉及一种高压清洗机(10),其带有电动马达(16)、以电动马达(16)驱动的用于输送清洁液的泵(18)、用于手动地接通和关断电动马达(16)的主切换设备(40)、以及用于在电动马达(16)的不允许的电流消耗的情况下关断电动马达(16)的马达保护切换设备(70),其中,马达保护切换设备(70)能自动地触发并且紧接着能手动地复位。为了改进高压清洗机(10)使其具有较为简单的操纵,提出的是,能通过手动地操纵主切换设备(40)使马达保护切换设备(70)复位。(The invention relates to a high-pressure cleaning machine (10) having an electric motor (16), a pump (18) driven by the electric motor (16) for delivering cleaning fluid, a main switching device (40) for manually switching the electric motor (16) on and off, and a motor protection switching device (70) for switching the electric motor (16) off in the event of an impermissible current consumption of the electric motor (16), wherein the motor protection switching device (70) can be automatically triggered and subsequently reset manually. In order to improve the high-pressure cleaning machine (10) such that it has a comparatively simple operation, it is proposed that the motor protection switching device (70) can be reset by manually operating the main switching device (40).)

1. High-pressure cleaning machine having an electric motor (16), a pump (18) driven by the electric motor (16) for delivering cleaning liquid, a main switching device (40) for manually switching the electric motor (16) on and off, a motor protection switching device (70) for switching the electric motor (16) off in the event of an impermissible current consumption of the electric motor (16), wherein the motor protection switching device (70) can be automatically triggered and subsequently reset manually, characterized in that the motor protection switching device (70) can be reset by manually actuating the main switching device (40).

2. The high-pressure washer according to claim 1, characterized in that the main switching device (40) has an adjustment link (54), which can be moved back and forth between an on position and an off position, wherein the motor protection switching device (70) can be reset by the adjustment link (54) being moved from the on position to the off position.

3. The high-pressure washer according to claim 2, characterized in that the motor protection switching device (70) has at least one motor protection switch (72, 74), wherein in the event of an impermissible current consumption of the electric motor (16), a phase feeding the electric motor (16) can be interrupted by means of the motor protection switch (72, 74).

4. The high-pressure washer according to claim 2 or 3, characterized in that the motor protection switching device (70) has two, in particular identically designed, motor protection switches (72, 74) which, in the event of an impermissible current consumption of the electric motor (16), respectively interrupt one phase feeding the electric motor (16).

5. The high-pressure washer according to claim 3 or 4, characterized in that the motor protection switching device (70) has a movably supported return portion (76) which can be moved from a first position to a second position by the at least one motor protection switch (72, 74) in the event of an impermissible current consumption of the electric motor (16), wherein the return portion (76) can be moved from the second position to the first position by the adjustment link (54) of the main switching device (40) being moved from the on position to the off position.

6. The pressure washer according to claim 5, characterized in that the return portion is designed as a slide (76) that can be moved back and forth between the first position and the second position.

7. The pressure washer according to claim 5 or 6, characterized in that the adjusting element (54) has a rotatably mounted adjusting shaft (56) which can be rotated back and forth between the on position and the off position and on which a return element (78) is held in a rotationally fixed manner, wherein the return portion (76) can be moved from the second position into the first position when the adjusting shaft (56) is moved from the on position into the off position by means of the return element (78).

8. The high-pressure washer according to claim 7, characterized in that the main switching device (40) has a main switch (42) with a switching element (52) which can be moved back and forth between a release position, in which the main switch (42) releases the supply of power to the electric motor (16), and an interruption position, in which the main switch (42) interrupts the supply of power to the electric motor (16), wherein a switching element (58) is held on the adjusting shaft (56) in a rotationally fixed manner and the switching element (52) can be moved by the switching element (58) counter to a restoring force from the release position into the interruption position.

9. The pressure washer according to claim 8, wherein said main switch is a microswitch (42).

10. The pressure washer according to claim 8 or 9, characterized in that the switching element is designed as a switching tongue (52) which interacts with a switching tappet (50) of the main switch (40).

11. The high-pressure washer according to claim 8, 9 or 10, characterized in that the high-pressure washer (10) has a control mechanism (92) which moves the switching element (52) counter to the restoring force from the release position into the interruption position in dependence on the pressure or flow rate of the cleaning liquid delivered by the pump (18).

12. The high-pressure washer according to claim 11, characterized in that the control mechanism is designed as a control rod (92) which can be moved counter to the force of a return spring (100) in relation to the pressure or flow rate of the cleaning liquid delivered by the pump (18).

Technical Field

The invention relates to a high-pressure cleaning machine having an electric motor, a pump driven by the electric motor for delivering cleaning fluid, a main switching device for manually switching the electric motor on and off, and a motor protection switching device for switching the electric motor off in the event of an impermissible current consumption of the electric motor, wherein the motor protection switching device can be automatically triggered and subsequently can be manually reset.

Background

With this high-pressure cleaning machine, a cleaning fluid, preferably water, is placed under pressure and directed at the surface to be cleaned. The high-pressure washer has a pump which can be driven by an electric motor in order to put a cleaning liquid, preferably water, under pressure. The cleaning liquid can be supplied to the pump via a liquid supply line, for example a suction hose, and the cleaning liquid under pressure can be supplied by the pump via a liquid discharge line, for example a high-pressure hose, to a liquid discharge device, in particular a spray gun or a spray gun.

The electric motor can be switched on and off manually by means of the main switching device. The high-pressure washer additionally has a motor protection switching device, by means of which the motor can be automatically switched off in the event of an impermissible current consumption. The motor protection switching device can be designed, for example, as an overflow protection switching device having a bimetallic contact which is heated up so strongly in the event of an inadmissibly high current consumption of the electric motor that the power supply to the electric motor is interrupted by means of the bimetallic contact.

After the automatic triggering, the motor protection switching device must be manually reset by the user in order to end the interruption of the power feed to the electric motor. For this purpose, provision may be made for a user to have access to a resetting element which the user must manually actuate after the motor protection switching device has been triggered. However, this makes handling of the high-pressure washer difficult.

Disclosure of Invention

The object of the invention is therefore to develop a high-pressure cleaning machine of the type mentioned at the outset such that it has a comparatively simple handling.

In such a high-pressure cleaning machine, this problem is solved according to the invention in that the motor protection switching device can be reset by manually actuating the main switching device.

As mentioned at the outset, the user can switch the electric motor on and off by means of the main switching device. In the event of an impermissible current consumption, the motor protection switching device is automatically triggered, which interrupts the power supply to the electric motor. The impermissible current consumption can be caused, for example, by a mechanical overload of the electric motor. Of course, only when the user switches on the electric motor in advance by means of the main switching device, an impermissible current consumption can occur. The triggering of the motor protection switching device results in the electric motor no longer being supplied with electrical energy and consequently being shut down. This can be recognized by the user by setting his activity in the high-pressure washer. In the high-pressure washer according to the invention, the user then resets the motor protection switching device by manually actuating the main switching device. It is therefore not necessary for the user to operate a separate resetting element. The user can thus easily handle the high-pressure washer according to the invention even when the motor protection switching device is triggered.

In an advantageous embodiment of the invention, the main switching device has an adjustment link which can be moved back and forth between an on position and an off position, wherein the motor protection switching device can be reset by the adjustment link moving from the on position to the off position. To switch on the high-pressure washer, the user actuates the main switching device, so that the actuating element is moved from the off position into the on position. If the motor protection switching device detects that an inadmissible current consumption of the electric motor is present during operation of the high-pressure washer, the motor protection switching device interrupts the power supply. In this case, the user only needs to actuate the main switching device again, the actuating element moving from the on position back into the off position. This movement of the actuating element resets the motor protection switching device, i.e. the motor protection switching device again assumes a state in which the motor protection switching device does not interrupt the supply of power to the electric motor. The user can then switch on the high-pressure cleaning machine again in such a way that the actuating element is moved back from the off position into the on position.

It is particularly advantageous if the motor protection switching device has at least one motor protection switch, with which the phase feeding the electric motor can be interrupted in the event of an impermissible current consumption of the electric motor. As the electric motor, a single-phase or three-phase electric motor may be used. The single-phase electric motor has a single-phase supply and, in the event of impermissible current consumption, this phase of the supply can be interrupted by means of a motor protection switch. The three-phase electric motor has a three-phase supply (three-phase current), and the motor protection switching device has a plurality of motor protection switches, for example two motor protection switches, for monitoring the current consumption of the electric motor, by means of which one phase of the supply can be interrupted in each case with an impermissible current consumption.

It is particularly advantageous if the motor protection switching device has two identically designed motor protection switches, which each interrupt a phase feeding the electric motor in the event of an impermissible current consumption of the electric motor. In this embodiment of the invention, a three-phase electric motor can be used, which can be connected to a three-phase power supply system. In the event of an impermissible current consumption, the two phases of the supply can be interrupted by means of a motor protection switch of identical design. Using motor protection switches of the same design results in a cost reduction based on the larger part count associated therewith.

In an advantageous embodiment of the invention, the motor protection switching device has a movably mounted return portion which can be moved from a first position to a second position by at least one motor protection switch in the event of an inadmissible current consumption of the electric motor, wherein the return portion can be moved from the second position back to the first position by the movement of the actuating element of the main switching device from the on position to the off position. In this embodiment of the invention, the movably supported return portion is moved in order to reset the motor protection switching device. The override portion therefore assumes the first position until the motor protection switching device is triggered on the basis of an impermissible current consumption of the electric motor. The triggering of the motor protection switching device results in the movement of the return portion from the first position to the second position by the at least one motor protection switch. The callback portion occupies the second pose until the callback portion moves back to the first pose again. This return movement is preferably carried out by means of an adjustment element of the main switching device, which adjustment element moves from the on position to the off position for this purpose. The adjustment link applies a pull-back force to the pull-back portion when moving from the on position to the off position, the pull-back portion being rotated from the second attitude to the first attitude by the pull-back force.

The return portion is advantageously designed as a slider which can be moved back and forth between the first position and the second position.

In an advantageous embodiment of the invention, the actuating element of the main switching device has a rotatably mounted actuating shaft which can be rotated back and forth between an on position and an off position and on which the return element is held in a rotationally fixed manner, wherein the return portion can be moved from the second position into the first position when the actuating shaft is moved from the on position into the off position by means of the return element.

The adjustment element is preferably oriented perpendicularly to the longitudinal axis of the adjustment shaft.

The adjustment link may, for example, form an arm, a projection or a cam projecting laterally from the adjustment shaft, which arm, projection or cam actuates the adjustment portion of the motor protection switching device when the adjustment shaft is moved in rotation from the on position into the off position.

In particular, it can be provided that, when the actuating shaft is moved from the on position into the off position, the return link slides along the end face of the return portion and this return portion is thereby moved counter to the spring-elastic return force from the second position into the first position.

After triggering the motor protection switching device, the return portion projects into the movement region of the return link, so that it is detected by the return link when the return portion moves from the on position into the off position. If the return portion assumes its first position, it can be positioned outside the movement range of the return link, so that the return link, together with the adjustment shaft, can be moved back and forth between the on position and the off position without the return portion being moved there.

The main switching device preferably has a main switch with a switching element that can be moved back and forth between a release position in which the main switch releases the power feed to the electric motor and an interruption position in which the main switch interrupts the power feed to the electric motor. In the release posture of the switching element, the main switch releases the feeding of the electric motor, and in the interruption posture of the switching element, the main switch interrupts the feeding of the electric motor.

Advantageously, the switching ring can be used to move the switching element of the main switch from the release position to the interruption position in opposition to a restoring force, wherein the switching element is held in a rotationally fixed manner on the adjustment shaft, on which the restoring element, which is advantageously used for restoring the motor protection switching device, is also held in a rotationally fixed manner. The adjusting shaft can be twisted in order to actuate the main switch. When the adjusting shaft is moved from the off position into the on position, the switching element of the main switch is released by the switching element held in a rotationally fixed manner on the adjusting shaft, so that this switching element assumes its release position under the influence of the restoring force and the electric motor is therefore supplied with power. When the adjusting shaft is moved from the on position to the off position, the switching element is moved by the switching element counter to the return force into the interruption position, so that the electric motor is no longer supplied with power, and if the motor protection switching device is triggered beforehand, the return portion of the motor protection switching device is moved back from the second position into the first position by the return element held in a rotationally fixed manner on the adjusting shaft.

The switching element is advantageously oriented perpendicularly to the longitudinal axis of the adjusting shaft.

The switching element can, for example, form an arm, a projection or a cam projecting laterally from the adjusting shaft.

The main switch preferably has a microswitch. Depending on the power of the electric motor, the microswitch can directly switch the electric motor on and off, or it can interact with a relay or a contactor in order to switch the electric motor on and off.

In an advantageous embodiment of the invention, the switching element of the main switch is designed as a switching tongue which interacts with a switching plunger of the main switch.

It is particularly advantageous if the high-pressure washer has a control mechanism which, as a function of the pressure or flow rate of the cleaning liquid delivered by the pump, moves the switching element from the release position to the interruption position counter to the restoring force. In this embodiment of the invention, the switching element of the main switch can be moved from the release position into the interruption position as a function of the pressure or flow rate of the cleaning liquid delivered by the pump, so that the high-pressure washer is switched off. This may be the case, for example, when the user closes a liquid outlet, in particular a spray gun or a spray gun, arranged at the free end of the liquid outlet line, since by closing the liquid outlet, the pressure of the cleaning liquid delivered is increased until a predetermined maximum value is reached, on account of the continued activation of the pump. When this maximum value is reached, the switching element of the main switch is moved from the release position to the interruption position by means of the control mechanism, and the electric motor is switched off. If the user subsequently opens the liquid discharge device again, the pressure of the cleaning liquid decreases and the control device no longer exerts a force on the switching element of the main switch, so that the switching element automatically moves from the interruption position into the release position under the influence of the restoring force and thereby switches the electric motor on again.

Alternatively, it can also be provided that the control device moves the switching element of the main switch in dependence on the flow rate of the cleaning liquid delivered by the pump. The flow rate of the cleaning liquid under pressure due to the pump is related to whether the liquid discharge mechanism is open or closed. If the liquid discharge mechanism is closed, the flow rate of the cleaning liquid decreases, and the control mechanism moves the switching element of the main switch from the release posture to the interruption posture against the returning force, so that the electric motor is turned off. If the user subsequently opens the liquid discharge device again, the flow rate of the cleaning liquid rises and the control device no longer exerts a force on the switching element, so that the switching element moves again from the interruption position to the release position under the influence of the restoring force and the supply of current to the electric motor is released again.

The control mechanism is advantageously designed as a control rod which can be moved counter to the force of the return spring in relation to the pressure or flow rate of the cleaning liquid delivered by the pump. The control rod is advantageously fastened to a control piston which is mounted in a displaceable manner in the control chamber and which can be acted upon by pressurized cleaning liquid. The control piston may be supported on a return spring which loads the control piston with a return force. The position of the control piston in the control chamber is dependent on the pressure of the cleaning liquid delivered by the pump or on the flow rate of the cleaning liquid delivered by the pump. The change in position of the control piston causes a movement of the control rod, which can thus operate the switching element of the main switch in relation to the pressure or flow rate of the cleaning liquid delivered by the pump.

In the provision of the control mechanism explained above and the motor protection switching device explained above, the main switch can be manually actuated by a user. The main switch can on the other hand be actuated as a function of the pressure or flow rate of the cleaning liquid delivered by the pump, and, if the motor protection switching device interrupts the supply of power to the electric motor beforehand on the basis of an impermissible current consumption, the motor protection switching device can also be reset by actuating the main switching device, in particular by moving the actuating element of the main switching device from the on position into the off position.

Drawings

The following description of advantageous embodiments of the invention is intended to be explained in more detail with reference to the accompanying drawings. In the drawings:

FIG. 1 shows a front view of a high pressure washer;

FIG. 2 shows a cross-sectional view of the high pressure cleaner taken along line 2-2 of FIG. 1;

FIG. 3 shows an enlarged view of detail A of FIG. 2;

fig. 4 shows a simplified cross-sectional view of an adjusting element of the main switching device of the high-pressure cleaning machine of fig. 1, the adjusting element assuming an off position;

FIG. 5 shows a cross-sectional view of the adjustment link along line 5-5 of FIG. 4;

fig. 6 shows a simplified sectional view of the adjustment element corresponding to fig. 4, the adjustment element assuming the switched-on position;

FIG. 7 shows a cross-sectional view of the adjustment link along line 7-7 of FIG. 6;

fig. 8 shows a sectional view of the adjustment link corresponding to fig. 7 after triggering the motor protection switching device.

Detailed Description

An advantageous embodiment of the high-pressure cleaning machine according to the invention is shown schematically in the drawing and is designated in its entirety by reference numeral 10. The high-pressure cleaning machine 10 has a housing 12 in which a motor pump unit 14 is arranged, which has an electric motor 16 and a pump 18 driven by the electric motor 16. The cleaning liquid, preferably water, can be put under pressure by means of a pump 18. The cleaning liquid can be supplied to the pump 18 via the suction connection 20, and the cleaning liquid under pressure by the pump 18 can be discharged by the pump 18 via the pressure connection 22. A liquid carrying line, such as a suction hose, may be coupled to the suction fitting 20, and a liquid discharge line, such as a pressure hose, may be coupled to the pressure fitting 22. The liquid outlet line can carry a liquid outlet means, such as a spray gun or spray gun, which can be closed manually by the user, at its free end.

The running wheels 24, 26 are mounted on the housing 12 so as to be rotatable about a common axis of rotation 28. The high-pressure cleaning machine 10 can be moved along the ground by means of the running wheels 24, 26. For this purpose, the high-pressure washer 10 can be pivoted about a common axis of rotation 28 from its position of use, which is not shown in the figures, so that the high-pressure washer 10 can be moved in the manner of a two-wheeled hand truck.

In order to facilitate the transport of the high-pressure washer 10 by the user, the high-pressure washer 10 has a U-shaped push bow 30 which can be moved back and forth between a retracted position shown in fig. 1 and 2 and an extended position not shown in the figures. The push bow 30 has a first leg 32 and a second leg 34, which are rigidly connected to each other by a handle 36. In the moved-in position, the handle 36 occupies a significantly smaller distance from the housing 12 than in the moved-out position. In the removal position, the user can hold the handle 26 in the upright position in order to be able to move the high-pressure washer 10 in a simple manner.

For controlling the high-pressure washer 10, that is to say for switching the electric motor 16 on and off, the high-pressure washer 10 has a main switching device 40 with a main switch, which in the exemplary embodiment shown is designed as a microswitch 42 and is arranged in a switching box 44 that is sealed against water spray. The switch box 44 has a basin-shaped lower portion 46 and a cover 48.

The microswitch 42 has a switching plunger 50 shown in fig. 6, which can be actuated by a switching element in the form of a switching tongue 52. The switching tongue 52 interacts with an adjusting element 54, which has an adjusting shaft 56 mounted in a rotatable manner and a switching element in the form of a switching arm 58 held in a rotationally fixed manner on the adjusting shaft 56. The shift arm 58 is oriented perpendicular to the longitudinal axis 60 of the adjustment shaft 56 and forms a lateral projection or cam. The adjusting shaft 56 carries at its free end a rotary link 62, which is coupled via a switching lever 64 to a rotary knob 66 rotatably mounted on the housing 12. By rotating the knob 66, the adjusting shaft 56 and therewith also the switching arm 58 can be rotated back and forth between the on position shown in fig. 6, 7 and 8 and the off position shown in fig. 4 and 5. In the off position, the switching arm 58 is pressed against the switching tongue 52, which thus actuates the switching plunger 50 of the microswitch 42. As a result of this, the microswitch 42 interrupts the power supply to the electric motor 16. In the on position, the switching arm 58 releases the switching tongue 52. As a result of this, the microswitch 42 releases the feed to the electric motor 16.

The electric motor 16 is in the exemplary embodiment shown configured as a three-phase electric motor, which can be coupled to a three-phase power grid. The electric motor 16 is fed via a multicore supply cable 68, which is known per se and is therefore only schematically illustrated in fig. 2.

In order to protect the electric motor 16 from overloading, the high-pressure cleaning machine 10 has a motor protection switching device 70 with a first motor protection switch 72 and a second motor protection switch 74. The two motor protection switches 72, 74 are identically designed and provided for interrupting one phase, which feeds the electric motor 16, in each case when there is an impermissible current consumption of the electric motor. The two motor protection switches 72, 74 can have a bimetallic contact for this purpose. Such motor protection switches are known per se to the person skilled in the art and therefore do not need to be explained in greater detail at present.

In the event of an impermissible current consumption, the supply of power to the electric motor 16 is automatically interrupted by means of the motor protection switching device 70. To end the interruption of the power feed, the motor protection switching device 70 must be manually reset. For this purpose, the motor protection switching device has a return portion designed as a slider 76, which can be moved back and forth between a first position shown in fig. 5 and 7 and a second position shown in fig. 8. As long as there is no impermissible current consumption of the electric motor 16, the slide 76 assumes its first position and, in the event of impermissible current consumption of the electric motor 16, the slide 76 is moved by the motor protection switches 72, 74 into its second position.

In order to be able to reset the motor protection switching device 70, a return element in the form of a return arm 78 is held on the adjusting shaft 56 in the axial direction and in the circumferential direction offset from the switching arm 58 in a rotationally fixed manner, which is oriented perpendicularly to the longitudinal axis 60 of the adjusting shaft 56 and forms a lateral projection or cam. As the adjustment shaft 56 is twisted between the on position and the off position, the retraction arm 78 is also twisted. As is clear from fig. 8, if the slide 76 assumes its second position, it projects into the region of movement of the retraction arm 78. The precondition is that the user first switches the high-pressure washer 10 on by means of the main switching device 40, so that the switching arm 58 assumes its switched-on position shown in fig. 6 and 7, in which the microswitch 42 releases the supply of current to the electric motor 16. In the event of an inadmissible current consumption of the electric motor 16 during operation of the high-pressure washer 10, the slide 76 is moved into its second switching position by at least one of the motor protection switches 72, 74, as already explained. The power feed to the electric motor 16 is automatically interrupted by the motor protection switching device 70. The user can now turn the adjusting shaft 56 about its longitudinal axis 60 by actuating the rotary knob 66, so that the switching arm 56 is moved into its off position and at the same time, when the switching arm is moved from the on position into the off position, the return arm 78 slides along the end face 80 of the slide 76 and in the process moves the slide 76 back into its first position. Thereby resetting the motor protection switching device 70. By subsequent renewed actuation of the rotary knob 66, the switching arm 58 can be moved into its switched-on position again, in which the microswitch 42 releases the supply of current to the electric motor 16 again.

In addition to the main switching device 40, which can be used to switch the electric motor 16 on and off manually, and in addition to the motor protection switching device 70, which can be used to switch the electric motor 16 off automatically in the event of an impermissible current consumption, the high-pressure washer 10 also has a control device 90, with which the electric motor 16 can be switched on and off as a function of the pressure or flow rate of the cleaning liquid delivered by the pump 18. The control device 90 has a control mechanism in the form of a control rod 92 secured to a control piston 94. Control piston 94 is mounted in a control chamber 96 so as to be movable back and forth along a longitudinal axis 98 of control rod 92 and can be charged with cleaning liquid under pressure. For this purpose, the control chamber 96 is in flow communication with a pressure line of the pump 18, which opens into the pressure connection 22, via a connecting line known per se and not shown in the figures for a better overview. The control piston 94 is spring-loaded with a restoring force, which acts counter to the pressure loading, by a restoring spring 100 in one direction. The pressure loading of the control piston 94 is related in a manner known per se to the pressure of the cleaning liquid delivered by the pump 18 or to the flow rate of the cleaning liquid delivered by the pump 18. The flow rate can be correlated, for example, by a syringe having a through-opening which narrows first in the flow direction and then widens again being connected in the pressure line of the pump 18, from the narrowest point of which a transverse bore branches off. The pressure of the cleaning liquid in the transverse bores is related to the flow rate of the cleaning liquid. This pressure can act on the control piston 94 counter to the restoring force of the restoring spring 100.

Depending on the pressure of the cleaning liquid delivered by pump 18 or depending on the flow rate of the cleaning liquid delivered by pump 18, control piston 94 and therewith also control rod 92 are moved back and forth along longitudinal axis 98. The control rod 92 can assume a returned position, which is shown in solid lines in fig. 6, or an advanced position, which is shown in broken lines in fig. 6. This opens up the possibility of actuating the switching tongue 92 as a function of pressure or flow rate and, with this switching tongue, also actuating the switching plunger 50 of the microswitch 42.

As already mentioned, the liquid outlet line carries a liquid outlet mechanism on its free end, which can be opened and closed manually by a user. In order to discharge the pressurized cleaning liquid, the user opens the liquid discharge mechanism, so that the pressurized cleaning liquid can be directed onto the surface to be cleaned by means of the liquid discharge mechanism. The cleaning liquid discharge can be terminated by the user in such a way that the user switches off the liquid discharge mechanism. This increases the pressure delivered by the pump 18 due to the permanent operation of the pump 18. If the pressure of the cleaning fluid reaches a predetermined maximum value, the control piston 94 and therewith also the control rod 92 are moved into the advanced position shown in dashed lines in fig. 6, so that the microswitch 42 interrupts the power supply to the electric motor 16, without the user having to actuate the knob 66 for this purpose. If the user subsequently releases the liquid discharge by opening the liquid discharge mechanism, the pressure of the cleaning liquid delivered by the pump 18 drops and the control piston 94 and the control rod 92 are moved together by the return spring 100 into the return position shown in fig. 6 by solid lines, in which the microswitch 42 releases the supply of current to the electric motor 16 again. The user therefore has the possibility of switching the electric motor 16 on and off by switching the liquid discharge mechanism on and off without the user having to manipulate the knob 66 for this purpose.