Pressure cleaning machine

Abstract

Described is a high-pressure washer (100) comprising:-a pump (40) and an electric motor (50) configured to drive the pump (40), where the pump (40) is connected to an inlet conduit (15) for liquid to be pressurized and to a delivery conduit (20) for liquid pressurized by the pump (40); -an electronic circuit (200) controlling the power supply of the electric motor (50); -wherein the electronic circuit (200) comprises an electronic control unit (60) operably connected to the electric motor (50); characterized in that the electronic circuit (200) is configured to vary the rotational speed of the motor (50) by varying the waveform of the current supplied to the motor (50) in order to vary the flow rate of the liquid pressurized by the pump (40) in the delivery conduit (20).

Description

Technical Field

[0001] The present invention relates to pressure washers, ie high pressure cleaning devices for cleaning surfaces by producing jets of liquid under pressure. Background Art

[0002] As is known, a high-pressure cleaning device or pressure washer comprises a high-pressure pump adapted to pump a cleaning fluid, such as water, the delivery conduit of which is connected to a flexible hose connected to a dispensing gun of the pressurized liquid.

[0003] The dispensing spray gun generally comprises an elongated body provided with a handle to which a dispensing wand for supporting a dispensing nozzle is removably connected at its free end.

[0004] The dispensing spray gun then comprises a trigger which is arranged at the handle and which actuates a spray head suitable for allowing or interrupting the flow of cleaning fluid from the pump to the dispensing nozzle.

[0005] The fluid delivered to the spray gun is set at a certain pressure by an electric pump, which is a pump in which at least one electric motor is mechanically connected to the pump in order to supply mechanical energy to the pump in order to pressurize the fluid.

[0006] In known pressure washers, the pressure of the fluid delivered by the pump is regulated downstream of the pump, for example by activating a bypass to divert a portion of the pressurized fluid flow.

[0007] In this known solution, the pump always delivers a maximum fluid flow, so that the flow regulation dissipates the hydraulic energy still supplied by the pump.

[0008] From the above it can be seen that in systems of known type there is an unnecessary waste of hydraulic energy and therefore of electrical energy absorbed by the electric motor to drive the pump and therefore ultimately an undue power consumption by the electric motor driving the pump.

[0009] The object of the present invention is to overcome the disadvantages of the prior art by proposing a high-pressure cleaning machine which offers improved energy performance.

[0010] Another object of the present invention is to provide a high pressure cleaning machine that provides a plurality of operating modes available to the user.

[0011] Finally, a further object of the invention is to increase the versatility and ease of use of the high-pressure cleaning machine within the framework of a simplified, rational and robust construction solution.

[0012] These objects are achieved by the features of the invention set out in the independent claim. The dependent claims outline preferred and / or particularly advantageous aspects of the invention. Summary of the invention

[0013] In particular, the present invention provides a high-pressure cleaning machine, comprising:

[0014] a pump and an electric motor configured to drive the pump, wherein the pump is connected to an inlet conduit for the liquid to be pressurized and to a delivery conduit for the liquid pressurized by the pump;

[0015] - an electronic circuit for controlling the power supply to the electric motor;

[0016] - wherein said electronic circuit comprises an electronic control unit operatively connected to said electric motor;

[0017] Characterized in that the electronic circuit is configured to change the rotation speed of the motor by changing the waveform of the current supplied to the motor so as to change the flow rate of the liquid pressurized by the pump in the delivery pipe.

[0018] This solution makes it possible to regulate the motor speed and therefore the flow rate of the pressurized fluid in a manner that achieves significant energy savings.

[0019] According to an embodiment of the present invention, the electronic control unit is configured to change a waveform of the current supplied to the motor by interrupting the alternating current supplied to the motor at predetermined time intervals starting from a reference signal.

[0020] A high pressure washer is provided that allows easy and effective adjustment of water flow rate.

[0021] One aspect of the invention provides an electronic circuit comprising a zero crossing circuit configured to generate an electrical reference signal each time a sinusoidal waveform of a motor supply current crosses zero, and to make the signal available to the electronic control unit.

[0022] An advantage of this solution is that the zero crossing circuit allows monitoring the zero crossings of the AC power supply waveform to the motor in order to have a reference point for synchronous motor speed regulation.

[0023] According to an embodiment of the invention, the zero-crossing circuit comprises two diodes, each diode being connected to the AC power source via an anode and each diode having a cathode connected to a common node electrically connected to a contact of the control unit.

[0024] This solution has the advantage of providing a zero-crossing circuit that is cheap and easy to implement.

[0025] According to an embodiment of the invention, the electronic circuit comprises a triac electrically connected to the motor and provided with a gate connected to the electronic control unit, whereby the electronic control unit is configured to send a conduction signal to the triac according to the time interval.

[0026] The advantage of this solution is the simple and effective control of the conducting and blocking states of the triac, thereby controlling the power supply to the motor.

[0027] According to another embodiment of the invention, the electronic control unit is configured to send a turn-on signal to the triac at the end of a time interval calculated from a zero crossing of the sinusoidal waveform of the motor power supply current signaled by the zero crossing circuit.

[0028] An advantage of this embodiment is that during the time interval, since the triac is in a non-conducting state, the motor is not activated, resulting in a lower water flow rate and consequent energy savings.

[0029] According to yet another embodiment of the present invention, a photoelectric isolator is provided between the electronic control unit and the triac.

[0030] An advantage of this embodiment is that the opto-isolator electrically isolates the portion of the electronic motor control circuit that operates on direct current from the portion of the motor control circuit that operates on alternating current.

[0031] According to another embodiment of the present invention, a protection snubber is associated with a triac.

[0032] An advantage of this embodiment is that the snubber has the functionality of an electrical transient suppression circuit.

[0033] According to another embodiment of the present invention, the electronic circuit further comprises means for activating a bypass function to bypass the control of the electronic control unit when the AC power supply waveform of the motor changes.

[0034] An advantage of this embodiment is that the user can bypass the effect of the electronic control circuit by means of the starter device, ie interrupt the supply of AC current to the motor for a predetermined time interval, thereby ensuring that the motor driving the pump is continuously supplied with 100% power.

[0035] According to one aspect of the invention, the starting device comprises a switch, the switching of which generates a control signal at an input to the electronic control unit, wherein the electronic control unit is configured to continuously supply power to the motor upon receipt of the control signal.

[0036] An advantage of this embodiment is its simplicity, which is particularly economical and effective.

[0037] According to another aspect of the invention, the activating device of the bypass function comprises a switch associated with the pressure switch, the switching of which is controlled according to the actuation of the trigger of the dispensing spray gun, the control unit being programmed to detect the number of switching operations of the switch and to activate the bypass function when the number of switching operations of the switch is equal to a predetermined number (N) within a predetermined time interval (Δt).S ) to activate the bypass function.

[0038] This embodiment of the activation device has the advantage of allowing the user to activate the bypass function very quickly directly from the dispensing gun.

[0039] According to another aspect of the invention, the control unit is programmed to activate the bypass function at predetermined time intervals within the control unit.

[0040] An advantage of this aspect of the invention is that the operator does not have to manually deactivate the bypass function. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Further characteristics and advantages of the invention will become more apparent upon reading the following description, provided by way of non-limiting example, with the aid of the accompanying drawings.

[0042] Figure 1 is a schematic diagram of a high pressure cleaning machine according to a first embodiment of the present invention;

[0043] Figure 2 It shows the control Figure 1 A schematic diagram of a first embodiment of an electronic circuit of a motor of a high pressure cleaning machine;

[0044] Figure 3 is a schematic diagram of a pressure washer according to a second embodiment of the present invention;

[0045] Figure 4 It shows the control Figure 3 A schematic diagram of a second embodiment of an electronic circuit of a motor of a high pressure cleaning machine;

[0046] Figure 5 is a schematic diagram of a high pressure cleaning machine according to a third embodiment of the present invention;

[0047] Figure 6 It shows the control Figure 5 A schematic diagram of a third embodiment of an electronic circuit for a motor of a pressure washer;

[0048] Figure 7 is a schematic diagram showing a first operating step of the high pressure washer circuit of the present invention; and

[0049] Figure 8 is a diagram showing a second operating step of the high pressure washer circuit of the present invention. DETAILED DESCRIPTION

[0050] Specific reference Figure 1 , reference numeral 100 generally indicates a high pressure cleaning machine or a high pressure cleaning device.

[0051] The high pressure washer 100 comprises a box-like housing 10 , for example made of plastic material, to which preferably a handle and / or wheels (not shown) are associated for moving the high pressure washer itself.

[0052] The high-pressure cleaning machine 100 comprises a single inlet pipe 15 for the fluid to be pressurized, such as a single inlet conduit 15 for the fluid to be pressurized, which is suitable for connection to a source of the fluid to be pressurized, such as a tank or a water network.

[0053] The inlet duct is at least partially housed within the housing 10 .

[0054] The high pressure washer 100 further comprises a pressurized fluid delivery conduit 20 (eg a single pressurized fluid delivery conduit 20) and a distribution lance 25, wherein the delivery conduit 20 is fluidly connected to the distribution lance 25, for example by a flexible hose. The delivery conduit 20 is at least partially accommodated in the housing 10, for example.

[0055] The dispensing spray gun 25 comprises a body equipped with a handle 37 to which is associated in a removable manner, for example, a dispensing rod 30 equipped at one of its free ends with a dispensing nozzle 32 .

[0056] As an alternative to a wand, any other cleaning tool, such as a rotating brush, may also be associated with the dispensing lance 25 .

[0057] The dispensing spray gun 25 may include a trigger 35 that is movable between a first position, in which the dispensing spray gun does not dispense pressurized fluid, and a second position, in which the dispensing spray gun dispenses pressurized fluid.

[0058] In particular, the trigger 35 is disposed at the handle 37 of the dispensing spray gun 25 and actuates the valve between a first position in which the valve allows pressurized fluid to flow from the delivery conduit 20 to the dispensing nozzle and a second position in which the valve interrupts the flow of pressurized fluid from the delivery conduit 20 to the dispensing nozzle 32.

[0059] The high-pressure cleaning machine further comprises a pump 40 connected at an inlet to the inlet pipe 15 and at an outlet to the delivery pipe 20 , preferably the pump 40 having a fixed displacement.

[0060] The high pressure washer 100 also includes a motor 50 configured to drive a pump 40 operatively connected to the fluid inlet conduit 15 and the fluid delivery conduit 20. That is, the motor 50 is mechanically connected to the pump 40 to actuate the pump 40 to pressurize the fluid from the inlet conduit 15. Overall, the motor 50 and the pump 40 form an electric pump of the high pressure washer 100.

[0061] The electric motor 50 is adapted to be electrically connected to an electrical energy source, ie to an electrical distribution network and / or to a battery, for example housed within the housing 10 .

[0062] The high pressure cleaning machine 100 also includes an electronic circuit 200, which is equipped with an electronic control unit 60, see below. Figure 2 Describing the electronic circuit 200 in more detail; the circuit 200 is electrically connected to the motor to control its operation.

[0063] The high pressure cleaning machine 100 further comprises a pressure switch 70, which is located on the delivery pipe 20, for example, downstream of the pump 40 (i.e., between the pump 40 and the dispensing spray gun 25), wherein the pressure switch 70 has a movable rod 72 that overcomes the force of a spring 74, so that it can selectively act on an electric switch 75.

[0064] Next, the electrical switch 75 is preferably in the form of a normally closed (NC) switch, wherein in the normally closed position, the electrical switch 75 is connected to a power supply circuit for controlling the motor of the pump 40 via the electronic circuit 200; the electrical switch 75 can also be in a second open position, wherein it is connected to a common ground node of the circuit at a predetermined voltage (equal to zero).

[0065] Specifically, when the delivery pressure of the pump 40 is lower than a predetermined calibration value P th When the pressure switch 70 on the delivery pipeline 20 is normally closed (NC), the electric switch 75 of the pressure switch 70 is normally closed (NC), and when the pressure exceeds the calibration value P th When the electric switch 75 is automatically disconnected.

[0066] Opening the electrical switch 75 of the pressure switch 70 stops the pump 40, thereby providing a complete stop function, and occurs, for example, when the dispensing gun 25 is closed, thereby causing the pressure upstream thereof to increase.

[0067] Figure 1 Also shown is a power line 110 which comprises two cables, one L being the power line and the other N being the neutral phase.

[0068] The cables L and N are connected to a manually operated double pole switch 90 from which the power supply cable for the electric motor 50 driving the pump 40 is derived.

[0069] Figure 2 It shows the control Figure 1 FIG. 1 is a schematic diagram of a possible embodiment of an electronic circuit 200 of a motor 50 of a high pressure cleaning machine 100 .

[0070] The electronic circuit 200 serves as a driving circuit for the motor 50 and can be subdivided into a DC (Direct Current) part that operates with a direct current and an AC (Alternating Current) part that operates with an alternating current.

[0071] The electronic circuit 200 includes a triac 210 (or thyristor) electrically connected to the motor 50 and provided with a control gate connected to the electronic control unit 60. Specifically, the triac is switched by the electronic control unit 60 to control the supply of current to the motor 50 by means of the triac 210 in a manner as described below.

[0072] A protection circuit is also associated with the triac 210 to protect the triac 210 from electrical transients. In the example shown, the protection circuit may be provided with a snubber circuit 220 as is known.

[0073] An opto-isolator 250 is provided between the electronic control unit 60 and the triac 210. The function of the opto-isolator 250 is to electrically isolate the DC part of the electronic circuit 200 of the motor 50 operated by DC power from the AC part of the electronic circuit 200 operated by AC power. The opto-isolator 250 is an electronic component that uses optical signals to transmit electrical signals between the two parts of the circuit.

[0074] The electronic circuit 200 includes a DC power supply circuit 201 of the electronic control unit 60. In the embodiment shown, the power supply circuit 201 includes a transformer 240, a high voltage winding 241 of which is connected to the bipolar switch 90, and a low voltage winding 242 is connected to a rectifier 243, which generates a DC voltage signal to power the electronic unit 60. Preferably, the output of the rectifier is connected to the electronic control unit via a voltage regulator 244.

[0075] In the embodiment shown, the rectifier 243 is provided with a Greatz diode bridge, the output of which is connected to a voltage regulator 244, which in turn is electrically connected to the control unit 60. Other embodiments of the invention (not shown) may provide different solutions for the DC power supply circuit of the electronic control unit 60. For example, a variant may involve the use of an analog / digital (AC / DC) converter, the AC (alternating current) side of which is connected to the mains voltage via a bipolar switch, and the DC (direct current) side is connected to the control unit 60 to provide the energy required to power the control unit, and possibly also to generate a reference signal at each zero crossing of the voltage.

[0076] The zero-crossing circuit 245 is connected to the end of the low-voltage winding 242 of the transformer 240 and is electrically connected to the control unit 60 , and is adapted to generate a reference signal at a zero-crossing of the sinusoidal waveform of the supply current of the motor 50 .

[0077] The zero-crossing circuit 245 may include two diodes 246 and 247 , each diode being connected to the AC power source via an anode and each diode having a cathode connected to a common node 248 , which in turn is electrically connected to a contact of the control unit 60 .

[0078] In the embodiment shown, the zero-crossing circuit 245 may include two diodes 246 and 247, each diode being connected via an anode to a respective end of the low voltage winding 242 of the transformer, and each diode having a cathode connected to a common node 248, which in turn is electrically connected to a contact of the control unit 60. The common node 248 is connected to ground via a voltage regulator 249.

[0079] The states of the two diodes 246 and 247 change from a blocking state to a conducting state, and vice versa, which occurs at the zero crossing of the supply current of the motor 50, that is, at the transition from the negative half-wave to the positive half-wave of the supply current, and vice versa, and a rectified half-wave signal is generated, which can be provided to the electronic control unit 60 and used by the electronic control unit 60 as a reference signal of the sinusoidal waveform of the zero crossing of the supply current of the motor 50.

[0080] The electronic control unit 60 is programmed and configured to power the motor only after a preset time interval D depending on the reference signal generated by the zero-crossing circuit 245. At each zero crossing of the sinusoidal AC waveform of the power supplied to the motor 50 shown, the states of the two diodes change and a reference signal is generated which is acquired by the electronic control unit 60 and used by the electronic control unit 60 as the start time to calculate the time interval D for interrupting the power supplied to the motor 50.

[0081] Figure 8 The waveform of the motor power supply current is shown, in which it can be seen that each time the current passes from the negative half-wave to the positive half-wave, or vice versa, the motor power supply is interrupted for a time interval D.

[0082] The time interval D is set in the electronic control unit 60 to a value equal to 1 ms, for example, but may also be set to a different value.

[0083] The electronic control unit 60 may be programmed with a bypass function to override the control of the changes in the AC waveform supplied to the motor so that the motor may be powered continuously, i.e. without interruption of the power supply to the motor within a predetermined time interval D. The bypass function is activated by the user through an appropriate activation device. Furthermore, the control unit may be programmed to activate the bypass function only at predetermined time intervals.

[0084] According to the first embodiment of the present invention, Figure 1 and Figure 2, the means for activating the bypass function comprises a switch 75 associated with the pressure switch 70. In particular, the switching of the switch is controlled by the user by actuating the trigger of the dispensing spray gun. In fact, each time the user operates the trigger of the dispensing spray gun, the fluid pressure in the delivery pipe decreases. The decrease in the pressure value detected by the pressure switch causes the switching of the switch 75.

[0085] When the switch is in the NC position, the electronic control unit 60 is electrically connected to the switch 75 and is programmed to detect the number of switch operations, i.e. the number of trigger actuations of the dispensing spray gun, and to activate the bypass function whenever the number of switch operations within a predetermined time interval Δt is equal to a predetermined value Ns stored in the control unit 60.

[0086] As described above, activation of the bypass function provides a continuous supply of power to the motor without any control of the supply current waveform to allow the motor to operate at 100% of its power. Preferably, the control unit is programmed to switch on the bypass function at preset time intervals t Boost The bypass function is activated and thereafter deactivated by the control unit. Other embodiments of the invention may always provide for deactivation of the bypass function to occur as a function of the number of switching operations of the switch 75 associated with the pressure switch 70.

[0087] The second embodiment of the present invention, as Figure 3 and Figure 4 As shown, it is different from the first embodiment in terms of the activation device of the bypass function.

[0088] According to a second embodiment of the invention, the bypass function is activated by the user by activating a switch 150, for example, located on the housing of the high-pressure cleaning machine 100, the switching of which, i.e., the transition from the open position to the closed position, has the function of generating a control signal for the electronic control unit, so that it activates the bypass function by interrupting the control of the variation of the waveform of the alternating current supplying the motor, so as to allow the motor to be continuously powered.

[0089] In the particular embodiment shown, the switch 150 is provided as a push button, the pressure of which generates a control signal that can be used by the electronic control unit, which is configured to control the electric motor by interrupting the control (of the electronic control unit 60) of the waveform change of the alternating current supplied to the motor for a time t preset in the control unit upon receipt of the signal. Boost The motor 50 is continuously powered.

[0090] It should be noted that the circuit 200 also includes a known heat sink 170 .

[0091] Figure 5 and Figure 6A third embodiment of the present invention is shown which differs from the previous embodiments of the present invention in that it includes a pressure switch 80 instead of the pressure switch 70. The function of the pressure switch 80 is to control the switching of a switch 85 which is designed to cut off the power supply to the motor 50 when the spray gun is not delivering fluid under pressure. Figure 4 and Figure 5 As shown, the difference between the second and third embodiments of the present invention is that, in the second embodiment, the interruption of the power supply to the motor 50 is controlled by means of a triac 210, while in the third embodiment of the present invention, a switch 85 is provided on the power supply line of the motor 50 and acts directly on the power supply line of the motor 50 by interrupting at least one phase. In particular, the electric switch 85 of the pressure switch 80 located on the delivery pipe 20 is normally closed (NC) when the delivery pressure of the pump 40 is lower than a predetermined calibration value Pth, and is automatically disconnected when the pressure exceeds the calibration value Pth.

[0092] The switching of the electrical switch 85 of the pressure switch 80 from the closed position to the open position causes an interruption of the power supply to the motor and a subsequent stopping of the motor 50 and thus of the pump 40, thereby ensuring a total stopping function and occurring, for example, when the dispensing gun 25 is closed, resulting in an increase in the upstream pressure.

[0093] The operation of the high pressure cleaning machine 100 according to the present invention is as follows.

[0094] In the idle state, the double pole switch 90 is open and the dispensing gun 25 is not dispensing fluid.

[0095] In this configuration, the motor 50 is idle and the pump 40 is also idle.

[0096] When the delivery pressure of the pump 40 is zero, the switch 75 of the pressure switch 70 is in the closed position (NC).

[0097] When the operator wants to start the pressure washer, the operator operates the double pole switch 90 to energize the motor 50 .

[0098] In this position, the pump 40 is activated and the delivery pressure reaches a value higher than the calibrated value P th The value of .

[0099] When the pressure exceeds the set value P th When the pressure switch 70 disconnects the normally closed (NC) switch 75, and the rod 72 of the second pressure switch 75 overcomes the spring 74 along Figure 1 Moving in the direction of arrow G, the normally closed (NC) switch 75 opens and the motor 50 is deactivated.

[0100] When the operator wishes to dispense pressurized water, he / she opens the dispensing spray gun 25 with the trigger 35, and the water (or fluid) pressure upstream of the spray gun 25 is reduced.

[0101] This causes the rod 72 of the switch 75 of the second pressure switch 70 to be moved along with the Figure 1 Pushing in the direction opposite to the arrow F returns the switch 75 to the normally closed (NC) position and the motor 50 starts. When the operator wishes to interrupt the dispensing of pressurized water, he / she must simply release the trigger 35 by closing the dispensing spray gun 25, so that the pressure upstream of the spray gun rises to the set value P th As above, the normally closed (NC) switch 75 of the pressure switch 70 is opened in the above-described manner, thereby causing the motor 50 to be deactivated.

[0102] Figure 7 is a schematic diagram showing a sinusoidal waveform S of the current supplied to the motor 50 , ie, a waveform including a plurality of positive half-waves and negative half-waves.

[0103] Specifically, referring to a power supply with a frequency of 50 Hz, each sine wave has a duration of 20 ms (milliseconds), ie, 1000 ms / 50=20 ms.

[0104] Since the zero-crossing circuit 245 exists in the electronic circuit 200 , each time the sinusoidal waveform S of the supply current of the motor 50 crosses zero, an electrical reference signal P is generated and sent to the electronic control unit 60 .

[0105] Since there are 2 zero crossings per cycle, there is a 10ms period after each zero crossing detection, which can be managed as follows.

[0106] refer to Figure 8 After each time the supply current of the motor 50 passes through zero, the electronic control unit 10 interrupts the power supply to the motor 50 at a predetermined time interval D (eg Figure 5 The dotted area N in FIG. 1 is schematically represented).

[0107] At the end of the time interval D, the electronic control unit 60 sends a current signal to the gate of the triac 210 , thereby ensuring a predictable level of power reduction of the motor 50 , which in the example results in the motor 50 being powered at 80% of the power.

[0108] This process is repeated with positive and negative half-waves of the supply current to the electric motor 50 .

[0109] As another example, we note that if instead the motor 50 is powered at the beginning of the 10 ms period, without applying any delay D, it will be powered at 100%. Conversely, if the motor 50 is powered at the end of the 10 ms period, the motor remains off. If the selected delay D is, for example, 5 ms, the motor 50 will be powered only at half power.

[0110] Referring to the second and third embodiments of the present invention, the user's action on the switch 150 generates an input control signal to the electronic control unit 60, which is configured as a bypass function to bypass the control of the waveform variation of the AC power supplied to the motor, thereby allowing the motor to be powered continuously. In the second and third embodiments shown, the control unit 60 can be programmed to switch on the AC power only at predetermined time intervals t boost Activate the bypass function.

[0111] In this case, the preset time t in the control unit boost Within (eg, 30 seconds), the motor 50 will always be powered at 100% power, providing a boost function as needed.

[0112] Alternatively, according to the first embodiment shown, activation of the bypass function can be delegated to activation means comprising a trigger 35 of the dispensing gun 25 .

[0113] In this case, whenever the movable trigger 35 of the dispensing spray gun 25 is activated, the fluid pressurized by the pump is dispensed by the spray gun 25 through the dispensing wand 30 and the dispensing nozzle 32, and at the same time, a pressure change occurs in the delivery pipe 20. In this case, the pressure switch 70 records the pressure change.

[0114] More specifically, the rod 72 of the first pressure switch 70 moves along the Figure 1 , and acts on the electrical switch 75 in such a way that it moves from a first normally closed (NC) position connected to the electronic control unit 60 to a second position connected to the common ground node. The opening of the switch 75 is detected by the electronic control unit 60.

[0115] Thus, each time the trigger 35 is pulled, a signal is sent to the electronic control unit 60 , so that activation of the boost function can be commanded according to the number of signals received from the control unit 60 within the reference time interval Δt.

[0116] In practice, the number of signals Ns generated due to the change in the trigger position of the spray gun is predefined in the electronic unit 60 as a predetermined time interval Δt, which determines the setting of the time interval D. Specifically, if the user presses and releases the spray gun trigger a certain number of times greater than or equal to the predetermined number of signals Ns within the reference interval Δt, the control unit 60 is configured to set the spray gun trigger at a specific preset time t.boost The motor 50 is powered continuously for a period of time (eg, 30 seconds) so that the boost function is activated during this time interval.

[0117] The invention described herein allows a user to operate pressure washer 100 by managing the speed of motor 50 in at least two different modes.

[0118] The invention thus conceived is susceptible to several modifications and variations, all of which fall within the scope of the inventive concept. In addition, all details may be replaced by other technically equivalent elements. In practice, the materials used and the accidental shapes and sizes may vary as required without departing from the scope of protection of the appended claims.

Claims

1. A high pressure cleaning machine (100), comprising: a pump (40) and an electric motor (50) configured to drive the pump (40), wherein the pump (40) is connected to an inlet conduit (15) for the liquid to be pressurized and to a delivery conduit (20) for the liquid pressurized by the pump (40); - an electronic circuit (200) for controlling the power supply to the electric motor (50); - wherein the electronic circuit (200) comprises an electronic control unit (60) operatively connected to the electric motor (50); It is characterized in that the electronic circuit (200) is configured to change the rotation speed of the motor (50) by changing the waveform of the current supplied to the motor (50) so as to change the flow rate of the liquid pressurized by the pump (40) in the delivery pipe (20).

2. The high pressure cleaning machine (100) according to claim 1, wherein: The electronic control unit (60) is configured to change a waveform of the current supplied to the motor (50) by interrupting the alternating current supplied to the motor (50) at predetermined time intervals (D) starting from a reference signal.

3. The high pressure cleaning machine (100) according to claim 2, wherein: The electronic circuit (200) comprises a zero crossing circuit (245) configured to generate the electrical reference signal each time the sinusoidal waveform of the motor supply current crosses zero and to make the signal available to the electronic control unit (60).

4. The high pressure cleaning machine (100) according to claim 3, wherein: The zero-crossing circuit comprises two diodes (246, 247), each of which is connected to an AC power source via an anode, and each of which has a cathode connected to a common node (248), which in turn is electrically connected to a contact of the control unit (60).

5. The high pressure cleaning machine (100) according to claim 3, wherein: The electronic circuit (200) comprises a triac (210) which is electrically connected to the motor (50) and is provided with a gate connected to the electronic control unit (60), wherein the electronic control unit (60) is configured to send a conduction signal to the triac (210) according to the time interval (D).

6. The high pressure cleaning machine (100) according to claim 5, wherein: The electronic control unit (60) is configured to send the turn-on signal to the triac (210) at the end of the time interval (D), wherein the time interval (D) is calculated based on the zero crossing of the sinusoidal waveform of the current supplied to the motor (50) detected by the zero crossing circuit (245).

7. The high pressure cleaning machine (100) according to claim 5, wherein: A photoelectric isolator (250) is provided between the electronic control unit (60) and the triac (210).

8. The high pressure cleaning machine (100) according to claim 2, wherein: The electronic circuit (200) further comprises means for activating a bypass function for bypassing the control of the electronic control unit (60) when the waveform of the alternating current supplied to the motor changes.

9. The high pressure cleaning machine (100) according to claim 8, wherein: The starting device comprises a switch (150), the switching of which generates a control signal at an input to the electronic control unit (60), wherein the electronic control unit (60) is configured to continuously supply power to the motor (50) upon receipt of the control signal.

10. The high pressure cleaning machine (100) according to claim 8, wherein: The activation device of the bypass function comprises a switch (75) associated with the pressure switch (70), the switching of the switch (75) is controlled according to the actuation of the trigger of the dispensing spray gun, the control unit (60) is programmed to detect the number of switching operations of the switch, and activate the bypass function when the number of switching operations of the switch within a predetermined time interval (Δt) is equal to a predetermined number (Ns).

11. The high pressure cleaning machine (100) according to claim 9 or 10, wherein: The control unit is programmed to transmit the signal at predetermined time intervals (t boost ) activates the bypass function.

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