Pressure washer with controlled cleaning agent injection system

Abstract

A pressure washer system is disclosed, comprising a washing liquid input (1), a washing liquid output (2), a pump unit (4), and a cleaning agent injection system (5). The system includes a Venturi nozzle (7) configured to draw cleaning agent into a first pipeline (3) via a second pipeline (6). A solenoid valve (8) is operatively connected to the second pipeline (6) and controlled by a control unit (9), which regulates the flow of cleaning agent into the pressurized washing liquid. In various embodiments, the control unit (9) uses pulse width modulation (PWM). The system may include multiple cleaning agent tanks (A, B), additional solenoid valves (8), and a user interface for selecting cleaning programs or initiating a calibration procedure. Optional sensors for flow, pressure, temperature, and cleaning agent level may be provided.

Description

[0001] Pressure washer with controlled cleaning agent injection system

[0002] Technical field of the invention

[0003] The present invention relates to pressure washers with cleaning agent supply.

[0004] Background of the invention

[0005] A pressure washer is a device that uses a high-pressure stream of water to remove dirt, and other contaminants from surfaces. It works on the principle of utilizing pressurized water to increase the cleaning power and efficiency. Pressure washers are typically connected to a washing liquid source, such as a water hose. The water flows into the pressure washer through an inlet. The heart of a pressure washer is the pump. The pump pressurizes the incoming water and can be powered by an electric motor or a fuel engine, depending on the type of pressure washer. Fuel- powered models are more powerful and often used for heavy-duty tasks. The pressurized water is then directed through a high-pressure hose to a spray gun or wand. The hose is specially designed to withstand the high pressure. At the end of the spray gun or wand, there is a nozzle that can be adjusted to control the spray pattern and pressure. Pressure washers typically come with various nozzle tips, each designed for different cleaning tasks. The most common nozzle tips include 0- degree (high-pressure pencil jet), 15-degree (high-pressure cone), 25-degree (high- pressure fan), and 40-degree (low-pressure fan). The operator controls the flow of pressurized water by pulling the trigger on the spray gun. Releasing the trigger stops the flow of water. When the trigger is squeezed, pressurized water is forced through the nozzle, creating a high-pressure stream. The narrow spray pattern and high pressure allow the water to effectively remove e.g., dirt from surfaces.

[0006] Some pressure washers have a built-in cleaning agent tank or a separate cleaning agent injection system. This allows the operator to apply cleaning agents, such as detergents to the surface, which can help with more effective cleaning. The choice of cleaning agent depends on the cleaning task and the type of surface to be cleaned. Pressure washer cleaning agents come in various formulations for specific purposes, such as concrete cleaning, vehicle washing, house siding cleaning, or general surface cleaning. Using the appropriate cleaning agent can enhance the cleaning performance of the pressure washer by helping to break down and remove specific types of dirt and grime. The cleaning agent is mixed with the high-pressure water stream and applied to the surface. The built-in cleaning agent tank is a reservoir or container that the operator can fill with a cleaning agent, such as a liquid detergent, or a specialized pressure washer cleaning agent. The pressure washer’s pump is designed to draw cleaning agent from this tank when needed. There is usually a dedicated nozzle or setting on the spray gun or wand to allow the operator to switch from using pure water to a mixture of water and cleaning agent. Larger pressure washers for industrial use may be equipped with a control interface and / or control knobs mounted on the pressure washer itself. Upon activation of the cleaning agent setting, the pressure washer draws the cleaning agent from the tank and mixes it with the pressurized water before spraying it onto the surface to be cleaned.

[0007] A venturi system is commonly used in pressure washers to draw cleaning agent from the tank into the waterline. A venturi is a specially designed component that uses the flow of high-pressure water to create a vacuum, which, in turn, draws in and mixes a cleaning agent with the water stream. The venturi nozzle is typically located at the end of a cleaning agent pipeline operatively connected to the general water pipeline, typically opening into the water pipeline near the inlet side of the pump. The venturi nozzle is designed with a constriction or narrow section in the flow path. When the pressure washer gun is activated, high-pressure water is forced past the outlet of the venturi nozzle at a high velocity, thereby creating a low- pressure area due to the Venturi effect. This low-pressure area thereby draws in cleaning agent from the cleaning agent tank via the cleaning agent pipeline.

[0008] The main problem with the venturi system solution is its accuracy. It is difficult for the operator to set a precise dosing ratio, resulting in either too much or too little consumption of cleaning agent. The only way the operator can check the consumption of cleaning agent is by visual control of the cleaning agent level in the tank.

[0009] Summary of the invention

[0010] It is an object of the present invention to provide a system that overcome the above- mentioned problems. The present invention relates to a pressure washer system, preferably operated by a user, and more particularly to a pressure washer comprising an improved cleaning agent dosing system. The system utilizes a Venturi nozzle in combination with an electronically controlled solenoid valve to regulate the introduction of a cleaning agent into a washing liquid pipeline.

[0011] In one aspect, the pressure washer comprises a washing liquid input, a washing liquid output, a first pipeline connecting the input and output, and a pump unit adapted to pressurize the washing liquid. A second pipeline connects a cleaning agent supply unit to the first pipeline via a Venturi nozzle. A solenoid valve is operatively arranged along the second pipeline and is controlled by a control unit. The control unit regulates the solenoid valve to open or close, thereby controlling the flow of cleaning agent into the washing liquid stream. In some embodiments, the solenoid valve is actuated using a pulse width modulation (PWM) signal for improved dosing precision and energy efficiency.

[0012] In further embodiments, the pressure washer may comprise multiple cleaning agent supply units and corresponding solenoid valves, enabling selection between different cleaning agents or the simultaneous delivery of a mixture. The cleaning agent injection point may be located upstream or downstream of the pump unit, and a check valve may be included in the cleaning agent line to prevent backflow and maintain consistent dosing.

[0013] Additional embodiments include a heating system for the washing liquid, comprising a heat exchanger and a burner in thermodynamic communication. The cleaning agent may be introduced into the system either before or after the heating stage, and the temperature of the washing liquid may be regulated by the control unit based on input from a temperature sensor.

[0014] The invention provides an enhanced pressure washer system with improved dosing accuracy, energy efficiency, operational control, and cleaning performance, particularly suited for applications requiring varied or precise cleaning agent delivery. Brief description of the figures

[0015] Figure 1 shows a schematic representation of core parts of a pressure washer according to various embodiments of the present invention.

[0016] Figure 2 shows a schematic representation of core parts of a pressure washer according to various embodiments of the present invention.

[0017] Figure 3 shows a perspective view of a pressure washer according to various embodiments of the present invention.

[0018] Figure 4 shows a perspective view of a pressure washer according to various embodiments of the present invention, where parts have been removed to better show the pump unit.

[0019] Figure 5 shows a schematic representation of parts of a pressure washer according to various embodiments of the present invention.

[0020] Detailed embodiments of the invention

[0021] The present invention will now be described in further detail with reference to exemplary embodiments. It should be understood that the described embodiments are illustrative only and not limiting, and that variations and modifications may be made without departing from the scope of the invention as defined by the appended claims.

[0022] The invention relates to a pressure washer system configured to deliver a pressurized washing liquid, optionally combined with one or more cleaning agents, for cleaning surfaces. More particularly, the invention provides a pressure washer incorporating an improved cleaning agent injection system utilizing a Venturi nozzle in combination with solenoid valve control. This arrangement allows for enhanced dosing precision, improved energy efficiency, and increased operational flexibility. In various embodiments, the pressure washer includes a control unit configured to operate one or more solenoid valves that regulate the flow of cleaning agents into a pressurized washing liquid stream. The control unit may employ pulse width modulation (PWM) or other signal control methods to modulate the flow rate of the cleaning agent. The cleaning agent is introduced via a Venturi system, which may be positioned either upstream or downstream of the pump unit, depending on the specific design and use case.

[0023] Further embodiments allow for the use of multiple cleaning agent supply units and solenoid valves, enabling the operator to switch between or mix different cleaning agents as required. In some configurations, the pressure washer may also be equipped with a heating system for delivering heated washing liquid, wherein the cleaning agent is introduced before or after the heating stage.

[0024] A first aspect relates to a pressure washer, preferably for use by an operator, the pressure washer comprising a washing liquid input adapted to connect to a washing liquid source, a washing liquid output, a first pipeline in washing liquid communication with the washing liquid input and washing liquid output, a pump unit operatively connected to the first pipeline, and adapted for pressurizing the washing liquid received via the washing liquid input, a first cleaning agent supply unit adapted for delivering cleaning agent, and a second pipeline operatively connected to the first pipeline and to the cleaning agent supply unit, wherein the second pipeline is connected to the first pipeline via a venturi nozzle, wherein a first solenoid valve is operatively connected to the second pipeline and to said first cleaning agent supply unit, wherein the pressure washer further comprises a control unit configured to regulate the flow of cleaning agent from said first cleaning agent supply unit and into said first pipeline by operating the first solenoid valve to open or close.

[0025] Definitions and terminology

[0026] As used in the specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" or "approximately" one particular value and / or to "about" or "approximately" another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about", it will be understood that the particular value forms another embodiment.

[0027] It should be noted that embodiments and features described in the context of one of the aspects of the present invention also apply to the other aspects of the invention.

[0028] In the present context, the term “cleaning agent” encompasses a wide variety of substances used to remove dirt, grime, stains, and other contaminants from surfaces. Cleaning agents include not only detergents, but also soaps, acids, alkalis, solvents, abrasives, and other chemicals or mixtures designed for cleaning purposes.

[0029] The “washing liquid” may, for example, be water, an aqueous solution, a solvent, or a mixture thereof, constituting an operational liquid directed to a specific cleaning purpose.

[0030] The term “Venturi nozzle” refers to a component configured to exploit the Venturi effect, whereby fluid passing through a constricted section of a pipe undergoes a pressure drop, thereby creating suction capable of drawing a secondary fluid, such as a cleaning agent, into the main fluid stream.

[0031] The term “control unit” refers to an electronic control system comprising hardware and software components, which may include a microcontroller, processing unit, memory, firmware, and communication interfaces. The control unit may be operatively connected to sensors, actuators (e.g., solenoid valves), user interfaces, and other components to perform the control functions described herein.

[0032] The term “user interface” refers to any system or component that enables interaction between the operator and the pressure washer, including but not limited to buttons, touchscreens, displays, keypads, wireless controls, and audible or visual indicators. A “cleaning program” refers to a predefined set of operating parameters for the pressure washer, such as pump pressure, washing liquid temperature, cleaning agent dosing amount, and duration, which are optimized for specific cleaning tasks such as vehicle washing or degreasing.

[0033] A “dosing parameter” refers to any internal value or control setting used by the control unit to regulate the amount of cleaning agent introduced into the washing liquid. This may include valve duty cycle, pulse width, timing signals, or calculated flow durations.

[0034] A “calibration parameter” is a dosing parameter that is adjusted based on the properties of a particular cleaning agent. These may include fluid-specific viscosity, density, or suction characteristics and are typically determined via a calibration procedure as described herein.

[0035] The phrase “thermodynamic communication” refers to the transfer of thermal energy between components, typically via a shared wall or conductive surface, such that heat is exchanged without fluid mixing.

[0036] A “coiled pipe”, as used in relation to heat exchangers, refers to a pipe arranged in a helical or spiral form to increase the surface area for heat transfer in a compact configuration.

[0037] The term “continuous flow mode” refers to an operational state in which a solenoid valve remains open to allow uninterrupted flow of cleaning agent during active operation.

[0038] The term “pulsed dosing mode” refers to an operational state in which the solenoid valve is opened and closed at regular or irregular intervals, such as under pulse width modulation (PWM) control, to deliver discrete amounts of cleaning agent in a controlled manner. Solenoid valve control and functionality

[0039] The inventors of the present invention utilize a solenoid valve to regulate the cleaning agent flow. A solenoid valve is a type of electromechanically operated valve that uses an electric current to generate a magnetic field, which then moves a plunger attached to the valve’s mechanism to control the flow of a medium. The core component of the solenoid valve is the solenoid, a coil of wire that becomes magnetized when an electric current passes through it. The generated magnetic field pulls on a ferromagnetic plunger inside the coil, overcoming a spring or other force, to open or close the valve. The valve returns to its default position when the current is discontinued, either by the force of the spring or by gravity, depending on the design.

[0040] Pulse width modulation (PWM) control

[0041] In one or more embodiments, the control unit is configured to regulate the flow of cleaning agent from the cleaning agent supply unit and into the first pipeline by operating the solenoid valve via a pulse width modulation signal. Control of solenoid valves is typically achieved through electronic means. Pulse width modulation (PWM) involves varying the width of the pulses in a digital signal to control the amount of power delivered to the solenoid. By adjusting the duration (width) of these pulses, one can finely tune how much the valve opens or closes, thereby controlling the flow rate more precisely than simply turning the valve fully on or off.

[0042] This method of control is particularly advantageous for the present invention where variable flow rates of cleaning agent is needed. Furthermore, the use of PWM reduces the energy consumed by the solenoid, as the coil is only fully powered during the pulse and not continuously. This not only saves energy but also reduces heat generation, prolonging the life of the valve.

[0043] Venturi nozzle positioning

[0044] In one or more embodiments, the second pipeline is connected to the first pipeline via a venturi nozzle upstream to the pump unit.

[0045] In one or more embodiments, the second pipeline is connected to the first pipeline via a venturi nozzle downstream to the pump unit. In principle, it is the construct of the pressure washer that determines which of the two embodiments to use. Implementing cleaning agent injection on the low-pressure side can be simpler and more cost-effective. On the other hand, when cleaning agent is introduced into the high-pressure washing liquid stream after it leaves the pump unit, it undergoes mixing and pressurization simultaneously, resulting in thorough mixing under high pressure. Incorporating of a check valve positioned upstream to the venturi in the cleaning agent line can be a practical and effective way to improve the performance and reliability of the cleaning agent injection system in a pressure washer. It helps address concerns related to backflow, maintains cleaning agent concentration, and enhances the efficiency of the cleaning process.

[0046] Multi-tank and multi-valve configurations

[0047] In one or more embodiments, the pressure washer further comprises a second cleaning agent supply unit adapted for delivering cleaning agent, and a second solenoid valve operatively connected to the second pipeline, wherein the control unit is configured to regulate the flow of cleaning agent from said second cleaning agent supply unit and into said first pipeline by operating the second solenoid valve to open or close. This configuration allows the user to mix different types of cleaning agents and to vary the ratio between them, depending on the type of dirt to be removed or the type of surface to be treated.

[0048] In one or more embodiments, the pressure washer further comprises a second cleaning agent supply unit adapted for delivering cleaning agent, wherein the control unit is configured to regulate the flow of cleaning agent from said first and second cleaning agent supply units and into said first pipeline by operating the first solenoid valve to open or close.

[0049] In one or more embodiments, the cleaning agent supply unit(s) comprises a plurality of cleaning agent tanks.

[0050] In one or more embodiments, the first solenoid valve is operatively connected to at least two of said plurality of cleaning agent tanks, e.g., all. In one or more embodiments, the first solenoid valve is operatively connected to at least one of said plurality of cleaning agent tanks, and wherein a second solenoid valve is operatively connected to at least one other of said plurality of cleaning agent tanks. In one embodiment, each solenoid valve is operatively connected to a single cleaning agent tank.

[0051] General use and context

[0052] The invention relates to a pressure washer using a washing liquid, which washer is preferably to be used by an operator.

[0053] In the present context, the term “in general” when used when mentioning a feature relating to the present invention, it must be understood that the feature may be used with all embodiments of the invention, even if the mentioning is made in the detailed part of the document.

[0054] In general, a pressure washer is used for spraying pressurized washing liquid on to a surface to remove loose paint, mould, grime, dust, mud, and dirt from the surfaces of objects, such as buildings, vehicles, and concrete surfaces. The pressure washing machines are normally operated by an operator controlling the direction of the washing liquid as well as the temperature and the amount or pressure of washing liquid.

[0055] Calibration procedure for cleaning agent dosing

[0056] In some use cases, particularly those requiring precise detergent-to-water ratios, variations in the viscosity and specific gravity of different cleaning agents may result in inaccurate dosing, even when the dosing system is calibrated for standard conditions. While the system is typically calibrated using a reference fluid with properties similar to tap water, the actual fluid properties of detergents may vary considerably.

[0057] To address this, the pressure washer system may include a calibration mode or procedure that enables the user to calibrate the dosing system to a specific cleaning fluid. This procedure can be implemented via the user interface and comprises the following steps: - The user initiates the calibration process using the control unit interface;

[0058] - The detergent suction hose is inserted into the desired cleaning agent;

[0059] - The user activates the pressure washer (e.g., by pressing the spray gun handle) and allows the machine to operate for a defined interval or until an automatic stop is triggered;

[0060] - The user collects and measures the amount of cleaning agent consumed during this process;

[0061] - The measured volume or weight is input into the user interface; and

[0062] - The control unit uses the entered volume to adjust the internal dosing parameters, thereby calibrating the system for the specific fluid.

[0063] This calibration process enables the control unit to adapt the operation of the solenoid valve (e.g., PWM settings or open / close cycles) to compensate for the actual properties of the cleaning agent. Once calibration is complete, the pressure washer can maintain an accurate and consistent mixing ratio for that specific fluid.

[0064] This functionality is particularly useful in professional cleaning applications where detergent concentration must be controlled precisely for performance, safety, or regulatory reasons.

[0065] Flow and pressure feedback control

[0066] In one or more embodiments, the pressure washer comprises one or more sensors configured to detect operational parameters such as flow rate or pressure within the first pipeline. The control unit is operatively connected to such sensors and may use the measured data to dynamically adjust the operation of the solenoid valve, such as by modifying the pulse width modulation (PWM) signal. This allows for real-time compensation for changes in flow characteristics due to pressure fluctuations, nozzle changes, or temperature variations, thereby maintaining a consistent cleaning agent mixing ratio.

[0067] Temperature-based dosing adjustment

[0068] In one or more embodiments, the pressure washer further comprises a temperature sensor configured to detect the temperature of the washing liquid. The temperature sensor may be located within or adjacent to the first pipeline, particularly downstream of any heat exchanger. The control unit is operatively connected to the temperature sensor and may adjust the operation of the solenoid valve based on the detected temperature. This feature enables the system to account for the temperature-dependent viscosity or reactivity of certain cleaning agents, thereby improving dosing accuracy and cleaning performance.

[0069] Cleaning program selection

[0070] In one or more embodiments, the control unit is configured to execute predefined cleaning programs that define specific parameters for washing liquid pressure, temperature, and cleaning agent dosing. These programs may be selected via a user interface and can correspond to specific applications, such as vehicle washing, industrial degreasing, or surface preparation. Each cleaning program may store or reference a particular set of calibration parameters for one or more cleaning agents, allowing for repeatable and optimized cleaning results.

[0071] Graphical user interface and notifications

[0072] In one or more embodiments, the control unit is operably connected to a graphical user interface (GUI), which may be a touchscreen, display panel, or other user- operable device. The GUI may be configured to display operational parameters such as current dosing level, selected cleaning program, and calibration status. Additionally, the GUI may present visual or audible alerts to the user, such as low cleaning agent level warnings, tank selection confirmations, or maintenance reminders.

[0073] In some embodiments, the user interface allows for manual entry or adjustment of dosing parameters, and may support language localization, password protection, or usage logging for commercial applications.

[0074] Cleaning agent level monitoring

[0075] In one or more embodiments, the pressure washer comprises level sensors positioned in one or more cleaning agent tanks. The sensors are configured to detect when the level of cleaning agent falls below a predefined threshold. The control unit receives signals from the level sensors and may generate a notification through the user interface to alert the operator that refilling is required. This helps avoid interruptions in operation due to unexpected depletion of cleaning agents.

[0076] Backflow prevention

[0077] In one or more embodiments, the second pipeline comprises a check valve arranged upstream of the venturi nozzle. The check valve is configured to allow flow of the cleaning agent toward the venturi nozzle while preventing backflow of washing liquid into the cleaning agent supply unit. This feature enhances safety, maintains dosing accuracy, and protects the cleaning agent reservoir from contamination or pressurization.

[0078] Automatic line purging

[0079] In one or more embodiments, the control unit is configured to initiate a purging sequence of the second pipeline. This may occur automatically upon system shutdown, startup, or at user-defined intervals. During purging, the solenoid valve is actuated to allow flow of clean water or air through the second pipeline to flush out any residual cleaning agent. This helps prevent clogging, sedimentation, or chemical degradation of components.

[0080] Continuous and pulsed dosing modes

[0081] In one or more embodiments, the control unit is configured to operate the solenoid valve in either a continuous flow mode or a pulsed dosing mode. In continuous mode, the valve remains partially or fully open for a sustained period. In pulsed mode, the valve opens and closes at defined intervals based on a control algorithm or PWM signal. The selection of dosing mode may depend on the selected cleaning agent, application type, or user input.

[0082] The following detailed description refers to illustrative embodiments depicted in the accompanying figures and is intended to provide a comprehensive understanding of the technical features and functionality of the invention.

[0083] Embodiments illustrated in figures

[0084] Figure 1 illustrates an embodiment of a pressure washer according to the invention.

[0085] The present embodiment is shown mobile (here wheeled), but the scope of the invention is generally suitable for any type of pressure washer, such as stationary and / or liftable (e.g., by a crane) pressure washers. The embodiment comprises a low pressure (relative to the output) washing liquid input 1 adapted to connect to a washing liquid source (not shown), a high pressure (relative to the input) washing liquid output 2, a first pipeline 3 in washing liquid communication with the washing liquid input 1 and washing liquid output 2, a pump unit 4 operatively connected to the first pipeline 3, and adapted for pressurizing the washing liquid received via the washing liquid input 1 , a cleaning agent supply unit 5 adapted for delivering cleaning agent, and a second pipeline 6 operatively connected to the first pipeline 3 and to the cleaning agent supply unit 5. The second pipeline 6 is connected to the first pipeline 3 via a venturi nozzle 7 and opens into the first pipeline 3 at the low- pressure side. In Figure 2, a different embodiment is shown where the second pipeline 6 opens into the first pipeline 3 at the high-pressure side. In the latter, a check valve 10 is positioned upstream to the venturi nozzle 7 in the cleaning agent line to improve the performance and reliability of the cleaning agent injection system. It helps address concerns related to backflow, maintains cleaning agent concentration, and enhances the efficiency of the cleaning process. Such a valve is not necessary when the venturi nozzle 7 opens into the first pipeline 3 at the low- pressure side.

[0086] In general, the pressure washer comprises a control unit 9, preferably with a user interface operably connected thereto, configured to regulate the flow of cleaning agent from the cleaning agent supply unit 5 and into the first pipeline 3 by operating a solenoid valve 8 to open or close. In the shown examples in Figures 1 and 2, the cleaning agent supply unit 5 comprises two cleaning agent tanks A, B. Each tank A, B is operatively connected to a solenoid valve 8. In alternative embodiments, a single solenoid valve is operatively connected to more than one tank, such as all tanks.

[0087] Heated pressure washer variant

[0088] In Figures 3 and 4, an exemplary pressure washer according to various embodiments of the present invention is shown. This type of pressure washer is configured to provide heated washing liquid as shown in Figure 5, and the cleaning agent is delivered to the first pipeline 3 as shown in Figure 2. A heat exchanger 11 (see Figure 5) is operably connected to the first pipeline 3 on the high-pressure side, downstream to the venturi nozzle 7, thereby also allowing the cleaning agent delivered into the first pipeline 3 to be heated. In principle, and in another embodiment, the cleaning agent may be delivered into the first pipeline 3 downstream to the heat exchanger 11 . The heat exchanger 11 is heated by a burner 12 in thermodynamic communication with the heat exchanger 11 , the burner 5 applies heat to the heat exchanger 11 and to the washing liquid held in the heat exchanger 11 . The burner 12 receives fuel through a fuel input 13, which is connected to a fuel tank 14 (see Figures 3 and 4). The amount of fuel fed to the burner 12 may be controlled by a fuel valve and a fuel pump (not shown). According to the shown embodiment, the burner 12 also comprises an air intake 15 and an air fan 16, which provide a proportional air inlet to the burner 12. The pressure washer also comprises an igniter 17, which is adapted to ignite the burner 12 when the fuel starts flowing to the burner 12.

[0089] The control unit (not shown in Figure 5) may also be configured to control the amount of fuel to be supplied to the burner 12 via the fuel input 13, normally by switching the fuel pump on or off, or by closing or opening the fuel valve. The control unit may also control the temperature of the washing liquid by increasing or decreasing the speed of the fuel pump, thereby controlling the amount of fuel flowing into the burner 12 and the heat provided by the burner. To provide a temperature control the control unit may receive a signal from a temperature sensor that is configured to register and transmit the temperature, or a corresponding temperature, of the washing liquid to the control unit.

[0090] That the burner 12 is in thermodynamic communication with the heat exchanger 11 means that the two units exchange energy, e.g., through a common wall.

[0091] The burner 12 and the heat exchanger 11 may be positioned inside a burning chamber 18, as shown in Figure 5. Such a burning chamber 18 may then comprise an outlet 19 for exhaust gas. Normally or generally, the heat exchanger 11 and the burning chamber 18 comprise at least one common wall or surface providing the “thermodynamic communication” where heat is transferred from burning chamber 18 heated by the burner 12 to the washing liquid separated from the burning chamber 18 by the surfaces of the heat exchanger 11 . According to the shown embodiment, the heat exchanger 11 is formed as a coiled pipe, however, the shape of the heat exchanger 11 is not essential to the present invention. Many other shapes and constructions of heat exchangers may be used to obtain the desired effect.

[0092] The burning chamber 18 may be surrounded by an insulating space 20, which insulating space 20 may hold an amount of washing liquid for preheating. The insulating space 20 may completely cover the burning chamber 18 in such way that an operator operating the pressure washer cannot get in direct contact with the surfaces of the heated burning chamber 18, why the insulating space 20 also provides a protective cover.

[0093] References

[0094] 1 Washing liquid input

[0095] 2 Washing liquid output

[0096] 3 First pipeline

[0097] 4 Pump unit

[0098] 5 Cleaning agent supply unit

[0099] 6 Second pipeline

[0100] 7 Venturi nozzle

[0101] 8 Solenoid valve

[0102] 9 Control unit

[0103] 10 Check valve

[0104] 11 Heat exchanger

[0105] 12 Burner

[0106] 13 Fuel input

[0107] 14 Fuel tank

[0108] 15 Air intake

[0109] 16 Air fan

[0110] 17 Igniter

[0111] 18 Burning chamber

[0112] 19 Outlet

[0113] 20 Insulting space

Claims

Claims1 . A pressure washer, preferably for use by an operator, the pressure washer comprising:- a washing liquid input (1) adapted to connect to a washing liquid source,- a washing liquid output (2);- a first pipeline (3) in washing liquid communication with the washing liquid input (1 ) and washing liquid output (2);- a pump unit (4) operatively connected to the first pipeline (3), and adapted for pressurizing the washing liquid received via the washing liquid input (1);- a first cleaning agent supply unit (5) adapted for delivering cleaning agent; and- a second pipeline (6) operatively connected to the first pipeline (3) and to the first cleaning agent supply unit (5); wherein the second pipeline (6) is connected to the first pipeline (3) via a venturi nozzle (7); characterized in that a first solenoid valve (8) is operatively connected to the second pipeline (6) and to said first cleaning agent supply unit (5); wherein the pressure washer further comprises a control unit (9) configured to regulate the flow of cleaning agent from said first cleaning agent supply unit (5) and into said first pipeline (3) by operating the first solenoid valve (8) to open or close.

2. The pressure washer according to claim 1 ; wherein the control unit (9) is configured to regulate the flow of cleaning agent from said cleaning agent supply unit (5) and into said first pipeline (3) by operating the solenoid valve (8) via a pulse width modulation (PWM) signal.

3. The pressure washer according to any one of the claims 1-2; wherein the second pipeline (6) is connected to the first pipeline (3) via a venturi nozzle (7) upstream to the pump unit (4).

4. The pressure washer according to any one of the claims 1-2; wherein the second pipeline (6) is connected to the first pipeline (3) via a venturi nozzle (7) downstream to the pump unit (4).

5. The pressure washer according to any one of the claims 1-4; further comprising:- a second cleaning agent supply unit adapted for delivering cleaning agent; and- a second solenoid valve operatively connected to the second pipeline; wherein the control unit is configured to regulate the flow of cleaning agent from said second cleaning agent supply unit and into said first pipeline by operating the second solenoid valve to open or close.

6. The pressure washer according to any one of the claims 1-4; further comprising:- a second cleaning agent supply unit adapted for delivering cleaning agent; wherein the control unit is configured to regulate the flow of cleaning agent from said first and second cleaning agent supply units and into said first pipeline by operating the first solenoid valve to open or close.

7. The pressure washer according to any one of the claims 1-6; wherein the cleaning agent supply unit(s) (5) comprises a plurality of cleaning agent tanks (A, B).

8. The pressure washer according to claim 7, wherein the first solenoid valve (8) is operatively connected to at least two of said plurality of cleaning agent tanks (A, B), preferably all.

9. The pressure washer according to claim 7, wherein the first solenoid valve (8) is operatively connected to at least one of said plurality of cleaning agent tanks (A, B), and wherein a second solenoid valve (8) is operatively connected to at least one other of said plurality of cleaning agent tanks (A, B).

10. The pressure washer according to any one of the preceding claims, wherein the control unit is configured to perform a calibration procedure to determine a dosing parameter specific to a selected cleaning agent.11 . The pressure washer according to claim 10, wherein the control unit comprises or is operably connected to a user interface; wherein the calibration procedure comprises:- initiating the calibration process via the user interface,- dispensing a known volume of cleaning agent,- receiving input of the measured volume or weight dispensed, and- adjusting a dosing control parameter based on said measured volume.

12. The pressure washer according to claim 11 , wherein the control unit adjusts a pulse width modulation (PWM) signal to a solenoid valve based on the result of the calibration procedure.

13. The pressure washer according to any one of claims 10-12, wherein the control unit stores calibration data for a plurality of different cleaning agents.

14. The pressure washer according to any one of claims 10-13, wherein the user interface allows selection of a previously calibrated cleaning agent profile.

15. The pressure washer according to any one of the preceding claims, wherein the control unit is configured to receive input from a sensor for detecting flow rate or pressure in the first pipeline (3), and to adjust the operation of the solenoid valve (8) accordingly.

16. The pressure washer according to any one of the preceding claims, further comprising a temperature sensor configured to measure the temperature of the washing liquid, wherein the control unit is configured to adjust the cleaning agent dosing based on the measured temperature.

17. The pressure washer according to any one of the preceding claims, wherein the control unit is configured to activate or deactivate the cleaning agent supply based on a cleaning program selected by the operator.

18. The pressure washer according to any one of the preceding claims, wherein the control unit comprises or is operably connected to a graphical user interface (GUI) configured to display dosing parameters, calibration status, or cleaning agent selection.

19. The pressure washer according to any one of the preceding claims, wherein the user interface includes a notification system configured to alert the operator when the cleaning agent tank is empty or below a threshold.

20. The pressure washer according to any one of the preceding claims, further comprising a check valve located in the second pipeline (6) upstream of the venturi nozzle (7) to prevent backflow of washing liquid into the cleaning agent supply unit (5). 21 . The pressure washer according to any one of the preceding claims, wherein the control unit is configured to perform periodic cleaning or purging of the second pipeline (6) to prevent clogging or residue buildup.

22. The pressure washer according to any one of the preceding claims, wherein the control unit is configured to operate the solenoid valve (8) in a continuous flow mode or a pulsed dosing mode.

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