Pressure washer with burner control

Abstract

The present disclosure relates to pressure washer, preferably for use by an operator. The pressure washer comprises a burner (5), a vibration sensor (9), and a control unit (8). The control unit (8) is configured to receive vibration data from the vibration sensor (9), and to translate these vibration data into an operational state of the burner (5), such as on or off, or a specific duty cycle configuration.

Description

[0001] Pressure washer with burner control

[0002] The present disclosure relates to a hot liquid pressure washer, preferably to be used by an operator, the hot liquid pressure washer comprises a heat exchanger, a burner, and a control unit configured to control the amount of fuel supplied to the burner.

[0003] Background

[0004] Pressure washers using a burner for providing heated liquid for washing are generally known and different means are used to control the temperature of the heated liquid used for washing.

[0005] One way to control the temperature of the washing liquid is to place a temperature sensor in or close to the flow of washing liquid. However, if a temperature drop is caused by the burner being extinguished, then the detection of a reduced temperature will be delayed relative to the switching off the burner, and the burner may continue to pump fuel into the burning chamber without igniting the fuel.

[0006] US 6.435.424 Bl discloses a hot water pressure washer 10 comprising an improved temperature control system which hot water pressure washer comprises a water supply 12 connected to a positive displacement water pump 14. The pump 14 provides water to a heat exchanger 16 through which the water flows. A water flow switch 18 sensing water flow in the input water supply line 20 is positioned in the input water supply line 20 between the water pump 14 and the heat exchanger 16. A burner unit 22 is positioned in a thermodynamic relationship with heat exchanger 16 and receives burner fuel from a fuel source via a fuel inlet line 24. A fuel solenoid 26 (e.g., an oil valve) also referred to as a fuel switch is associated with burner unit 22 and the fuel inlet line 24 controls, in part, the flow of fuel into burner unit 22. A timer circuit 30 is connected to the water flow switch 18 via a line 32 as well as to the fuel switch 18. A temperature selection switch 36 (e.g., a potentiometer) associated with timer circuit 30 allows operators to select a desired water temperature. Hot water 38 leaves heat exchanger 16 via a water discharge line 40 and an operator-controlled discharge valve 42 is positioned between the water discharge line 40 and a water output 44. This disclosure eliminates the use of temperature sensor and thermostat.

[0007] It is known to register whether a burner is ignited or not by detecting if light is transmitted from the burner. However, the light sensor often needs maintenance as it is gradually covered by soot over time. Summary

[0008] Thus, an object of the present disclosure is the provision of a pressure washer with reduced need for service, better control of the washing liquid temperature, and with an improved mechanism for detecting when the burner is operative.

[0009] The present disclosure provides an improved method and apparatus for detecting whether a burner is working properly. The solution according to the disclosure provides an immediate state of the burner and therefore prevents wastage of fuel and makes it possible to optimize control of the temperature of the washing liquid.

[0010] An advantage of the present disclosure is that a type of fuel and / or a contamination of fuel used in a pressure washer may be determined based on the vibration data. This allows to inform the user of the pressure washer about a failure to happen, schedule a maintenance of the pressure washer, and / or allow for environmental reporting based on the fuel type and / or combustion. In turn, the determination and / or detection of fuel type and / or contamination may allow for automatic adjustment of system parameters.

[0011] A first aspect relates to a pressure washer, preferably for use by an operator, the pressure washer comprises:

[0012] - a heat exchanger having a washing liquid inlet adapted to connect to a washing liquid source and having a washing liquid outlet providing discharge of washing liquid;

[0013] - a heater comprising a burner in thermodynamic communication with the heat exchanger and adapted to apply heat to the heat exchanger and thereby to the washing liquid in the heat exchanger, said burner adapted to receive an amount of fuel through a fuel input connecting a fuel source to the burner;

[0014] - a control unit configured to control the amount of fuel to be supplied to the burner via the fuel input; and

[0015] - a vibration sensor, wherein the control unit is configured to receive vibration data from the vibration sensor, e.g., vibration data associated with the burner, and to translate these vibration data into an operational state of the burner, such as on or off, or a specific duty cycle configuration.

[0016] In one or more embodiments, the heat exchanger is positioned inside a burning chamber, which burning chamber comprises an outlet for exhaust gas. In one or more embodiments, the heat exchanger is positioned inside a burning chamber comprising an outlet for exhaust gas and the burning chamber is surrounded by an insulating space, which insulting space may hold an amount of liquid, such as washing liquid for preheating.

[0017] In one or more embodiments, the vibration sensor is an acoustic pressure sensor, e.g., a microphone registering sound, i.e., vibration in air molecules, which acoustic sensor may comprise a hose connected to a measure point and to a transducer.

[0018] In one or more embodiments, the vibration sensor comprises a vibrometer or vibration meter configured to measure frequency of vibrations in at least one direction.

[0019] In one or more embodiments, the vibration sensor is configured to register vibrations with a frequency between 10 Hz and 2,000 Hz, preferably between 20 Hz and 100 Hz.

[0020] In one or more embodiments, the vibration sensor, or at least the sensing part of the vibration sensor, e.g., a measuring point, is positioned close to or in contact with the burner, or close to or in contact with a burning chamber. In one or more example embodiments, the vibration sensor , or at least the sensing part of the vibration sensor, e.g., a measuring point, is positioned in the vicinity of or in contact with the burner, or in the vicinity of or in contact with the burning chamber.

[0021] In one or more embodiments, the pressure washer comprises an operator handle configured to control outflow of washing liquid during operation.

[0022] A second aspect relates to a method for controlling operation of a pressure washer, which method comprises the following steps:

[0023] - heating washing liquid in a heat exchanger with a burner, the burner comprising an igniter and is adapted for receiving a flow of fuel;

[0024] - measuring vibration data for the pressure washer, e.g., in form of a value x;

[0025] - comparing the vibration data, such as the measured value x, with pre-determined vibration data associated with at least two know operational states si, s2, ..., sn for the pressure washer, such as one or more pre-determined values for at least two known operational states si, s2, sn for said pressure washer, and

[0026] - determining the operational state of the burner, such as on or off, or a specific duty cycle configuration, e.g., based on the vibration data and / or the comparison.

[0027] A third aspect relates to a method for controlling operation of a pressure washer, which method comprises the following steps:

[0028] - heating washing liquid in a heat exchanger with a burner, the burner adapted for receiving a flow of fuel;

[0029] - measuring vibration data for the pressure washer in form of a value x;

[0030] - comparing the measured value x with one or more pre-determined values for at least two known operational states si, s2, sn for said pressure washer, and

[0031] - determining the operational state of the burner, such as on or off, or a specific duty cycle configuration.

[0032] Preferably, the at least two operational states of the burner are si) the burner is ignited, and s2) the burner is not ignited.

[0033] In one or more embodiments, if the vibration data is indicative of pre-determined vibration data, such as a value, corresponding to the operational state s2, the fuel supply is discontinued to the burner, or the igniter is re-activated, and optionally, an alarm is set.

[0034] In one or more embodiments, if x corresponds to a pre-determined value corresponding to the operational state s2, the fuel supply is discontinued to the burner, or the igniter is reactivated, and optionally, an alarm is set.

[0035] In one or more embodiments, if the vibration data is indicative of pre-determined vibration data, such as a value, corresponding to the operational state si, the fuel supply is continued to the burner.

[0036] In one or more embodiments, if x corresponds to a pre-determined value corresponding to the operational state si, the fuel supply is continued to the burner. In one or more embodiments, when the operational state of the burner is determined to be erroneous, the method further comprises turning off the flow of fuel and / or activating an alarm, e.g., by sound or by light, in order to draw an operator's attention. An erroneous operational state of the burner may e.g., be, or be due to a sooted burner, water in the fuel, an unignited burner, a clotted fuel filter, a burned fuse, e.g., operably coupled to the igniter, a malfunctioning air fan, or the like.

[0037] 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.

[0038] It should be noted that embodiments and features described in the context of one of the aspects of the present disclosure also apply to the other aspects of the disclosure.

[0039] Brief description of the figures

[0040] Figure 1 shows an embodiment of an apparatus according to the disclosure.

[0041] Figure 2 shows distribution of frequencies for a turned-on pressure washer where the burner has not been ignited and is not burning.

[0042] Figure 3 shows distribution of frequencies for a turned-on pressure washer where the burner has been ignited and is burning.

[0043] Detailed description

[0044] The disclosure relates to a pressure washer using heated washing liquid, which washer is preferably to be used by an operator.

[0045] In the present context, the term "in general" when used when mentioning a feature relating to the present disclosure, it must be understood that the feature may be used with all embodiments of the disclosure, even if the mentioning is made in the detailed part of the document.

[0046] 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.

[0047] A pressure washer according to the disclosure comprises a heat exchanger 1 having an inlet 2 for washing liquid and an outlet 4 for washing liquid, through which outlet 4 the washing liquid is discharged. The inlet 2 for washing liquid is configured to connect to a washing liquid source 3, which may be a connection to a reservoir comprising a washing liquid, such as water, an aqueous solution, a solvent, or a mixture thereof, constituting an operational liquid directed to a specific purpose.

[0048] The pressure washer also comprises a heater comprising a burner 5, which burner 5 is in thermodynamic communication with the heat exchanger 1. That the burner 5 is in thermodynamic communication with the heat exchanger means that the two units exchange energy, e.g., through a common wall. The burner 5 is configured to apply heat to the heat exchanger 1 and to the washing liquid confined by the heat exchanger 1, and the burner 5 is adapted to receive fuel during operation through a fuel input 6 connecting a fuel source 7 to the burner 5.

[0049] Further, the pressure washer comprises a control unit 8, which is configured to control the amount of fuel being supplied to the burner via the fuel input 6. The control unit 8 may have other functions during operation of the pressure washer, e.g., the control unit 8 may also be used to maintain a steady temperature of the washing liquid during operation by increasing or decreasing the amount of fuel supplied to the burner 5.

[0050] Also, the pressure washer comprises a vibration sensor 9, and the control unit 8 is configured to receive vibration data from the vibration sensor 9, translate the vibration data into an operational state of the burner 5, such as on or off, or a specific duty cycle configuration, and preferably create a response to the operational state if a pre-set condition is obtained. In one or more example embodiments, the operational state of the burner 5 may be indicative of a type of fuel in the pressure washer, such as a type of fuel provided in the fuel source 7, and / or a contamination of the fuel used in the pressure washer. In other words, the operational state of the burner may comprise or be indicative of information regarding the type of fuel provided in the pressure washer, such as information on the type of fuel combusted or burned by the burner 5. For example, it has been determined in the present disclosure that the acoustic footprint of the burning of a fuel may be different for different fuel types. To translate the vibration data into an operational state of the burner may comprise to translate the vibration data into and / or determine an operational state indicative of a fuel type burned by the burner. For example, a type of fuel may be one or more of: natural gas, kerosene, diesel, biogas, biodiesel, heating oil (such as diesel containing one or more additives), and jet fuel. A contamination of the fuel used in the pressure washer may for example be water, sod, and / or lime contamination. It may be appreciated that determining an operational state of the burner indicative of a contamination of the fuel used in the pressure washer may comprise determining an erroneous operational state of the burner. For example, when it is determined that contamination is present in the fuel, an operational state of the burner may be set to be an erroneous operational state. An erroneous operational state of the burner may e.g., be, or be due to a sooted burner, water in the fuel, an unignited burner, a clotted fuel filter, a burned fuse, e.g., operably coupled to the igniter, a malfunctioning air fan, or the like.

[0051] In one or more example embodiments, to translate the vibration data into an operational state of the burner or a specific duty cycle configuration comprises to determine an operational state of the burner indicative of a type of fuel and / or a contamination of the fuel used in the pressure washer.

[0052] In one or more example embodiments, to determine an operational state of the burner indicative of a type of fuel used in the pressure washer comprises to determine an operational state of the burner indicative of a type of fuel during ignition of the burner, such as ignition of fuel at the burner. In other words, the vibration data measured during an ignition of the burner may be associated with an acoustic footprint specific to a fuel type.

[0053] The vibration data may be seen as associated with the burning flame of the burner, such as associated with a combustion of fuel at the burner. For example, the vibration data may be used to determine a main frequency component, such as a center frequency, amplitude, and / or bandwidth. The main frequency component may be a main frequency component of the vibration data associated with an ignition of the burner. In other words, the vibration data may be used to determine a center frequency, amplitude, and / or bandwidth of the ignition. The vibration data, such as the main frequency component, may be compared to pre-determined vibration data, such as predetermined acoustic footprints for known fuel types. In other word, the control unit may be configured to determine a fuel type in the pressure washer based on a comparison of the vibration data and pre-determined vibration data, such as a comparison of a main frequency component and pre-determined main frequency components of known fuel types.

[0054] An advantage of the present disclosure is that a type of fuel and / or a contamination of fuel used in a pressure washer may be determined based on the vibration data. This allows to inform the user of the pressure washer about a failure to happen, schedule a maintenance of the pressure washer, and / or allow for environmental reporting based on the fuel type and / or combustion. In turn, the determination and / or detection of fuel type and / or contamination may allow for auto system parameters adjustment. In general, the vibration sensor 9, in combination with the control unit 8, may at least be able to detect and identify two operational states; a first state, where the pressure washer is turned on, i.e., is in use, and the burner is on, i.e., burning fuel; and a second state, where the pressure washer is turned on, i.e., in use, but the burner is off, i.e., the burner is not ignited and does thus not burn fuel. In both the first and the second state, fuel may be supplied to the burner 5 by the control unit 8, e.g., either upon instructions from an operator or upon a program defining a duty cycle.

[0055] The operations of the pressure washer, such as the control unit, may be embodied in the form of executable logic routines (for example, lines of code, software programs, etc.) that are stored on a non-transitory computer readable medium (for example, memory) and are executed by the control unit, such as a processor circuitry of the control unit.

[0056] Furthermore, the operations of the pressure washer, such as the control unit, may be considered a method that the pressure washer, such as the control unit is configured to carry out. Also, while the described functions and operations may be implemented in software, such functionality may as well be carried out via dedicated hardware or firmware, or some combination of hardware, firmware and / or software.

[0057] Memory of the pressure washer, such as of the control unit, may be one or more of a buffer, a flash memory, a hard drive, a removable media, a volatile memory, a non-volatile memory, a random-access memory (RAM), or other suitable device. In a typical arrangement, memory may include a non-volatile memory for long term data storage and a volatile memory that functions as system memory for the control unit, such as processor circuitry of the control unit. The memory may exchange data with the control unit, such as processor circuitry, over a data bus. Control lines and an address bus between the memory and the control unit, such as processor circuitry also may be present. The memory may be considered a non-transitory computer readable medium.

[0058] The memory may be configured to store information such as vibration data, e.g., predetermined vibration data, and operational state data and processing algorithms as disclosed herein in a part of the memory. During normal operation of the pressure washer according to the disclosure, the control unit 8 preferably controls the inlet of fuel to the burner 5, and thereby controls the heating of the washing liquid in the heat exchanger while the pressure washer is in use. The control unit 8 is during normal operation preferably under the control of an operator who may control both amount and temperature of the discharged washing liquid leaving the pressure washer during the outlet 4 for washing liquid. Alternatively, the pressure washer may be controlled by a program executed by the control unit 8, which program controls a duty cycle controlling both amount and temperature of discharged washing liquid for a specific period. If the burner 5 unintentionally turns off, the control unit 8 may continue to doze fuel into the burner 5 and optionally into a burning chamber 10. To avoid such spilling of fuel, the inlet of fuel from the fuel source 3, which is normally dozed by a fuel pump should be turned off if the burner is switched off.

[0059] According to the present disclosure, the controller unit may be used to determine whether the burner follows a pre-set pattern of periods where the burner is switched on or off.

[0060] In general, the control unit 8 may control the speed of a fuel pump or a fuel valve in order to control the fuel input to the burner 5. The control unit 8 may also set an alarm, e.g., by sound or by light in order to draw the operator's attention to the fact that a problem has arisen that needs to be dealt with.

[0061] The burner and the heat exchanger 1 may be positioned inside a burning chamber 10, such a burning chamber 10 may then comprise an outlet 11 for exhaust gas. Normally or generally, the heat exchanger 1 and the burning chamber 10 comprise at least one common wall or surface providing the "thermodynamic communication" where heat is transferred from burning chamber heated by the burner 5 to the washing liquid separated from the burning chamber 10 by the surfaces of the heat exchanger 1. According to the shown embodiment, the heat exchanger 1 is formed as a coiled pipe, however, the shape of the heat exchanger 1 is not essential to the present disclosure, many other shapes and constructions of heat exchangers may be used to obtain the desired effect.

[0062] The burning chamber 10 may be surrounded by an insulating space 12, which insulting space 12 may hold an amount of liquid such as washing liquid for preheating. The insulating space 12 may completely cover the burning chamber 10 in such way that an operator operating the pressure washer cannot get in direct contact with the surfaces of the heated burning chamber 10, why the insulating space 12 also provides a protective cover.

[0063] The vibration sensor 9 may comprise a vibrometer or vibration meter configured to measure frequency of vibrations in at least one direction. The vibration sensor 9 may be an acoustic pressure sensor, i.e., a microphone that registers sound, i.e., vibration in air molecules. An acoustic sensor 9 may comprise a hose 9a through which air may flow, which hose 9a is connected to a measure point 9b at one end and to a transducer 9c at the opposite end. The transducer 9c may be configured to convert the input from the measured point 9b to an electric signal.

[0064] A vibration sensor 9 as defined in the present document does not include light sensors, however, a light sensor may be applied together with the vibration sensor 9 according to the present disclosure as a light sensor may transmit further data to the control unit 8 in which data may be used to control the burner 5 or other controllable units of the pressure washer. In general, the vibration sensor 9 may be configured to register vibrations having a frequency between 10 Hz and 2000 Hz, preferably between 20 Hz and 100 Hz. However, the frequency range is determined relative to the specific pressure washer or type of pressure washer.

[0065] The vibration sensor 9, or at least the sensing part of the vibration sensor 9, i.e., the measuring point 9b, is preferably positioned close to or in contact with the burner 5, or alternatively, close to or in contact with a burning chamber 10. In this context "close to" must be understood as being a distance short enough for the sensor to pick up signals which during operation is transmitted by the burner 5. For example, close to may be seen as the vibration sensor 9, or at least the sensing part of the vibration sensor 9, i.e., the measuring point 9b, may be positioned at a distance of less than or equal to 50 cm from the burner 5 and / or the burning chamber 10.

[0066] In one or more example embodiments, the vibration sensor 9, or at least the sensing part of the vibration sensor 9, e.g., the measuring point 9b, is positioned in the vicinity of or in contact with the burner 5, or in the vicinity of or in contact with the burning chamber 10. For example, in the vicinity of may be seen as the vibration sensor 9, or at least the sensing part of the vibration sensor 9, i.e., the measuring point 9b, may be positioned at a distance of less than or equal to 50 cm from the burner 5 and / or the burning chamber 10.

[0067] Normally, a pressure washer according to the disclosure comprises an operator handle 18, which operator handle 18 is configured to control outflow of washing liquid during operation through the outlet 4 for washing liquid.

[0068] The present disclosure also relates to a method for controlling operation of a pressure washer, which method comprises the following steps:

[0069] - heating washing liquid in a heat exchanger with a burner, the burner adapted for receiving a flow of fuel;

[0070] - measuring vibration data for the pressure washer, e.g., in form of a value x;

[0071] - comparing the vibration data with pre-determined vibration data associated with at least two known operational states for the pressure washer, such as the burner, and

[0072] - determining the operational state of the burner (optionally, also the operational state of the pressure washer), such as on or off, or a specific duty cycle configuration (e.g., duty cycles for controlling the on time and off time of a fuel solenoid controlling the fuel flow to the burner). It may be appreciated that the determination of the operational state of the burner may be based on the vibration data and / or the comparison of the vibration data with the one or more pre-determined values for at least two known operational states. In one or more example embodiments, comparing the vibration data with pre-determined vibration data comprises comparing a measured value x with one or more pre-determined values for at least two known operational states si, s2, sn for said pressure washer.

[0073] The determination of the operational state of the pressure washer may e.g., be:

[0074] — if x = si: the burner is ignited and fuel flows to the burner,

[0075] — if x = s2: the burner is not ignited and fuel flows to the burner,

[0076] -- si and x ^ s2.: the operational state of the pressure washer may be uncertain, and the operator may be requested to check various parts of the pressure washer, such as burner-indicator, fuel pump 13, air fan operation, or other specific equipment.

[0077] In one or more example embodiments, the vibration data, such as the measured value x, comprises a frequency (including a set of frequencies), or a value, such as pressure variations, which can be translated into a value x for frequency. For example, the vibration data may comprise and / or be used to determine a main frequency component, such as a center frequency, amplitude, and / or bandwidth

[0078] Figure 1 illustrates an embodiment of a pressure washer according to the disclosure. The embodiment comprises a heat exchanger 1 comprising a washing liquid inlet 2 adapted to connect to a washing liquid source 3 and having a washing liquid outlet 4 providing discharge of washing liquid. The heat exchanger 1 is heated by a burner 5 in thermodynamic communication with the heat exchanger 1, the burner 5 applies heat to the heat exchanger 1 and to the washing liquid held in the heat exchanger 1. The burner 5 receives fuel through a fuel input 6, which is connected to a fuel source 7. The amount of fuel fed to the burner 5 is controlled by a fuel valve 15 and a fuel pump 13. According to the shown embodiment, the burner 5 also comprises an air intake 16 and an air fan 17, which provide a proportional air inlet to the burner 5. The pressure washer also comprises an igniter 19, which is adapted to ignite the burner 5 when the fuel starts flowing to the burner 5.

[0079] The pressure washer also comprises a control unit 8, which is configured to control the amount of fuel to be supplied to the burner via the fuel input 6, normally by switching the fuel pump 13 on or off, or by closing or opening the fuel valve 15, such as a fuel solenoid valve, thereby e.g., defining a duty cycle of the fuel supply. The control unit 8 may also control the temperature of the washing liquid by increasing or decreasing the speed of the fuel pump 13, thereby controlling the amount of fuel flowing into the burner 5 and the heat provided by the burner. To provide a temperature control the control unit 8 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 8. The pressure washer further comprises a vibration sensor 9, which in the shown embodiment comprises a measure point 9b in close contact with either the burner, or e.g., the air intake and a transducer 9c being part of the control unit 8, and a hose 9a connecting the measure point 9b with the transducer. The control unit 8 is configured to receive vibration data from the vibration sensor 9, and to translate these vibration data into an operational state of the burner 5. The operational state may be "on", i.e., the burner 5 is ignited, or "off", i.e., the burner 5 is not ignited, or "Above a frequency level" as a frequency level may indicate a problem with the burner 5, or a specific duty cycle configuration, i.e., the burner 5 (or the fuel pump or fuel valve) is turned on and off according to a pre-set program.

[0080] According to the shown embodiment, the burner 5 burns inside, and heats, a burning chamber 10 comprising an outlet 11 for flue gases.

[0081] The control unit 8 is configured to turn off the inlet of fuel to the burner 5, when the burner 5 is not burning, i.e., when the burner 5 does not have a flame. If the fuel is not turned off when the burner 5 does not have a flame, fuel is continuously pumped into the burner 5 and may either flow out of the pressure washer or may flow into the burning chamber 10 and collect at the bottom of the burning chamber 10.

[0082] The contact surface of the heat exchanger 1 being in thermodynamic communication with the burner 5 is positioned inside the burning chamber 10. According to the shown embodiment, the contact surface is an outer surface of a coiled pipe whereas the washing liquid is transported inside the coiled pipe from a washing liquid inlet 2 to a washing liquid outlet 4. From the outlet 4 for washing liquid the heated washing liquid flows to an outlet nozzle and the outlet of washing liquid from the outlet nozzle may be controlled by an operator handle 18.

[0083] The inlet 2 for washing liquid to the heat exchanger 1 is connected to a washing liquid source 3. The washing liquid source may be a tank with water e.g. demineralized or deionized water, or a tank with a pre-mixed washing solution e.g. an aqueous soap-solution, or a tank with a solvent or the like.

[0084] The shown embodiment comprises an insulating space or chamber 12 which surrounds the burning chamber 10. The insulating chamber 12 may have a double function as the insulating chamber 12 may isolate the burning chamber 10 from the surroundings and thereby protect the operator from getting in contact with the heated surfaces of the burning chamber 10, and also, the insulating chamber 12 may provide a pre-heating of the washing liquid by creating a reservoir 20 of preheated washing liquid which makes it possible to save energy as well as making the pressure washer more compact. A low-pressure pipe 22 connects the reservoir 20 of the insulating chamber 12 with a washing liquid pump 21, and a high-pressure pipe 23 connects the washing liquid pump 21 with the inlet 2 of the heat exchanger 1.

[0085] A by-pass valve 24 connects the high-pressure pipe 23 with the low-pressure pipe 22 and allows washing liquid to be circulated during a warm-up period.

[0086] Figure 2 illustrates how frequencies as a function of decibel can be measured by a microphone at an outer wall of the burner 5 in a state where the burner is "off", i.e., the burner 5 is not burning / not ignited. In this operational state, the burner 5 has a distinctive peak at 44 Hz, such as 44 Hz +- 5 Hz, (6.9 dB).

[0087] Figure 3 illustrates how frequencies as a function of decibel can be measured by a microphone at an outer wall of the burner 5 in a state where the burner is "on", i.e., the burner 5 is burning / ignited. In this operational state, the burner 5 has a distinctive peak at 69 Hz, such as 69 Hz +- 5 Hz, (-1.1 dB, differing almost 6 dB from the measurements in the "off" state). The burner 5 may have different distinctive peaks dependent on the type of fuel used, e.g., the type of fuel present in the pressure washer.

[0088] It is to be noted that the words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements.

[0089] It is to be noted that the term "indicative of" may be seen as "associated with", "related to", "descriptive of", "characterizing", and / or "defining". The terms "indicative of", "associated with", "related to", "descriptive of", "characterizing", and "defining" can be used interchangeably. The term "indicative of" can be seen as indicating a relation. For example, operational state indicative of a fuel type may comprise one or more fuel type parameters.

[0090] It is to be noted that the word "based on" may be seen as "as a function of" and / or "derived from". The terms "based on" and "as a function of" can be used interchangeably. For example, a parameter determined "based on" a data set can be seen as a parameter determined "as a function of" the data set. In other words, the parameter may be an output of one or more functions with the data set as an input.

[0091] A function may be characterizing a relation between an input and an output, such as mathematical relation, a database relation, a hardware relation, logical relation, and / or other suitable relations.

[0092] It should further be noted that any reference signs do not limit the scope of the claims, that the examples may be implemented at least in part by means of both hardware and software, and that several "means”, "units" or "devices" may be represented by the same item of hardware.

[0093] The various example methods, devices, and systems described herein are described in the general context of method steps or processes, which may be implemented in one aspect by a computer program product, embodied in a computer-readable medium, including computer-executable instructions, such as program code, executed by computers in networked environments. A computer-readable medium may include removable and nonremovable storage devices including, but not limited to, Read Only Memory (ROM), Random Access Memory (RAM), compact discs (CDs), digital versatile discs (DVD), etc. Generally, program circuitries may include routines, programs, objects, components, data structures, etc. that perform specified tasks or implement specific abstract data types. Computer-executable instructions, associated data structures, and program circuitries represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes.

Claims

Claims1. A pressure washer, preferably for use by an operator, the pressure washer comprises:- a heat exchanger (1) having a washing liquid inlet (2) adapted to connect to a washing liquid source (3) and having a washing liquid outlet (4) providing discharge of washing liquid,- a heater comprising a burner (5) in thermodynamic communication with the heat exchanger (1) adapted to apply heat to the heat exchanger (1) and to the washing liquid in the heat exchanger (1), said burner (5) adapted to receive an amount of fuel through a fuel input (6) connecting a fuel source (7) to the burner (5); and- a control unit (8) configured to control the amount of fuel to be supplied to the burner via the fuel input (6), characterized in that the pressure washer further comprises a vibration sensor (9), and the control unit (8) is configured to receive vibration data from the vibration sensor (9), and to translate these vibration data into an operational state of the burner (5), such as on or off, or a specific duty cycle configuration.

2. The pressure washer according to claim 1, wherein the heat exchanger (1) is positioned inside a burning chamber (10), which burning chamber (10) comprises an outlet (11) for exhaust gas.

3. The pressure washer according to any one of the claims 1-2, wherein the heat exchanger (1) is positioned inside a burning chamber (10) comprising an outlet (11) for exhaust gas and the burning chamber (10) is surrounded by an insulating space (12) which insulting space (12) may hold an amount of liquid such as washing liquid for preheating.

4. The pressure washer according to any one of the claims 1-3, wherein the vibration sensor (9) is an acoustic pressure sensor, e.g., a microphone registering sound, i.e. vibration in air molecules, which acoustic sensor may comprise a hose (9a) connected to a measure point (9b) and to a transducer (9c).

5. The pressure washer according to any one of the claims 1-4, wherein the vibration sensor (9) comprises a vibrometer or vibration meter configured to measure frequency of vibrations in at least one direction.

6. The pressure washer according to any one of the claims 1-5, wherein the vibration sensor (9) is configured to register vibrations with a frequency between 10 Hz and 2,000 Hz, preferably between 20 Hz and 100 Hz.

7. The pressure washer according to any one of the claims 1-6, wherein the vibration sensor (9) or at least the sensing part of the vibration sensor (9), e.g., a measuring point, is positioned in the vicinity of or in contact with the burner (5), or in the vicinity of or in contact with a burning chamber (10).

8. The pressure washer according to any one of the claims 1-7, wherein the pressure washer comprises an operator handle configured to control outflow of washing liquid during operation.

9. The pressure washer according to any of claims 1-8, wherein to translate the vibration data into an operational state of the burner (5) or a specific duty cycle configuration comprises to determine an operational state of the burner (5) indicative of a type of fuel and / or a contamination of the fuel used in the pressure washer.

10. The pressure washer according to claim 9, wherein to determine an operational state of the burner (5) indicative of a type of fuel used in the pressure washer comprises to determine an operational state of the burner (5) indicative of a type of fuel during ignition of the burner (5).

11. A method for controlling operation of a pressure washer, which method comprises the following steps:- heating washing liquid in a heat exchanger (1) with a burner (5), the burner (5) adapted for receiving a flow of fuel;- measuring vibration data for the pressure washer;- comparing the vibration data with pre-determined vibration data associated with at least two known operational states si, s2, ...., sn for said pressure washer, and- determining the operational state of the burner (5), such as on or off, or a specific duty cycle configuration.

12. The method according to claim 11, wherein the vibration data comprises a frequency, or a value, such as pressure variations, which can be translated into a value x for frequency.

13. The method according to any one of the claims 11-12, wherein when the operational state of the burner (5) is determined to be erroneous, the method further comprises turning off the flow of fuel and / or activating an alarm, e.g., by sound or by light, in order to draw an operator's attention.

14. The method according to any of claims 11-13, wherein determining the operational state of the burner (5) or a specific duty cycle configuration comprises determining an operational state of the burner indicative of a type of fuel used in the pressure washer.

15. The method according to claim 14, wherein determining the operational state of the burner (5) indicative of a type of fuel used in the pressure washer comprises to determine an operational state of the burner (5) indicative of a type of fuel during ignition of the burner (5).

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