Pressure washer with diagnostic indicators
Contents
1. The other input voltage is derived from the reference voltage via a voltage divider The input voltages for the OpAmp 82 cause the output voltage of the OpAmp to be ata low value that turns the bypass transistor 94 off With the bypass transistor 94 turned off the indication current flows through the LED 74 As a result the LED 74 generates light to indicate that the motor is operating nor mally In an alternative embodiment as shown in FIG 7 a pres sure washer 100 is equipped with a communication circuit 101 The communication circuit controls a radio frequency RF transceiver 102 to send and receive radio frequency signals The wireless communication capability of the pres sure washer 100 can be used for various purposes For instance the RF communication circuit may serve the func tion of a tracking device To that end the communication circuit may be programmed to transmit the serial number of the pressure washer and or other information that may be used to identify the pressure washer The RF transmission may be received by a receiver at a service center 103 or by a mobile monitoring device 104 Moreover the RF transmis sion may also include diagnostic data indicative of the opera tion conditions detected by the diagnostic circuit 36 This enables the receiver of the RF transmission from the machine to determine the status of the pressure washer in the field and if necessary to contact the user of the pressure washer to corre2. easily corrected In accordance with a feature of the invention a diagnostic circuit 36 is provided in the electrical pressure washer 10 for detecting operating conditions of the pressure washer and a diagnostic indication panel 38 is provided with indicator lights 39 to indicate the detected operation conditions for viewing by the user The diagnostic indication panel 38 allows the user to see easily the operating conditions of the washer so that the user can take proper corrective actions based on the diagnostic information shown by the indicator lights For instance if an indicator light shows that the GFCI 20 is tripped the user can correct the problem easily by resetting the GFCI Information about which action to take based on which indicator light is on or off may be provided in a trouble shooting chapter in the user s manual for the pres sure washer Even if the user lacks the technical knowledge to understand the meaning of the indicator lights or to follow the instructions in the manual to correct the problems the indi cator lights allows the user to report the problem to a remote service center which can then identify the possible causes of the problem based on the status of the indicator lights For instance as shown in FIG 3 the user 40 can contact a service center 42 of the manufacturer via telephone and tells the service representative 43 the On Off states of the indicator lights in the diagnostic indicator panel 38 of th
3. the capacitor 80 is automatically switched in to power the components of the diagnostic circuit 36 To reduce the energy consumption of the diagnostic indi cation assembly that includes the diagnostic circuit and the indication panel light emitting diodes LED s are used as the indicator lights In the illustrated embodiment the diag 20 25 30 35 40 45 50 55 60 65 6 nostic circuit includes LED s 70 77 that are marked respec tively on the display panel FIG 1 as Check GFCI No AC Power AC OK AC Low Motor OK Detergent ON Low Water Flow and Motor Over temperature respec tively To simplify the control logic of the diagnostic circuit 36 and to reduce the cost for implementing the circuitry low cost operational amplifies OpAmp 81 84 are used to detect the different operation conditions The OpAmps 81 84 are of a low power type to further reduce the power consumption of the diagnostic circuit The OpAMps 81 84 are connected to respective indicator LED s 72 76 to selectively turn the LED s on or off depending on the operation conditions detected In the implementation of FIG 6 the OpAmps 81 84 are used basically as voltage comparators Each OpAmp compares an input voltage with a reference voltage via appropriate voltage dividers which is provided by a zener diode 88 DIODE 16 in the circuit of FIG 6 The input voltage for each OpAmp is a v
4. the invention for detecting operation conditions of the pressure washer and indicating the detected conditions to a user for diagnostic problem shooting purposes FIG 2 is a schematic functional diagram that identifies components of the electrical pressure washer FIG 3 is a schematic diagram depicting a user of the electrical pressure washer contacting a remote service center for reporting problems and diagnostic information provided by indicators on the pressure washer FIG 4 is a schematic diagram showing a power cord of an embodiment of the pressure washer with a plug having a built in ground fault circuit interrupter GFCI and wiring for markets where GFCI is not required FIG 5 is a schematic diagram showing an optically coupled sensing circuit over a breaker of the GFCI for sensing whether AC power is present at the plug FIG 6 is an electronic circuit schematic diagram showing a diagnostic circuit in the pressure washer for detecting opera tion conditions of the pressure washer and operating light emitting diodes to indicate the detected operation conditions FIG 7 is a schematic diagram showing a pressure washer of an embodiment that transmits RF signals for wireless com munication with a monitoring device and FIG 8 is a schematic diagram showing a pressure washer of another embodiment that has a global positioning system module DETAILED DESCRIPTION OF THE INVENTION Turning to the drawings and referring first to F
5. the service technician 106 can learn the identity of the pressure washer where the machine is and whether the machine is operating properly Thus if the pressure washer 110 is left in the field or is stolen the RF transmission sent by the communication circuit 101 of the pressure washer can be used to track the location of the pressure washer and the identification infor mation encoded in the transmission allows the receiver to identify the pressure washer The identification information in the wireless transmission also allows the monitoring device to remotely monitor the inventory of pressure washers at a store To that end the GPS locator function of the machine may be activated at the time the pressure washer 110 is pur chased by a customer at a store The GPS locating transmis sion from the pressure washer 10 may also be triggered in response to commands sent remotely by the service center 103 over RF transmission In view of the many possible embodiments to which the principles of this invention may be applied it should be recognized that the embodiments described herein with respect to the drawing figures are meant to be illustrative only and should not be taken as limiting the scope of the invention Therefore the invention as described herein contemplates all such embodiments as may come within the scope of the following claims and equivalents thereof What is claimed is 1 An electrical pressure washer comprising a housin
6. washer to properly identify the possible reasons why the pressure washer is not functioning as expected It is a related goal of the invention to provide means for assisting the user in checking important operation conditions that affect the operation of the pressure washer so that the user can quickly and easily identify the possible cause for the apparent malfunction of the pressure washer and take appro priate measures to correct the problem The foregoing objects are achieved by the invention which provides an electrical pressure washer that has a diagnostic circuit for detecting operation conditions that may affect the normal operation of the pressure washer and has indicators for indicating the operation conditions to the user to assist the user in diagnosing potential problems when the pressure washer is not operating normally With the operation condi tion indicators the user may be able to identify the condition that causes the apparent malfunction of the pressure washer and correct the problem by himself Alternatively the user may contact the technical service of the manufacturer seller of the pressure washer and identify the operation conditions as indicated by the indicators on the pressure washer and receive instructions to correct the problem if the problem can be easily corrected by the user BRIEF DESCRIPTION OF THE DRAWINGS FIG 1 is a perspective view of an electrical pressure washer that implements an embodiment of
7. 3 operation of the pressure washer and a plurality of indicators indicating the detected operation conditions such as ground S lication file fi let h history a a a See Demenees fault low pressure overheating etc A voltage drop across the 56 References Cited power cord of the pressure washer is monitored and used to identify several of the operating conditions A way of con U S PATENT DOCUMENTS necting and controlling light emitting diodes used as indica 4 697 464 A 10 1987 Martin oo 731866 3 Wr lights is provided to allow energy efficient operation ofthe 5 040 950 A 8 1991 Dalquist etal 417 234 indicator lights 5 220 935 A 6 1993 Bailey et al 5 381 962 A 1 1995 Teague veces 239 526 21 Claims 8 Drawing Sheets IE IF EE aE ST 26 LLAGNOSTIC COREOT OLTL ET SOLACE US 8 074 668 B2 Sheet 1 of 8 Dec 13 2011 U S Patent US 8 074 668 B2 Sheet 2 of 8 Dec 13 2011 U S Patent LIS7 ALY DP DPLLSONDYS U S Patent Dec 13 2011 Sheet 3 of 8 US 8 074 668 B2 ee we PUBLIC TELEPLSO WET WORR Lig 2 US 8 074 668 B2 Sheet 4 of 8 Dec 13 2011 U S Patent O MMNGIL OMVAIILISY O LOS XOLO NOVUTY LOH Z Stk LNS LMS LISIIS PD WLS ON EOD IE US 8 074 668 B2 Sheet 5 of 8 Dec 13 2011 U S Patent eo Gry 7 a FF lo LOH XIXH IIF 6 de oe TILE Canad Lf ISNIS QMO WIM _ goe Ne ZF
8. ASF US 8 074 668 B2 Sheet 6 of 8 Dec 13 2011 U S Patent SARLI ASO NO AS Pl OL DVL TY 0 LO US 8 074 668 B2 Sheet 7 of 8 Dec 13 2011 U S Patent KA A KT FOIA T B A OY D a TLT g C7 la ATTN a LASSI IA D NOULE AMUWVIVG es LIM FIINGOML TY YTS S PSY POIIMS SETI gcu COL EO PO EO US 8 074 668 B2 Sheet 8 of 8 Dec 13 2011 U S Patent LAID FLLSONLLAD PAIVAFT ENL NOLIN OLV FVL GON LO LI IIX D VOALEAINSTINIVOD QF SP FINS SIATS US 8 074 668 B2 1 PRESSURE WASHER WITH DIAGNOSTIC INDICATORS TECHNICAL FIELD This invention relates generally to pressure washers and more particularly to a pressure washer that has indicators for indicating operating conditions of the pressure washer to provide diagnostic information to a user BACKGROUND OF THE INVENTION A pressure washer is a device that outputs a high pressure jet of water that can be used to wash surfaces such as wood tile concrete etc Many pressure washers are powered by electricity and designed for household and light commercial use Such an electrical pressure washer typically includes an electrical motor for pressurizing water from a low pressure source e g a garden hose to a much higher pressure The pressurized water then goes through a flexible hose to an application wand or lance which is fitted with a nozzle with
9. IG 1 an electrical pressure washer 10 in an embodiment of the inven tion includes a housing 11 that contains an electrical motor 12 US 8 074 668 B2 3 FIG 2 for pressurizing water received from a low pressure water source through a water inlet 13 FIG 2 to provide an output high pressure water stream A power cord 14 of a pre selected length connects the pressure washer to an AC outlet 16 from which the pressure washer draws the power needed for operating the motor An on off switch 17 on the housing 11 of the pressure washer is used to turn the pressure washer on or off by connecting or breaking the AC power to the motor On the distal end of the power cord 14 is an AC plug 18 to be plugged into a receptacle of the AC outlet 16 In the illustrated embodiment the power cord includes a ground fault circuit interrupter GFCI 20 that is integrated with the AC plug 18 The GFCI is not required however in regions where the electrical safety code does not call for such a device The pressure washer 10 further includes a flexible high pressure hose 21 One end of the pressure hose has a connector 22 that can be connected to a fitting 24 on the housing to form a leak proof connection The other end of the hose 21 is connected to an application wand 25 with a trigger 26 for opening or closing a valve in the wand to control the water flow The pressure washer further includes a nozzle 28 that can be connected to the wand 25 such that pressuriz
10. US008074668B2 az United States Patent 10 Patent No US 8 074 668 B2 Alexander et al 45 Date of Patent Dec 13 2011 54 PRESSURE WASHER WITH DIAGNOSTIC 5 661 623 A 8 1997 McDonald et al INDICATORS 5 745 043 A 4 1998 Lemke etal w 340 815 4 5 749 526 A 5 1998 Laabs et al 239 307 5 757 162 A 5 1998 Weber woes 318 821 75 Inventors Gus Alexander Inverness IL US Mike Hanson Lakewood IL US FOREIGN PATENT DOCUMENTS DE 227568 A 9 1985 73 Assignee FNA IP Holdings Inc Elk Grove DE 100 29 375 Al 3 2002 Village IL US OTHER PUBLICATIONS Notice Subject to any disclaimer the term of this U S Patent amp Trademark Office International Search Report in patent is extended or adjusted under 35 International Patent Application No PCT US2005 006570 Dec 18 2006 U S C 154 b by 1490 days EP Supplementary Search Report for EP Application No EP 21 Appl No 10 790 527 05724165 dated Jul 15 2011 3 5 cited by examiner 22 Filed Mar 1 2004 Primary Examiner Michael Barr 65 Prior Publication Data Assistant Examiner Jason Riggleman US 2005 0189437 Al Sep 1 2005 74 Attorney Agent or Firm Cook Alex Ltd 51 Int Cl 57 ABSTRACT BOSB 3 00 2006 01 An electrical pressure washer includes a diagnostic circuit for G2 US le Sie aae 134 113 134 58 R detecting operation conditions that may affect the normal 58 Field of Classification Search 134 11
11. a fixed or variable aperture and has a trigger for turning high pressure water jet on or off To enhance the cleaning power of the water stream some pressure washers have a chemical tank for storing a liquid detergent and have an operation mode in which the detergent is extracted from the tank by means of vacuum suction and mixed into the water stream Although an electrical pressure washer is a relatively simple device its operation may be affected by various con ditions and may appear to an inexperienced user to be mal functioning even ifthe machine is actually in good shape For instance an electrical pressure washer may be required by safety code or regulations to be equipped with a ground fault circuit interrupter GFCI for protecting a user from electrical shocks A GFCI however may sometimes be accidentally tripped and the AC power to the motor will be cut off as a result In such a situation the pressure washer can be put back in operation by simply resetting the GFCI Nevertheless an inexperienced user who is unaware of the existence and or function of the GFCI may think that pressure washer is bro ken As another example when the pressure washer is put in the chemical suction mode the pressure of the water jet is significantly lower than that in the normal operation mode A user however may not know or remember to check that the pressure washer is in the chemical suction mode and may jump to the conclusion that the pressure
12. ct the problem to restore the normal operation of the washer Alternatively the pressure washer may be equipped with a modem 105 The communication circuit 101 is programmed such that it automatically dials up to a pre programmed num ber of the service center 103 when the modem is plugged into a telephone line Once the phone connection is made the communication circuit 101 transmits information including the serial number of the pressure washer and the operation conditions This enables a service technician 106 at the ser vice center 103 to identify the potential problems of the unit without having to physically examine the machine In yet another embodiment as shown in FIG 8 the pressure washer 110 is further equipped with a global positioning system GPS module 111 The GPS module 111 receives radio signals from GPS satellites 112 By triangulation of signals from three of the GPS satellites 112 the GPS module 20 25 30 35 40 45 50 55 60 65 8 111 can pinpoint its current location The communication circuit 101 of the pressure washer 110 then transmits RF signals containing information ofits current location its iden tification and its operational status as detected by the diag nostic circuit 36 The transmission and reception of the RF signals may utilize the infrastructure provided by a cellular phone network When the RF signals is received by the ser vice station 103 or a mobile monitoring unit 104
13. ctrical motor a diagnostic circuit for detecting a voltage drop over the power cord and determining an operation condition based on the voltage drop an indication panel having at least one indicator light for indicating the operation condition a sensing wire connecting the diagnostic circuit to the distal end of the power cord for detecting the voltage drop over the power cord a ground fault circuit interrupter wherein the diagnostic circuit further detects whether a breaker of the ground fault circuit interrupter is open 20 25 30 35 40 45 50 55 60 10 wherein the diagnostic circuit further detects whether an AC voltage is present at the plug before the ground fault circuit interrupter and wherein the plug further includes a light emitter on an input end of the plug and an optical receiver connected to the sensing wire the light emitter emitting light when an AC voltage is present at the plug 16 An electrical device comprising an electrical motor a sensing circuit a power cord having a plug at a distal end for connecting AC power to the electrical motor the power cord having a Hot wire a Return wire a Ground wire and a sensing wire connected to the sensing circuit for the sensing circuit to detect a voltage at the plug wherein the plug further includes a light emitter on an input end of the plug and an optical receiver connected to the sensing wire the light emitter emitting light when a
14. d by the sensing circuit is that the electrical motor is operational 19 The electrical pressure washer of claim 17 wherein the operation condition detected by the sensing circuit is that a water pressure at the water input port is low 20 The electrical pressure washer of claim 17 wherein the pressure washer further includes a chemical tank for storing a liquid detergent and wherein the operation condition detected by the sensing circuit is that the pressure washer is in a mode of extracting the liquid detergent from the chemical tank for mixing in the water stream 21 The electrical pressure washer of claim 17 wherein the operation condition detected by the sensing circuit is that a thermal protection circuit of the electrical motor is open for protecting the electrical motor from overheating
15. e pressure washer Based on that information the service representative 43 can make a decision or informed guess of what the cause of the problem may be and give the user instructions over the telephone to try various corrective measures to change the operation conditions to put the pressure washer back in the normal operation mode In this way the user 40 can have the problem corrected easily and promptly As a result the user is much less likely to unnecessarily return the machine to the shop send the machine in for repair or call for a visit by a service person The contacts between the user 40 and the service center 42 is of course not limited to a telephone conversation and can be made via for example e mail or video conferencing over the Internet or other forms of remote communications To protect the diagnostic circuit 36 from exposure to water or other elements the diagnostic circuit is mounted inside the housing 11 of the pressure washer The diagnostic circuit 36 operates indicator lights 39 in the diagnostic indication panel 38 which is mounted on the housing at a location that is easily viewable but well protected from accidental impact In the embodiment shown in FIG 1 the diagnostic indication panel 38 is located on the upper front surface of the housing adja cent a handle 15 of the pressure washer The indicator panel 38 includes lights for indicating for example the presence of the AC power at the GFCI plug the AC v
16. ed water is ejected through an output opening 29 of the nozzle when the user pulls the trigger 26 on the wand 25 The size of the output opening 29 of the nozzle 28 is preferably adjustable to allow the pressurized water stream coming out of the nozzle to be adjusted from a wide fan spray to a focused pencil thin stream Referring now to FIG 2 to provide enhanced clearing power of the pressurized water stream liquid detergent or the like may be added to the water stream To that end the pressure washer includes a chemical tank 31 for containing the liquid detergent 32 A vacuum generated by the pressur ized water pumped out through the nozzle 28 is used to provide suction of the detergent from the chemical tank The detergent extracted by the vacuum from the chemical tank is mixed with the water stream and ejected through the nozzle 28 When the pressure washer is put in the chemical suction mode the pressure of the water stream ejected through the nozzle is significantly lower than that when the pressure washer is in the normal operation mode As mentioned before the operation of the pressure washer 10 is affected by various factors and there are multiple con ditions that will make the pressure washer appear that it is not function properly Such conditions are often difficult to understand or identify by an inexperienced user who has not read the manual for the pressure washer or cannot compre hend the explanations and instruction
17. g including a water inlet port and a water outlet port the housing containing an electrical motor that is adapted to pressurize water received through the water inlet port and to output pressurized water through the water outlet port an application wand connected to the water outlet by a hose and having a nozzle for outputting the pressurized water the housing further including a diagnostic circuit and an indication panel a power cord connected to the electrical motor for deliver ing AC power to the electrical motor and having a plug at a distal end wherein the diagnostic circuit includes a plurality of opera tional amplifiers each operational amplifier determin ing the presence of a different operation condition of the pressure washer based on a comparison between a detected voltage drop over a return wire of the power cord and a corresponding reference voltage wherein the indication panel comprises a plurality of indi cator lights that are connected to the diagnostic circuit with each indicator light each corresponding to said different operation condition and being adapted to be illuminated when the diagnostic circuit has determined that the respective operation condition is present 2 The electrical pressure washer of claim 1 wherein one of the respective operation conditions is that the electrical motor is operational 3 The electrical pressure washer of claim 1 wherein one of the respective operation conditions is t
18. hat a water pressure at the water input port is low 4 The electrical pressure washer of claim 1 further com prising a chemical tank for storing a liquid detergent and US 8 074 668 B2 9 wherein one of the respective operation conditions is that the pressure washer is in a mode of extracting the liquid detergent from the chemical tank for mixing with water received through the inlet port 5 The electrical pressure washer of claim 1 wherein one of the respective operation conditions is that a thermal protec tion circuit of the electrical motor is open for protecting the electrical motor from overheating 6 The electrical pressure washer of claim 1 wherein one of the respective operation conditions is that an AC voltage at the electrical motor is low 7 The electrical pressure washer of claim 1 wherein the plug of the power cord includes a ground fault circuit inter rupter 8 The electrical pressure washer of claim 1 further includ ing a sensing wire connecting the diagnostic circuit to the distal end of the power cord for detecting the voltage drop over the return wire of the power cord 9 The electrical pressure washer of 8 further comprising a ground fault circuit interrupter wherein the diagnostic circuit further detects whether a breaker of the ground fault circuit interrupter is open 10 The electrical pressure washer of claim 9 wherein the diagnostic circuit further detects whether an AC voltage is present at
19. ived from the LED On the other hand ifthe LED 59 is off due to the absence of an AC voltage between the Hot and Return terminals 61 and 62 the pho totransistor 60 is off Based on the on off state of the pho totransistor 60 as sensed through the sensing wire 54 the diagnostic circuit 18 can decide whether AC power is present at the plug input Referring now to FIG 6 the detection of the presence of AC power at the plug before the GFCI in turn allows the diagnostic circuit to determine whether the GFCI breaker 56 is open If AC power is present at the plug but not at the motor the diagnostic circuit 18 can deduce that the GFCI breaker 56 is open and can indicate this condition by turning on an indicator light 70 marked Check GFCI On the other hand if no AC power is detected at the plug input the diagnostic circuit turns on a No AC indicator light 71 to indicate that there is no AC power This condition may occur if for instance the user forgets to connect the plug to a wall outlet or if a circuit breaker before the wall outlet is open To power the diagnostic indication assembly so that the indicators can be used to indicate the operation conditions even after the AC power is cut off a backup capacitor 80 of a sufficiently large value e g 0 1 farad is used in the diagnos tic circuit to store energy If the On Off switch 17 on the pressure washer is in the On position but the AC power to the pressure washer is cut off
20. n AC voltage is present at the plug and wherein the plug of the power cord has a ground fault circuit interrupter wherein the sensing circuit further detects through the sensing wire whether a breaker of the ground fault cir cuit interrupter is open and whether an AC voltage is present at the plug before the ground fault circuit inter rupter wherein the sensing circuit senses a voltage drop over the Return wire by detecting the voltage at the plug the voltage drop being indicative of an amount of current drawn by the electrical motor and wherein the electrical device is a pressure washer compris ing a water inlet port for receiving water from a water source a water outlet port wherein the electrical motor is in fluid communication with the water inlet port and the water outlet port for pressurizing the water received through the water inlet port and pumping the pressurized water through the water outlet port and an application wand connected to the water outlet by a hose and having a nozzle for outputting a pressurized water stream 17 The electrical pressure washer of claim 16 wherein the sensing circuit detects an operation condition of the pressure washer based on the voltage drop and wherein the pressure washer further includes an indication panel having at least one indicator light for indicating the detected operation con dition 18 The electrical pressure washer of claim 16 wherein the operation condition detecte
21. ns fall into four separate ranges When the pressure washer is operating normally the motor current stays in a high current range and varies depending to differ ent degrees on the AC rms voltage at the motor the type of nozzle used and the shape of the output water stream at the nozzle When the pressure washer is in the chemical suction mode the motor current is significantly lower than that of the normal operation When the inlet water pressure is low the low water flow causes the motor current to fluctuate rapidly but the averaged value of the motor current is fairly stable and stays below the motor current in the chemical suction mode thus providing a good indication of the presence of the low inlet pressure condition When the thermal protection circuit in the motor winding is opened the motor is not drawing any current The lack of motor current together with the detection that the AC voltage is detected at the motor indicates that the thermal protection circuit in the motor may be opened In according with another feature of the embodiment to minimize the current required to operate the LED s the LED s 72 77 are connected in series such that the same cur rent hereinafter the indicator current can flow through selected LED s to turn those LED s on The efficiency of power usage is further enhanced by using the indicator cur rent 90 to charge the backup capacitor 80 by connecting the US 8 074 668 B2 7 capacit
22. oltage derived from voltages detected in the electrical system of the pressure washer Such detected voltages include the AC power voltages and as mentioned above the voltage drop over the Return wire as detected through the sensing wire In accordance with a feature of the embodiment the volt age detected through the sensing wire enables the determina tion of multiple operation conditions As already described above the sensed voltage at the plug end of the power cord 14 is used together with the voltage detected at the motor to determine whether there is no AC power at the plug 18 or the GFCI breaker 56 may be open In the circuit of FIG 6 the voltage drop over the Return wire is further used to determine whether the motor is in normal operation condition i e Motor OK whether the pressure washer is in the chemical suction mode i e Detergent On whether the inlet water pressure is low i e Low Water Flow or whether the thermal protection circuit for the motor is opened to prevent the motor from overheating i e Motor Over temperature As described above the voltage drop over the Return wire can be used to determine the root mean square rms value of the current following through the motor 12 of the pressure washer It has been experimentally discovered in connection with this invention that the root mean square values of the current drawn by the motor 12 corresponding to these four operation conditio
23. oltage seen by the motor whether the over temperature protection for the motor is on whether the pressure washer is in the chemical suction mode etc Indicators for other types of operation conditions may also be included In accordance with a feature of a preferred embodiment the amount of electrical current drawn by the motor 12 of the pressure washer is detected and used to determine several operation conditions of the pressure washer To that end in accordance with another feature of the embodiment the amount of the electrical current is determined by detecting the voltage drop across one of the power conductors in the power cord 14 In the illustrated embodiment the voltage drop is measured across the Return wire of the power cord As shown in FIG 4 the plug 18 with integral GFCI receives the Hot US 8 074 668 B2 5 Return and Ground components of the standard AC voltage e g 120V from a wall outlet or the like On the other side of the plug the power cord 14 connecting the plug to the pres sure washer main body includes a Hot wire 50 a Return wire 51 anda Ground wire 52 The voltage drop across the Return wire 51 provides a useful indication of the current drawn by the motor 12 For instance as measured on one pressure washer a 36 5 foot Return wire of 16 AWG has a resistance of about 0 173 ohm With a current draw of 9 17 Amps a voltage drop of about 1 5 3 Vrms is created over the Return wire The detected voltage dr
24. op over the Return wire 51 divided by the known resistance of the wire provides the amount of current flowing through the wire To measure the voltage drop over the Return wire 51 of the power cord a sensing wire 54 is added to the standard three wires 50 52 of the power cord 14 and runs along the three wires Thus the power cord 14 now contains four wires Hot Return Neutral and the sensing wire The sensing wire 54 allows the diagnostic circuit 36 to detect the voltage on the Return wire at the remote plug end of the power cord Turning to FIG 5 the sensing wire further allows the diagnostic circuit 18 to detect whether the AC power is present at the plug 18 before the GFCI breaker 56 Since for safety reasons the sensing wire 54 should not have a direct electrical contact with the plug input upstream of the GFCI breaker 56 an optical coupling assembly 57 is used to sense the presence of AC power As shown in FIG 5 a light emitting circuit 56 comprising a simple power supply and a light emitting diode LED 59 is connected across the Hot terminal 61 and Return terminal 62 at the input end of the plug 18 When AC power is present at the plug upstream of the GFCI the LED 59 is energized to emit light On the other side of the GFCI breaker 56 the sensing wire 54 is connected to a pho totransistor 60 that is positioned to receive the light generated by the LED 59 If the LED 59 is on the phototransistor 60 is turned on by the light rece
25. or in series to the chain of LED s During operation when the AC power is available the indicator current flows through one or more of the LED s 72 77 depending on the operation conditions detected by the OpAmps 81 84 and flows into the backup capacitor 80 to charge the capacitor until the voltage across the capacitor reaches a value set by the zener diode 91 When the AC power is cut off the energy stored in the backup capacitor 80 is used to power the opera tion of the diagnostic circuit 36 to turn either of the LED s 70 and 71 on to indicate to the user that the GFCI should be checked or there is no AC power at the plug 18 To control the On Off state of each of the LED s 72 77 a plurality of bypass transistors 92 97 are provided such that each LED has a corresponding bypass transistor connected in parallel therewith When the bypass transistor is turned on the indicator current will flow through the bypass transistor instead of the LED As a result the LED is turned off i e it does not emit light The On Off state of the bypass transistor is controlled by an associated Op Amp depending on whether the operating condition monitored by that OpAmp is present By way of example if the pressure washer is being used and the motor 12 is running normally the voltage drop over the Return wire is of a value indicating that the motor current is in the high range The voltage drop is presented as one of the input voltages for the OpAmp 82
26. s in the manual As a result the user tends to assume that the pressure washer is broken or faulty even though some of the conditions affecting the performance of the machine can be easily corrected For instance if the GFCI 20 on the plug 18 of the power cord is tripped AC power is cut offat the plug end of the power cord and the pressure washer 10 cannot be turned on by operating the on off switch 17 on the housing Also if the user inserts a long extension cord between the pressure washer and the AC wall outlet 16 instead of plugging the power cord directly into the wall outlet a substantial voltage drop may develop across the extension cord due to the resistance of the extension cord and the large amount of current drawn by the motor 12 of the pressure washer As a result the voltage seen by the motor is significantly lower than the standard AC voltage causing the pressure of the water stream to drop noticeably Moreover a user may forget that the washer is put in the chemical suction mode and view the weaker water stream in that mode as a sign that there is something wrong with the pressure washer Such inability of the user to identify the true problems causing an 0 a 5 40 45 50 55 65 4 the pressure washer to stop working normally can incur tre mendous overheads for the manufacturer or distributor of the pressure washer in handling unnecessary returns or providing field service for conditions that can be
27. the plug before the ground fault circuit interrupter 11 The electrical pressure washer of claim 1 wherein the plurality of indicator lights are light emitting diodes 12 The electrical pressure washer of claim 11 wherein a subgroup of the light emitting diodes are wired in series 13 The electrical pressure washer of claim 12 wherein each light emitting diode in the subgroup has a bypass tran sistor connected in parallel with said each light emitting diode for selectively diverting current away from said each light emitting diode 14 The electrical pressure washer of claim 13 wherein the diagnostic circuit includes a backup capacitor for powering the diagnostic circuit in absence of AC power and wherein the backup capacitor is connected in series to the light emit ting diodes in the subgroup such that a current for energizing the light emitting diodes also charges the backup capacitor 15 An electrical pressure washer comprising a water inlet port for receiving water from a water source a water outlet port an electrical motor in fluid communication with the water inlet port and the water outlet port for pressurizing the water received through the water inlet port and pumping the pressurized water through the water outlet port an application wand connected to the water outlet by a hose and having a nozzle for outputting a pressurized water stream a power cord having a plug at a distal end for connecting AC power to the ele
28. washer is defective Also the pressure washer will not work properly if the AC voltage supplied to it is low which may happen if the user plugs the pressure washer into a long extension cord which introduces a substance voltage drop due to the large amount of current drawn by the pressure washer Thus inexperienced users often find it difficult to identify the reasons why their electrical pressure washers do not work as expected Such difficulties present a serious problem to the manufacturer of the pressure washers due to the increased cost for providing consumer services When a user plugs in a newly purchased pressure washer and does not get the expected high pressure water jet he may think that the machine is defective and decide to return it to the store where he bought it The allegedly bad machine is then returned the manufacturer even if it is fully functional A user may also call in for service under warranty when his pressure washer stops pumping water As a result a service technician may have to be dispatched to service the machine in the field even if the problem can be simply corrected by resetting the GFCI 20 25 30 35 40 45 50 55 60 65 2 switching from the chemical suction mode to the normal operation mode or removing the extension cord etc SUMMARY OF THE INVENTION In view of the foregoing it is a general goal of the invention to provide a way to enable a user of an electrical pressure
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