Patent Application
20060245941
The present invention relates to pressurized flow devices such as pressure washers, and more particularly, to a flow control for such a device.
Pressure washers are well known devices for providing water, or other fluid, from an external source such as a garden hose through a spray nozzle at high pressure. Typically, pressure washers are used to clean surfaces requiring the washing fluid to be delivered under pressure. The fluid is pressurized at a pump assembly, preferably driven by a motor, and delivered through a pathway which can be opened or closed to selectively allow fluid to spray from the nozzle. Fluid can be delivered from the nozzle at a pressure in the vicinity of about 1200 to 1500 psi.
Conventional pressure washers are typically either in free-standing form provided with an elongate hose and/or spray nozzle, or in the form of a portable, hand held unit. Typically in the portable version of a pressure washer, the pump is switched on and off by an electric switch as needed. However, in the free-standing form, the motor typically operates continuously whether the liquid pathway is opened or closed. To turn on and off the motor, a user must physically move the switch from an “on” position to an “off” position, otherwise if the power cord is plugged into an electrical outlet, the motor will continue to run. Such operation of the motor when the pathway is closed, or operation when the electric motor is started without the fluid being supplied to the pressure washer (running the pump dry), can damage the system. Frequently observed damage resulting from improper operation includes pump overheating and pump failure. Further, damage to the pressure washer components can cause electrical and mechanical hazards.
One technique for protecting the system found in the prior art is to selectively bypass the pumped liquid back to the pump inlet when the liquid outlet pathway is closed. The recirculation of the fluid is controlled by a valve to prevent overheating of the pressure washer due to operation of the components without fluid flowing through the system. Some pressure washers have a time limit in which the fluid may be circulated in the bypass mode. However, beyond this amount of time, damage to the pressure washer can occur.
Another disadvantage of some conventional pressure washers is that they operate on a full pressure “on” or spot pressure system. In the full pressure “on” system, the pressure washer motor is turned on when the system senses a high pressure spike in the pump head, i.e. when the fluid pressure sensed in the pump is high resulting from fluid being introduced into the pump. However, such “hard start” systems start from zero pressure and go to full pressure (generally about 1600 psi or above) in a short period of time, which may cause premature deterioration of valves, hoses and other components.
Further, in the conventional full pressure “on” system the motor is turned off (or alternately the washer goes to bypass mode) based on a pressure spike above the normal operating pressure of the unit, i.e. when the fluid is not permitted through the fluid outlet and back pressure in the pump results in a high pressure spike (generally about 1800-2000 psi). This configuration is also problematic when there are internal leakages in the pumps, hoses or fittings because these leakages will alleviate the pressure in the pump head. Subsequently, the device sensing the pressure is exposed to abrupt high and low pressure spikes and the pressure washer will cycle on and off if unattended.
Accordingly, there is a need for an improved pressure washer and a method of switching the motor on and off which prevents damage to the pressure washer caused by full pressure “on” starts.
There is a further need for an improved pressure washer and a method of switching the motor on and off which prevents the pressure washer from cycling on and off due to leaks in the pressure washer.
The present invention relates to a pressure washer having an inlet and an outlet, and a pump assembly in fluid communication with the inlet and the outlet. The pressure washer has a motor which drives a pump assembly. A flow switch is disposed upstream of the pump assembly, and is electrically connected to the motor. Configured to be extended with a biasing structure towards the inlet, an axially displaceable flow plunger seals the pump assembly from fluid communication with the inlet. The flow plunger is also configured to be retracted when a fluid force of a fluid from the inlet overcomes the bias of the biasing structure. When the flow plunger is retracted, the flow plunger automatically turns the pressure washer motor on.
Another aspect of the present invention relates to a soft start system for a pressure washer having an inlet and an outlet, and a pump assembly in fluid communication with the inlet and the outlet. The pressure washer has a motor which drives a pump assembly. A flow switch is disposed upstream of the pump assembly, is electrically connected to the motor, and has a circuit configured to be opened or closed. At least two contacts are disposed on the circuit and are configured to displace and electrically connect in the presence of a magnetic field to close the circuit. Further, at least one magnet is disposed in the switch and moveable with respect to the contacts. Configured to be extended with a biasing structure towards the inlet, an axially displaceable flow plunger seals the pump assembly from fluid communication with the inlet. The flow plunger is also configured to be retracted when a fluid force of a fluid from the inlet overcomes the bias of the biasing structure. When the flow plunger is retracted, the flow plunger automatically turns the pressure washer motor on and drives the pump assembly to deliver fluid under pressure through the outlet.
Another aspect of the present invention is a flow switch for a pressure washer electrically connected to a motor and located in an inlet conduit. The flow switch is located downstream of an inlet and upstream of a pump assembly, and automatically turns the motor on. The flow switch includes an axially displaceable flow plunger configured to be extended and retracted within the inlet conduit under a biasing force. When the flow plunger is extended under the biasing force, the inlet is sealed off from fluid communication with the pump assembly, and when the flow plunger is retracted by fluid force overcoming the biasing force, the inlet is in fluid communication with the pump assembly. The retraction of the flow plunger automatically turns the motor on.
Additionally, the present invention relates to a pressure washer having an inlet and an outlet, an inlet conduit in fluid communication with the inlet, and a pump assembly in fluid communication with the inlet and the outlet. The pressure washer has a motor which drives the pump assembly. A flow switch is disposed in the inlet conduit, and is electrically connected to the motor. The flow control switch includes a reed switch having a circuit configured to be closed when a fluid force is exerted on the switch and opened in the absence of the fluid force. When the circuit is closed, the motor is automatically turned on and when the circuit is opened, the motor is automatically turned off.
Referring to
Referring now to
Between the pump assembly 16 and the fluid inlet 12 is an inlet conduit 32, including a first conduit 34 and a second conduit 36, which define a first passage 38 and a second passage 40, respectively. Both the first conduit 34 and the second conduit 36 are preferably generally cylindrical. Forming a generally “T”-shape, the first passage 38 is the top of the “T” and extends from the fluid inlet 12, while the second passage 40 is the leg of the “T” and is in fluid communication with and is generally perpendicular to the first passage. The second passage 40 is preferably connected to the pump assembly 16 with fasteners such as bolts 42 so that the pump assembly is in fluid communication with the inlet 12.
A flow switch 44 including a flow plunger 46 and a contact portion 48 (
The flow plunger 46 has an axial length which is preferably greater than the diameter of the second passage 40. When the flow plunger 46 is extended, the lip 62 of the flow plunger 46 seals an inlet side 64 of the first passage 38 from the second passage 40 to prevent the fluid communication between the inlet 12 and the second passage 40. Extension of the flow plunger 46 also prevents fluid communication between the inlet 12 and the pump assembly 16. The second passage 40, however, is in fluid communication with the switch side 50 of the first passage 38.
On the switch side 50 of the first passage 38, an externally threaded fitting 66 having a generally cylindrical shape has an interior end 68 and an exterior end 70. The interior end 68 is mated into the first passage 38 to seal the first conduit 34 from fluid flow out through the switch side 50, while the exterior end 70 is outside of the first conduit 34. An additional seal, such as an 0-ring 72, is preferably disposed at the junction of the interior end 68 of the fitting 66 with an end 74 of the first conduit 34 opposite the inlet 12. The cylindrical shape of the fitting 66 is coaxial with the first conduit 34, and has an inner diameter sufficient to allow the fitting to circumscribe other parts of the switch 44. At the interior end 68, the fitting 66 preferably has a relatively small inner diameter, while at the exterior end 70, the fitting preferably has a relatively large inner diameter, as will be described with more particularity later.
Referring back to
At the free end 78 of the shaft 76, a fluid foil 80 is preferably disposed which controls the direction of fluid flow around the elongated shaft and tempers any fluid turbulence in the inlet conduit 32. Having a generally cylindrical shape, the fluid foil 80 gradually increases in radius until it is coextensive with the shaft 76. The shaft 76 preferably has an outer diameter about one-third the inner diameter of the first passage 38, although other configurations are contemplated.
A biasing structure 82 such as a compression spring is seated, or alternatively attached, at the interior end 68 of the fitting 66 and is disposed in a cavity 84 formed between the threaded portion of the fitting 66 and the elongated shaft 76. The extending end of the biasing structure 82 abuts, or alternatively is attached, to the flow plunger 46. Providing an outwardly biasing force, the spring 82 biases the flow plunger 46 axially away from the fixed fitting 66 and in the direction of the inlet 12 to seal the pump assembly 16 from fluid communication with the inlet.
Along the shaft 76 at the inlet side 64 of the first conduit 34, a preferably ring-shaped clip 86 (
When the flow plunger 46 is retracted in response to flow through the inlet 12, i.e. when the fluid pressure against the flow plunger overcomes the bias of the spring 82, the flow plunger displaces relative to the first passage 38 of the inlet conduit 32 away from the inlet 12, and further, displaces relative to the shaft 76. The flow plunger 46 also displaces relative to the second passage 40, opening the path for fluid communication between the first passage 38 and the second passage 40 to deliver fluid from the inlet 12 to the pump assembly 16.
Having a generally tubular shape that is axially aligned with and located in the inlet conduit 32, the elongated shaft 76 defines a chamber 88 within which the contact portion 48 of the switch 44 is disposed. In the preferred embodiment, the contact portion 48 of the switch 44 and the flow plunger 46 are axially displaceable relative to one another.
The contact portion 48 of the switch 44 preferably includes a reed switch 89 having an electrical circuit 90 configured to be opened or closed, as is known to one skilled in the art. The contact portion 48 of the switch 44 has bridging components including a first contact 94 and a second contact 96 which are electrically connected by a flow path connector 98. A vacuum tube 97 preferably encapsulates the first and second contacts 94, 96 to protect the reed switch 89 from contamination.
The first contact 94 is rigidly supported at one end 100 by a switch housing 102, which is introduced and seated in the fitting 66 from the exterior end 70 of the fitting. While seated in the fitting 66, the first contact 94 and the switch housing 102 are generally coaxial with the fitting, the shaft 76 and the first passage 38. A free end 104 of the first contact 94 extends into the chamber 88.
The second contact 96 has a fixed end 106 connected to an inside wall 108 of the shaft 76 and a free end 110 extends into the chamber 88 in the generally opposite direction of the first contact 94. In a first position, the contacts 94, 96 are generally parallel in alignment and opposed with respect to each other, and are further generally parallel to the axis of the first passage 38. The contacts 94, 96 are preferably made of a suitable material, or plurality of materials, that will displace in the presence of a magnetic field.
Another component of the switch 44 is at least one magnet 112 operatively coupled to the flow plunger 46. In the preferred embodiment, a plurality of magnets 112 are disposed in a symmetrical arrangement within the cylindrical housing 52 of the flow plunger 46. Preferably, the magnets 112 are axially arrayed about the axis of the flow plunger 46 to provide a predetermined magnetic field around the contacts 94, 96. In an alternate embodiment, a single cylindrical magnet 112 generally circumscribes the elongate shaft 76, however, any configuration of magnets 112 is contemplated that results in the desired magnetic field required for operation of the switch 44.
In the preferred embodiment, the magnets 112 are inserted into the flow plunger 46 from an opening 114 on a trailing end 116 of the housing 52 such that the magnets are located between the inner radial wall 54 and the outer peripheral wall 56. The opening 114 is sealed with a cap 118 to prevent displacement of the magnets 112 relative to the flow plunger 46. However, other methods of attaching the magnets 112 to the flow plunger 46 are contemplated. In an alternate embodiment, the magnets 112 are operatively displaced with respect to the contacts 94, 96 without being attached to the flow plunger 46. Further, it should be appreciated that the materials used for the housing 52, the conduits 34, 36 or any other part of the switch 44 should not interfere with the influence of the magnets 112 on the contacts 94, 96.
For actuating the automatic switching of the motor 30, each contact 94, 96 is configured to be displaced towards the other in the presence of a predetermined magnetic field. When the flow plunger 46 is retracted, the magnets 112 are displaced towards the contact portion 48 such that the magnets generally circumscribe the shaft 76 at the location of the contacts 94, 96. The predetermined magnetic field displaces the first and the second contacts 94, 96 toward each other until the electrical circuit is closed, preferably by physical contact of the first and second contacts 94, 96. When the electrical circuit is closed, and if power is being provided to the motor 30 electrically (or alternately, or if combustion fuel is provided), the motor is automatically turned on to activate the pump assembly 16.
Alternatively, it is contemplated that the contacts 94, 96 can be configured to be displaced towards each other without the presence of a magnetic field, or that some other switch components may be employed for use with a flow plunger configuration.
A control wire 120 preferably extends from the switch 44, preferably from the first contact 94, through the shaft 76 towards the switch side 50 of the first conduit 34. The wire 120 is preferably generally axially aligned with the first passage 38 and circumscribed by the switch housing 102, however other configurations are contemplated. Extending out from the switch housing 102, the control wire 120 is preferably connected to the motor 30 such that when the circuit closes in the switch 44, the current travels to the motor and the motor automatically turns on to actuate the pump assembly 16. The circuit closes when the flow plunger 46 is retracted due to the fluid force of the fluid 30 in the inlet conduit 32 overcoming the biasing of the biasing structure 82.
Thus, if the trigger 28 is depressed and there is power to the motor 30, the motor turns on preferably almost immediately, or after a slight delay, after the fluid 20 enters the inlet 12 so that pumping does not occur without the presence of fluid in the pump assembly 16. In other words, when the trigger 28 is first squeezed it allows low pressure fluid to flow through the system which causes the flow switch 44 to turn the motor 30 on. This causes the pressure to rise to about 1200 to 1500 psi in approximately 0.5 seconds. Also, since the switch 44 detects the presence of flow, or a certain amount of flow, the pump assembly 16 can be started “soft” at a lower pressure of preferably about 40 psi, as compared to around 1600 psi in conventional pressure washers. When the motor 30 is automatically turned on, the pressure of the fluid 20 at the outlet 14 is initially relatively low and increases in pressure to a predetermined pressure.
The switch 44 automatically turns the motor 30 of the pressure washer 10 off under three conditions. The first condition is when the trigger 30 on the spray gun 22 is released which results in zero fluid flowing through the outlet 14, which in turn results in zero fluid through the system and a pressure build-up in the pressure washer 10. Since the flow plunger 46 is retracted and the second conduit 36 is in fluid communication with the first conduit 34 behind the flow plunger, the pressure behind the flow plunger (in combination with the spring force of the flow plunger) counters the force of the fluid 20 at the inlet 12. Thus, the flow plunger 46 is pushed from a retracted position by the back pressure in the pressure washer 10 to an extended position. When this occurs, the circuit in the switch 44 is opened and the current to the motor 30 is cut. To resume operation of the pressure washer 10, the trigger 28 in the spray gun 22 is squeezed, which alleviates the back pressure downstream of the flow plunger 46, which retracts the flow plunger to permit fluid communication between the inlet 12 and the pump assembly 16, and which allows current to flow to the motor 30.
The second condition when the motor 30 is turned off (or remains off) is when no fluid 20, or a negligible amount of fluid insufficient to counter the bias of the biasing structure 82, is flowing through the inlet 12. The amount of flow required to retract the flow plunger 46 is preferably about 1.6 to 1.75 gallons per minute, although this amount can vary depending on the strength of the biasing structure 82. The third condition is when the motor 30 is manually shut-off directly at the motor housing.
Although the flow switch 44 of the present invention obviates the need for a bypass system to recirculate fluid to prevent overheating of component parts, it is preferably that a bypass system is incorporated, as is known in the art.
While specific embodiments of the present electrical control for pressurized flow device have been shown and described, it will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing form the invention is its broader aspects and as set forth in the following claims.
