FLOW CONTROL VALVE FOR A PRESSURE WASHER

Abstract: Disclosed is a flow control valve (10) for a pressure washer (11) powered by a prime mover (27), e.g., an electric motor (27a) or an internal combustion engine (27b). The valve (10) has a housing (33) containing a piston assembly (34) and the assembly (34) has a mechanism (96) coupled to it for controlling prime mover power. The piston assembly (34) includes a first piston (39) sealing against the housing (33) and dividing the housing interior into two chambers (35, 37). Such first piston (39) is spring-biased to a first position during periods when no output flow is being demanded from the washer (11). The assembly (34) also has a second piston (59) spring-biased to seal against the first piston (39) during periods of no flow. When flow is demanded by opening the nozzle (19), the pressure in the second chamber (37) diminishes. And when the difference between the pressure in the second chamber (37) and that in the first chamber (35) exceeds a predetermined value, the assembly (34) shifts to a second position, causing the mechanism (96) to actuate the prime mover (27).

Description: Title: FLOW CONTROL VALVE FOR A PRESSURE WASHER Field of the Invention This invention relates generally to power plants and, more particularly, to pressure washers supplying high pressure liquid, e.g., water, from a hose. Background of the Invention Pressure washers are in common use and find utility for washing truck bodies, walls of buildings, sidewalks, removing paint and stain and a host of other applications where high pressure liquid such as water is applied to a surface. A known type of pressure washer includes an electric motor driving a water pump, the source of water for which may be a garden hose. A high pressure hose extends from the pump to a hand-operated nozzle manipulated by the user to start and stop the flow of water . Water-type pressure washers are often configured in one of two arrangements. In the first, a bypass valve recirculates water to the pump inlet when the user closes the nozzle to stop the flow of water. A feature of this arrangement is that the user, who may be some distance from the washer, need not return to the washer to shut off the motor. But as a consequence, the electric motor runs continuously and electrical power is wasted during periods when no water is being demanded. In addition, wear on the pump and motor is increased, thus reducing service life. And the washer construction is made more complex in that additional components are needed to control heat buildup due to water recirculating at elevated pressure. And there is another disadvantage of the arrangement described above. If the user neglects to connect a source of water to the pressure washer while the electric motor is running, the pump operates dry and serious damage can result . Another known arrangement addresses the matters of wasted electrical power and increased wear by extending a two-wire electrical cable to a motor on-off switch adjacent to the nozzle. When the nozzle is closed to shut off the flow of water, the switch is actuated to turn off the motor. Disadvantages of this arrangement include the need to run the electrical cable to the nozzle and the fact that an electrical switch (probably operating at line voltage) is adjacent to such nozzle. An improved pressure washer flow control valve which addresses and resolves disadvantages of known arrangements and which is useful with washers having engine or electric motor prime movers would be an important advance in the art. Objects of the Invention It is an object of the invention to provide a flow control valve which overcomes some of the problems and shortcomings of known pressure washer configurations. Another object of the invention is to provide a flow control valve which controls a pressure washer to conserve electrical power. Another object of the invention is to provide a flow control valve which avoids motor and pump wear during periods when no water is being demanded from the washer. Yet another object of the invention is to provide a flow control valve which prevents the pressure washer pump from running dry. Another object of the invention is to provide a flow control valve which helps avoid pump overheating. Still another object of the invention is to provide a flow control valve which obviates the need to run electrical cable to the nozzle of the pressure washer. Another object of the invention is to provide a flow control valve which is useful with pressure washers having engines or electric motors as prime movers . How these and other objects are accomplished will become apparent from the following descriptions and from the drawings. Summary of the Invention The invention involves a valve for controlling the flow of water from a prime-mover-powered pressure washer. The valve includes a generally cylindrical housing in which is mounted a piston assembly having coacting first and second pistons. The assembly has a mechanism, e.g., a rod and switch, coupled to it for controlling prime mover power . More specifically, the first piston is mounted for sliding movement in the housing, seals against such housing and divides the housing interior into first and second pressure chambers. There is a flow passage extending between the pressure chambers. The first piston is spring biased to a first position and moves between the first position and a second position. The piston assembly also has a second piston, the head of which fits in a cavity in the first piston. The second piston is also spring biased to a first position and in such position, the head seals against a sealing surface of the cavity. When no flow is being demanded from the pressure washer, the assembly is at a standby position and in such standy position, the first and second pistons are in their respective first positions. In the standby position, the mechanism prevents prime mover power from being transferred to the pressure washer pump. Several arrangements involving different types of prime movers and control thereof are described in the detailed description. The pressure in the second chamber relative to the pressure in the first chamber is a function of whether or not flow is being demanded from the pressure washer. When no flow is needed, the pressure in the second chamber is substantially equal to the pressure in the first chamber. But when flow is being demanded, the pressure in the second chamber is less than that in the first chamber by at least some predetermined value. Stated in other words, the assembly is in its first or standby position when the difference between the pressure in the second chamber and the pressure in the first chamber is less than a predetermined value. And the assembly is in its second or operating position when the difference between the pressure in the second chamber and the pressure in the first chamber is greater than a predetermined value. When the assembly is in the operating position, the head of the second piston is spaced from the sealing surface of the first piston. In another aspect of the invention, the mechanism includes an actuator device, e.g., a rod, extending through the housing and a control device coacting with the actuator device for controlling power to the washer. If the prime mover is an electric motor, the control device is preferably an electric switch for starting and stopping the motor. Or the electric switch may control a clutch interposed between the pump and any type of prime mover. And another approach involves using a control device to regulate the setting of the governor of an internal combustion engine. A new method for controlling power transmitted from a prime mover to a pressure washer pump includes the steps of providing a flow control valve having a housing and a high pressure hose connected to the housing and terminated in a nozzle having open and closed positions. A piston assembly divides the housing interior into first and second pressure chambers and the hose is in flow communication with the second chamber. A mechanism is coupled to the assembly and has operating and standby positions for controlling prime mover power. The mechanism is retained in the standby position when the difference between the pressure in the second chamber and the pressure in the first chamber is less than a predetermined value. And the mechanism is moved to the operating position when the difference between the pressure in the second chamber and the pressure in the first chamber is greater than a predetermined value . In a more specific aspect of the method, the retaining step includes maintaining the user-operated nozzle in its closed position. And the moving step includes manipulating the nozzle to the open position. In another aspect of the method, the prime mover is an electric motor and the moving step includes applying electrical power to the motor. In the alternative, the moving step includes engaging a clutch interposed between the prime mover and the pump or includes resetting the governor on the prime mover. Other details of the invention are set forth in the following detailed description and in the drawings. Brief Description of the Drawings FIGURE 1 is a perspective view of an exemplary pressure washer. Parts are broken away. FIGURE 2 is a representative side elevation view of the pressure washer hand-grip piece with the on/off lever shown in the "off" position. Parts are broken away. FIGURE 3 is a representative side elevation view of the pressure washer hand-grip piece with the on/off lever shown in the "on" position. Parts are broken away. FIGURE 4 is a symbolic representation of a prime mover embodied as an electric motor and driving a pressure washer pump. FIGURE 5 is a symbolic representation of a prime mover embodied as a governor-equipped internal combustion engine driving a pressure washer pump. FIGURE 6 is a symbolic representation of a prime mover embodied driving a pressure washer pump through a clutch which may be engaged or disengaged. FIGURE 7 is a cross-sectional view of the new flow control valve in its prime-mover-standby position. FIGURE 8 is a cross-sectional view of the new flow control valve in its prime-mover-operating position. Detailed Descriptions of Preferred Embodiments Before describing the new flow control valve 10 and method, it will be helpful to have an understanding of some of the features of a pressure washer 11. Referring to FIGURES 1, 2 and 3, a pressure washer 11 has a high pressure water pump 13, a source of "input water" for which may be a garden hose. Water is delivered from a pump outlet 15 to a high pressure hose 17 terminated by a wand-like nozzle 19, a specific embodiment of which includes a "gun-like" user-controlled handgrip piece 21 with lever 23. (As used in this specification, the term "nozzle" means any device or mechanism manipulated by the user, e.g., the handgrip piece 21 and lever 23, to turn water flow on and off . ) Unless water is being demanded, the nozzle 19 is normally closed. When the user needs high pressure water from the nozzle 19, s/he manipulates the nozzle 19 to its open position and water is expelled from the outlet piece 25 to the atmosphere. The pressure washer 11 also has a prime mover 27 such as an electric motor 27a or an internal combustion engine 27b. FIGURE 4 shows the pump 13 driven by a prime mover 27 embodied as an electric motor 27a while FIGURE 5 shows such pump 13 driven by a prime mover 27 embodied as an internal combustion engine 27b. In the arrangement of FIGURE 5, the engine 27b has a governor 29 and in a specific aspect of the invention described below, the new valve 10 is used to establish the goernor setting. FIGURE 6 shows another arrangement involving a prime mover 27 and a pump 13 with a clutch 31 interposed between them. In another specific aspect of the invention, the new valve 10 is used to engage or disengage the clutch 31. When considering the following specification, the convenience of operation afforded by the new valve 10 will be better appreciated by recognizing that the hose 17 may be quite long. That is, there may be a substantial distance between the nozzle 19 and the prime mover 27. Referring next to FIGURES 7 and 8, details of the new valve 10 and of its operation will now be set forth. The valve 10 has a generally cylindrical housing 33, the interior of which is divided by a piston assembly 34 into a first chamber 35 and a second chamber 37. Such assembly 34 includes a first piston 39 having a rim portion 41, the perimeter of which is in sliding engagement with the interior wall 43. Sealing between the rim portion 41 and the wall 43 is effected by a wiper seal 45. The valve 10 has an inlet port 49 in flow communication with the first chamber 35. Understanding the operation of the valve 10 (which is set out in detail below) will be aided by appreciating two aspects of the valve 10 and the pressure washer 11. One is that if a garden hose is attached to the pump 13 and the sill cock is turned on but the prime mover 27 is inoperative, water flows to the first chamber 35 and the pressure in such chamber 35 is substantially equal to tap pressure, e.g., 40 - 60 psi . On the other hand, when the prime mover 27 starts to drive the pump 13, a check valve "stops off" the low-pressure flow path and the pressure in the chamber 35 rises to, nominally, pump outlet pressure, e.g., over 1000 psi. The first piston 39 also has a flow passage 51 extending between the chambers 35, 37. Such passage 51 comprises a cross-bore 53 and an axial bore 55 in flow communication with one another. When, as shown in FIGURE 8, the head 57 of the second piston 59 is away from the sealing surface 63 in the cavity 65 of the first piston 39, water is permitted to flow through the second piston 59, the mixing venturi 67 (if the washer 11 is so equipped) , and the outlet 69 to the hose 17. (It is to be appreciated that the piston 39 is shown to include a separate body 71 and rim portion 41 only for purposes related to manufacturing. Once assembled, the body 71 and rim portion 41 are fixed with respect to one another. ) The first piston 39 also has a guide 73 which supports a first compression spring 75. One end of the spring 75 bears against the housing wall 43 and the other spring end bears against a shoulder 77 on the piston 39. In the absence of a countervailing force, the spring 75 urges the first piston 39 to the first position shown in FIGURE 7. The guide 73 has at least one aperture 79 providing flow communication between the second chamber 37 and the cavity 65 of the first piston 39. The first piston 39 also has an actuator device 81 attached to the piston 39 and extending through an opening in a piston stop 83 and through another opening in a piston cap 85. The stop 83 seals against the wall 43 and once assembled there, does not move. Similarly, the cap 85 is fixed in place during assembly and does not move during operation of the valve 10. The manner in which the actuator device 81 is used to control prime mover power to the pump 13 is explained below. Referring further to FIGURES 7 and 8, the piston assembly 34 also includes the second piston 59 having a hemispherical head 57, a guide rim 87 and a stem 89. The head 57 is urged against the surface 63 by the second spring 90. When the second piston 59 moves relative to the first piston 39, the guide rim 87 slides along the surface of the cavity 65. A second point of support for the piston 59 is provided by a guide lip 91 formed on the first piston 39. The diameter of the opening defined by the lip 91 and the diameter of the stem 89 are cooperatively sized for sliding clearance therebetween. The second piston 59 has a flow path which includes a cross hole 93 and an axial hole 95 which are in flow communication with one another. It is to be noted that when the second piston 59 is in its first position as shown, the piston head 57 seals against the surface 63, preventing water flow from the first chamber 35 through the flow passage 51 to the second chamber 37 or beyond. And when the second piston 59 is in the second position as shown in FIGURE 8, the head 57 is away from the surface 63 and water is free to flow through the passage 51, through the path defined by holes 93, 95 and beyond. Referring to FIGURES 4 through 8, the washer 11 has a mechanism 96 comprising control device 97 coacting with the actuator device 81 for controlling power to the washer 11. If the prime mover 27 is an electric motor 27a, the control device 97 is preferably an electric switch 97a for starting and stopping the motor 27a. Or the electric switch 97a may control a clutch 31 as shown in FIGURE 6. And another approach involves using a control device 97 such as a switch 97a to regulate the setting of the governor 29 of an internal combustion engine 27b as shown in FIGURE 5. In a specific embodiment, the electric switch 97a is normally closed and when the prime mover 27 is an electric motor 27a, the switch 97a is in series with the motor 27b as shown in FIGURE 4 or is in series with the coil of a relay, the contacts of which control the motor 27b. Operation For the first part of this description, it is assumed that the pressure washer 11 has never been used and that neither the chambers 35, 37 nor the outlet 69 or hose 17 contain any water. It is also assumed that the chambers 35, 37 outlet 69 and hose 17 are at ambient air pressure, i.e., 0 psi gauge, and that the nozzle 19 and its piece 21 are closed as shown in FIGURE 2 wherein the lever 23 is in the "off" position. Under those conditions, the springs 75, 90 bias the pistons 39, 59 leftwardly (as viewed in FIGURES 7 and 8), the actuating device 81 depresses the button 99 of the normally-closed switch 97a, thereby opening it. Therefore, the valve 10 and mechanism 96 are in the standby position and the prime mover 27 is unable to provide driving power to the pump 13. When a garden hose is connected to the pump 13 prior to driving the pump 13 with a prime mover 27, the first chamber 35 fills with water at, e.g., 60 psi. Since the second chamber 37 is then nominally at zero psi, the force of the springs 75, 90 is overcome, both pistons 39, 59 move rightwardly, the device 81 moves away from the switch 97a and the mechanism 96 thus assumes its operating position. The switch 97a is thereby actuated to cause the prime mover 27 to provide driving power to the pump 13. The pump 13 thereupon fills both chambers 35, 37, the outlet 69 and the hose 17 with water at high pressure. (By a known construction, the nozzle 19 permits air in the hose 17 to vent to atmosphere but does not permit water to pass therethrough unless the nozzle 19 is intentionally opened.) With the pressure in both chambers 35, 37 now substantially equalized at some high pressure (i.e., well above tap water pressure), the springs 75, 90 urge the pistons 39, 59 leftwardly to their first positions and the valve 10 and the mechanism 96 assume the standby position. (This filling cycle during which the prime mover 27 drives the pump 13 is very brief and may last a few seconds or less . ) It is now assumed that the user wishes to obtain high pressure water from the nozzle 19. The nozzle 19 is opened by moving the lever 23 to the "on" position as shown in FIGURE 3, thereby causing the pressure in the hose 17, the outlet 69 and the second chamber 37 to diminish. When the difference in pressure between that in the second chamber 37 and that in the first chamber 35 exceeds a predetermined value, e.g., 75 - 100 psi, the pistons 39, 59 move to their second positions as shown in FIGURE 8 and the valve 10 and mechanism 96 move to the operating position. When that occurs, the actuating device 81 moves rightwardly away from the control device 97 and the prime mover 27 is caused to power the pump 13. High pressure water flows through the bore 53 and the bore 55, around the head 57 and through the hole 93 and the hole 95 to the outlet 69 and to the nozzle 19 until the nozzle 19 is again shut off. From the foregoing, it is now apparent that prime mover power to the pump 13 may be controlled by only manipulating the nozzle 19. In other words, the user need not walk from the nozzle 19 to the pressure washer 11 to turn off or otherwise disable the prime mover 27. Steps and time are saved. And it is also apparent that if the source of water from the exemplary garden hose fails, the pump 13 no longer provides high pressure water to the inlet port 49. Irrespective of whether the nozzle 19 is open or closed, pressures in the chambers 35, 37 soon become about equal to one another, the pistons 39, 59 are spring biased to their first positions and the prime mover 27 is disabled. Thus, the pump 13 is prevented from running dry. The new valve 10 and pump 13 may be plumbed to one another using hoses or the like. However, in a highly preferred embodiment, the valve 10 is an integral part of the pump 13 as indicated in FIGURES 4, 5 and 6. As used in this specification, terms such as "leftwardly" and "rightwardly" are used solely for purposes of explaining the drawings. Such terms are not intended to be limiting. While the principles of the invention have been shown and described in connection with a few preferred embodiments, it is to be understood clearly that such embodiments are by way of example and are not limiting. For example, the electric switch 97a is described as being normally closed and held open when the valve 10 is in the standby position. Persons of ordinary skill in the art will immediately recognize how to configure a circuit using a normally-open switch. Such variations are clearly within the scope of the invention.

Claims: CLAIMS What is claimed is: 1. A flow control valve for a pressure washer powered by a prime mover, the valve including: -a housing; -a piston assembly in the housing and having a mechanism coupled thereto for controlling prime mover power; and wherein the piston assembly includes : -a first piston spring-biased to a first position and sealing against the housing; and -a second piston spring-biased to seal against the first piston when the first piston is in the first position. 2. The valve of claim 1 wherein : -the housing has a pressure chamber; -the second piston is in a cavity in the first piston; and -the first piston includes a flow passage extending between the pressure chamber and the cavity. 3. The valve of claim 2 wherein: -the first piston includes a sealing surface; and -the second piston includes a head sealed against the surface when the first piston is in the first position. 4. The valve of claim 1 wherein: -the piston assembly divides the housing interior into first and second pressure chambers; -the assembly is in the first position when the difference between the pressure in the second chamber and the pressure in the first chamber is less than a predetermined value. 5. The valve of claim 1 wherein: -the piston assembly divides the housing interior into first and second pressure chambers; -the assembly is in a second position when the difference between the pressure in the second chamber and the pressure in the first chamber is greater than a predetermined value . 6. The valve of claim 5 wherein: -the first piston has a sealing surface; and -the second piston has a head spaced from the sealing surface when the assembly is in the second position. 7. The valve of claim 1 wherein the mechanism includes : -an actuator device extending through the housing; and -a control device coacting with the actuator device for controlling power to the washer. 8. A method for controlling power transmitted from a prime mover to a pressure washer pump and including the steps of : -providing a flow control valve having a housing, a piston assembly dividing the housing interior into first and second pressure chambers, a hose in flow communication with the second chamber and terminated by a nozzle, and a mechanism coupled to the assembly and having operating and standby positions for controlling prime mover power; -retaining the mechanism in the standby position when the difference between the pressure in the second chamber and the pressure in the first chamber is less than a predetermined value; and -moving the mechanism to the operating position when the difference between the pressure in the second chamber and the pressure in the first chamber is greater than a predetermined value . 9. The method of claim 8 wherein the nozzle has open and closed positions and the retaining step includes maintaining the nozzle in its closed position. 10. The method of claim 8 wherein the nozzle has open and closed positions, and: -the moving step includes manipulating the nozzle to the open position.

Inventors: HOENISCH HERB, KERN ROBERT D, RUEHLOW GERALD C, SODEMANN WES, YANG FRED, HOENISCH, HERB, KERN, ROBERT, D., RUEHLOW, GERALD, C., SODEMANN, WES, YANG, FRED
Applicants: GENERAC CORP, GENERAC CORPORATION
Application year: 1997
Main classification: F16K
IPC codes: F04B49