Method and apparatus for controlling the flow of cleaning liquid through a high-pressure cleaner

Abstract: In a method and an apparatus for controlling the flow of cleaning liquid in a high-pressure cleaner and of the kind comprising the formation of a primary flow path for the cleaning liquid to parts of the high-pressure cleaner comprising a) an inlet conduit (1) for cleaning liquid at a relatively low pressure (P 1 ), a motor-pump unit (6, 2), the suction side of which is connected to the inlet conduit (1), and the pressure side (8) of which, in which there is a pressure (P 2 ), is connected to the nozzle inlet part of an injector (9), the outlet of which is connected to a cleaning gun (11) having means (12) for varying the amount of cleaning liquid being ejected, and b) an automatic control unit (20) for controlling the cleaning liquid flowing through and comprising b1) a housing (17) with an internal cylindrical chamber, in which b2) a spring-loaded (28) piston (43) with end surfaces having differing effective surface areas is supported sealingly and slidingly and thus dividing the chamber into three part-chambers (23, 24, 25), of which the first (23) is connected to the suction inlet (37) of the injector (9) via a pressure-control conduit (15), in which there is a pressure (P 3 ), and the second chamber (24) is connected to the pressure side (8) of the pump (2) via a pressure-control conduit (14), and the third chamber (25) is connected to the inlet conduit (1) via a pressure-control connection (13, 26), as well as b3) a switching rod (35) connected to the piston (43) and by the latter being movable towards and away from an operating member on a start/stop switch (16) inserted in the power supply circuit of the motor (6) so as to be able to make or break the supply circuit for the motor, whereas the method comprises the following steps c and d: c) during the operation of the high-pressure cleaner a resultant hydraulic force on the piston (43) is created so as to cause the latter to be in a position, in which it acts upon the switching rod (35) for connection and operation of the start/stop switch (16) for the motor-pump unit (6, 2), and d) by changing the adjustment means (12), a relatively large quantity of cleaning liquid per unit time is ejected at a relatively low pressure, so that a relatively low pressure (P 3 ) is created across the suction inlet part (37) of the injector (9), the main new feature is e) that in order to exploit said relatively low pressure (P 3 ) a secondary flow path for the cleaning liquid is established through parts of the high-pressure cleaner by additionally providing flow channels for cleaning liquid in the piston (43) so as to make it possible to supply additional cleaning liquid to the liquid flow of the primary flow path from the secondary flow path extending from the inlet conduit (1) via the pressure-control connection (13, 26), the chambers (25, 23) on each side of the piston (43) and the pressure-control conduit (15) to the injector (9) and the latter's suction inlet (37). The method and the apparatus according to the invention make it possible to achieve a control of the flow of the cleaning liquid being more variable and yet more reliable than has previously been possible.

Description: TECHNICAL FIELD The present invention relates to a known method and a know apparatus of the type set forth in the preambles of claims 1 and 3, respectively. BACKGROUND ART A number of different methods and apparatuses are known, all being variants of the type referred to above. Thus, e.g. methods are known, in which high-pressure cleaners with automatic control valves are used, said control valves having influence on the flow of cleaning liquid and being connected to sensors sensitive to the outlet pressure and/or the volume of flow from the cleaning gun. The adjustment of the desired flow of cleaning liquid takes place on the basis of the changes occurring in the volume of flow and/or the outlet pressure as sensed by the sensors, in that the valves will be controlling the motor-pump unit and set the latter to the desired mode of operation, e.g. full, partial or no flow corresponding to the motor-pump unit being driven without limitation, with partial return flow or full return flow, respectively. In recent years, the development of dedicated control methods for high-pressure cleaners has in this connection especially been concentrated on providing automatic control units, which in addition to influencing the flow of cleaning liquid directly, at the same time in certain operating modes can influence the start/stop function of the motor-pump unit indirectly. These known high-pressure cleaners with automatic control units, of which the latter alone comprise a considerable number of components, are usually provided with other control components, such as e.g. for relieving the pressure in the units during operating modes, in which the flow is interrupted temporarily, for which reason they are partly relatively complicated and hence relatively costly to manufacture, partly not quite as reliable in operation as could be desired, especially considering that it must be possible to operate high-pressure cleaners under optimal safety conditions for the personnel using them. DISCLOSURE OF THE INVENTION It is the object of the present invention to provide a method and an apparatus of the kind referred to initially, capable of being used in connection with control of the flow of cleaning liquid to be ejected in varying quantities from the cleaning gun with a view to adapt the volume of flow of cleaning liquid to each particular cleaning situation for the surface to be cleaned, as simply and safely as possible and at the lowest possible cost, and this object is achieved by means of the steps and features set forth in the characterizing clauses of claims 1 and 4, respectively. Thus, the present invention provides a method of controlling the flow of cleaning liquid to be ejected from the cleaning gun, in a simple manner making it possible to operate the high-pressure cleaner in an advantageous manner with varying and - if so desired - extra large volumes of cleaning liquid being supplied to the primary flow path from a secondary flow path, and - not least - with highly reliable operation and under optimal safety conditions in all modes of operation. Likewise, the present invention provides an apparatus comprising a high-pressure cleaner having a smaller number of components, for this reason being considerably simpler in construction and hence considerably cheaper to manufacture, and in addition more reliable in operation and hence more safe and reliable in use than the previously known high-pressure cleaners. With a high-pressure cleaner, in which the piston in the automatic control unit in an operational mode, in which the ejection of additional cleaning liquid is desired, may be made to function as a valve for the supply of additional cleaning liquid via a secondary flow path to the cleaning liquid already flowing through the primary flow path, it is ensured in a simple manner partly that additional cleaning liquid is not delivered to the cleaning gun except when it is open, partly that it is sufficient to have one single connection to the injector, resulting in a considerably simplified and safer construction, especially because it is possible with advantage to utilize the pressure-control conduits already present. Further, the control function, previously being taken care of in a number of different single units, is now unified in a single unit. Additional advantageous embodiments of the method and the apparatus according to the invention, the effects of which are explained in the following detailed portion of the present description, are set forth in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS In the following detailed portion of the present description, the invention will be explained in more detail with reference to the exemplary embodiment of an apparatus according to the invention shown in the drawings, in which Figure 1 is a diagrammatic view of the high-pressure cleaner, in which the automatic control unit is shown in an operational mode comprising ejection of cleaning liquid at a relatively high pressure, and in which the primary flow path is shown with fully black arrows, and Figure 2 shows the apparatus in the same manner as in Figure 1, but in an operational mode, in which cleaning liquid is ejected at a relatively low pressure, and in which additional cleaning liquid is supplied via the secondary flow path shown with the arrows having black contours only. DESCRIPTION OF THE PREFERRED EMBODIMENT The embodiment of a high-pressure cleaner to be used in accordance with the invention and shown in the drawing comprises an inlet conduit (1), advantageously adapted to be connected to a suitable source of cleaning liquid, normally constituted by water, such as an ordinary water supply, a high-pressure pump (2) comprising an inlet valve (3), a cylinder (4) with associated movable piston (5), a motor (6) and an outlet valve (7), the latter through a first outlet conduit (8) being connected to the nozzle inlet part of an injector (9), the outlet of which is connected through a second outlet conduit (10) to a cleaning gun (11), the latter advantageously comprising adjustment means for adjusting the flow resistance for the outflowing cleaning liquid. Likewise, the embodiment of a high-pressure cleaner shown in the drawing comprises an automatic control unit (20) for regulation and control of the cleaning liquid flowing through, said unit (20) being fluidically connected, partly to the inlet conduit (1) through a first pressure-control conduit (13), partly to an outlet conduit (8) through a second pressure-control conduit (14) as well as to the suction inlet part (37) of the injector (9) through a third pressure-control conduit (15). Electrically, the unit (20) is connected to the power supply circuit of the motor (6) in a manner not shown through a start/stop switch (16). The following explanation will demonstrate in more detail how the automatic control unit (20) co-operates with the remaining components in the high-pressure cleaner. The automatic control unit (20) comprises a generally cylindrical housing (17), which is hollow and likewise having a cylindrical internal shape, one end of which is permanently closed, while the opposite end is closed by a gland (18), the latter advantageously co-operating with a partition (19) and possibly a third chamber (25) constituting the guides for the piston assembly (43). The piston assembly (43) is mainly cylindrical in shape and divides the cavity between the gland (18) and the partition (19) in two spaces or chambers (23, 24), of which the first chamber (23) lies between the internal end wall of the gland (18) and the piston assembly (43), while the second chamber (24) lies between the piston assembly (43) and the partition (19). Through the gland (18) a switching rod (35) extends, advantageously being permanently secured to one end of the piston assembly (43), while its free end is movable towards and away from an operating member on the start/stop switch (16) so as to cause the switch to make or break the power supply circuit to the motor (6). The opposite end of the piston assembly (43) may advantageously comprise a cylindrical part (36) with reduced diameter co-operating with the cylindrical surface of the third chamber (25) in the housing (17). This third chamber (25) may be made to communicate with the second chamber (24) through a relief channel (27). The second chamber (24) accommodates a spring (28) acting upon the piston assembly (43) with a given force in the direction towards the right in the drawing. The piston assembly (43) is advantageously composed of at least two piston parts (22, 21), of which the first piston part (22), situated in the first chamber (23), may have its end facing the gland (18) adapted to form a loose or fixed connection to the switching rod (35). Consquently, the opposite end faces the second piston part (21), and may advantageously be secured by means of a securing device, such as a split pin or the like. Otherwise, the piston assembly (43) may comprise channels for cleaning liquid to flow through, or else the two piston parts (22, 21) may comprise channels allowing cleaning liquid to flow through. The arrangement of a piston assembly (43) composed of two parts (22, 21) makes it easy to manufacture and assemble the piston assembly, and also to dismantle it in connection with repairs and maintenance, and also makes easy and simple to place in position the remaining components associated with the piston. The piston part (21), in the exemplary embodiment shown constituting the relatively largest part of the piston assembly (43), is generally shaped as a hollow cylinder, the outside and inside walls of which both have a stepped configuration comprising three steps of successively decreasing diameter. The end with the largest diameter is placed to embrace part of the first piston part (22). The opposite end, i.e. the cylindrical part (36) with reduced diameter, in which a duct (32) is formed, protrudes into the third chamber (25). Inside the central section of the second piston part (21) a check valve is arranged, in the example shown consisting of a spring (29) and a ball (30), of which the spring (29) abuts against both the internal end surface on the first piston part (22) and against the ball, the latter abutting against a seat in the second piston part (21). In this manner, the spring (29) acts upon the ball (30) with a given force in the direction towards the left in the drawing. The movement of the piston assembly (43) in the cavity in the housing (17) of the control unit (20) may advantageously be defined, partly by the end of the first piston part (22) facing the gland (18), partly by the step surface connecting the end part (36) and the central section of the second piston part (21). As will be evident from e.g. Figure 1, the first chamber (23) is connected to the suction inlet part (37) of the injector (9) through the third pressure-control conduit (15), the second chamber (24) is connected to the first outlet conduit (8), i.e. to the pressure side of the pump (2), via the second pressure-control conduit (14), while the third chamber (25) and the connecting duct (26) are connected to the inlet conduit (1) through the first pressure-control conduit (13). As may be seen on Figure 1, the piston assembly (43) is advantageously constructed in such a manner, that there is a small difference between the effective piston-pressure areas in the first and the second chamber, so that in an operating situation, in which the pressure in the chambers (23, 24) are equal ( P 2 = P 3 ), i.e. when for instance the cleaning gun (11) is made inactive, the piston assembly (43) will move in a given desired direction. In the example shown in the drawing, the piston-pressure area is largest on the part of the piston assembly (43) facing the chamber (23), i.e. in this case the piston will move towards the left in the drawing. As will likewise be understood, the movements towards the left may be counteracted somewhat by the spring (28) acting upon the piston assembly (43) in the opposite direction. When the transition step surface between the end part (36) and the central section abuts against the partition (19), the piston assembly (43) will have carried out a movement causing the switching rod (35) to be no longer in engagement with or pressing against the operating member of the switch (16), i.e. the power supply circuit for the motor (6) is interrupted and the pump (2) stops. During the movement of the piston assembly (43), the relief channel (27) will be connected to the third chamber (25), thus causing a general pressure relief of the whole system in the high-pressure cleaner. The lowering of the pressure is in fact controlled by the spring (28), since the force, with which the spring acts upon the piston assembly (43), decides for how long the relief channel (27) is connected to the pressure-control connection (13, 26) comprising the connecting duct (26) and the first pressure-control conduit (13), in which there is normally a pressure P 1 that is less than P 2 and P 3 , the pressure normally being water-mains pressure, i.e. from 0 to approximately 10 bars. When the force on the spring (28) is substantially equal to or somewhat larger than the resultant hydraulic force on the piston assembly (43), the latter will slowly slide backwards towards the right in the drawing until the relief channel (27) has moved past the seal (34) at the partition (19), after which a position of equilibrium for the piston assembly (43) will be established. Normally, this equilibrium position will be adjusted to occur at a pressure of about 20 bars, but may naturally be selected according to need. The length of the switching rod (35) and the part of movement of the piston assembly (43) to this equilibrium position are attuned to each other in such a manner, that the operating member on the start/stop switch (16) is not actuated, i.e. the power supply circuit for the motor (6) is still interrupted, this meaning that the pump (2) is likewise inoperative. Not until the cleaning gun (11) is actuated again, i.e. when cleaning liquid again can flow through it, the motor (6) and the pump (2) are again set in motion. When the cleaning gun (11) is opened, an immediate lowering of pressure occurs in the first chamber (23) via the third pressure-control conduit (15) and in the second chamber (24) via the second pressure-control conduit (14). Subsequently, the resultant hydraulic force on the piston assembly (43) will make the latter move towards the right in the drawing, i.e. the switching rod (35) is made to engage or press on the operating member of the start/stop switch (16) so that the power supply to the motor (6) is connected and the motor can drive the pump (2). I.e. the high-pressure cleaner will now run in e.g. normal high-pressure operation, with the primary liquid-flow path through the high-pressure cleaner being open to the cleaning liquid and extending from the inlet conduit (1) through the pump (2) and the first outlet conduit (8), the injector (9) and the second outlet conduit (10) to the cleaning gun (11) and the adjustment means (12), consequently at a high pressure and with a relatively small quantity of liquid per unit time out through the outlet nozzle of the cleaning gun (11). Thus, during normal operation, the pressure P 2 will correspond approximately to the output pressure of the pump, normally lying in the interval 80-120 bars, both in the second pressure-control conduit (14) and in the second chamber (24), and a pressure P 3 in the first chamber (23) being less than the pressure P 2 due to the lowering of pressure in the suction inlet (37) of the injector (19) caused by the flow of the cleaning liquid through the latter, hence also in the first chamber (23) via the third pressure-control conduit (15). In the third chamber (25), the connecting duct (26) and the first pressure-control conduit (13), the inlet pressure of the cleaning liquid will reign. Thus, the resultant hydraulic force on the piston assembly (43) will make it remain in the position shown to the right in the drawing. In this normal operating condition, the adjustment means (12) on the cleaning gun (11) for varying the quantity of cleaning liquid to be ejected will be set to a relatively small outflow opening for the cleaning liquid. As mentioned above, it is desirable in many situations to be able to change the operation of the high-pressure cleaner from normal operation at a high pressure to a operating condition, in which the pressure is somewhat lower. This is especially desired in situations requiring flushing or rinsing after an effective cleaning at a high pressure, or if it is desired to soak or soften dirt on the surface to be cleaned before high pressure is applied to the cleaning liquid and consequently to the high-pressure cleaner. In many cases of flushing at a low pressure, the quantity of cleaning liquid is, however, experienced as being insufficient, and for this reason it is desirable to be able to increase the quantity of liquid in a simple manner. By adjusting the outflow adjustment means (12) in a manner to increase the outflow opening for the cleaning liquid, the flow velocity of the cleaning liquid will increase, thus creating a lower pressure in the suction inlet of the injector (9) and hence in the third pressure-control conduit (15) and likewise in the first chamber (23). At the same time, this reduced pressure causes the check valve (29, 30) in the piston assembly (43) to open, thus allowing additional cleaning liquid to flow via the secondary flow path extending from the inlet conduit (1), through the first pressure-control conduit (13), the connecting duct (26) and the third chamber (25), through the inlet duct (32), the check valve (29, 30) and the piston assembly (43), such as through flow ducts (not shown) in the first piston part (22), to the first chamber (23) and from the latter to the cleaning gun (11) via the third pressure-control conduit (15), the injector (9) and the latter's suction inlet (37) as well as the second outlet conduit (10). Thus, a simple and reliable flow passage for additional cleaning liquid has been established in a simple manner by using the pressure-control conduits already described, and trials have shown that with the normal pressure conditions mentioned above, it is possible to increase the quantity of cleaning liquid from e.g. 7 l/min. to 12 l/min. The magnitude of the lower pressure required to open the check valve (29, 30) can be determined by the characteristics of the spring (29), and will also depend on the pressure P 1 of the cleaning liquid reigning in the inlet conduit (1). LIST OF PARTS P 1 pressure P 2 pressure P 3 pressure 1 inlet conduit 2 high-pressure pump 3 inlet valve 4 cylinder 5 piston 6 motor 7 outlet valve 8 first outlet conduit 9 injector 10 second outlet conduit 11 cleaning gun 12 adjustment means 13 first pressure-control conduit 14 second pressure-control conduit 15 third pressure-control conduit 16 start/stop switch 17 housing 18 gland 19 partition 20 automatic control unit 21 second piston part 22 first piston part 23 first chamber 24 second chamber 25 third chamber 26 connecting duct 27 relief channel 28 spring 29 spring 30 ball 31 seal 32 inlet duct 33 channel 34 seal 35 switching rod 36 cylindrical part/end part 37 suction inlet part 43 piston assembly

Claims: Method for controlling the flow of cleaning liquid in a high-pressure cleaner and of the kind comprising the formation of a primary flow path for the cleaning liquid to parts of the high-pressure cleaner comprising a) an inlet conduit (1) for cleaning liquid at a relatively low pressure (P 1 ), a motor-pump unit (6, 2), the suction side of which is connected to the inlet conduit (1), and the pressure side (8) of which, in which there is a pressure (P 2 ), is connected to the nozzle inlet part of an injector (9), the outlet of which is connected to a cleaning gun (11) having means (12) for varying the amount of cleaning liquid being ejected, and b) an automatic control unit (20) for controlling the cleaning liquid flowing through and comprising b1) a housing (17) with an internal cylindrical chamber, in which b2) a spring-loaded (28) piston (43) with end surfaces having differing effective surface areas is supported sealingly and slidingly and thus dividing the chamber into three part-chambers (23, 24, 25), of which the first (23) is connected to the suction inlet (37) of the injector (9) via a pressure-control conduit (15), in which there is a pressure (P 3 ), and the second part-chamber (24) is connected to the pressure side (8) of the pump (2) via a pressure-control conduit (14), and the third part-chamber (25) is connected to the inlet conduit (1) via a pressure-control connection (13, 26), as well as b3) a switching rod (35) connected to the piston (43) and by the latter being movable towards and away from an operating member on a start/stop switch (16) inserted in the power supply circuit of the motor (6) so as to be able to make or break the supply circuit for the motor, whereas the method comprises the following steps c and d: c) during the operation of the high-pressure cleaner a resultant hydraulic force on the piston (43) is created so as to cause the latter to be in a position, in which it acts upon the switching rod (35) for connection and operation of the start/stop switch (16) for the motor-pump unit (6, 2), and d) by changing the adjustment means (12), a relatively large quantity of cleaning liquid per unit time is ejected at a relatively low pressure, so that a relatively low pressure (P 3 ) is created across the suction inlet part (37) of the injector (9), characterized in e) that in order to exploit said relatively low pressure (P 3 ) a secondary flow path for the cleaning liquid is established through parts of the high-pressure cleaner by additionally providing flow channels for cleaning liquid in the piston (43) so as to make it possible to supply additional cleaning liquid to the liquid flow of the primary flow path from the secondary flow path extending from the inlet conduit (1) via the pressure-control connection (13, 26), the part-chambers (25, 23) on each side of the piston (43) and the pressure-control conduit (15) to the injector (9) and the latter's suction inlet (37). Method according to claim 1, characterized in that the flow of additional cleaning liquid in the piston (43) from the inlet (1) to injector (9) occurs by opening a check valve (29, 30) in the piston (43), the opening characteristics of said check valve determining the moment in time and the quantity of the additional supply of cleaning liquid. Apparatus for controlling the flow of cleaning liquid through a high-pressure cleaner and of the type, in which a primary flow path for the cleaning liquid is established through parts of the high-pressure cleaner comprising a) an inlet conduit (1) for cleaning liquid at a relatively low pressure (P 1 ), a motor-pump unit (6, 2), the suction side of which is connected to the inlet conduit (1) and the pressure side (8) of which, in which there is a pressure (P 2 ), is connected to the nozzle inlet part of an injector (9), the outlet part of which is connected to a cleaning gun (11) with adjustment means (12) for varying the amount of cleaning liquid being ejected, as well as b) an automatic control unit (20) for controlling the flow of cleaning liquid and comprising b1) a housing (17) with a cylindrical internal chamber, in which a spring-loaded (28) piston (43) having end surfaces with differing effective surface areas is supported sealingly and slidingly and thus dividing the chamber into three part-chambers (23, 24, 25), of which the first (23) is connected to the suction inlet (37) of the injector (9) via a pressure-control conduit (15), in which there is a pressure (P 3 ), and the second part-chamber (24) is connected to the pressure side (8) of the pump (2) via a pressure-control conduit (14), and the third part-chamber (25), by means of a partition (19) being separated from the second chamber (24) and in which one end (36) of the piston (43) is supported, is connected to the inlet conduit (1) via a pressure-control connection (13, 26), as well as b2) a switching rod (35) connected to the piston (43) and by the latter being movable towards and away from an operating member on a start/stop switch (16) inserted in the power supply circuit of the motor (6) in order to in this manner to be able to make and break the supply circuit for the motor, characterized in c) that the piston (43) comprises at least one through-flow duct so as to allow additional cleaning liquid to be supplied through a secondary flow path extending from the inlet conduit (1) via the pressure-control connection (13, 26), the part-chambers (23, 25) on each side of the piston (43) and the pressure-control conduit (15) to the ejector (9) and the latter's suction inlet (37). Apparatus according to claim 3, characterized in that the flow of additional cleaning liquid through the piston (43) from the inlet (1) to the injector (9) occurs upon opening of a check valve comprising a ball (30) and a spring (29) in the piston (43). Apparatus according to claim 3 or 4, characterized in that the piston (43) consists of two piston parts (21, 22), in which a through-flow duct (32) for the check valve (29, 30) is formed.

Inventors: NIKOLAJSEN MARTIN, NIKOLAJSEN, MARTIN
Applicants: KEW IND AS, KEW INDUSTRI A/S
Application year: 1995
Main classification: B05B1
IPC codes: B08B3