WO1988001912A1

WO1988001912A1 - High pressure liquid delivering device especially for cleaning

Info

Publication number: WO1988001912A1
Application number: PCT/DK1986/000104
Authority: WO
Inventors: Jo^/rgen SCHMIDT
Original assignee: Westergaard, Knud, Erik
Priority date: 1986-09-16
Filing date: 1986-09-16
Publication date: 1988-03-24

Abstract

In an apparatus for delivering liquid at high pressures, especially for cleaning purposes, with a pump (1), a flow-controlled by-pass valve (2) and injector means (9) for controlling the by-pass valve (2) and for aspirating concentrated cleaning liquid to be mixed with carrier liquid from an inlet (6) for the latter, the novel feature is that the injector means (9) comprises separate injectors (9a, 9b) for the two functions mentioned. With this arrangement, the risk of aggressive cleaning liquid damaging the control member (10) for the by-pass valve (2) is eliminated or considerably reduced, as the path from the inlet (7) for the cleaning liquid to the control member (10) goes through both injectors (9a, 9b), while in previous arrangements there was a direct path, only one single common injector having been used.

Description

High pressure liquid delivering device especially for cleaning.

TECHNICAL FIELD

The present invention relates to an apparatus of the kind set forth in the preamble of claim 1.

BACKGROUND ART

Apparatus of this kind are known, e.g. from the specifi¬ cation of the West German Patent No. 3.248.622. In the previously known apparatus of this kind, one common in- jector is used as injector means to perform the functions set forth in items f_l and f_2 of the preamble of claim 1. This entails a direct connection between the pressure- sensitive member controlling the by-pass valve and the non-return valve, through which the secondary liquid is supplied to the apparatus for mixing with the primary liquid. When using the apparatus for cleaning purposes, the secondary liquid is usually a concentrated solution having strongly aggressive and/or corrosive properties, and the direct connection mentioned carries with it a definite risk of the secondary liquid in more or less diluted or concentrated form coming into contact with the pressure-sensitive member controlling the by-pass valve. Due to the aggressive and/or corrosive nature of the secondary liquid, this may cause damage to the pres- sure-sensitive member. and/or associated gaskets, O-rings or the like, eventually rendering the pressure-sensitive member inoperative, either in a position where the by- -pass valve is permanently open preventing the pump from delivering at high pressure, or in a considerably more dangerous position, in which the by-pass valve is per¬ manently closed and unable to protect the pump from be¬ ing overheated when operating against a closed outlet.

DISCLOSURE OF THE INVENTION

It is the object of the present invention to eliminate or at least mitigate the inconvenience mentioned above, and this object is attained by arranging the apparatus in the manner set forth in the characterizing clause of claim 1. With this arrangement with separate injectors, the path from the secondary inlet to the pressure-sen¬ sitive member is considerably more tortuous than in the previous arrangement with a common injector, and the risk of the pressure-sensitive member being damaged by the aggressive secondary liquid is correspondingly re¬ duced.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be explained in the follow¬ ing with reference to the single Figure of the drawing, in a simplified and diagrammatic manner showing a pre¬ ferred practical embodiment of an apparatus according to the present invention for use in so-called high- -pressure cleaning operations.

DESCRIPTION OF THE PREFERRED EMBODIMENT The apparatus shown in the Figure comprises the follow¬ ing components: a) a high-pressure pump 1, normally of the displace¬ ment type, b) a by-pass valve 2 connected between the pressure side 3 and the suction side 4 of the pump 1, c) an outlet 5 connected to the pressure side 3 of the pump 1 and adapted to be connected to a cleaning im¬ plement, such as a water-jet pistol (not shown) of a known type, said implement being intended to be directed against a surface or an object to be clea¬ ned, d) an inlet 6 for cleaning liquid, such as water, nor- mally without additives, e) an inlet 7 with a non-return valve 8 for additives in liquid form, such as concentrated detergent so¬ lution or the like, and f) injector means 9 inserted in the conduit between the pressure side 3 of the pump 1 and the outlet 5 and adapted f1) partly through a first injector 9a to act upon one side of a piston 10 adapted to control the by-pass valve 2, said piston 10 on the other side being ac- ted upon by the pressure at the pressure side 3 of the pump 1, and f2) partly through a second injector 9b to aspirate li¬ quid additive from the inlet 7 through the non-re¬ turn valve 8, all the components mentioned being interconnected in the manner shown in the Figure.

Apart from the novel construction and functioning of the injector means 9 comprising the two injectors 9a and 9b, the arrangement shown is known in principle, e.g. form the specification to the West German Patent No. 3.248.622 mentioned above.

During normal functioning of the apparatus shown, the pump 1 delivers cleaning liquid, such as water, supplied through the inlet 6 from a suitable source (not shown), through its pressure side 3, the injector means 9 and the outlet 5 to the cleaning implement (not shown) men¬ tioned above under item c. When the jet nozzle in the cleaning implement is being kept open, such as by actu¬ ating a trigger-like member, the liquid will flow freely towards "the cleaning implement, and due to this liquid flow, the first or upstream injector 9a will cause a re¬ duction of pressure to take place on the right-hand si¬ de of the piston 10, so that the piston 10, assisted by a compression spring 11, will tend to close the by-pass valve 2, the pressure on the left-hand side of the pi¬ ston 10 being substantially the same as the delivery pressure of the pump 1. At the same time, the second or downstream injector 9b will be able to aspirate liquid additive from a suitable source (not shown) connected to the inlet 7.

If, during normal operation of the pump 1, i.e. whilst it is being kept running at its normal speed by its mo¬ tor (not shown), the valve in the cleaning implement is closed, such as by releasing the trigger-like member mentioned above, then the free flow of liquid through the injectors 9a and 9b will cease, with the result i) that the pressure on the right-hand side of the pi¬ ston 10 will rise and the piston will open the by- -pass valve 2, thus avoiding overheating of the pump 1, and ii) that liquid additive will no longer be aspirated into the main flow of liquid from the inlet 6. (The leftward movement of the piston 10 is caused by the difference in effective piston area on both sides of the piston, the left-hand side having a smaller area due to the effective area of the valve 2 on the left-hand side being acted upon by low pressure at the suction side 4 of the pump 1. )

If there were direct communication between the non-re¬ turn valve 8 and the right-hand side of the piston 10, such as is the case with the previously known arrange¬ ment mentioned above, the liquid additive present in the conduit between the non-return valve 8 and the injector means might, especially during long periods of non-use, diffuse into the space around the piston 10 and cause damage to gaskets and the like, as such liquid additi¬ ves are usually by their very nature very aggressive and/or corrosive. An even worse situation may arise, if transient conditions during the transition from one operating mode to another cause liquid additive to be aspirated directly and in concentrated form into the space around the piston 10.

In the arrangement shown, the risk of liquid additive entering the space around the piston 10 is eliminated or at least considerably reduced, as the previous di¬ rect communication between the non-return valve 8 and the right-hand side of the piston 10 is replaced by the considerably more tortuous path through the two injec¬ tors 9b and 9a respectively.

To prevent the pressure drop across the two injectors 9a and 9b being excessive as compared to the pressure drop in the previously known arrangement having only a single injector, the first or upstream injector 9a is constructed without the usual diffuser portion, so that the jet from its drive nozzle 12a impinges upon the en¬ try portion of the drive nozzle 12b of the second or downstream injector 9b. To this end, the flow cross-sec- tional area of the upstream drive nozzle 12a is prefe¬ rably of the order of 30 per cent greater than that of the downstream drive nozzle 12b, and the two drive nozz¬ les 12a and 12b are - of course - placed in mutual coax¬ ial alignment as shown. In this manner, the hydraulic po- wer expended in the first or upstream injector 9a is re¬ latively small, and with careful design and dimensioning it is possible to bring the total pressure drop across the two injectors 9a and 9b at least within the same or¬ der of magnitude as that in the previously known arrange- ment mentioned above and having only a single injector.

It is possible to arrange the two injectors in parallel instead of in series as shown and still obtain the ad¬ vantages mentioned above, but for reasons of efficient production it is - at least at the present stage of de¬ velopment - preferred to use the arrangement shown with the two injectors in series.

If the two injectors were interchanged, i.e. the first injector 9a acting upon the piston 10 being placed down- stream of the second injector 9b aspirating the liquid additive, some of the advantage mentioned above would be lost, because there could remain a mixture of pure clea¬ ning liquid (e.g. water) and additive in the space be¬ tween the two injectors, and this mixture could then un- der certain conditions diffuse or be aspirated into the space at the right-hand side of the piston 10. For this reason, the arrangement shown with the first injector 9a upstream of the second injector 9b is obviously to be preferred.

It is also possible to use more than two injectors, e.g. three with one for controlling the by-pass valve and the two others for aspirating two components of an additive, the components of which are not to be mixed with the car¬ rier liquid and hence with each other until immediately before use. This could be useful when using the appara¬ tus as a fire-fighting appliance for supplying carbon- -dioxide foam or the like.

Claims

C A I M S

1. A high-pressure liquid delivery apparatus of the kind comprising: a) a high-pressure pump (1), b) a by-pass valve (2) connected between the pressure side (3) and the suction side (4) of the pump (1), c) an outlet (5) connected to the pressure side (3) of the pump (1 ) and adapted to be connected to a liquid- -directing implement, such as a water-jet pistol in- tended to be directed against a surface or an object to be treated, d) primary inlet (6) for primary liquid connected to the suction side (4) of the pump (1), e) a secondary inlet (7) with a non-return valve (8) for secondary liquid, and f) injector means (9) inserted in the outlet between the the pressure side (4) of the pump (1) and the outlet

(5) and adapted f1) partly to act upon a pressure-sensitive control mem- ber (10) adapted to control the by-pass valve (2), and f2) partly to aspirate secondary liquid from the secon¬ dary inlet (7) through the non-return valve (8), c h a r a c t e r i z e d in g) that the injector means (9) comprise at least two separate injectors, viz. gl) a first injector (9a) adapted substantially solely to act upon said pressure-sensitive member (10), and g2) a second injector (9b) adapted substantially solely to aspirate secondary liquid from said secondary in¬ let (7).

2. An apparatus according to claim 1, c h a r a c¬ t e r i z e d in that the injectors (9a, 9b) are con¬ nected in series, i.e. with one (9a) upstream of the ot- ther (9b).

3. An apparatus according to claim 1, c h a r a c¬ t e r i z e d in that the first injector (9a) is pla¬ ced upstream of the second injector (9b).

4. An apparatus according to claim 2 or 3, c h a- r a c t e r i z e d in that the upstream-most injector is formed without an outlet diffuser and so placed in relation to the downstream-most injector, preferably co- axially therewith, that the liquid jet from the upstream- -most injector impinges directly upon the drive-liquid entry opening in the downstream-most injector.

5. An apparatus according to claim 4, c h a r a c- -t e r i z e d in that the flow cross-sectional area of the drive nozzle in the upstream-most injector is ap¬ proximately 30 per cent greater than that of the drive nozzle in the downstream-most injector.

6. An apparatus according to claim 1, c h a r a c¬ t e r i z e d in that the two injectors are arranged in parallel, i.e. with their upstream drive inlets and their downstream outlets respectively substantially con- nected together.

7. An apparatus according to one or a number of the claims 1-6, c h a r a c t e r i z e d in that it com¬ prises at least three injectors, of which one is adapted to act upon said pressure-sensitive member (10), and the two or more further injectors are adapted to aspirate two or more components of a two-component or multi-com¬ ponent secondary liquid.