EP1664618A1

EP1664618A1 - Device for generating and maintaining a desired pressure/flow

Info

Publication number: EP1664618A1
Application number: EP04775422A
Authority: EP
Inventors: Knut Meyer
Original assignee: Lagafors Fabriks AB
Current assignee: Lagafors Fabriks AB
Priority date: 2003-09-16
Filing date: 2004-09-14
Publication date: 2006-06-07
Anticipated expiration: 2024-09-14
Also published as: SE526018C2; ATE421069T1; SE0302470L; DE602004019113D1; EP1664618B1; WO2006019341A1; SE0302470D0

Abstract

The water conduit system (1) is connected to at least two water cylinders (3, 4), each of which uses its piston (11, 12) to deliver high-pressure water into the system. The pistons are connected to a drive unit (19, 20) for moving the pistons in and out of the cylinders in order to maintain the desired water pressure. The drive unit comprises a hydraulic device with a drive cylinder for each water cylinder.

Description

DEVICE FOR GENERATING AND MAINTAINING A DES IRED PRESSURE / flow The present invention relates to an apparatus for generating and maintaining a desired pressure/flow in a water conduit system with a number of take-off points for connection of closable and openable high pressure water nozzles for use in high pressure water spraying, for example cleaning.

Within, for example, the food industry, there are two different methods of cleaning, namely low pressure systems and high pressure systems. In many cases, high pressure systems are preferred in a fixed installation which is placed in a separate facility or a so-called pumping centre which comprises a plurality of pumps and from which extends a conduit system out to the different washing stations or take-off points out in different premises. All users are connected to the same conduit system and are required to use the same water pressure. The control system included in the existing installations uses the water pressure as a control signal. Further, the nozzles are dimensioned so as to give the predetermined system pressure at the flow from one pump, which implies that the system constantly uses one pump per user. The control system is operative to select at random a pump which is to start in the event of a pressure drop with a view to distributing wear on the pumps as evenly as possible. In currently employed pumping centres, use is essentially made only of electrically driven piston pumps of the plunger type. The relatively small cylinders used in such pumps require high speeds and many strokes per minute, which results in considerable wear. The degree of efficiency of the prior art pumps is further closely adapted to a specific pressure/flow combination, for which reason the application of so-called speed regulation gives a limited effect. This is moreover a major inconvenience.

The task forming the basis of the present invention is to realise a pump capable of delivering pressure/flows of 80 to 100 bar/17 to 20 1/min with a good margin. In addition, the pressure/flow should be regulated, which implies a pump which within given performance parameters permits, without any deterioration in efficiency, a higher flow compensated by lower pressure or conversely higher pressure compensated by lower flow. In addition, the present invention has for its object to make for a system which rapidly compensates for pressure/flow variations in the water conduit. The pressure at a take-off point should not fall appreciably when another take-off point in the system is opened. Further, the pressure at one take-off point should not be increased appreciably because of another take-off point in the system being closed. The present invention relates to an apparatus for generating and maintaining a desired pressure/flow in a water conduit system with a number of take-off points for connection of closable and openable high pressure water nozzles for use in high pressure water spraying, for example cleaning.

Within, for example, the food industry, there are two different methods of cleaning, namely low pressure systems and high pressure systems. In many cases, high pressure systems are preferred in a fixed installation which is placed in a separate facility or a so-called pumping centre which comprises a plurality of pumps and from which extends a conduit system out to the different washing stations or take-off points out in different premises. AU users are connected to the same conduit system and are required to use the same water pressure. The control system included in the existing installations uses the water pressure as a control signal. Further, the nozzles are dimensioned so as to give the predetermined system pressure at the flow from one pump, which implies that the system constantly uses one pump per user. The control system is operative to select at random a pump which is to start in the event of a pressure drop with a view to distributing wear on the pumps as evenly as possible. In currently employed pumping centres, use is essentially made only of electrically driven piston pumps of the plunger type. The relatively small cylinders used in such pumps require high speeds and many strokes per minute, which results in considerable wear. The degree of efficiency of the prior art pumps is further closely adapted to a specific pressure/flow combination, for which reason the application of so-called speed regulation gives a limited effect. This is moreover a major inconvenience.

The task forming the basis of the present invention is to realise a pump capable of delivering pressure/flows of 80 to 100 bar/17 to 20 1/min with a good margin. In addition, the pressure/flow should be regulated, which implies a pump which within given performance parameters permits, without any deterioration in efficiency, a higher flow compensated by lower pressure or conversely higher pressure compensated by lower flow. In addition, the present invention has for its object to make for a system which rapidly compensates for pressure/flow variations in the water conduit. The pressure at a take-off point should not fall appreciably when another take-off point in the system is opened. Further, the pressure at one take-off point should not be increased appreciably because of another take-off point in the system being closed. This task is solved in the apparatus disclosed by way of introduction according to the present invention in that the water conduit system is connected to at least two water cylinders each with its piston for feeding high pressure water in the water conduit system, and the pistons are connected to a drive unit for driving the pistons in the water cylinders for generating and maintaining a predetermined water pressure in the water conduit system. The drive unit is a hydraulic assembly with a drive cylinder for each water cylinder. The drive cylinders are single-action. The single-action drive cylinders are provided with a return conduit with a dump valve. The drive cylinders are double-action. The water cylinders are connected to the water conduit system via valves for discharging high pressure water in the water conduit system and for the admission of incoming water. The valves for incoming water are arranged to fill the water cylinders with incoming water and thereby return the pistons therein to their starting position with the cylinders filled. The water cylinders are positioned in line with each of their drive cylinders. The water cylinders and drive cylinders are disposed in parallel with each other with the water cylinders straight above the drive cylinders.

As a result of the present invention, there will be attained an apparatus for generating high pressure water in a water conduit system with a number of take-off points which, in principle, will be totally independent of one another as regards both water flow and water pressure as well as in respect of pressure reduction on opening of a plurality of take-off points and pressure elevation on closing of a number of take-off points while one is open. In that the apparatus according to the invention can be driven with a hydraulic assembly, this results in considerably better service life. Hydraulic oil is an optimum fluid to be pumped at high pressure. In addition, it is a lubricant and is slightly compressible, which gives extremely favourable conditions with long service intervals. Thanks to the high oil pressure, it is possible to use large water cylinders, which entails low speeds and minimised wear also on the water side. The use of hydraulic pumps makes for a considerably greater pressure/flow range with a high degree of efficiency, since the hydraulic oil permits the use of more sophisticated pumps, for example an angle disk pump with a pressure compensated strong length. The angle disk pump operates at a predetermined pressure of the oil and compensates for flow variations in fractions of a second by changing the angle and thereby the stroke length. By such means, the pressure water take-off points will be substantially independent of each other. The cylinder unit is considered as a fixed switch between oil and water, which implies that the water pressure under any circumstances has the same ratio to the oil pressure. This implies, for example, that with a ratio of 1:2, there will be obtained 100 bar/50 1/min of water at an oil pressure/flow of 200 bar/25 1/min. An apparatus according to the present invention will have an extremely long service life and requires minimal service. Major advantages reside essentially in the fact that users sense only very slight water hammers or jolts when other users open or close a nozzle, and in the fact that the pump may be regulated with respect to pressure/flow, that the construction will be more robust than traditional plunger pumps, with longer service intervals as a result, and that the pump reduces pressure drop and pressure hammers in the system to hardly noticeable pulses in the system. As a result of the apparatus according to the present invention, there will further be realised a perfect and endurable barrier against the penetration of impurities into the water system.

The present invention will now be described in greater detail with reference to the accompanying drawings. Fig. 1 shows a diagram of an apparatus according to one embodiment of the present invention. Fig. 2 is a perspective view of a prototype of the embodiment of fig. 1. Fig. 3 is a front elevation of a part of the apparatus of fig. 2. Fig. 4 shows a part from above of the apparatus of fig. 2. Fig. 5 is a front elevation of the apparatus of fig. 2. Fig. 6A is a view of a single-action cylinder unit according to the present invention. Fig. 6B is a side elevation of the cylinder unit shown in Fig. 6A. Fig. 7 shows a hydraulic diagram for the unit illustrated in fig. 6A and 6B. Fig. 8 is a longitudinal section through a cylinder unit of double-action type for an embodiment of the apparatus according to the present invention. Fig. 9 shows a similar longitudinal section to fig. 8 with the piston in its opposing position. Fig. 10 shows a hydraulic diagram for an apparatus of the type illustrated in figs. 8 and 9.

An apparatus according to the present invention will be described in greater detail hereinbelow with reference to figs. 1-5 in connection with the use thereof for generating high pressure water in a water conduit system with a number of take-off points for the connection of openable and closable nozzles. The water conduit system in Fig. 1 carries reference numeral 1. The water conduit system 1 is supplied with incoming water via a faucet 2. Between the water conduit system 1 and the faucet 2 for incoming water, there are disposed a number of valves for connection of two water cylinders 3 and 4. A non-return valve 5 is disposed between the water conduit system 1 and the faucet. A safety valve 6 is further connected to the water conduit system 1 and relieves the pressure in the water conduit system 1 if the pressure exceeds a predetermined level, e.g. 10 bar. The water cylinder 3 is connected to the water conduit system 1 via two non-return valves 7 and 8, while the water cylinder 4 is connected to the water conduit system 1 via two non-return valves 9 and 10. The non-return valves 7 and 8 serve to admit incoming water into the water cylinders 3 and 4, while the non¬ return valves 8 and 9 serve for releasing high pressure water into the water conduit 1 from the water cylinders 3 and 4. The water cylinders 3 and 4 each have a plunger or piston 11 and 12. The piston 11 is in communication with a piston 13 in a hydraulic cylinder 14 via a rod 15. The piston 12 in the water cylinder 4 is in communication with a piston 16 in a hydraulic cylinder 17 via a rod 18. The hydraulic cylinders 14 and 17 are single-action and are supplied with driving hydraulic fluid from a hydraulic oil unit 19 via a valve 20. The single-action hydraulic cylinders 14, 16 may be provided with a return conduit R which includes a dump valve, whereby the dependence on the water pressure is reduced. The hydraulic oil unit 19 has a pressure-regulating pump with the possibility of manual adjustment of the maximum pressure. Suitable values may be a pressure of 220 bar and a flow of 25 1/min.

A pressure sensor is further connected to the water conduit system 1. At the non-return valve 5, there is provided a water flow sensor 22 of, for example, the Hall effect type. At the water cylinder 3, there is provided a position sensor 23 of the photo-diode type and the water cylinder 4 is provided with a position sensor 24 of the photo-diode type. The pistons 11 and 12 each have a plate 25 and 26, respectively, for breaking the light communication in the photo-diode sensors 23, 24.

The photo-diode sensors or photodetectors 23 and 24 emit a signal as soon as the light is broken by means of the plates 25 and 26 at the latest approx. 200 msec before each respective water cylinder 3, 4 is emptied. When the light beam is broken, this implies that each respective water cylinder 3, 4 is almost empty and that it is time to start the second water cylinder. As long as the light beams at the photodetectors 23, 24 are not broken, this implies that the water cylinder 3, 4 is not empty and can deliver high pressure water. The apparatus according to the present invention illustrated in fig. 1 operates in substantially the following manner. When the water cylinder 3 is almost empty, the plate 25 breaks the signal from the photodiode 23 and activates the direction valve 20. When the water cylinder 4 is almost empty, the signal from the photodiode 24 is broken by the plate 26 and the current to the direction valve is deactivated. The water cylinders 3, 4 are returned and filled with water because of force of gravity and the water pressure of the incoming which may amount to approx. 3-5 bar. It is appropriate if the filling of the water cylinders 3, 4 takes a slightly shorter period of time than emptying of the water cylinders. In order to save gaskets, reduce wear and save energy, the apparatus is switched a "standby" position when no consumption of high pressure water takes place. However, brief disruptions (shorter than approx. 3 minutes) do not lead to any "standby" position.

In the apparatus according to the present invention, it is possible to provide two "standby" positions. When the pressure sensor 21 is broken, the oil pressure in the installation is reduced from a maximum 220 bar to approx. 15 bar. In this second "standby" position, the main motor in the main motor in the hydraulic oil unit 19 is shut off, when the flow detector 22 shows "0 flow", the pressure valve is opened roughly 3 minutes after receiving the signal. When the flow detector 22 is in the "low pressure area", there will, under normal operations, occur brief disruptions in the flow (the water flow for refilling the cylinders 3 and 4 is larger than the consumption flow). However, these disruptions are always much shorter than 3 minutes.

The pressure valve 21 is activated when the flow detector 22 shows "flow". The main motor in the hydraulic oil unit 19 is shut off when the pressure valve 21 has been open for approx. 5 minutes. The main motor is restarted when the flow detector 22 shows "flow". The apparatus is suitably provided with a level gauge for low oil volume and for high oil temperature. An indicator light on the regulator unit shows "error" and the main motor is stopped in the event of too low oil level or too high oil temperature.

The shortest period of time which the direction valve 20 is activated should not be shorter than 1.3 seconds. If one of the photodetectors' 23, 24 light beam is broken for a briefer period of time once the second photodetector has been broken, switching of the valve 20 is delayed for 1.3 seconds instead of, as in normal operational conditions, immediately implementing the valve switch.

Figs. 6A and 6B show the hydraulic cylinders 14 and 17 and fig. 7 shows a hydraulic diagram for the hydraulic cylinders 14 and 17. Fig. 2 shows a photographic, perspective view of a prototype of an apparatus according to the present invention, while drawing figs. 3-5 show views of parts of the apparatus shown in fig. 2. The parts shown in these figures have the same reference numerals as in fig. 1.

Figs. 8 and 9 show a water cylinder 3, 4 with a double-action hydraulic piston 27. Fig. 8 shows the hydraulic piston in its lower position, with the water cylinders 3, 4 filled with water, while fig. 9 shows the hydraulic piston in its upper position with the water cylinder in its upper position and emptied.

The major difference between the unit shown in figs. 8 and 9 and the unit described above is that the hydraulic piston 15, 18 is of double-action type. The piston 13, 16 is moved from its lower position illustrated in fig. 8 to its upper position with hydraulic oil which is fed in to the inlet 28 and from the upper position in fig. 9 to the lower position in fig. 8 by means of hydraulic oil which is fed through the inlet 29.

Fig. 10 shows a hydraulic diagram for operation of the double-action hydraulic cylinders 27 shown in figs. 8 and 9. The function of an apparatus with the double-action cylinders 27 will be substantially the same as the single-action cylinders. It should be observed that, regardless of whether the hydraulic cylinders are single-action or double-action, the water cylinders 3, 4 are single-action.

In one embodiment according to figs. 1-5 with both single-action water cylinders 3, 4 and single-action hydraulic cylinders 14, 17, incoming water should, as was mentioned previously, return the pistons 11, 12. For achieving superior function, it is appropriate that the pressure of the incoming water is approx. 2.7 bar for attaining sufficiently high return speed so as to have time at maximum flow of 50 1/min. In reality, incoming water pressure in a factory can fall to practically 0 bar when the water take-off is at its greatest and is seldom much higher than 2 bar. In the prototype according to figs. 2-5, it has therefore been necessary to employ a pressure booster on the incoming water. The problem may eventually be remedied with the aid of a so-called dumping function on the return oil. This implies that the flow resistance on the return oil will be lower and thereby the pressure of the incoming water need not be so high. The problem with exclusively single-action cylinders is essentially solved with the aid of double-action cylinders according to figs. 8, 9 and 10.

It may further be appropriate to provide both of the drive systems, i.e. single-action or double- action drive cylinders, with valve arrangements that permit start of a piston before the other has reached the turning position. This leads to the maintenance of the pressure in the water system.

The positional disclosures in the following tables are to be found in fig. 6.

The positional disclosures in the following table are to be found in fig. 10.

The following values relate to the embodiment in Fig. 10

Flow = 42 litre/min Pressure = 150 bar Trial pressure = 180 bar Magnet voltage = XXXX Electric motor = 11 KW

Many modifications are naturally possible without departing from the scope of the inventive concept as defined in the appended claims.

Claims

1. An apparatus for generating and maintaining a desired pressure/flow in a water conduit system (1) with a number of take-off points for the connection of closable and openable high pressure water nozzles for use in high pressure water spraying, e.g. cleaning, characterised in that the water conduit system (1) is connected to at least two water cylinders (3, 4) each with its piston (11, 12) for infeed of high pressure water in the water conduit system (1), and that the pistons (11, 12) are connected to a drive unit (19, 20) for driving the pistons (11, 12) in the cylinders (3, 4) for generating and maintaining a predetermined water pressure in the water conduit system (1).

2. The apparatus as claimed in claim 1, characterised in that the drive unit (19, 20) is a hydraulic assembly with one drive cylinder (14, 17) for each water cylinder (3, 4).

3. The apparatus as claimed in claim 2, characterised in that the drive cylinders (14, 17) are single-action.

4. The apparatus as claimed in claim 3, characterised in that the single-action drive cylinders (14, 17) are provided with a return conduit which includes a dump valve.

5. The apparatus as claimed in claim 2, characterised in that the drive cylinders (14, 17) are double-action.

6. The apparatus as claimed in claim 1, characterised in that the water cylinders (3, 4) are connected to the water conduit system (1) via valves (5-10) for the discharge of high pressure water into the water conduit system (1) and the admission of incoming water.

7. The apparatus as claimed in claim 6, characterised in that the valves (5, 7 and 5, 9, respectively) for incoming water are operative to fill the water cylinders (3, 4) by the admission of incoming water and thereby return the pistons (11, 12) therein to the starting position with the cylinders (3, 4) filled.

8. The apparatus as claimed in claims 2 and S, characterised in that the water cylinders (3, 4) are positioned in line with each one of the drive cylinders (14, 17).

9. The apparatus as claimed in claim 8, characterised in that the water cylinders (3, 4) and the drive cylinders (14, 17) are disposed in parallel with one another, with the water cylinders (3, 4) straight above the drive cylinders (14, 17).