WO1991000986A1

WO1991000986A1 - Flow detection

Info

Publication number: WO1991000986A1
Application number: PCT/AU1990/000296
Authority: WO
Inventors: Philip G. Tassicker
Original assignee: Tekelek Pty. Ltd.
Priority date: 1989-07-10
Filing date: 1990-07-10
Publication date: 1991-01-24

Abstract

A fluent material flow detector detecting a threshold flow rate rather than a quantitative value. Movement of a magnetic material (31) and a detector (33) sensitive to magnetic field changes determines whether flow is occurring. A threshold value determines whether a certain flow condition is deemed to be flow or not. Circuitry enables the flow detector to be used in a variety of process control applications.

Description

This invention relates to a means for fluent material flow detection and indication thereof.

BACKGROUND OF THE INVENTION

The presence or absence of fluid movement through a pipe, conduit or other fluent material communication means can be of great importance to the control and operation of many domestic, agricultural and industrial processes.

A fluent material may comprise gas, liquid or slurry matter and may also include different states of that matter, e.g. water, water vapour and crushed ice.

The flow of these materials in controlled processes sometimes require quantitative measurement and at other times only requires that its movement or flow be detected.

Prior means of flow detection and measurement have commonly used intrusive means, for example impellers and vanes to which are imparted energy from the flow of the material. The energy imparted is then translated into electromagnetic meter movement, mechanical element movement or electrical signals. These types of detection means are primarily used to provide rate of flow or quantitative flow values.

it has been found that the quantitative nature of these detection means provide a limited dynamic range of flow rate measurement and detection. It has further been found that their degree of intrusion, the corrosive and other deleterious effects of the matter on the measurement devices and their maintenance and repair have an unduly restrictive effect on the circumstances of their use and add to the expense of manufacture and maintenance in various systems.

SUMMARY OF THE INVENTION

A flow detector is disclosed of simple and reliable configuration which comprises a means for the detection of the flow of fluent material, wherein the detector comprises at least one magnet, a detector electrically responsive to magnetic field variation, retention means for retaining at least one magnet such that the detector is within the field of the magnet wherein said magnet is located by said retention means so as to undergo random movement effected by flow of said fluent material past the magnet thereby stimulating random electrical signals in the detector to indicate fluent material flow.

It is a preferred aspect of this invention that the signal output from the detector is compared with a preset threshold level and when that level is exceeded the flow detector output is representative of the flow of fluent material past the detector means. It is yet a further aspect of this invention that the threshold level may be adjustable.

It is a still further feature of this invention to provide a signal output from the flow detector which is indicative of the presence or absence of flow and which may thereby be used to control a wide variety of fluent material processes.

It is yet a further preferred aspect of this invention to provide a means to detect the flow of fluent material which minimises impedance to fluent material flow.

It is also a further preferred feature of this invention that the flow detection device is simple to instal and to replace in use or alternatively easily incorporated into pumps or other like devices.

A number of embodiments of the invention will now be described but it will be understood that the invention need not be limited by these particular configurations without departing from the inventive matter disclosed in the broad statement of claims hereafter.

DETAILED DESCRIPTION OF THE DRAWINGS

The following embodiment is described hereunder with reference to, and is illustrated in, the accompanying drawings, in which:-

Fig. 1 depicts a schematic drawing of a gravity feed hot water service incorporating the flow detection device and an associated circulator pump,

Fig. 2 depicts a schematic drawing of the flow detection device located within a fluid communication pipe of the hot water system, and

Fig. 3 depicts a section view taken along line a-a of the communication pipe and the detection device as depicted in Fig. 1.

Fig. 4 depicts a schematic functional block diagram of the flow detection device and its associated electronic circuit means.

In this embodiment, a domestic hot water service using a gravity feed hot water service 10 commonly has the tank located in the ceiling of the domestic premises. The height of that tank above the hot water outlets determines the head pressure of the system. As will therefore be apparent this pressure is usually quite low and small in comparison to the mains cold water supply pressure. A hot water outlet pipe 11 communicates hot water from the tank 10 into a system of hot water supply pipes which distributes the hot water throughout the domestic premises. A system that does not have a booster pump, or as it is commonly referred to a circulator pump, relies on the head pressure of the tank to supply hot water to those hot water outlet locations. In the example of a shower arrangement, the hot water is allowed to flow and mix with incoming cold water to eventually exit the shower rose. It has been found however that when another hot water tap is operated and the hot water head pressure is then shared amongst the two outlets that the pressure drop at the location is mixed which then imbalances the pressure and therefore affects the temperature of the mixed water exiting from the shower rose. This temperature imbalance favours the cold rather than the hot and the person using the shower is required then to adjust the flow of either cold or hot water to recreate the desired mixed temperature. Of course when the external hot water tap is then switched off a similar imbalance of temperature occurs again and adjustment is again necessary.

It is common for booster pumps 15 to be located in line with the hot water service outlet pipe and to be switched ON when hot water is required and thereby supply substantially constant hot,water pressure to the hot water system and its outlets. The booster pump is then switched OFF when no longer required. It has been common for manual switching of the booster pump to be controlled by the users of the hot water system, while paddle wheel and impeller flow measurement devices to detect flow have had limited application in these circumstances, primarily because they are expensive to purchase and aintaia compared with the cost of manual means to control booster pumps and other like devices.

Alternatively, pressure switches have been found to be unreliable and more importantly incapable of detecting very low pressure changes as will occur when low flow rates are experienced.

In an embodiment of the invention there is provided a flow detector apparatus 12, which is shown in greater detail in

Figs. 2 and 3, but which is located on a right angled bend of the hot water outlet pipe. An access cap 13 allows replacement of a portion of the flow detector apparatus. A flow detector electronics enclosure 14 is located in the proximity of the flow detection device as shown in Fig. 1 and depicted in greater detail in Figs. 2 and 3.

A booster pump 15 is located in line with the hot water outlet pipe whereby it supplies substantially constant higher pressure when operated, of hot water into the distribution pipes 16 and 17 of the domestic premises, although it may be used exclusively on the shower supply pipe.

A hot water shower tap 18 controls the flow of hot water into the shower mixing bridge 21, while cold water shower tap 20 controls the flow of cold water from the water pipe 19 into the shower mixing bridge 21. The mixed hot water then is communicated to the shower rose fitting 23 and the shower rose 24 via the shower water pipe 22.

When either the hot water shower tap 18 or for example a hot water basin tap 25 are opened the flow of hot water from the tank 10 will be detected by the flow detector apparatus 12 which signals via the flow detector electronics 14 for the hot water booster pump 15 to be brought into operation. Thus, a higher and substantially constant pressure can be supplied to the hot water outlets which may comprise the basin and the shower outlets whether they are on singly or together.

As shown in Fig. 2, the direction of flow of the water as indicated by arrow 26 is such that it is directed past and upon a water flow detector apparatus which comprises a retention means 27 which is shown as being suspended within a vertical portion of the hot water outlet pipe 16. A flow detector access cap 13 has attached thereto retaining lug 28 for locating in an approximately coaxial location to the pipe 16 a flexible and movable retention means 27 having a ball shaped portion 29 at its upper end to allow movement of the retention means. At the lower end of the retention means there is a magnet encapsulation portion 30. The retention means 27 comprises a flexible member 27a made of a nitrile material of approximately 2.5 mm outer diameter and has elastic characteristics such that it may be deformed and will elastically return to its original shape. It has been found that this particular material is well capable of withstanding the effect of water turbulence and vibration over an extended period while maintaining its elastic properties and effectively encouraging the randomness of the movement of the encapsulated magnet. A variety of materials may be suitable for different types of fluent material. Indeed, although not shown, an arrangement using two retention means for two magnets which are orientated with like poles adjacent further enhances the amount and randomness of their movement because of their mutual repulsion.

The magnet encapsulation portion is made from a nylon material or other suitable inert material which may be moulded or turned into a cylindrical tube-like structure, in which the magnet 31 may be secured by glue or other such substance. It will be apparent however that a variety of encapsulation methods are possible, indeed incorporation by moulding of the magnet 31 into the free end of the retention means 27 may also be possible.

The magnet 31 has a field which extends outwards from its location and it is necessary for a magnetic field detection device to be located within a usable field strength range of the magnets location. In this embodiment a Hall Effect device 33 is located as shown in Fig. 2 such that the magnetic field associated with magnet 31 intersects its active area. It will be apparent to those skilled in the art that a Hall Effect device, a magneto resistive device or other electronic means will be available to effect the required response and thereby detect the changing magnetic field. A variety of circuit means may also be used to process the signal produced or induced in the detector element, which may also have means to adjust the threshold at which flow is detected by the flow detector apparatus and which can thereby signal external devices for the purposes of process control. The direction of water flow from the flow detector apparatus is depicted by arrow 34.

Fig. 3 depicts a top view of the spacial relationship of the magnet encapsulation portion 30 and its magnet 31 in relation to the detector device 33 and its associated electronics within the electronics enclosure 14.

It will be apparent that the configuration of the retention means flexible member 27a whereby it is affixed to retaining lugs 28 which themselves are attached to a flow detector access cap, enables it to be removed with ease for inspection or replaced when necessary. The cap simply screws on and off a standard T-junction portion of the hot water piping system.

It will also be clearly apparent to those skilled in the art that a great variety of electronic signal processing means will be available to detect and interpret the signals which are stimulated in the detector device so that a suitable control signal can be generated. In this embodiment as depicted in Fig. 4, the random detector signal is amplified, filtered and applied to a known comparator device to produce an output signal representative of the detector device being stimulated above a preset threshold level. In this embodiment the output of a detector device 33 is coupled by a lead 34 into an alternating current-coupled amplifier 35 and passed via lead 36 to a rectifier and low Pass filter 37. Lead 38 from the output of the Low Pass filter 37 passes the filtered signal to a comparator 39. Variable resistor 40 indicates schematically that the signal level to the second input of the comparator 39 may be preset and varied according to the application. Indeed very low flow rates, as low as 1-2 litres/minute have been reliably detected and appropriate threshold signal levels set.

The comparator compares the signal from the two inputs and a signal on output lead 41 will indicate that the detector input signal is greater than the preset signal level. The signal present on lead 41 is used to control a switching device 42 which is shown in this embodiment to comprise a relay which is wired to supply power to an external device for example the booster pump 15. The switching device however may comprise a 5 variety of electronic means for the switching of voltages and current loads of a number of different pumps, heating elements and other control process devices.

It will be further apparent that a variety of delays and 10 additional logical operations may be performed on the output of the detector thereby increasing the application of a reliable detection of flow apparatus. Additionally, when inputs from a number of flow detectors are analysed in a pre-programmed way, control of the sequence of a process or processes can be 15 confidently implemented.

It will be further apparent that the arrangement of the magnet within or in the proximity of fluid flow can be such that a retention means as described is not required. For

20 example, a magnet may be retained in a cage-like structure which is located within a fluid communication means and having openings therein to allow the flow of fluent material therethrough. A magnet contained within the cage-like container is thereby free to move as it is impinged upon by the

25 fluent flow and its movement will thus be capable of being detected by detector means to indicate the presence of flow. Alternatively, a further possible configuration comprises a flow detector .using a retained movable member located within the flow path which when buffeted by the turbulence in the

30 flow, vibrates and moves the member such that by mechanical means between the member and a magnet, the magnet is moved and a detector device is thereby stimulated to provide a signal indicative of the flow of fluid material through the communication element.

35

It has also been demonstrated that large pipes benefit from the use of two mutually opposing magnets located in proximity to each other and in the vicinity of the detector means as previously described.

Claims

The claims defining the invention are as follows:

1. A flow detector for detection of flow of fluent material comprising, at least one magnet, a detector means electronically responsive to magnetic field variation, at least one retention means for retaining said at least one magnet such that the detector is within the field of the magnet and located so as to have the magnet randomly moved by flow of fluent material thereby stimulating electrical signals in the detector means to indicate fluent material flow.

2. A flow detector according to claim 1 wherein said retention means is located within the direct flow of fluent material.

3. A flow detector according to claim 2 wherein said retention means comprises a flexible member retained at one of its ends and free at its other end, having attached at its free end said at least one magnet wherein said magnet is located in the proximity of the detector means.

4. A flow detector according to claim 1 further comprising, signal comparison means for comparing the output signal from the detector means with a preset signal value representative of a threshold level wherein an output signal is generated by the comparison means when the output signal from the detector means exceeds the threshold level.

5. A flow detector according to claim 4 wherein the comparison means has an adjustable preset signal input means which may be adjusted to control the threshold level representative of movement of the magnet and thereby indicative of fluent material flow.

6. A flow detector according to claim 4 further comprising signal processing means between the output of the detector means and the signal comparison means comprising, amplifier means for amplifying the output signal of the detector means, filter means receiving the output of the amplifier means and modifying its signal characteristics and providing an input signal to the signal comparison means.

7. A flow detector according to claim 1 wherein said retention means comprises a container means having openings therein to allow the flow of fluent material therethrough, wherein said magnet is free to move within said container means.

8. A flow detector according to claim 1 wherein said one at least retention means is located adjacent another retention means wherein said magnets contained within said retention means are orientated with like poles adjacent.

9. A flow detector substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.