GB1569105A - Creación de Inventos y Patentes con Inteligencia Artificial

GB1569105A – Electric switch device for monitoring fluid flow
– Google Patents

GB1569105A – Electric switch device for monitoring fluid flow
– Google Patents
Electric switch device for monitoring fluid flow

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Publication number
GB1569105A

GB1569105A
GB4273875A
GB4273875A
GB1569105A
GB 1569105 A
GB1569105 A
GB 1569105A
GB 4273875 A
GB4273875 A
GB 4273875A
GB 4273875 A
GB4273875 A
GB 4273875A
GB 1569105 A
GB1569105 A
GB 1569105A
Authority
GB
United Kingdom
Prior art keywords
flap
control device
switch
flow
fluid medium
Prior art date
1976-10-28
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)

Expired

Application number
GB4273875A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

Imperial Chemical Industries Ltd

Original Assignee
Imperial Chemical Industries Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1976-10-28
Filing date
1976-10-28
Publication date
1980-06-11

1976-10-28
Application filed by Imperial Chemical Industries Ltd
filed
Critical
Imperial Chemical Industries Ltd

1976-10-28
Priority to GB4273875A
priority
Critical
patent/GB1569105A/en

1980-06-11
Publication of GB1569105A
publication
Critical
patent/GB1569105A/en

Status
Expired
legal-status
Critical
Current

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Classifications

H—ELECTRICITY

H01—ELECTRIC ELEMENTS

H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES

H01H35/00—Switches operated by change of a physical condition

H01H35/24—Switches operated by change of fluid pressure, by fluid pressure waves, or by change of fluid flow

H01H35/40—Switches operated by change of fluid pressure, by fluid pressure waves, or by change of fluid flow actuated by devices allowing continual flow of fluid, e.g. vane

H01H35/405—Switches operated by change of fluid pressure, by fluid pressure waves, or by change of fluid flow actuated by devices allowing continual flow of fluid, e.g. vane the switch being of the reed switch type

Description

(54) ELECTRIC SWITCH DEVICE FOR MONITORING FLUID FLOW
(71) We, IMPERIAL CHEMICAL IN
DUSTRIES LIMITED, Imperial Chemical
House, Millbank, London SW1P 3JF, a
British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to an electric switch device for monitoring fluid flow and in particular to a control device comprising an electric switch actuated in response to changes in the rate of flow of a fluid.
Control devices are known which sense a change in the rate of flow of a fluid and which thereupon operate an electric switch, the switch itself operating other apparatus designed either to compensate for the change in flow rate, or possibly avert or at least give warning of a hazardous situation arising as a result of the change in flow rate. Such a control device is necessary, for example, to ensure the maintenance of safe conditions in purged analysis houses or other controlled-atmosphere chambers or laboratories, or for maintaining a steady rate of flow of gas or liquid to an apparatus such as a chemical reaction vessel. We have now devised an improved control device which is particularly reliable in long term operation and which has the advantage of being free of bearings which often give trouble during prolonged periods of operation, particularly when used in corrosive fluids.
According to the present invention there is provided a control device responsive to changes in the rate of flow of a flowing fluid medium, comprising a flexible flap anchored adjacent to an electric switch such that movement of the flap may actuate the switch, the flap being movable in the fluid medium by reason of deformation of the flap in response to changes in the rate of flow of the fluid medium, and the switch and the flap being arranged such that the switch acts as a stop limit for movement of the flap when the flap is deformed in response to flow of the fluid medium.
The flexible flap is made of a material chosen so that it will not deteriorate under the conditions of use. Continued flexibility of the flap is essential to the efficient operation of the control device and therefore if and when the material of the flap changes its characteristics, the flap should normally be renewed. The flap should be capable of being deformed continuously for long periods without exhibiting signs of fatigue as a result of continuous flexing.
Some degree of resilience is desirable in the flexible flap in order that it may return to a natural undeformed condition by reason of its inherent resilience. If necessary a restoring force may be applied to the flap, for example by means of a spring or a weight, but a simpler construction may be adopted where the flap returns to a rest position by reason only of its inherent resilience.
The flap may be mounted in any convenient plane but horizontal or vertical planes are preferred. Preferably the flap is mounted in a plane substantially at a right angle to the direction of flow of the fluid medium.
The material of which the flap is made may be a metal, plastic, rubber, leather or other suitably flexible material, preferably in the form of a flat sheet or film. The sheets or films preferred are those of organic polymers, including synthetic and natural plastics and rubbers, and especially preferred are dimensionally stable sheets or films including biaxially-oriented films of, for example, polyethylene terephthalate or polypropylene, and fabric reinforced sheets of flexible plastics and rubbers. Films which are dimensionally stable at elevated temperatures, for example 100″C, may be provided for operation in warm fluids, for example in heated air-conditioning systems.
For operation at temperatures below ambient, for example in refrigeration systems or cooled air-conditioning systems, rubbery films are preferred, especially films of low-temperature rubbers for example silicone rubbers or ethylene/propylene copolymer rubbers.
The flap may conveniently be attached by one end to and located inside ducting for the fluid medium so that it protrudes in the flow of the fluid. Alternatively it may be attached to a rigid structure located adjacent to the ducting and suitably positioned such that the flap may be responsive to changes in the rate of flow of fluid through the ducting. The flap preferably is placed adjacent to an orifice in the ducting and an especially preferred arrangement is one in which a flap of a suitable size completely covers an orifice in the ducting. In this latter arrangement, the sensitivity of the flap to small changes in the flow of fluid through the ducting is more readily controlled.
The degree of resilience and flexibility required in the flap will depend upon the particular application in mind, the type of fluid, the rates of flow of the fluid to be encountered, and the sensitivity required.
Similarly, the thickness and other dimensions of the flap may be determined according to the same parameters. Thus, films of plastics materials, for example from 5 ym to 500 pm, may be suitable for construction of a flap used in sensing a gentle flow of most gases, especially air, but thicker films or sheets may be necessary for sensing flowing liquids or rapidly flowing gases. The latter films or sheets are most suitably of natural rubber or leather, optionally bonded to or strengthened with fabric.
The switch may be a conventional electric switch, preferably a bi-polar, stopgo or on! off switch controlling other apparatus not forming part of this invention but which may be closely associated with the invention. For example the switch may control means such as pumps, compressors, flow gauges and fluid reservoirs for regulating the flow of the fluid to which the control device is responsive.
Alternatively the switch may be used to control apparatus not directly connected with the fluid medium to which the control device is responsive. For example, if the control device is mounted in a stream of air and made responsive to changes in the flow of the air, then the switch might be used to regulate make-up gases, e.g. oxygen for the air.
The switch may control other apparatus by known, conventional means of operation, the most common of which are electrical and pneumatic means.
The control device is especially applicable to the control of atmosnheric conditions pertaining in a chamber, room, laboratory, cabinet or other confined snace.
The device may be used, for example, to ensure that a constant, or at least a minimum, rate of flow of air or other gas or vapour is maintained in or out of the confined space in question. The flap may be mounted over a port hole in the chamber, room, etc. and the control device may be used to ensure that the pressure inside the chamber is always either greater than or less than that outside, the switch being used to operate apparatus, for example a fan or compressor, which will restore the desired condition inside the chamber.
Actuation of the electric switch as a result of movement of the flap may be achieved by a variety of means, including for example mechanical, optical or electrical means. For example, the actuator may trip a spring-loaded arm or it may be a mirror causing reflection of light to a photsensitive element. It is desirable that actuation of the switch causes no drag on the deformation of the flap and therefore non-mechanical methods of actuation are preferred.
Electrical actuation of the switch is the most versatile method of actuation and is preferred. This means of actuation may take a variety of forms, including for example magnetic, capacitive, or resistive means. Magnetic actuation is the especially preferred form and many switches are commercially available which are actuated by the proximity of a magnet or other mass of magnetic material and are suitable for use in the present control device.
It may be necessary to mount a switchactuator on that portion of the flap which moves in response to changes in the rate of flow of fluid. For example, using a magnetically operated switch, if the movable portion of the flap is not made of a magnetic material it is necessary to attach a magnetic material, for example a small sheet, bar or stud of a ferro-magnetic material, e.g. iron or nickel, to the movable portion of the flap in order to actuate the switch. Preferably the switch is situated in a fixed location which may conveniently be in the flow of fluid adjacent to the movable portion of the flap. For magnetically operated switches, the actuator is suitably a mass of ferro-magnetic material attached to the movable portion of the flap which throws the switch according to whether it is close to or far removed from a magnetic component in the switch, for example a solenoid.
A capacitive switch may be actuated by the proximity of a piece of metal on the flap, for example aluminium or copper.
In all cases, it is the position of the actuator which determines the operation of the switch and the movement of the actuator from one position to another which causes the switch to throw. In other respects the construction of the electrical switch itself may be entirely conventional.
It may be convenient to locate the switch, for example by suspension from ducting, in the fluid medium adjacent the flap. Accordingly it may be necessary to prevent corrosion of the terminals and contacts of the switch by the components of the fluid medium, and this may be done for example by encasing the switch in a protective casing, jacket or sleeve. If the switch is encased, remote (e.g. magnetic, capacitive) actuation has obvious advantages in that the switch can be operated through the casing or even through a complete encap sulation of the switch which may be desirable to isolate the switch from corrosive conditions, for example on a chemical plant.
The switch circuit is intrinsically safe by virtue of the low voltage at which it may be caused to operate.
The switch is mounted so that it acts as a stop limit for the movement of the flap when the flap is deformed in response to flow of the fluid medium. If the flow rate is greater than a predetermined value, the flap is held firmly against the body of the switch by the flow of the fluid, and the switch is actuated when the flow of fluid falls below the predetermined value. There is an advantage in this arrangement in that if the fluid flow rate is not steady at a high rate of flow. above the predetermined value, the switch may be made insensitive to small fluctuations in flow rate while remaining sensitive to a drastic reduction in flow rate to below the predetermined value which represents the dangerous situation to be averted. The threshold level may be predetermined by a choice of the dimensions and materials used in the con struction of the flap and the degree of change in fluid flow rate to which the switch responds may be chosen to be less than and equal to any desired proportion of the normal fluid flow rate. Thus for example the switch could be actuated when the flow rate of the fluid fell to say 50% of the normal flow rate.
A complete reversal of the fluid flow may be easily and immediately detected by the control device, whatever mode of operation of the flap is selected. If the flap is arranged to cover an orifice from which the flow of fluid emerges, a reversal of the fluid flow would cause the flap to seal the orifice and thus not only cause the switch to be actuated but also cause the flat, to seal the orifice against further flow of fluid through the orifice in the reverse direction.
Such a control device is useful for emergency control switching of fluids particularly when any appreciable reversed flow of fluid would be hazardous.
A particular embodiment of the invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a side-elevation, in part-section, of a control device comprising a flap and a conventional magnetically-actuated electrical switch, used to control for example ventilation or air-conditioning apparatus (not shown in Figure 1), and
Figure 2 is an elevation of the front face of the flap viewed in the direction of the arrow shown in Figure 1.
An aperture (1) in the wall (2) of an airfilled chamber, room or house (not shown in full) is defined by internal flange (3) losely covered by a vertical curtain of flat plastic film (4). The film (4) is suspended vertically from a clamping bar (5) arranged in a horizontal plane well above the flange (3).
A small magnet (6) is attached to the lower central region of the film (4) on the opposite face from that which touches the flange (3).
A magnetically-operated electrical reedswitch encased in a protective tube (7) is mounted on a spur (8) bolted at (12) to the interior of a protective housing (9) open to the atmosphere at its lower end (10). An electric cable (11) connects the reed-switch electrically to ventilation or air-conditioning apparatus, not shown. The reed-switch in its protective tube is positioned such that its magnetically sensitive region (13) may be closely approached by the magnet (6) whenever the film curtain (4) is blown away from the flange (3) by a flow of gas through the aperture (1) from the chamber, room or house.
In its position of rest as shown in the drawing and especially if the flow of gas is inwards from the opening (10), i.e. from left to right through the aperture (1), the film is pressed tightly against the flange (3) and seals against further ingress of gas, thus acting as a one-way valve. However, when there is a steady flow of gas outwards through opening (10), i.e. from right to left through aperture (1), the film is deformed away from the flange (3) and if the flow is sufficiently strong and steady the magnet (6) is held against the tube (7) of the reed-switch.
It can be arranged that a proportion, for example 50%, of the normal flow of fluid desired through the aperture is sufficient to move the film (4) carrying the magnet (6) towards the tube (7) and the remaining proportion of the flow merely holds the curtain in position in contact with the tube (7) against the gravitational forces and the inherent resilience of the curtain. Thus small variations in the flow rate of fluid through the apertures (11) and (10) are not detected in this arrangement and the switch is insensitive to all but major changes in flow. Thus only when the fluid flow falls to less than a predetermined proportion of normal will the switch be actuated by movement of the magnet (6) out of contact with tube (7). When the flow of fluid ceases, or is reversed in direction, the switch is sure to operate because the film (4) returns to the position of rest against the flange (3).
The control device shown in the drawings is especially useful for regulating the supply of fresh air flowing through a chamber from which the aperture (1) is the main fluid outlet. The device will enable adjustment of the air flow or one or more components thereof to maintain a desired atmosphere in the chamber, and furthermore will ensure that should the supply of air fail then no toxic or other hazardous vapours can enter the chamber from the outside before the fresh air supply is restored. This arrangement is suitable for use in portable analysis houses fitted with instruments, which houses may be transported to and used in potentially hazardous areas of, for example, chemical plant, oil installations, mines, etc. The analysis house purged with fresh air regulated by the control device provides a safe working area in which personnel are able to perform analysis over long periods of time without the need for protective clothing, breathing apparatus, masks, ect. All instruments, supplies and other equipment in hazardous areas is required to be intrinsically safe electrically and the control device described inherently fulfils these requirements. Friction, which might cause sparks or generate heat, is kept to the absolute minimum and the electrical contacts for the switch are encased in a protective tube which may be supplied by an intrinsically safe electrical circuit.
WHAT WE CLAIM 1S:- 1. A control device responsive to changes in the rate of flow of a flowing fluid medium, comprising a flexible flap anchored adjacent to an electric switch such that movement of the flap may actuate the switch, the flap being movable in the fluid medium to actuate the switch by reason of deformation of the flap in response to a change in the rate of flow of the fluid medium, and the switch and the flap being arranged such that the switch acts as a stop limit for movement of the flap when the flap is deformed in response to flow of the fluid medium.
2. A control device as claimed in Claim 1 in which the switch is actuated by mag netic means.
3. A control device as claimed in Claim 2 in which a mass of ferro-magnetic material is attached to the moving portion of the flap which acts as actuator for the switch.
4. A control device as claimed in any one of Claims 1 to 3 in which the flap is attached by one end to and located inside ducting for the fluid medium.
5. A control device as claimed in any one of Claims 1 to 3 in which the flap is attached by one end to a rigid structure adjacent to ducting for the fluid medium.
6. A control device as claimed in Claim 4 or 5 in which the flap is adjacent an orifice in the ducting and is of a size such that it completely covers the orifice.
7. A control device as claimed in Claim 1 in which the rate of flow of the fluid medium sufficient to cause the flap to contact the switch stop limit is less than the normal rate of flow of the fluid medium.
8. A control device as claimed in any one of the preceding claims in which the switch controls means for regulating the flow of fluid to which the device is responsive.
9. A control device as claimed in any one of the preceding claims in which the flap is made of a resilient material.
10. A control device as claimed in any one of the preceding claims in which the flap is located in a plane substantially at a right angle to the direction of flow of the fluid medium.
11. A control device as claimed in any one of the preceding claims in which the flap is in the form of a flat sheet or film.
12. A control device as claimed in any one of the preceding claims in which the flap is made of a plastics or rubber material.
13. A control device responsive to changes in the rate of flow of a flowing fluid medium substantially as herein described with particular reference to the accompanying drawings.
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. normal will the switch be actuated by movement of the magnet (6) out of contact with tube (7). When the flow of fluid ceases, or is reversed in direction, the switch is sure to operate because the film (4) returns to the position of rest against the flange (3). The control device shown in the drawings is especially useful for regulating the supply of fresh air flowing through a chamber from which the aperture (1) is the main fluid outlet. The device will enable adjustment of the air flow or one or more components thereof to maintain a desired atmosphere in the chamber, and furthermore will ensure that should the supply of air fail then no toxic or other hazardous vapours can enter the chamber from the outside before the fresh air supply is restored. This arrangement is suitable for use in portable analysis houses fitted with instruments, which houses may be transported to and used in potentially hazardous areas of, for example, chemical plant, oil installations, mines, etc. The analysis house purged with fresh air regulated by the control device provides a safe working area in which personnel are able to perform analysis over long periods of time without the need for protective clothing, breathing apparatus, masks, ect. All instruments, supplies and other equipment in hazardous areas is required to be intrinsically safe electrically and the control device described inherently fulfils these requirements. Friction, which might cause sparks or generate heat, is kept to the absolute minimum and the electrical contacts for the switch are encased in a protective tube which may be supplied by an intrinsically safe electrical circuit. WHAT WE CLAIM 1S:-

1. A control device responsive to changes in the rate of flow of a flowing fluid medium, comprising a flexible flap anchored adjacent to an electric switch such that movement of the flap may actuate the switch, the flap being movable in the fluid medium to actuate the switch by reason of deformation of the flap in response to a change in the rate of flow of the fluid medium, and the switch and the flap being arranged such that the switch acts as a stop limit for movement of the flap when the flap is deformed in response to flow of the fluid medium.

2. A control device as claimed in Claim 1 in which the switch is actuated by mag netic means.

3. A control device as claimed in Claim 2 in which a mass of ferro-magnetic material is attached to the moving portion of the flap which acts as actuator for the switch.

4. A control device as claimed in any one of Claims 1 to 3 in which the flap is attached by one end to and located inside ducting for the fluid medium.

5. A control device as claimed in any one of Claims 1 to 3 in which the flap is attached by one end to a rigid structure adjacent to ducting for the fluid medium.

6. A control device as claimed in Claim 4 or 5 in which the flap is adjacent an orifice in the ducting and is of a size such that it completely covers the orifice.

7. A control device as claimed in Claim 1 in which the rate of flow of the fluid medium sufficient to cause the flap to contact the switch stop limit is less than the normal rate of flow of the fluid medium.

8. A control device as claimed in any one of the preceding claims in which the switch controls means for regulating the flow of fluid to which the device is responsive.

9. A control device as claimed in any one of the preceding claims in which the flap is made of a resilient material.

10. A control device as claimed in any one of the preceding claims in which the flap is located in a plane substantially at a right angle to the direction of flow of the fluid medium.

11. A control device as claimed in any one of the preceding claims in which the flap is in the form of a flat sheet or film.

12. A control device as claimed in any one of the preceding claims in which the flap is made of a plastics or rubber material.

13. A control device responsive to changes in the rate of flow of a flowing fluid medium substantially as herein described with particular reference to the accompanying drawings.

GB4273875A
1976-10-28
1976-10-28
Electric switch device for monitoring fluid flow

Expired

GB1569105A
(en)

Priority Applications (1)

Application Number
Priority Date
Filing Date
Title

GB4273875A

GB1569105A
(en)

1976-10-28
1976-10-28
Electric switch device for monitoring fluid flow

Applications Claiming Priority (1)

Application Number
Priority Date
Filing Date
Title

GB4273875A

GB1569105A
(en)

1976-10-28
1976-10-28
Electric switch device for monitoring fluid flow

Publications (1)

Publication Number
Publication Date

GB1569105A
true

GB1569105A
(en)

1980-06-11

Family
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Application Number
Title
Priority Date
Filing Date

GB4273875A
Expired

GB1569105A
(en)

1976-10-28
1976-10-28
Electric switch device for monitoring fluid flow

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GB1569105A
(en)

Cited By (2)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

GB2238664B
(en)

1989-12-02
1994-06-22
Powered Showers Plc
Flow switch assembly

GB2310538A
(en)

1996-02-20
1997-08-27
Elfab Ltd
Fluid flow detection device

1976

1976-10-28
GB
GB4273875A
patent/GB1569105A/en
not_active
Expired

Cited By (2)

* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

GB2238664B
(en)

1989-12-02
1994-06-22
Powered Showers Plc
Flow switch assembly

GB2310538A
(en)

1996-02-20
1997-08-27
Elfab Ltd
Fluid flow detection device

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