GB2161957A - Fluidic diverter valve - Google Patents

Abstract

A monostable fluidic switch is provided with mechanical means 12-14 to operate it directly, that is to say without the need to use ducted fluid for the control functions. The operating mechanism alters the internal asymmetry of the device and thereby causes switching. The method used involves either blocking an exhaust vent or moving the supply orifice with blocking an entrainment vent or by respect to the sidewalls. <IMAGE>

Description

SPECIFICATION Fluidic diverter valve The invention is a switching device whereby a flowstream of air or other fluid is diverted into one or other of two ducts under the command of a two-state mechanical or electrical signal.

Such a device has hitherto been realised by means of a mechanically or solenoid operated spool valve or poppet valve or a combination of both. A characteristic common to all poppet valves and to most spool valves is that the force required to operate them arises mainly from the use of springs and sliding seals in their construction. Some of the operating force is used to overcome the effects of pressure particularly in poppet valves, however this influence is negligible when the pressure is low.

If it is intended to use a valve of one of the types mentioned above to divert the flow of fluid at low pressure, the effort required to operate it is dominated by spring force and seal friction and the solenoid or other operator must be larger and consume more energy than if it had to work against pressure force alone.

When the pressure is low, that is to say less than 0.5 bar, a fluidic wall attachement ampti- fier, which exploits the principle of turbulent reattachment, may be used as a diverter valve. The same device is known also as a fluidic switch, the preferred name for the purpose of description. The traditional method of operating such a switch is by conducting fluid to control ports. Although the power required in the flow to the control ports is small, and in any case less than the power in the diverted flowstream because the switch is an amplifier, it is necessary to provide mechanical valves to modulate the control flow.

The object of the invention is to provide a diverter valve in the form of a fluidic switch operated by mechanical means or by a solenoid whose rating depends almost entirely on the pressure of the flowstream and, if the pressure is low, both the force required and the rating are small. Moreover the means of operation act directly on the fluidic switch and there is no need of flow for control purposes.

Fluidic switches are already well known but their construction and operation will be described to the extent required to clarify the working of the invention.

Figure la shows in a diagrammatic way a traditional fluidic switch of the bistable type.

Fig. 1 b shows the monostable type. The figures are section diagrams showing the arrangement of passages inside solid blocks of material. The passages have rectangular cross sections of uniform thickness in the direction perpendicular to the plane of the diagram. For the sake of brevity, the description of operation refers to air as the working fluid although both types of fluidic switch will work with any fluid capable of turbulent flow.

Reference numbers which are repeated relate to parts with identical function.

The bistable and monostable versions of the fluidic switch differ in the matter of symmetry.

The bistable switch of fig. 1 a is intended to be symmetrical in the arrangement of passages so that when compressed air is applied to inlet port 1 a jet of air emerges from oifice 2 and attaches to one or other of sidewalls 3 or 4 in a random way and passes to the adjacent outlet port 5 or 6. Once the flow is established on one sidewall it will remain attached in a stable manner. In effect, the attachment of flow imposes assymmetry on the flow pattern within a symmetrical arrangement of flow passages. In order to make the switch change from one state to the other, air is injected into the appropriate control port. If for example the flow is attached to sidewall 3, air at sufficient pressure applied to control port 9 overcompensates for the assymmetry caused by the attachment and the flow switches to the other side where it attaches to sidewall 4 and emerges from outlet port 6.

This state will persist even after the influence at control port 9 is removed.

The monostable switch of fig. 1 b is constructed deliberately with assymmetry in the form and arrangement of sidewalls 3 and 4 with respect to orifice 2. In the simplest version the side walls are symmetrical but the orifice is placed nearer to sidewall 3 than to sidewall 4 with the effect that the flow from orifice 2 attaches preferentially to sidewall 3.

Assymmetry of construction is enhanced by the presence of only one control port 9, adjacent to sidewall 3, on the other side there is the entrainment vent 11. Air applied at sufficient pressure to control port 9 overcomes the combined effect of assymmetrical construction and unilateral attachment and causes the flow to switch to the other side where it attaches to sidewall 4 and emerges from outlet port 6. This state depends on the continuing flow of air through control port 9.

When the control flow ceases the main flow revers to sidewall 3 and outlet port 5.

A common feature of both types of fluidic switch is the provision of exhaust vents 7 and 8. When an outlet port is connected to a restrictive duct, as is often the case when a switch is put to practical use, not all the flow coming from orifice 2 can pass through the outlet port and surplus flow escapes from the adjacent exhaust vent.

According to the invention there is provided a fluid flow diverter having an inlet passage to an inlet orifice; a first outlet passage to a first outlet port; and a second outlet passage to a second outlet port; there being an assymmetric relationship between the inlet orifice and the outlet passages such that in a first operating state of the diverter fluid flowing from the inlet orifice attaches to the wall of one of the outlet passages to exit from the diverter via the outlet port of this outlet with no flow from the outlet port of the other outlet passage; the diverter having means operable mechanically to alter said assymmetric relationship to change-over the diverter to a second operating state in which fluid flowing from the inlet orifice attaches to the wall of said other outlet passage to exit from the diverter via the outlet port of this other outlet passage with no flow from the outlet port of said one outlet passage.

Fig. 2 shows one embodiment of the invention where a monostable fluidic switch is provided with mechnical means to block the entrainment vent and thereby to operate the switch.

Figure 3 shows a second embodiment where a monostable fluidic switch is provided with mechanical means to block an exhaust vent and thereby to operate the switch.

Figure 4 shows a third embodiment of the invention where a fluidic switch is provided with mechanical means to move the supply orifice bodily in relation to the sidewalls and thereby to operate the switch.

In fig. 2 the arrangement of internal passages is the same as in fig. 1 b. Mechanical means to operate the switch comprise plunger 12, solenoid 13 and spring 14. Energising solenoid 1 3 causes plunger 1 2 to compress spring 14 and to block entrainment vent 11.

Alternative mechanical means to operate the switch, not illustrated, comprise a lever or a perforated plate arranged so that displacement or rotation or both blocks vent 11. The normal state of the switch is with the flow attached to sidewall 3 and vent 11 open.

Blocking vent 11 causes over compensation for the combined effect of the assymmetry of construction and of attachment of flow to sidewall 3 and causes the flow to switch in a process which is explained as follows. Flow from orifice 2 has the nature of a submerged jet consequently there is entrainment of air which augments the main flow past sidewall 3 towards outlet port 5 and most of the augmenting flow comes from the entrainment vent 11. Entrainment continues even after vent 11 is blocked causing a lowering of pressure on that side of the jet. There is no similar effect on the other side consequently there is a pressure difference across the width of the jet and the flow bends towards sidewall 4 where it attaches in a stable manner and emerges from outlet port 6. This is the operated state of the switch, it persists for as long as vent 11 is blocked.The switch reverts to the normal state when vent 11 is opened again.

The second embodiment of the invention comprises a monostable fluidic switch as shown in fig. 3 where the arrangement of internal passages may differ from that shown in fig. 1 b by having no control port (9) and no entrainment vent (11) but this difference is not essential. Mechanical means to operate the switch consist of a plunger 12, solenoid 1 3 and spring 14. Energising solenoid 1 3 causes plunger 1 2 to compress sring 14 and to block exhaust vent 7. Alternative mechanical means to operate the switch, not illustrated, comprise a lever or a perforated plate arranged so that movement or rotation or both blocks vent 7.

In the applications envisaged for this embodiment outlet port 7 is connected to a restrictive duct with the effect that, in the normal state of the switch with flow attached to sidewall 3, not all the flow coming from the orifice 2 can pass through outlet port 5 consequently some of the flow escapes by the exhaust port 7. When port 7 is blocked there is a pressure rise in the region of sidewall 3 and at the same time the surplus flow is forced towards sidewall 4 and outlet port 6.

The consequent over compensation for the combined effects of assymmetry of construction and attachment to sidewall 3 causes the flow to switch in a stable manner to sidewall 4 and outlet port 6. This is the operated state of the switch, when exhaust vent 7 is opened the flow reverts to the normal state.

The third embodiment of the invention comprises a fluidic switch with symmetrical sidewalls 3 and 4 in the form shown in fig. 4.

The orifice 2 is a passage in the movable block 1 6 connected to a supply of compressed air by the flexible duct 1 7. The mounting 1 8 of duct 1 7 is rigidly attached to the body of the fluidic switch by bracket 21.

Also mounted on bracket 21 is electromagnet 1 9 arranged to cooperate with armature 20 mounted on the movable block 1 6. Block 1 6 and orifice 2 are normally in the first location as depicted in fig. 4 where orifice 2 is nearer to sidewall 3 than to sidewall 4 so that flow from orifice 2 attaches preferentially to sidewall 3. The switch is then in the normal state and flow emerges from outlet port 5. In this embodiment of the invention the assymmetry of the switch is varied by moving the block 1 6 under the influence of electromagnet 1 9. When electromagent 1 9 is energised orifice 2 is moved through and beyond the axis of symmetry to a location where it is nearer to sidewall 4 than to sidewall 3. In consequence of the movement of the orifice 2 the switch is in the operated state, the flow attaches preferentially to sidewall 4 and the outlet flow comes from port 6. Releasing the electromagnet allows block 1 6 to move back to the first location and the switch to revert to the normal state. Alternative means to operate the switch, not illustrated, comprise a plunger or lever whereby block 1 6 can be moved from the first state to the operated state.

It will be apreciated that in each of the fluidic switches described above with refer ence to Figs. 2, 3 and 4, the orifice 2 is an inlet orifice at the end of an inlet passage; the sidewalls 3 and 4 are sidewalls of first and second outlet passages to the outlet ports 5 and 6 respectively; and there is in each of these outlet passages at least one orifice (9 or 11, also 7 or 8 in Fig. 2-7 or 8 in Fig. 3 and in Fig. 4) opening from the outlet passage in addition to the outlet port thereof. In each of the switches of Figs. 2 and 3 the orifice in one only of the outlet passages (orifice 11 in Fig. 2, orifice 7 in Fig. 3) has associated with it a blocking member that is the plunger 1 2.

Movement of this blocking member serves mechanically to alter the assymetric relationship between the inlet orifice and the outlet passages, this orifice and the outlet passages having one form of such a relationship when the orifice 11 (Fig. 2) or 4 (Fig. 3) is open and a different form when this orifice is closed by the blocking member. In the switch of Fig.

4 it is bodily movement of the inlet orifice, by operation of the electromagnet 19, that serves mechanically to alter the assymetric relationship between the inlet orifice and the outlet passages.

Claims (8)

1. A fluid flow diverter having an inlet passage to an inlet orifice; a first outlet passage to a first outlet port; and a second outlet passage to a second outlet port; there being an assymetric relationship between the inlet orifice and the outlet passages such that in a first operating state of the diverter fluid flowing from the inlet orifice attaches to the wall of one of the outlet passages to exit from the diverter via the outlet port of this outlet passage with no flow from the outlet port of the other outlet passage; the diverter having means operable mechanically to alter said assymetric relationship to change-over the diverter to a second operating state in which fluid flowing from the inlet orifice attaches to the wall of said other outlet passage to exit from the diverter via the outlet port of this other outlet passage with no flow from the outlet port of said one outlet passage.

2. A diverter as claimed in claim 1, wherein there is at least one orifice opening from each outlet passage in addition to the outlet port thereof; and wherein said means comprises a blocking member associated with this one orifice of one only of the two outlet passages, the diverter being in one or other of its operating states when this one orifice is open, and being changed-over to the other of its operating states by movement of the blocking member to close this one orifice.

3. A diverter as claimed in claim 2, wherein said one orifice is an entrainment vent.

4. A diverter as claimed in claim 2, wherein said one orifice is an exhaust vent.

5. A diverter as claimed in claim 2, 3 or 4, wherein the blocking member is moved by actuation of a solenoid.

6. A diverter as claimed in claim 1, wherein said means is arranged to move the inlet orifice relative to the outlet passages from a first position in which the diverter is in one of its operating states, to a second position in which the diverter is in the other of its operating states.

7. A diverter as claimed in claim 6, wherein said means is an electromagnet cooperating with a movable mount of the inlet port.

8. A fluid flow diverter, substantially as hereinbefore described with reference to Fig.

2, 3 or 4 of the accompanying drawings.