GB2198260A - Fluidic devices - Google Patents

Abstract

A bistable amplifier 14 has output passages 21, 22 connected to the opposed jets of an opposed jets pressure transformer 15 whose jets deliver to an otherwise closed connecting passage. Outputs 28, 29 of the transformer are alternately pressured and vented for example to operate a pulse column 13. The amplifier 14 may be supplied from an oscillator 30 which may include a further 52 amplifier 48. <IMAGE>

Description

Fluidic devices This invention relates to fluidic devices.

According to this invention a fluidic device comprises a bistable amplifier having an output which can be switched between two passages, and an opposed jet pressure transformer having inlets to said opposed jets connected respectively to said passages.

An oscillator may be connected to supply control pressures to control ports of said amplifier.

There may be an amplifier for amplifying output pressure signals of the oscillator before they are fed to the control ports.

The invention may be performed in various ways and one specific embodiment with possible modifications will now be described by way of example with reference to the accompanying diagramatic drawings, in which: Figure 1 shows a fluidic drive unit; Figure 2 is a perspective view of a power output arrangement; and Figure 3 is a circuit corresponding to Figure 2.

A fluidic power output or drive unit 10 provides reciprocating air in a line 11 to push liquid 12 in a pulse-limb of a pulse column 13 up and down. One example of operation of a pulsed column is described in British Patent Specification 2016739A. The drive unit 10 could also be used for driving single-acting fluidic pumps but it is better suited for pulsing and mixing applications where the pressure amplitudes are lower but the frequency and flow amplitudes are higher than in pumps. The pulsed output is obtained from an unvented bistable amplifier 14 in association with an opposed jet pressure transformer (OJPT) 15. The amplifier 14 acts as a flow diverter.

The amplifier 14 has a. supply passage or channel 16 leading to a reduced-section outlet portion 17 feeding to an outlet chamber 18. Also communicating with the inlet side of the chamber 18 are opposed transverse control passages 19, 20.

The chamber 18 has two outlet passages 21, 22 which lead respectively to opposed ends of the transformer 15 which has a central chamber 23 having enlarged end regions 24, 25 into which deliver respectively opposed jets 26, 27.

A transverse vent passage 28 leads from region 24 and a transverse outlet passage 29 leads from region 25 and is connected to pipe 11.

The power output stage 10 may be part of a drive unit or system including an oscillator 30 and, preferably, a buffer stage 31 to amplify the control signals from the oscillator 30, the frequency of the oscillator being controlled by valve 32 for adjusting the air supply volume and pressure. The oscillator 30 may have feedback connections including reservoirs 33, 34 and .restrictors (not shown).

The oscillator provides alternating control signal pulses at ports 19, 20 to switch the output from amplifier 14 between passages 21, 22. When a pulse is supplied at passage 19 the output from the amplifier goes to passage 22, when a pulse is supplied at passage 20 the output from the amplifier goes to passage 21.

Because of the operation of the transformer 15, when the amplifier output goes to passage 22, there is suction at passage 29, output at vent 28 and a back pressure in passage 21 at the chamber 18. When the amplifier output goes to passage 21, there is suction at vent 28, output pressure at passage 29 and a back pressure in passage 22 at chamber 18.

In either case the back pressure at chamber 18 helps to keep the flow from chamber 18 in the direction it is at that time, until a change in pulse or control pressure at ports 19, 20.

The pressure feedback helps to stabilize the amplifier 14 and thus to reduce the effects in it of air compressibility.

The power output stage is typically part of a system which in its entirety is called a "drive-unit". This includes an oscillator and possibly a buffer stage to amplify the signals from the oscillator. The frequency of the oscillator may be controlled by a valve in the air supply to it.

The most important aspect of the system is the power output stage. This uses the OJPT 15 connected to the bistable amplifier 14 so that when flow is switched to one jet of the OJPT, the other jet experiences a backpressure which is fed back to the bistable amplifier helping to keep the flow switched in the given direction.

This may be referred to as "positive pressure feedback".

This pressure feedback occurs whichever direction the amplifier is switched since the system is symmetrical. A great benefit is the fact that the pressure feedback helps to pressurise the whole bistable amplifier. This reduces the adverse effects of air compressibility in it.

Referring to Figure 3, high pressure air supply in line 16 goes through line 41 including needle valve 40 to oscillator 30 which is in the form of a vented amplifier with feedback.

The oscillator 30 has vessels 33, 34 connected to vented amplifier 42 having vents 43 and output lines 44, 45 including restrictors 46, 47, leading to an unvented buffer amplifier 48 whose outputs 49, 50 leadwto.an unvented power amplifier 14 which receives air from line 16 via line 51 including needle valve 52. Vessels 33, 34 communicate respectively with lines 44, 45 through lines 53, 54 including restrictors 55. Vessels 33, 34 communicate with control ports in amplifier 42 via lines 56, 57 including needle valves 58, 59 which permit flow from the respective vessel. The needle valves 58, 59 improve the controlability of the system, enabling the frequency and relative phase-lengths of the oscillations to be adjusted.

There may be a plurality of buffer amplifiers in series.

The buffer amplifier 48 and power amplifier 14 can be vented or unvented.

Pressure air goes on line 60 to the amplifier 18.

Instead of common value 40 there could be separate needle values in the supplying lines to values 42, 48.

It will be observed that in the power transformer the opposed jets deliver to an otherwise closed connecting passage between jet chambers.

Claims (4)

Claims

1. A fluidic device comprising a bistable amplifier having an output which can be switched between two passages, and an opposed jet pressure transformer having inlets to said opposed jets connected respectively to said passages, the jets delivering to an otherwise closed connecting passage.

2. A fluidic device as claimed in Claim 1 in which an oscillator is connected to supply control pressures to control ports of the amplifier.

3. A fluidic device as claimed in Claim 2, including fluidic amplifyiing means for amplifying output pressure signals of the oscillator before the signals are fed to the control ports.

4. A fluidic device substantially as hereinbefore described with reference to and as shown in the accompanying drawings.