This invention relates to intermittent operation of valves, such as in fluid systems and particularly, but not exclusively, in compressed air systems having valve operating controls including condensate exhaust controls.

Condensate comprising water and usually other substances such as oil collect in components of compressed air systems, such as in air receivers and filters. The condensate is normally exhausted from a component by means of a float operated valve which opens if the condensate level rises to a certain level. A difficulty with this exhaust system is that debris in the condensate commonly interferes with correct functioning of the float and valve operation.

It is an object of the present invention to provide an effective and versatile intermittent valve operating control for use in a fluid system e.g. a compressed air system.

It is a further object to provide a valve control which is simple to install and which enables ready replacement of an associated faulty valve.

According to the present invention there is provided a valve operating control for a fluid system, the system including a component from which a fluid is to be intermittently transferred, the system further including a selectively operable fluid transfer valve mounted and operable to open to allow transfer of the fluid from the component, the valve comprising a solenoid valve operable in response to energisation of its associated solenoid, the solenoid being arranged in a housing and being supplied with power from a power source through a solenoid connector provided on the solenoid housing, the valve operating control being for controlling operation of the fluid transfer valve, the valve operating control including a control connector of complementary formation to the solenoid connector so as to be coupled in use to the solenoid connector, the valve operating control further including a power switching means operative to switch electrical power from the power source to the control connector so as to power the solenoid, a selectively adjustable timer means for controlling operation o^ the power switching means and being

adjustable so as to enable user determination and control of the duration of solenoid energisation and the intervals between successive solenoid energisations, and a control housing mounting the control connector and accommodating the power switching means and the timer means so as to enable the valve operating control to be disconnected from the solenoid valve housing and re-connected to the solenoid housing as a unit, the timer means including a user operable duration selector for enabling selective adjustment of the duration of solenoid energisation, the duration selector being operative to enable a user to select any one of a number of possible durations of solenoid energisation, the timer means including a duration timer circuit responsive to the duration selector and operable to generate a valve operating signal at the end of the selected duration to cause a predetermined change of state of the power switching means, the timer means further including a user operable interval selector for enabling selective adjustment of the interval between successive solenoid energisations, the interval selector being operative to enable a user to select any one of a number of possible intervals between successive solenoid energisations, the timer means including an interval timer circuit responsive to the interval selector and operable to generate a valve operating signal at the en of the selected interval to cause a predetermined change of state of the power switching means.

The solenoid connector preferahly comprises a DI type plug and the control connector comprises a complementary DIN socket exposed on the control housing so as to provide a compact and replaceable valve operating control.

The power source may comprise an AC source, and the valve operating control may include a full wave rectifier arranged and operative to provide regulated DC power for the timer means.

The duration selector preferably includes a switch which is user operable to select one of a predetermined number of possible solenoid energisation durations, the duration selector further including duration display means operative in response to user operation of the duration selector switch to provide a visual display of the particular selected solenoid energisation duration. In this embodiment, the duration display means may comprise a plurality o* light sources, each one o ^~~ the lig ^κ t sources being orovidec for ε respective one of the possible durations and being energised upon user selection o* the respective duration.

The timer circuit may include a logic circuit operative to compare the elapsed time since a start of the duration with the selected duration and being operative to cause the generation of the valve operating signal when the elapsed time corresponds to the selected duration.

The interval selector preferably includes a switch which is user operable to select one of a predetermined number of possible intervals between successive solenoid energisations, the interval selector further including interval display means operative in response to user operation of the interval selector switch to provide a visual display of the particular selected interval between successive solenoid energisations. The interval display means may comprise a plurality of light sources, each one of the light sources being provided for a respective one of the possible intervals and being energised upon user selection of the respective interval.

The interval timer circuit may include a logic circuit operative to compare the elapsed time since a start of the interval with the selected interval and being operative to cause the generation of the valve operating signal when the elapsed time corresponds to the selected interval, the control including a reset generator operative to generate a reset signal after the selected interval, the reset signal causing the commencement o ^f the duration of solenoid energisation.

A test circuit may be ^' provided v/hich is selectively operable by the user, the test circuit being operable to cause operation of a display means operative to provide a visual display o^ the particular user selected duration or interval, the test circuit thereby enabling visual verification of correct functioning of the display means. The test circuit is preferably further operable to generate a test valve operating signal v/hich is applied to the power switching means to cause operation thereof for the duration of the test valve operating signal, the power switching means reverting to its initial state at the end of the test valve operating signal duration. The test circuit preferably includes a test gate for generating a test signal to initiate the functions of the test circuit, the test gate having inputs connected to the duration selector and to the interval selector and the test gate being operable upon simultaneous operation of both the duration and interval selectors to cause generation of the test signal .

Possible and preferred features of the present invention will now be described with particular reference to the accompanying drawings.

However it is to be understood that the features illustrated in and described with reference to the drawings are not to be construed as limiting on the scope of the invention. In the drawings:

Fig. 1 is a schematic side view of a valve and valve operating control which can incorporate the invention,

Fig. 2 is a circuit diagram for a valve operating control embodying the present invention, and Fig. 3 is a front view of a housing usable in the present invention.

In the drawings, a compressed air system has a component in such as an air receiver or filter in which condensate collects. A valve 11 is connected to the component 10 in a known way so as to exhaust the condensate when the valve 11 is open. The valve 11 has an associate* solenoid 12 which when energised operates the valve 11. The valve 11 could be normally open and held closed when the solenoid is energised or vice versa as circumstances of use require.

The solenoid 12 preferably has a standard ϋl l plug configuration of pins 13, 14 v/hich project from the solenoid housing.

The exhaust control 15 comprises a control connector 16 having sockets 17 in use receiving the pins 13, 1Δ so that power supplied to contacts associated v/ith the sockets 17 is connected to the solenoid 72. Power switching means I ^s is provided to switch electrical power from a power source (not shown) connected to power cable 19 to the control connector 15 so as to power the solenoid 12. The switching means IS includes triac and driver 20 although a relay may alternatively be used for switching pov/er to the connector IS. The triac and driver 20 may have a high power capability so that the exhaust control 15 could be used to control operation of two or more solenoid valves simultaneously by switching power via a connector to both of the respective solenoids.

The triac and driver 20 is operated by timer means 21 operative so that the duration of solenoid energisation and the interval between successive energisations are bot ^μ determined by the timer means 21. These may be both selectively adjustable. For example, the timer means 21 may comprise an oscillator and registers which give an output signal to change the state of the triac and driver 2~ when the accumulated count in the registers reach selectable values.

Other electronic, electro-mechanical or mechanical timer devices will obviously be usable although electronic timers are preferred for compactness and reliability. To power the timer means 21, a full wave rectifier, and regulated voltage supply of standard design may be used so as to utilise whatever source of power is being used for solenoid energisation.

The power switching means 18, timer means 21 and connector 15 are all provided in a common housing 22 so that these components can be connected and disconnected from the solenoid 12 as a unit. Thus if valve 11 and/or solenoid 12 are faulty, the disconnection of the unit

22 enables simple replacement o"P the faulty comρonent(s).

Referring to Fig. 2 power from the power supply is supplied to input leads 30 and the power switching means T ⁰ ., which may be a triac and driver for example, switches power to the output leads 31 which are connected to the connector 16. Across t ^h e leads 31 is an indicator light such as an LED 32 which indicates when the power is being supplied to an associated connector.

A DC power supply 33 provides a regulated power supply for the remainder of- the circuit. ,- lamp such as an LED 34 is connected across the output of the supply 33 so as to indicate an "on" state of the electronic circuit as indicated by the existence of a voltage at the output of the supply 33.

The timer means 21 which controls operation o ^f the power switching means 18 includes a user operable duration selector 35 v/hich enables selection o ^f the duration of solenoid energisation-. The duration selector 35 enables the user to select any one of a number o possible durations. In the circuit of Fig. 2 there is provided a tv/o bit up/down counter 36 which enables for example the selection of any one of four states corresponding to four possible durations, e.g. 0.5, 1, 2, 5 seconds. The selected duration is set by the user operable push button switch 37 provided on the housing (Fig. 3). The counter 36 can be cycled through the four possible states under control of the switch 37.

The duration selector 35 further includes duration display means 38 shown as an array of LEPs -39 operative in response to user operation of the switch 37 to provide a visual display of the particular selected duration. respective one of the LEDs 39 is energized upon user selection of the respective duration, the decoder 40 being operative to determine the particular selecte state o the counter 35 and cause operation of the appropriate LED 39.

The timer means 21 includes a duration timer circuit ^{[ ~} responsive to the duration selector 35 and operable to generate a valve operating signal on output line 43 at the end of the selected duration to cause a predetermined change of state of the power switching means 18. The timer circuit 42 includes a counter £4 supplied with clock pulses from clock generator 45 so as to be operative as an elapsed time counter, the timer circuit 42 including also a logic circuit 46. The logic circuit 46 compares the elapsed time since the start of the duration as represented by the pulse count stored in counter 44 with the selected generation as represented by the state of counter 36 and causes the generation of the valve operating signal on line 43 when the elapsed time corresponds to the selected duration.

The valve operating signal on line 43 is applied to set-reset latch 50 which creates an output signal on line 51 which causes operation of the switching means 18.

Analogous in construction an ^rl operation in all respects to the duration selector 35 and timer circuit 42 is the interval selector 5F and interval timer circuit 62 v/hich together enable user selection of the interval between successive solenoid energisations. The interval selector 55 includes switch 57 which is used to set the state o ^f two bit up/down counter 56 e.g. corresponding to intervals of say 3, 10, 30, 45 minutes. The decoder 60 monitors the state of the counter 56 and causes the appropriate LED 59 of the display means 58 to be illuminated on the housing front panel (Fig. 3).

The interval timer circuit 62 includes counter 64 and logic circuit 66 which generates a valve operating signal on line 63 when the elapsed time corresponds to the selected desired interval between successive solenoid energisations. The signal on line 63 is applied to the set/reset latch 50 which operates as a reset generator whic ^h is operative to generate a reset signal on line y after the selected interval, the reset signal causing the resetting of the counter 4-^ and thereby causing the commencement of the duration o solenoid energisation. In the circuit of Fig. 2 there is also a test circuit 1 ^~ which is selectively operated by the user and v/hich causes operation of the display means 38, ^~~ to enable visual verification o^ correct functioning of the display means. This is achieved by application o^ signals froπ the test circuit ⁷ 0 to the counters 36, 55. ^£ 1so the

test circuit 70 is operable to generate a test valve operating signal on line 71 which is applied to the switching means 18 through the gate 72 to cause operation of the switching means 1? for the duration of the test valve operating signal on line 71. The test circuit 70 includes a test gate 74 for generating a test signal, the test gate 74 having inputs 75, 76 connected to the duration selector 35 and interval selector 55 in such a way that simultaneous operation of both the duration and interval selector switches 37, 57 causes generation of the test signal at output 77. In addition to the circuit components illustrated, there may be a memory having an associated low power battery or the like, the memory storing the user selected duration and interval values and being arranged, e.g. in association with the counters 36, 56, to retain that data in the event of a power supply failure. In this way upon reconnection of power to the circuit the user is not obliged to reselect the duration and interval values.

Also there may be a power-up circuit so that after a longer period of power failure or upon initial installation there may be default values of the duration and interval, e.g. two seconds and ten minutes respectively, so that the counters 36, 56 do not adopt arbitrary values upon initial power up.

Although not illustrated, there may be a delay circuit associated with the duration and interval selectors 35, 55 to enable verification of genuine user operation of the switches 37, 57 before the counters 36, 56 change state.

It will be seen that the preferred embodiment of the valve operating controls illustrated in the drawings can enable operation of the solenoid valve automatically both in duration of valve openiny and intervals between successive valve openings. The user can select among the choice of intervals and durations. The circuit and valve operation can be tested. The provision of the control connector and timer in the housing enables the entire control to be compact and readily removed for replacement of the associated valve, solenoid etc. e.g. for maintenance purposes. Also of course the installation and operation of the control will be seen to be particularly simple. The timer and duration and interval selection circuitry can in fact be an integrated circuit.

The invention can be used not only for exhausting refuse fror condensers, filters, etc. in compressed air systems, but also in other environments where automatic intermittent valve operation is desirable such as for blowing out air lines, for automatic dispensing of fluid doses, draining condensate from steam or other fluid systems, air pulsing systems.

It is to be understood that various alterations, modifications and/or additions may be made to the features of the possible and preferred embodiments) of the invention as herein described without departing from the scope of the invention as defined in the claims.