Transcript Time delay valve

Pneumatics Module 9
TIME DELAY VALVE
OBJECTIVES
Demonstrate an understanding of the
different types of time delay valves.
 Identify the normally closed time delay valve.
 Identify the main parts of the time delay
valve.
 Draw a pneumatic circuit diagram that
consists of a time delay valve, normally
closed.
 Simulate pneumatic circuit that consists of a
time delay valve using Fluid SIM software.
 Build a pneumatic circuit that consists of a
time delay valve as per specific requirements.

TIME DELAY VALVE

Pneumatic time elements can be formed
very simply from combinations of three
valves: directional control valve, throttle
valve and reservoirs.
 Time
FUNCTION
delay valve is used to
delay the output signal.
 The time delay valve is
actuated by a pneumatic
signal through the tank
after a preset time delay
has elapsed. The returned
to the normal position via
return spring when the
signal is terminated.
SYMBOLS
Time Delay Valve N/C
Time Delay Valve N/O
DESIGN
The time delay valve is a combination of a 3/2
way valve, one way flow control valve and air
reservoir.
 The 3/2 way valve can be normally open or
normally closed. The delay time is generally
ranging between (0-300) seconds for both
types of valves (normally opened and normally
closed).
 By using additional reservoirs, the delaying
time can be extended.
 The type of the time delay valve whether
normally opened or normally closed is
determined according to the type of the 3/2
way valve if it is N/O or N/C.

DESIGN
3/2 way valve N/C
3/2 way valve N/O
PRINCIPLE OF OPERATION



The following operational principle applies for a time delay
valve in normally closed position.
The compressed air is supplied to the valve at connection 1.
The control air flows into the valve at 12 through a one way
flow control valve and depending on the setting of the
throttling screw, a greater or lesser amount of air flows per
unit of time into the air reservoir, when the necessary
control pressure has built up in the air reservoir, the pilot
control of the 3/2 way valve is moved downwards. This
blocks the passage from 2 to 3. The valve disc is lifted from
its seat and thus air can flow from1 to 2 .
The time required for pressure to build up in the air
reservoir is equal to the control time of the valve.
PRINCIPLE OF OPERATION

Un-actuated Position
 Actuated
Position
TIME BEHAVIOR OF CIRCUITS WITH
TIME DELAY VALVES

The time response and behavior of the
pneumatic circuits with time delay valves
varies according to the following two
factors:
1) Type of 3/2 way valve if it is N/O or
N/C.
2) The direction of the check valve in
the one way flow control valve.
(Direction of throttling).
TIME RESPONSE WITH DELAY ON
TIME RESPONSE WITH DELAY OFF
PRACTICAL TASK 1

A double acting cylinder is used to press glued
components together. Upon operation of a push
button, the clamping cylinder extends. Once the
fully advanced position is reached, the cylinder
is to remain for a time of T = 6 seconds and
then retract to the initial position
automatically. The cylinder retraction is to be
adjustable. A new start cycle is only possible
after the cylinder has fully retracted.
SOLUTION USING THE OLD TIME DELAY
VALVE
SOLUTION USING THE NEW TIME
DELAY VALVE
SOLUTION DESCRIPTION


The limit switch 1S2 must be actuated as a start condition.
And by pressing the push button switch 1 S1, two signals will
reach the two pressure valve 1 V1, which in turn will pass the
pressure signal to port 14 of the 5/2 way valve 1V3. The
valve 1V3 reverses resulting in advancing the piston rod of
the cylinder 1A with a specific speed according to the
setting of the one way flow control valve 1 V4.
When the cylinder reaches the forward end position, it will
activate the limit switch 1S3. The air reservoir of the time
delay valve starts filling up, and after the adjusted time
elapsed, the valve 1V2 will pass the pressure signal to port
12 of the valve 1V3. The valve 1V3 reverses, and the piston
rod retracts to the initial position with adjusted speed
determined by the one way flow control valve 1V5.
REVIEW
SHEETS 1 & 2