ATM 322 Basic Pneumatics H.W.6 Modules 5 7

Transcription

1 ATM 322 Basic Pneumatics H.W.6 Modules 5 7 Name: Answer Key Mark: Question I: Write (T) for True and (F) for false sentences. A) For the time dependant process control; Step enabling conditions are generated via timers at constant speed. T B) For the process dependant process control; Step enabling conditions depend purely on the stroke dependant signals of the controlled systems. T C) The time delay valve returns to normal position via spring. T D) In the time delay valve; the delay time is generally s. F E) The type of the time delay valve whether normally opened or closed depends on the one way flow control valve. F F) For the time delay valve; The time required for pressure to build up in the air reservoir is equal to the control time of the valve. T G) For the shuttle valve; if a compressed air signal is applied to input X or input Y, this will produce a signal at output Z. T H) For the Two Dual pressure valve; if one input signal is applied, there will be no output signal. T I) Sequence control is divided into two subgroups: Time dependant and speed dependant. F Question II: Draw the equivalent circuit to the AND function controlling a double acting cylinder.

2 Question III: Answer the questions shown below. [marks] A) Name and define the two types of sequence control. i) Time dependant sequence control: A sequence control where the switching conditions are dependent only on time. ii) Process dependant sequence control: A sequence control system where the switching conditions are dependent only on signals from the system being controlled. B) When do we use displacement step diagrams? We use displacement step diagrams when we want to represent the desired motion of all actuators in the case of multiple cylinder circuits. C) In case of multiple actuators, the representation of the desired motion of all actuators is described using displacement step diagram. D) Name the valves that are used to eliminate signal overlap. roller lever valves with idle return or toggle lever valves, time delay valves, reversing valves or sequencers. E) Draw the displacement step diagram for both actuators 1A and 2A; knowing that cylinder 1A starts first.

3 F) Draw the displacement step diagram for each of the following sequences. i) C+B+A+C-B-A- iii) C+C-B+B-A+A- G) Find the sequence of operation for the given displacement step diagram.

4 A+B+B-C+A-C- H) State the function of the time delay valve. Time delay valve is used to delay the output signal. I) The time delay valve consist of 3 parts, name them. Air reservoir, 3/2 DCV N/C or N/O, one way flow control valve. J) How can the delay time be extended? By using additional reservoirs. K) Explain how the time delay valve works. Label the ports (1,2,3,12) 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 Question IV: Draw the ISO symbols for each of the following. Time Delay Valve N/C Time Delay Valve N/O Shuttle Valve Two Dual Pressure Valve

5 Pressure Regulating Valve Pressure Sequence Valve Question V: Draw the pneumatic circuit diagram for each of the following. A) 1-Double acting cylinder will extend when 3/2 way valve is actuated (Keep pressing) 2-The double acting cylinder will retract when push button is released.

6 B) 1- The cylinder has to be operated by operating the four valves at the same time. 2- Releasing any valve results in attracting the cylinder back to its initial position C) A double acting cylinder is used to press together glued components. Upon operation of a push button valve, the clamping cylinder (1A) extends. Once the fully advanced position is reached, the cylinder is to retract automatically to the initial position. The cylinder speed is to be adjustable. A new start cycle is only possible after the cylinder has fully retracted.

7 Question VI: Choose the correct answer. 1. The main purpose of the is to accept the pneumatic signals from two different locations. A. Shuttle Valve B. 3/2 Directional control valve N/C C. Quick Exhaust Valve D. One way Flow Control Valve E. 5/2 double pilot DCV 2. Which valve works as an AND gate? A. Two Dual Pressure Valve B. 3/2 Directional control valve N/C C. Quick Exhaust Valve D. One way Flow Control Valve E. 5/2 double pilot DCV

8 3. In the shuttle valve; if signals are present at both inputs, the signal reaches the output. A. With the higher pressure B. With the lower pressure C. Arriving last D. Arriving first None of the above