Single stroke control system

In a single cycle control system for a machine is which fluid pressure controls the starting and stopping of the machine and having a vertically reciprocable part which is movable through a downstroke and then through an upstroke during each cycle, said system having:

• a pair of valves connected to control said fluid pressure such that the machine is stopped if either valve is closed;
• a pair of solenoids for controlling said valves individually such that each solenoid must be energized to open the corresponding valve;
• a first relay;
• a pair of run switches, each having normally-closed contacts which are closed when the switch is released and normally-open contacts which are closed when the switch is operated;
• an energization circuit for said first relay including the normally-closed contacts of said two run switches;
• and second and third relays operatively connected to said solenoids such that both said second and third relays must be energized for both said solenoids to be energized throughout substantially the entire downstroke of the machine;
• the improvement which comprises:
• an initial energization circuit for said second relay which includes normally-open contacts of said first relay, whereby said first relay must be energized through said normally-closed contacts of both run switches before the second relay can be energized;
• an initial energization circuit for said third relay which includes normally-open contacts of said second relay, whereby said second relay must be energized before said third relay can be energized;
• and holding circuits for the second and third relays which include normally-open contacts of the second and third relays;
• said holding circuits for said second and third relays being connected to said normally-open contacts of both run switches, whereby releasing either run switch from its operated position will open both said holding circuits and thus de-energize the second and third relays.

In a single cycle control system for a machine in which fluid pressure controls the starting and stopping of the machine, said control system having:

• first and second normally-closed valves connected to control said fluid pressure such that the machine is stopped if either valve is closed;
• first and second solenoids for causing the corresponding valves to open in response to the energization of the respective solenoids;
• run switch means for starting the machine;
• and circuit means for energizing said solenoids in response to the operation of said run switch means, whereby to open said valves and start the machine;
• the improvement which comprises:
• a first holding circuit connected directly to said first solenoid and operable to maintain the latter energized independent of said run switch means following the opening of said first valve, said holding circuit including a normally-open limit switch which is closed by the machine during its cycle of operation and is opened later near the end of said cycle;
• and a second holding circuit connected directly to said second solenoid and operable to maintain the latter energized independent of said run switch means following the opening of said second valve, said second holding circuit being separate from said first holding circuit and including a normally-open limit switch which is closed by the machine during its cycle of operation and is opened later near the end of said cycle.

In a single cycle control system for a machine in which fluid pressure controls the starting and stopping of the machine, said control system having:

• first and second normally-closed valves connected to control said fluid pressure such that the machine is stopped if either valve is closed;
• first and second solenoids for causing the corresponding valves to open in response to the energization of the respective solenoids;
• run switch means for starting the machine;
• a first relay operatively connected to be energized before said run switch means is operated to start the machine;
• a second relay operatively connected to said run switch means to be energized in response to said operation of the run switch means;
• and a third relay operatively connected to said second relay to be energized in response to the latter's energization and operatively connected to said first relay to de-energize the latter in response to the energization of the third relay;
• the improvement which comprises an initial energization circuit for each solenoid comprising:
• a normally-closed set of contacts of said first relay, and a normally-open set of contacts of said third relay connected between said run switch means and the respective solenoid for energizing the latter when said run switch means is operated while said first relay is de-energized and said third relay is energized.