| 摘要 |
<p>The supply of operating air or oil to a press, shears or like machine is controlled by a pair of spool valves (10,14) connected in a series and each operates a pair of switches (20,22). The switches connect dc current to the solenoids via external relays (26,28) which open and close the valves. The external relays are standard components on the switchboard of the machine subject to control. Sharing the control between two valves allows malfunction in either valve to indicate the system needs correction while at the same time preventing supply to the machine. The switches are coupled to the dc switchboard of the machine by cables and thus can be retrofitted.</p> |
