| 摘要 |
PROBLEM TO BE SOLVED: To scarcely take place a fault by a reduction in number of switches by providing a switch detecting and operating switching elements to a phase when the elements are disposed at a closed position and not operating when the elements are disposed at its open position at an either one element. SOLUTION: When opposed switching elements 3a, 3b of an upper stage are closed, opposed ends 10 of the elements 3a, 3b approach, and when opposed switching elements 3c, 3d of a lower stage are closed, opposed ends 10 of the elements 3c, 3d approach. At the elements 3a, 3b of the upper stage, a single switch 9 is mounted at the oppose end 10 of the one element 3a. At the elements 3c, 3d of the lower stage, a single switch 9 is mounted at the opposed end 10 of the one element 3c. The switches 9 are constituted of a non-contact type proximity switch for detecting metal. When the element 3 is made of metal, only when the elements 3 are disposed at the closed position, it is operated, but when the elements 3 are disposed at the open position, it is not operated.
|
