| 摘要 |
1,182,780. Electrically tripped switches. MIDLAND ELECTRIC MFG. CO. Ltd. 13 Nov., 1967 [19 Sept., 1966], No. 41670/66. Heading H1N. An overload relay includes two slidable bars 18, 24, having abutments 19 and being linked so as to be displaced as a unit by the free ends of three bimetallic strips 17, one for each phase, whereby a switch 31 is actuated upon overload via a pivoted operating member 26 moved by the sliding movement of the bars 18, 24, but uneven loading of the phases causes one bimetallic strip 17 to move to a lesser extent, holding back bar 24 and causing relative longitudinal movement of the bars 18, 24, and transverse movement of bar 18 because of the linkage between the bars, such transverse movement turning a catch 53 to release a spring-loaded hammer member 50 which engages the switch operating member 26 to actuate switch 31. Upon overload, the end of bar 18 engages a floating abutment 27 pivotally mounted on member 26 and carrying a compensating bimetallic strip 28 with one end engageable against an adjustable stop 29, adjustable by a manually operable pivoted lever 30 for ambient temperature compensation and current setting. The abutments 19 are adjustable, and the catch 53 has an adjustable abutment 56 engageable by bar 18 on transverse movement thereof. The switch operating member 26 is coupled to a slidable actuating element 32 which has an adjustable abutment 44 engageable against a pivoted member 37 which actuates the three-pronged snap-acting element 33 of switch 31. Pivoted member 37 is mounted on an eccentric trunnion 45 on the end of a rotatable pin 46 for adjustment of the axis of pivotal movement of member 37 when initially setting the switch. A removable stop 40 makes switch 31 retractive or stable in two positions, a spring- loaded plunger 41 being used for re-setting the switch 31 by a cam 42 thereon displacing the member 35 in which the shorter limbs 34 of the snap-acting element 33 engage. Plunger 41 also actuates an auxiliary switch 43 which is normally closed. The body 11 of the overload relay also houses an auxiliary switch device 63 including a rotatable cam 66 for operating a normally open switch 64 in series with the switch 43 and the switch 31. In use, switch 64 is bridged by hold-on contacts of the contactor (not shown) with which the relay is used, the switch 64 being closed, e.g. for starting of a motor. The relay is used with two contactors for controlling forward and reverse running of an A.C. motor (not shown), and device 63 includes a further switch 82, Fig. 4 (not shown), operated by a lobe 70 on cam 66 which has a ramp 69 acting on the plunger 68 of switch 64. |
