Patent GB-454054-A (GB)
Title: Improvements in and relating to electric circuit controlling devices
IPC: H01H37/60
Filed: 1935-11-04
Abstract: 454,054. Electrically - released switches; thermal switches. BRITISH THOMSON - HOUSTON CO., Ltd., Crown House, Aldwych, London. Nov. 4, 1935, No. 30464. Convention date, Nov. 2, 1934. [Class 38 (v)] A circuit-controlling device comprises circuitcontrol means having operating means for causing the circuit-control means to open and close the circuit, and a trip member mounted for movement from a normal to a tripped position to operate the control means to open the circuit independently of the operating means. A latch forms a connection between the trip member and a releasing member and a spring is mounted so as to apply a bias to both members. Overload means normally restrain one of the members against the bias and the latch restrains the other member, the overload means being operable upon overload to release the one member for movement to release the connection between the members, whereupon the trip member operates the control means to open the circuit. As applied to the control of the motor of a refrigerator by means of a low boiling-point fluid in a bulb (not shown), the latter is connected by pipe 52 to a bellows 50 secured at 56, 60 to the frame and acting on one side of a lever 34, pivoted at 36, a spring 68 acting on the other side to provide the restoring force. Lever 34 has upstanding arms 44 in which are pivoted the ends of a U -shaped lever 41 connected by an over-centre spring 35 to an arm 28, which is pivoted at 30 and carries the movable contact 16 co-operating with the fixed contact 14. When the motor is thus in operation and the temperature drops, spring 68 rotates lever 34 clockwise and carries the pivots of 41 across the spring axis 35, which snaps over from stop 90 to stop 91 and rotates 28 to open contacts 14, 16. For temperatureadjustment, spring 68 seats in a member 72 in threaded engagement with a screw 74, the axial position of which is fixed by a U-shaped locking member 78 and collar 80 on the screw. Anti-clockwise rotation of knob 82 therefore moves the seat 72 to compress the spring 68. Manual opening of circuit. The member 28 has an extension 110, a part 113 of which co-operates with a surface 114 of a cam 115. A trip-lever 120, Fig. 11, is pivoted at 121 and has an arm 120<a> normally engaging a bimetalstrip latch 124. A plunger 136 passes through the end plate 138 of lever 120 and engages by means of an end 140 a cut-away surface 142 on the under face of cam 115. A spring 150 between the plate 138 and shoulder 152 of the plunger 136 biasses the latter against the cam, but its movement is prevented by the engagement of a cam 155 on the plunger with a cam 159 on lever 120 so long as the latter is held by the latch 124. When button 170 is pulled, the surface 177 rotates the plunger 136 anticlockwise to move 155 clear of 159 so that spring 150 forces the plunger 136 towards the button 170. The cam surface 114 then engage part 113 of extension 110 to move 28 anticlockwise and open the circuit. To reclose, button 170 is pushed in and cam 155 pushes cam 159 clear, whereupon spring 150 restores the parts to their original positions, Figs. 10<a>, 11. Overload opening of circuit. Strip 124 moves clear of 120<a> and 120 rotates anticlockwise so that 159 moves clear of 155, thus allowing spring 150 to depress the plunger 136 and cam 115 and operate 28 by means of the extension 113. The surface 190 of the cam 115 engages the part 192 of lever 120 to deflect the latter and enable the strip 124 to return to its latching position. The strip 124 is heated by a series-coil 182 and is secured at one end in an insulating block 127 which is pivoted at 128 and carries an ambient-temperature compensating strip 130 with adjusting screw 134. Loose-handle arrangements. If the button 170 is held in closed-circuit position and the strip 124 deflects, the spring 150 acts through 138 on the lever 120 and an arm 117 thereon strikes an arm 116 on the extension of lever 28, so moving the latter to the off position irrespective of the position of spring 35. Defrosting and quick-freezing arrangements. A knob 180 in which the shank of cam 115 slides, is rotatable anti-clockwise to cause a considerably higher temperature, e.g. 50‹ F., to be necessary for the bellows to produce movement of lever 34, by applying additional spring-pressure on the latter in opposition to the bellows expansion. The spring 200 is coiled about post 202 and urges a lever 206 against a cam 218, which, when rotated by the knob 180, brings a recess 221 into register with 206 and allows spring 200 to rotate 206 and bring an arm 225 thereon against a roller 230 on an arm on lever 34. The bellows has thus to overcome both springs 68, 200 before it can move lever 34 to the closed position. The end 208 of spring 200 bears on a collar 209 on an adjusting screw 215 on the seat 72, so that the changes in the tension of spring 68 are compensated in the spring 200. When the bellows rotates lever 34, the roller 230 engages and deflects arm 225, so moving 206 clear of recess 221 and allowing spring 235 to restore knob 180. In this way normal operation is automatically restored after the defrosting process. Clockwise rotation of 180 allows quick-freezing by applying the force of a spring 258 in a direction to help the bellows. The cam 250 has a recess engageable with a lever 256, the end 272 of which co-operates with roller 230. In this case a temperature, e.g. of 6‹ F., is required to open the contact 16. A similar compensating arrangement for the end 260 of spring 258 is provided. In both cases the knob 180 can, if necessary, be forced back to the original position to restore normal operation of the refriger.tor. For maintaining a higher average temperature and so economically keeping beverages cool, knob 82 can be rotated anti-clockwise to minimum setting to bring notch 291 in cam 290 into register with the end 292 of arm 293 pivoted at 86, in which position a spring 296 causes arm 295 to engage lever 34, whereby the latter requires a higher temperature to close the contacts. Specifications 282,074, [Class 38 (v)], and 367,189 are referred to.