GB929813A - - Google Patents

Abstract

929,813. Thermal switches. GRINNELL CORPORATION. May 4, 1961 [Dec. 8, 1960], No. 16159/61. Class 38 (5). [Also in Group XXVIII] In apparatus for controlling the movement of part of a piping system the piston rod 58 of a hydraulic piston-cylinder unit 42 carries a sleeve 80 on which is mounted an arm 82 to which is attached a control rod 84 carrying a pair of switch arms 86, 88 having electrical contacts 116, 118 and a block 90 slidable on a rod 92 provided with stops 94, 96, and slidably mounted in a bracket 98. The rod 92 also mounts a block 100, and blocks 94, 100 embrace a pivoted switch lever 102 engageable with limit switches 106. These latter components operate to turn off the motor 50 and stop operation of the mechanism when the piston 46 reaches predetermined limits of travel so that if in the event of failure of the temperature-controlled switching the piston continues to move upwardly the block 90 will eventually engage stop 94 to move the rod 92 to actuate the upper switch 106 and stop the motor; the lower switch 106 is actuated in a similar manner when the piston moves downwardly and the blocks 90, 96 are brought into engagement. The temperature-control switch 110 includes a pivoted lever arm 122 provided with a contact 120 disposed between the contacts 116, 118 of the arms 86, 88 the arm being moved by a fluid pressure-operated bellows 150 connected with a fluid-filled coil 156 housed in a jacket 160 around the pipe 2. A scale 164 is calibrated in degrees of temperature. When the temperature of the pipe is at room temperature the motor 50 is switched off, and an increase in temperature causes the fluid 162 to expand and move the lever against the action of spring 154 to bring the contact 120 into engagement with contact 118 whereby the motor is started to cause the piston 46 to move in that direction which carries the switch arms 86, 88 downwardly ; the motor continues to run until the contact 118 moves out of engagement with the contact 120 at which point the motor stops to leave the piston 46 and the piping connection point 38 in a new position corresponding to the new and increased temperature. For each subsequent increase in temperature the operation of the switch unit is the same so that there is an intermittent on and off operation of the motor. If the changes in length of the apparatus are not linear with respect changes in temperature, a cam is inserted between the bellows 150 and arm 122 to provide the desired relationship of movement of one with respect to the other.