GB907388A - Electric door operator - Google Patents

Abstract

907,388. Control of A.C. motors. KAWNEER CO. Dec. 22, 1959 [Jan. 2, 1959], No. 43577/59. Class 38 (3). [Also in Group XXV] An electrically powered door operating appliance comprises a servomechanism for driving the door between closed and open terminal positions, the servomechanism including a servomotor supplied with a drive voltage derived by comparing a reference voltage representing the position to which the door is to be moved with a varying feedback voltage developed by a feedback means driven simultaneously with the door. The door 34, see Fig. 2, has an upper pivot 36 driven through a gear assembly 46 by an electric servomotor 44, the drive voltage for which is derived from a potentiometer network 47 which is unbalanced in response to the passage of a person over a treadle mat 42 and is rebalanced by a feedback device 50 comprising a variable transformer 94 controlled by a cam 110 secured to a shaft 76 in the gear assembly. Servomotor.-The servomotor 44 is a twophase squirrel-cage induction motor, the rotor of which rotates in response to a rotating magnetic field produced by two separate field windings, a reference winding 60 continuously energized from an A.C. source 63 and a control winding 48 energized by a voltage differing in phase by 90 degrees supplied by the unbalanced potentiometer network 47. The motor also includes a damping winding 56 energized by a constant voltage D.C. controlled by a pair of switches 170, 174 operated in response to the position of the door by a cam 180. The D.C. is derived from a conventional rectifier type circuit 58 (Fig. 8) connected in parallel with the primary winding 91 of the transformer 90 (see below) and comprising a resistance 126, rectifiers 123, 124 and a capacitance 128. An inductance 186 is serially connected with the damping winding 56 to counteract the effect of the capacitance 128. Potentiometer network.-The network 47 (Fig. 4) comprises a first branch 92 formed by the secondary winding of a step-up transformer 90 connected to the A.C. source 63 and a second branch formed by the variable transformer 94. The centre arm 96 comprises the primary winding 98 of a step-up transformer which supplies the drive voltage to the control winding 48 of the motor, one end 96a of the arm being connected by a switch 97 in response to actuation of the treadle mat 42 to one of two voltage levels 100, 104 on the winding 92 and the other end 96b being connected to a slider 99 movable along the winding 94. Feedback device.-The slider 99 is moved through a rack-and pinion connection 118, 120 by a bar 116 carrying a follower 114 engaging the cam groove 112 of the cam 110. When the door is closed and set to open to the left the follower is located at 137 (Fig. 3) and the slider 99 is at the voltage level 102 which is equal to voltage level 100. When the switch 97 moves to voltage level 104 in response to actuation of the treadle mat the unbalanced network provides a drive voltage for the motor and during the first 2¢ degrees of door movement the follower 114 moves along the portion 132 of the cam groove to the end of the portion 133 and the slider moves to voltage level 105. From the 2¢ degrees to 87¢ degrees position of the door, the follower travels along the portion 133 and the slider voltage remains constant, while during the last 2¢ degrees of opening movement the slider travels in the portion 134 and the slider moves to voltage 106 which is equal to voltage 104. During closing movement of the door the follower moves back to the point 137. If the door is moved accidentally from its closed position, e.g. by wind pressure, the follower moves in the portion 132, 131 towards the portions 133 or 130 and the slider moves towards voltages 105 or 101, respectively, thus providing a drive voltage to the motor so that the latter exerts an appropriate restoring force on the door. Motor interrupting sub-circuit. This operates to open-circuit the motor control winding 48 for a predetermined time interval (about threetenths of a second) and simultaneously energizes the damping winding 56 which thereby becomes quickly effective. The sub-circuit comprises a time pulse relay 190 (Figs. 7, 8), the coil 190a of which, when energized, opens a switch 192 in the circuit of the centre arm 96 of the potentiometer network and closes a switch 194 between the damping winding and the D.C. connection 144. The sub-circuit is set when both the terminals 176 and 172 of switches 174, 170, respectively, are closed, i.e. when the door is between its 30 degrees and 60 degrees open positions, and the D.C. voltage 144 is applied to both plates of a condenser 200. When either pair of contacts 172, 176 is opened, the voltage 144 is removed from the condenser plate 200b and a charging current flows through the winding 190a, energizing the latter. The sub-circuit is reset when the contacts are closed, the condenser discharging through a rectifier 196 and resistance 198. Control circuit; normal door operation.-The door operating appliance is intended during normal operation to open the door automatically when a person steps on to the approach side 42a of the treadle mat and to close the door after the person has left the exit side 42b. It also exerts a restoring torque (see above) when the door is moved accidentally from its closed position, e.g. by wind pressure, and prevents the door from opening automatically if a person is standing on the exit side 42b of the mat, thus avoiding the risk of injury. It also permits panic opening of the door in the opposite direction, and subsequently resets the door for normal automatic operation. Fig. 8 shows the condition of the control circuit when the door is closed, the motor control winding 48 being de-energized and the damping winding 56 being energized from the connection 144 of the D.C. circuit 58 through conductor 181, resistance 182, contacts 175 of switch 174, socket 165, plug 167, conductor 187, switch 162, inductance 186, the winding 56, and conductor 237 to earth. A person stepping on to the approach side 42a of the treadle mat closes a switch 80 which energizes an operating relay 140, powered from a short portion 143 of the secondary 92, to close switch 149 and complete the energizing circuit for a control relay 160 from the terminal 144, resistance 153, switch 149, switch 154, relay winding 160a, to earth. The control relay operates switch 97, which moves from voltage 100 to voltage 104 and unbalances the network 47 to provide the drive voltage to the motor the feedback device operating as described above to rebalance the network as the door opens. The control relay also de-energizes the damping winding by opening the switch 162, closes switch 164 which connects the damping winding to the switch 170, and closes switch 166, in parallel with switch 154. When the door reaches its 30 degrees open position the cam 180 operates switch 174 to close the contacts 176 and set the motor interrupting sub-circuit. On reaching the 60 degrees open position the switch 170 is operated, the opening of contacts 172 causing operation of the interrupting subcircuit and consequent interruption of the motor for a short duration, and the closing of contacts 171 completing a circuit for the damping winding from the connection 144 through conductor 181, resistance 182, contacts 171, socket 165, plug 167, conductor 184, switch 164, inductance 186, the winding 56 to earth. The door then moves from the 60 degrees to 90 degrees position under the influence of both the damping winding 56 and the control winding 48. When the person steps from the entrance side 42a to the exit side 42b of the treadle mat, whether or not the door is by then fully open, the switch 80 is opened, thereby de-energizing the operating relay 140, and a switch 82 is closed to energize a safety relay 150. If a short time interval occurs between the opening of switch 80 and the closing of switch 82, the control relay 160 is maintained energized by the discharge, through the winding 160a, of a condenser 173. The operation of the safety relay closes switch 152 to complete a second energizing circuit for the control relay 160, so that the door is held open so long as the person remains on the mat exit side 42b. When the person steps off the mat the safety relay is de-energized, the switch 152 opens and the control relay is de-energized so that the switch 97 returns to the voltage 100, thus unbalancing the potentiometer network, the switch 162 closes, thus connecting the switch 174 with the damping winding 56, and the switch 164 opens, thus disconnecting the switch 170 from the damping winding. The closing. movement of the door corresponds exactly to the opening movement just described, the interrupting sub-circuit being set at the 60 degrees open position and operated at the 30 degrees open position, to prevent the door from swinging violently should a person step on to the entrance side 42a of the mat during the predetermined time interval. Safety operation.-The door is prevented from opening if an inattentive person is standing on the mat exit side 42b. If this happens, the switch 82 is closed to energize the safety relay 150 which opens switch 154 so that the operating circuit for the control relay 160 through the switch 149 is opened. The door closing movement is also arrested should a person step on to the mat exit side 42b, for during normal closing movement the relays 140, 150 and 160 are all de-energized, and should the switch 82 be closed the safety relay is energized to close the switches 152 and 158 and open the switches 154 and 156. The opening of switch 156 opens the circuit between the primary winding 98 and the voltage 100 and thus de-energizes the control winding 48, while the closure of switch 158 completes an energization circuit for the damping winding 56. The door remains stationary even if another person steps on to the mat entrance side 42a since the operating circu