Motor and hoist control arrangement

Claim 2

A load-limiting motor control circuit arrangement comprising: means for sensing AC current flow to an AC motor, power disconnect means responsive to a power disconnect switching signal which is a function of the quantum value of said current flow for disconnecting power to said motor, and signal-gating means operative during motor start-up to gate said signal to prevent actuation of said current-sensing means during a selected period commencing with and terminating after start-up, said signal-gating means comprising a current-shunting circuit, said power disconnect switching signal being a current which is a direct function of the quantum value of the AC current flow to said motor, said power disconnect means comprising: a first normally cut-off electrical switch having a control electrode, a signal flow connection between said signal-gating currentshunting circuit and said control electrode, and a power disconnect relay responsive to cut-on of said normally cut-off electrical switch to disconnect power to said motor, said signal-gating means comprising: a second electrical switch having a control electrode, an anode and a cathode, an enabling circuit effecting an enabling signal and connected in control-biasing relation to said control electrode, means connecting said switch anode and cathode in controlled series shunt relation with said power disconnect switching signal, said power disconnect switching signal being AC, time-controlling means operative as a function of the passage of a selected time period after removal of said enabling signal at said control electrode to effect reduction of control bias to said second electrical switch control electrode below cut-off and to maintain said control bias in the below-cut-off condition during continued running of said motor thereafter, and means connecting said power disconnect switching signal in switch-controlling relation to said power disconnect normally cut-off first electrical switch.

Claim 3

The improvement according to claim 1, said signal gating second electrical switch and said power disconnect normally cut-off first electrical switch each comprising a respective controlled rectifier.

Claim 4

In a motor control circuit for an AC electric motor having an AC power source, the improvement comprising: motor current responsive means for detecting, and providing an electrical signal as a function of, current input to said motor, power disconnect means operating to disconnect electrical power to said motor in response to values of said signal indicating overload of said motor, and signal bypass means effectively shunting said signal away from said power disconnect means during initial current surge as a function of moTor start-up, and predetermined time interval time delay bypass disabling means effective to disable said bypass means after a selected predetermined time period from start-up.

Claim 5

In a motor control circuit for an AC electric motor having an AC power source, the improvement comprising: motor current responsive means for detecting, and providing an electrical signal as a function of, current input to said motor, power disconnect means operating to disconnect electrical power to said motor in response to values of said signal indicating overload of said motor, and signal bypass means effectively shunting said signal away from said power disconnect means during initial current surge as a function of moTor start-up, and predetermined time interval time delay bypass disabling means effective to disable said bypass means after a selected predetermined time period from start-up.

Claim 6

In a motor control circuit for an AC electric motor having an AC power source, the improvement comprising: motor current responsive means for detecting, and providing an electrical signal as a function of, current input to said motor, power disconnect means operative to disconnect electrical power to said motor in response to values of said signal indicating overload of said motor, and signal bypass means effectively shunting said signal away from said power disconnect means during initial current surge as a function of motor start-up, and time delay means effective to disable said bypass means after a selected time period from start-up, said power disconnect means comprising a first controlled rectifier and a motor power control relay responsive to actuation and deactuation of said controlled rectifier, said relay having power control contacts in power control relation to said motor, said signal bypass means comprising a bypass switch in controlled signal-shunting relation to said first controlled rectifier, said time delay means being connected in shunt-controlling relation to said bypass switch.

Claim 7

In a motor control circuit for an AC electric motor having an AC power source, the improvement comprising: motor current responsive means for detecting, and providing an electrical signal as a function of, current input to said motor, power disconnect means operative to disconnect electrical power to said motor in response to values of said signal indicating overload of said motor, and signal bypass means effectively shunting said signal away from said power disconnect means during initial current surge as a function of motor start-up, and time delay means effective to disable said bypass means after a selected time period from start-up, said power disconnect means comprising a first controlled rectifier and a motor power control relay responsive to actuation and deactuation of said controlled rectifier, said relay having power control contacts in power control relation to said motor, said signal bypass means comprising a bypass switch in controlled signal-shunting relation to said first controlled rectifier, said time delay means being connected in shunt-controlling relation to said bypass switch.

Claim 8

A motor control circuit according to claim 4, said time delay means comprising a resistance-capacitance discharging circuit, charging means selectively connecting capacitor-charging power to said discharging circuit, and charge-disconnect means responsive to start-up actuation of said motor to effectively disconnect said discharging circuit from said charging means and thereby initiate a discharge period for said resistance-capacitance discharging circuit, the operative condition of said bypass switch being controlled by the effective charge of said resistance-capacitance discharging circuit.

Claim 9

A motor control circuit according to claim 5, and a filter circuit between said motor current responsive means and said power disconnect means to prevent undesired actuation of said power disconnect means due to momentary signal fluctuations.

Claim 10

A motor control circuit according to claim 6, and a normally quiescent alarm responsive to actuation of said power disconnect to the power disconnect mode.

Claim 11

A motor control circuit according to claim 5, and motion enabling means enabling rotation of said motor in one mode of motor operation beyond the control of said power disconnect means.

Claim 12

In a motor control circuit for an AC electric motor having an AC power source, the improvement comprising: motor current responsive means for detecting, and providing an electrical signal as a function of, current input to said motor, power disconnect means operative to disconnect electrical power to said motor in response to values of said signal indicating overload of said motor, and signal bypass means effectively shunting said signal away from said power disconnect means during initial current surge as a function of motor start-up, and time delay means effective to disable said bypass means after a selected time period from start-up, said power disconnect means comprising a first controlled rectifier and a motor power control relay responsive to actuation and deactuation of said controlled rectifier, said relay having power control contacts in power control relation to said motor, said power disconnect means further comprising a protective filtering network normally connected in parallel relation to said first controlled rectifier, relay-holding circuit means responsive to actuation of said first controlled rectifier to power disconnect state to thereby shunt both of said first controlled rectifier and said filtering network, and reset means for resetting said relay-holding circuit means.

Claim 13

In a motor control circuit for an AC electric motor having an AC power source, the improvement comprising: motor current responsive means for detecting, and providing an electrical signal as a function of, current input to said motor, power disconnect means operative to disconnect electrical power to said motor in response to values of said signal indicating overload of said motor, and signal bypass means effectively shunting said signal away from said power disconnect means during initial current surge as a function of motor start-up, and time delay means effective to disable said bypass means after a selected time period from start-up, said power disconnect means comprising a first controlled rectifier and a motor power control relay responsive to actuation and deactuation of said controlled rectifier, said relay having power control contacts in power control relation to said motor, said power disconnect means further comprising a protective filtering network normally connected in parallel relation to said first controlled rectifier, relay-holding circuit means responsive to actuation of said first controlled rectifier to power disconnect state to thereby shunt both of said first controlled rectifier and said filtering network, and reset means for resetting said relay-holding circuit means.

Claim 14

A motor control circuit according to claim 9, said relay holding circuit means inCluding a normally inactive rectifier in shunt-connectable relation to said first controlled rectifier and being operatively connected in shunting and similarly polarized rectification relation to said first controlled rectifier in response to said actuation of said controlled rectifier to power disconnect relation.

Claim 15

A motor control circuit according to claim 10, said relay holding circuit means comprising switch contacts operated as a function of actuation of said power disconnect relay, said switch contacts including a double throw contact arm normally connecting said filter network in operative protective filtering relation to said first controlled rectifier and movable in response to actuation of said relay to shunt said filter network and controlled rectifier and to connect said normally inactive rectifier into series holding relation with said relay.

Claim 16

A motor control circuit according to claim 9, said power disconnect means including a free-wheeling diode in parallel with an actuating coil of said relay to insure continued holding operation thereof during succeeding AC cycle reversals.

Claim 17

A lift-weight-restricting hoist arrangement comprising a hoist having a lift drive arrangement, said lift drive arrangement comprising: an AC drive motor in lift-driving relation to said hoist, to apply a lifting power to the hoist, means for sensing current flow to said motor and effecting a power disconnect signal as a function of the quantum value of said current flow, power disconnect means responsive to said power disconnect signal for disconnecting power to said motor, and signal control means operative during motor start-up to to prevent effective application of said power disconnect signal to said power disconnect means for effective operation of said power disconnect means during a selected period commencing with and terminating after start-up.

Claim 18

A lift-weight-restricting hoist arrangement comprising a hoist having a lift drive arrangement, said lift drive arrangement comprising: an AC drive motor in lift-driving relation to said hoist, to apply a lifting power to the hoist, means for sensing current flow to said motor and effecting a power disconnect signal as a function of the quantum value of said current flow, power disconnect means responsive to said power disconnect signal for disconnecting power to said motor, and signal control means operative during motor start-up to to prevent effective application of said power disconnect signal to said power disconnect means for effective operation of said power disconnect means during a selected period commencing with and terminating after start-up.

Claim 19

An arrangement according to claim 13, said signal gating means being operative to prevent effective operation of said current sensing means through prevention of actuation thereof during said period.

Claim 20

A load-limiting motor control circuit arrangement comprising: means for sensing AC current flow to an AC motor, power disconnect means responsive to a power disconnect switching signal which is a function of the quantum value of said current flow for disconnecting power to said motor, and signal-gating means operative during motor start-up to gate said signal to prevent actuation of said current-sensing means during a selected period commencing with and terminating after start-up, said signal-gating means comprising a current-shunting circuit, said power disconnect switching signal being a current which is a direct function of the quantum value of the AC current flow to said motor, said power disconnect means comprising: a first electrical switch having a control electrode and two controlled current-conducting electrodes controlled by said control electrode and being normally in one electrical-conducting condition, a signal flow connection between said signal-gating current-shunting circuit and the said control electrode, and a power disconnect relay responsive to change of the electrical conducting-condition of said two controlled current-conducting electrodes from normal to disconnect power from said motor, said signal-gating means comprising: a second electrical switch having a control electrode, an anode and a cathode, an enabling circuit effecting an enabling signal and connected in control-biasing relation to said control electrode, means connecting said switch anode and cathode in controlled series shunt relation with said power disconnect switching signal, time-controlling means operative as a function of the passage of a selected time period after removal of said enabling signal at said control electrode to effect reduction of control bias to said second electrical switch control electrode below cut-off and to maintain said control bias in the below-cut-off condition during continued running of said motor thereafter, and means connecting said power disconnect switching signal in switch-controlling relation to said power disconnect first electrical switch.

Claim 21

A load-limiting motor control circuit arrangement comprising: means for sensing AC current flow to an AC motor, power disconnect means responsive to a power disconnect switching signal which is a function of the quantum value of said current flow for disconnecting power to said motor, and signal-gating means operative during motor start-up to gate said signal to prevent actuation of said current-sensing means during a selected period commencing with and terminating after start-up, said signal-gating means comprising a current-shunting circuit, said power disconnect switching signal being a current which is a direct function of the quantum value of the AC current flow to said motor, said power disconnect means comprising: a first electrical switch having a control electrode and two controlled current-conducting electrodes controlled by said control electrode and being normally in one electrical-conducting condition, a signal flow connection between said signal-gating current-shunting circuit and the said control electrode, and a power disconnect relay responsive to change of the electrical conducting-condition of said two controlled current-conducting electrodes from normal to disconnect power from said motor, said signal-gating means comprising: a second electrical switch having a control electrode, an anode and a cathode, an enabling circuit effecting an enabling signal and connected in control-biasing relation to said control electrode, means connecting said switch anode and cathode in controlled series shunt relation with said power disconnect switching signal, time-controlling means operative as a function of the passage of a selected time period after removal of said enabling signal at said control electrode to effect reduction of control bias to said second electrical switch control electrode below cut-off and to maintain said control bias in the below-cut-off condition during continued running of said motor thereafter, and means connecting said power disconnect switching signal in switch-controlling relation to said power disconnect first electrical switch.

Claim 22

A load-limiting motor control circuit arrangement comprising: means for sensing AC current flow to an AC motor, power disconnect means responsive to a power disconnect switching signal which is a function of the quantum value of said current flow for disconnecting power to said motor, and signal-gating means operative during motor start-up to gate said signal to prevent actuation of said current sensing means during a selected period commencing with and terminating after start-up, said signal-gating means comprising a current-shunting circuit, said power disconnect switching signal being a current which is a direct function of the quantum value of the AC current flow to said motor, said signal-gating means comprising: an electrical switch having a control electrode, an anode and a cathode, an enabling circuit effecting an enabling signal and connected in control-biasing relation to said control electrode, means connecting said switch anode and cathode in controlled series shunt relation with said power disconnect switching signal, time-controlling means operative as a function of the passage of a selected time period after removal of said enabling signal at said control electrode to effect reduction of control bias to said electrical switch control electrode below cut-off and to maintain said control bias in the below-cut-off condition during continued running of said motor thereafter, and means connecting said power disconnect switching signal in switch-controlling relation to said power disconnect means.

Claim 23

A load-limiting motor control circuit arrangement comprising: means for sensing AC current flow to an AC motor, power disconnect means responsive to a power disconnect switching signal which is a function of the quantum value of said current flow for disconnecting power to said motor, and signal-gating means operative during motor start-up to gate said signal to prevent actuation of said current sensing means during a selected period commencing with and terminating after start-up, said signal-gating means comprising a current-shunting circuit, said power disconnect switching signal being a current which is a direct function of the quantum value of the AC current flow to said motor, said signal-gating means comprising: an electrical switch having a control electrode, an anode and a cathode, an enabling circuit effecting an enabling signal and connected in control-biasing relation to said control electrode, means connecting said switch anode and cathode in controlled series shunt relation with said power disconnect switching signal, time-controlling means operative as a function of the passage of a selected time period after removal of said enabling signal at said control electrode to effect reduction of control bias to said electrical switch control electrode below cut-off and to maintain said control bias in the below-cut-off condition during continued running of said motor thereafter, and means connecting said power disconnect switching signal in switch-controlling relation to said power disconnect means.