US3735221A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electrical hoist control system
Assignee: Symons Corp
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Filing: 1971-03-08
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Granted: 1973-05-22
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Expires: 1991-03-08
Abstract
Abstract An electrical control system for raising and lowering a drumand-cable supported load. A reversible shunt wound drive motor which is connected to the drum is operable under the control of a continuously driven shunt wound generator. By measuring the amount of current flowing in the armature coil of the drive motor and varying the flow of current in the field coil thereof in relation to such armature current, the speed of the drive motor will become a direct function of the load which is placed on the latter. By reversing the polarity of the voltage which is supplied to the field coil of the generator, the direction of rotation of the drive motor may be reversed without disturbing the relationship between the load and the motor speed. Thus, whether the load is rising or descending, the greater its magnitude, the slower its speed. An electromechanical brake arrangement becomes automatically effective to lock the cable drum in a fixed position when load speed drops substantially to zero.
Inventors
- 👤 H Bell
- 👤 G Hay
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 07:00
CPC Classifications
B; B66; B66C; B66C13/00; B66C13/18; B66C13/22; B66C13/23; B66C13/24
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
222 words
In an electrical hoist control system for effecting raising and lowering of a cable-attached load and wherein the cable is wound upon a drum, the combination of: a reversible shunt wound direct current drive motor operatively connected to the drum in driving relationship, said motor having an armature winding and a field winding and being effective when driven in one direction to cause raising of the load and when driven in the opposite direction to cause lowering of the load, and control means automatically effective during driving of the motor in either direction to vary the speed of the motor,and consequently the speed of the load, in inverse proportion to the magnitude of the load , said control means embodying a main direct current amplifier effective selectively and continuously to apply varying voltage of opposite polarity to said armature winding to drive the motor in opposite directions, an additional direct current amplifier effective to supply current unidirectionally and continuously to said field winding to regulate the speed of said motor, and current sensing means responsive to an increase of current flow in said armature winding incident to an increase in the magnitude of the load for increasing the amount of current supplied to said field winding by said additional direct current amplifier in order thus to reduce the speed of the motor.
Claim 2
Dependent Claim
222 words
In an electrical hoist control system for effecting raising and lowering of a cable-attached load and wherein the cable is wound upon a drum, the combination of: a reversible shunt wound direct current drive motor operatively connected to the drum in driving relationship, said motor having an armature winding and a field winding and being effective when driven in one direction to cause raising of the load and when driven in the opposite direction to cause lowering of the load, and control means automatically effective during driving of the motor in either direction to vary the speed of the motor,and consequently the speed of the load, in inverse proportion to the magnitude of the load , said control means embodying a main direct current amplifier effective selectively and continuously to apply varying voltage of opposite polarity to said armature winding to drive the motor in opposite directions, an additional direct current amplifier effective to supply current unidirectionally and continuously to said field winding to regulate the speed of said motor, and current sensing means responsive to an increase of current flow in said armature winding incident to an increase in the magnitude of the load for increasing the amount of current supplied to said field winding by said additional direct current amplifier in order thus to reduce the speed of the motor.
Claim 3
Dependent Claim
78 words
A hoist control system as set forth in claim 1 and including, additionally, a holding brake for said drum and movable between a position of drum engagement and a position of drum release, spring means yieldingly maintaining said brake in its engaged position, and holding means automatically effective during driving of said motor in either direction for overcoming said spring means and maintaining the brake in its released position except when said motor closely approaches a static condition.
Claim 4
Dependent Claim
75 words
A hoist control system as set forth in claim 2 and wherein said holding brake is solenoid-actuated and includes a brake coil, a normally closed relay switch in series with said brake coil and a source of current, and a relay magnet coil in series with said armature winding, said relay switch opening when current in said armature winding approaches zero, whereby said brake coil is deenergized and said spring means applies said holding brake.
Claim 5
Dependent Claim
72 words
An electrical hoist control system as set forth in claim 1 and wherein said control means further embodies a generator having a single armature winding and a single field winding, and motor means for driving said generator, the generator field winding being electrically connected to the main direct current amplifier and the armature winding of the generator being electrically connected to the armature winding of the shunt wound direct current drive motor.
Claim 6
Dependent Claim
222 words
In a direct current electrical hoist control system for effecting raising and lowering of a cable-attached load and wherein the cable is attached to a rotary drum, the combination of a power supply unit establishing a source of current at a positive voltage and a source of current at a negative voltage, means establishing a common ground for said current sources, a reversible shunt wound drive motor including an armature winding and a field winding having one end grounded, a shunt wound generator including an armature winding having one end grounded and its other end connected to one end of the motor armature winding, and a field winding having one end grounded, a current measuring resistor connecting the other end of the motor armature winding to ground, a first amplifier responsive to the voltage drop across said resistor and having its output connected to the other end of said motor field winding, said resistor having an ohmic value sufficiently low as not appreciably to affect the flow of current through said motor armature winding, a second amplifier having its output connected to the other end of said generator field winding, a control switch connected to said power supply unit and effective selectively to supply current of opposite polarity to the input of said second amplifier, and motor means for driving said generator.
Claim 7
Dependent Claim
222 words
In a direct current electrical hoist control system for effecting raising and lowering of a cable-attached load and wherein the cable is attached to a rotary drum, the combination of a power supply unit establishing a source of current at a positive voltage and a source of current at a negative voltage, means establishing a common ground for said current sources, a reversible shunt wound drive motor including an armature winding and a field winding having one end grounded, a shunt wound generator including an armature winding having one end grounded and its other end connected to one end of the motor armature winding, and a field winding having one end grounded, a current measuring resistor connecting the other end of the motor armature winding to ground, a first amplifier responsive to the voltage drop across said resistor and having its output connected to the other end of said motor field winding, said resistor having an ohmic value sufficiently low as not appreciably to affect the flow of current through said motor armature winding, a second amplifier having its output connected to the other end of said generator field winding, a control switch connected to said power supply unit and effective selectively to supply current of opposite polarity to the input of said second amplifier, and motor means for driving said generator.
Claim 8
Dependent Claim
78 words
A direct current electrical hoist control system as set forth in claim 5 and wherein said control switch is in the form of a resistance having a grounded center tap which divides the resistance into a positive sector and a negative sector, the ends of said sectors being connected respectively to the sources of current established by said power supply, and a movable contact brush positionable along said resistance and connected to the input of said second amplifier.
Claim 9
Dependent Claim
64 words
A direct current electrical hoist control system as set forth in claim 6 and including, additionally, a solenoid-actuated normally engaged spring-loaded brake for said drum, a brake coil effective upon energization thereof to release said brake, a relay magnet effective upon energization thereof to energize said brake coil, said relay magnet being responsive to current flowing through the armature winding of said drive motor.
Claim 10
Dependent Claim
36 words
A direct current electrical hoist control system as set forth in claim 7 and wherein said relay magnet has one end grounded and its other end connected to said one end of the motor armature winding.
Claim 11
Dependent Claim
55 words
A direct current electrical hoist control system as set forth in claim 6 and including, additionally, time delay means interposed between said movable contact brush and the input of said second amplifier whereby changes in the flow of current from said contact brush are delayed in their transmission to the input of the second amplifier.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-05-21 | 1976-11-20 | 1977-05-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-05-21 | 1980-11-20 | 1981-05-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-05-21 | 1984-11-20 | 1985-05-22 | $7700.00 | Window Closed / Lapsed |