US3914671A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Control means for electric motors operated from batteries
Assignee: Cableform Ltd
•
Filing: 1974-04-01
•
Granted: 1975-10-21
•
Expires: 1994-04-01
Abstract
Abstract In a control means for a battery operated motor such as is used in a fork lift truck, the D.C. switch for controlling the supply of current in pulses to the motor is controlled by a demand signal below a predetermined motor output but the demand signal is modified above that output to reduce the speed of the motor with increasing torque so as to prevent damage to the motor, the transmission and the control means whilst still maintaining a high rating.
Inventors
- 👤 John Morton
- 👤 Keith Drummond Stevens
- 👤 Graham Spencer Thexton
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 09:37
CPC Classifications
H; H02; H02H; H02H7/00; H02H7/08; H02H7/0833; H02H5/00; H02H5/04; H02H5/042; H02P; H02P7/00; H02P7/06; H02P7/18; H02P7/24; H02P7/28; H02P7/285; H02P7/29
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
168 words
Control apparatus for a battery-operated electric motor, said apparatus comprising in combination: a D.C. motor, detecting means for detecting current and having an output, and a battery, all connected in series and in a closed circuit; D.C. switch means connected in series in said closed circuit for supplying pulsed direct current to the D.C. motor, said D.C. switch means being controllable by a demand signal supplied thereto; amplifier means for comparing a reference signal corresponding to a predetermined motor current with a second signal corresponding to the output from said detecting means, said amplifier means generating an output only when said current detected by said detecting means is more than said predetermined motor current; means for receiving said demand signal prior to supply to said D.C. switch means and said amplifier output and for controlling the demand signal supplied to said D.C. switch means so as to limit the output power of said motor whilst enabling the motor current to increase with reduction in speed of said motor.
Claim 2
Dependent Claim
168 words
Control apparatus for a battery-operated electric motor, said apparatus comprising in combination: a D.C. motor, detecting means for detecting current and having an output, and a battery, all connected in series and in a closed circuit; D.C. switch means connected in series in said closed circuit for supplying pulsed direct current to the D.C. motor, said D.C. switch means being controllable by a demand signal supplied thereto; amplifier means for comparing a reference signal corresponding to a predetermined motor current with a second signal corresponding to the output from said detecting means, said amplifier means generating an output only when said current detected by said detecting means is more than said predetermined motor current; means for receiving said demand signal prior to supply to said D.C. switch means and said amplifier output and for controlling the demand signal supplied to said D.C. switch means so as to limit the output power of said motor whilst enabling the motor current to increase with reduction in speed of said motor.
Claim 3
Dependent Claim
45 words
A control apparatus as claimed in claim, 1 wherein said amplifier output is indicative of the maximum demand signal permitted at the detected motor current, and said receiving means prevents the demand signal supplied to the D.C. switch means exceeding the said maximum demand signal.
Claim 4
Dependent Claim
62 words
A control means as claimed in claim 1, wherein the receiving means comprises a pair of diodes in parallel connected respectively to receive the said amplifier output and the said demand signal, the polarity of the diodes being such that the signal representative of the greater demand is trapped as a result of its respective diode being reverse-biased by the other signal.
Claim 5
Dependent Claim
60 words
Control means as claimed in claim 1 wherein the demand signal supplied to the D.C. switch means is varied in accordance with a signal derived from a temperature sensing element which senses the temperature of a part to be protected against excessive temperature rise so that the output power limit is cut-back when the temperature rises above a predetermined value.
Claim 6
Dependent Claim
16 words
Control means as claimed in claim 1, wherein the gain of the amplifier means is adjustable.
Claim 7
Dependent Claim
18 words
Control means as Claimed in claim 1 wherein the D.C. switch comprises thyristors controlled by a pulse generator.
Claim 8
Dependent Claim
29 words
Control means as claimed in claim 4, wherein the D.C. switch comprises thyristors and the temperature sensing element is a thermistor mounted on the heat sink of the thyristors.
Claim 9
Dependent Claim
38 words
Control means as claimed in claim 4, in which a plurality of temperature sensing elements are disposed about the control means and the apparatus controlled thereby and combined together in a circuit to vary the output power limit.
Claim 10
Dependent Claim
26 words
Control means as claimed in claim 1, wherein a fuse is provided in the battery circuit having a rating of less than the maximum motor current.
Claim 11
Dependent Claim
32 words
Control means as claimed in claim 9, wherein at least one interconnection between two adjacent cells of the battery includes a fuse having a rating of less than the maximum motor current.
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) | 1978-10-20 | 1979-04-21 | 1979-10-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-10-20 | 1983-04-21 | 1983-10-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-10-20 | 1987-04-21 | 1987-10-21 | $7700.00 | Window Closed / Lapsed |