US4550277A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Overload detection and warning system for electric motors in power tools and the like
Assignee: Black and Decker Inc
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Filing: 1984-09-24
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Granted: 1985-10-29
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Expires: 2004-09-24
Abstract
Abstract Thermal overload of the power tool is sensed by comparing a continually updated thermal model of the tool with a predetermined limit. The thermal model is updated in accordance with operating parameters such as motor speed and power delivered (conduction angle) and implemented using numerical integration based on a look-up table matrix. When overload is detected, power to the tool is gradually reduced, with attendant reduction in speed, followed by a cyclic or warbling increase and decrease in power to provide fluctuating low speed behavior, which may be readily recognized by the tool operator as an overload warning.
Inventors
- 👤 Joseph E. Carney
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 16:09
CPC Classifications
G; G05; G05B; G05B19/00; G05B19/02; G05B19/18; G05B19/406; G05B19/4062; H; H02; H02H; H02H6/00; H02H6/005; H02H7/00; H02H7/08; H02H7/085; H02H7/0856; H02H7/0858; Y; Y10; Y10S; Y10S388/00; Y10S388/90; Y10S388/903; Y10S388/923; Y10S388/934
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
76 words
A method for providing a warning that a given operating condition in a power tool has been detected, comprising the steps of: (a) gradually reducing the power delivered to the tool upon detection of said given operating condition until a predetermined non-zero reduced level is reached; and (b) thereafter cyclically increasing and decreasing the power delivered to said tool in predetermined amounts to cause the tool to discernably exhibit a cyclic behavior which constitutes said warning.
Claim 2
Independent Claim
76 words
A method for providing a warning that a given operating condition in a power tool has been detected, comprising the steps of: (a) gradually reducing the power delivered to the tool upon detection of said given operating condition until a predetermined non-zero reduced level is reached; and (b) thereafter cyclically increasing and decreasing the power delivered to said tool in predetermined amounts to cause the tool to discernably exhibit a cyclic behavior which constitutes said warning.
Claim 3
Dependent Claim
14 words
The method of claim 1 wherein the given operating condition is an overload condition.
Claim 4
Dependent Claim
24 words
The method of claim 1 wherein said step of detecting the given operating condition is performed by sensing the operating speed of the tool.
Claim 5
Dependent Claim
24 words
The method of claim 1 wherein said step of detecting the given operating condition is performed by monitoring the power delivered to the tool.
Claim 6
Dependent Claim
82 words
The method of claim 1 wherein said step of detecting the given operating condition is performed by: storing a thermal model value indicative of the operating condition of the tool; sensing the operating speed of the tool; monitoring the power delivered to the tool; periodically altering the thermal model value in accordance with the sensed operating speed and power delivered; and periodically testing the thermal model value to determine its relationship to a predetermined limit value corresponding to the given operating condition.
Claim 7
Dependent Claim
57 words
The method of claim 1 further comprising: storing a thermal model value indicative of the operating condition of the tool; periodically altering the thermal model value in accordance with actual operating conditions of the tool and testing the thermal model value to determine if it has reached a predetermined limit value corresponding to the given operating condition.
Claim 8
Dependent Claim
20 words
The method of claim 6 further comprising modifying the thermal model value when said predetermined reduced power level is reached.
Claim 9
Dependent Claim
27 words
The method of claim 1 further comprising responding to a reduction in said load upon the tool by terminating the cyclical increase and decrease in power delivered.
Claim 10
Dependent Claim
27 words
The method of claim 1 further comprising terminating the cyclical increase and decrease in power delivered in response to a reset signal initiated by the tool operator.
Claim 11
Dependent Claim
25 words
The method of claim 9 wherein the tool is provided with a manually operable trigger and said reset signal is initiated by releasing the trigger.
Claim 12
Dependent Claim
29 words
The method of claim 9 wherein the given operating condition is an overload condition and the reset signal is initiated by the removal of the load from the tool.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-10-28 | 1989-04-29 | 1989-10-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-10-28 | 1993-04-29 | 1993-10-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-10-28 | 1997-04-29 | 1997-10-29 | $7700.00 | Window Closed / Lapsed |