Patent US3764223A successfully refreshed from Google Patents.
US3764223A
Expired / Lapsed
US
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Method for locating and removing manhole covers
Assignee: LEE WAY TRENCHING Inc
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Filing: 1971-02-18
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Granted: 1973-10-09
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Expires: 1991-02-18
Abstract
Abstract The presence of a manhole cover in a roadbed under a layer of non-magnetic asphalt is detected and accurately located by a method in which magnetic detection apparatus have a detection alarm and employing inductive search coils is operative to sense the proximity of a metallic object, at least portions of which are magnetically detectable, through changes in coil inductance. The detectiom method and apparatus is capable of determining the thickness of the asphalt layer and heat is employed to efficiently melt through the asphalt in such a way as to permit removal of the cover without unnecessarily damaging the asphalt surface. Thereafter, the cover may be replaced in the road bed and resealed in place.
Inventors
- 👤 G Weekly
- 👤 F Lucero
- 👤 J Lucero
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 13:03
CPC Classifications
G; G01; G01V; G01V3/00; G01V3/08; G01V3/10; G01V3/101; G01V3/102; E; E01; E01C; E01C23/00; E01C23/06; E01C23/09; E01C23/0906; E01C23/0953; E01C23/14; E02; E02D; E02D29/00; E02D29/12; E02D29/14
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
127 words
A method of accurately locating and removing a manhole cover of predetermined size and shape which is covered by a layer of asphalt comprising the steps of: sensing the general location of the manhole cover within the asphalt layer; magnetically detecting the outer peripheral edge of the cover and marking on the asphalt layer the outline shape of the outer peripheral edge of the cover; melting through the asphalt layer around the peripheral edge of the cover by covering the asphalt layer with an insulating material and applying heat to the layer beneath the insulating material around the peripheral edge of the cover so as to separate the asphalt on the cover from the rest of the asphalt layer; and removing the cover from the asphalt layer.
Claim 2
Independent Claim
127 words
A method of accurately locating and removing a manhole cover of predetermined size and shape which is covered by a layer of asphalt comprising the steps of: sensing the general location of the manhole cover within the asphalt layer; magnetically detecting the outer peripheral edge of the cover and marking on the asphalt layer the outline shape of the outer peripheral edge of the cover; melting through the asphalt layer around the peripheral edge of the cover by covering the asphalt layer with an insulating material and applying heat to the layer beneath the insulating material around the peripheral edge of the cover so as to separate the asphalt on the cover from the rest of the asphalt layer; and removing the cover from the asphalt layer.
Claim 3
Dependent Claim
105 words
The method recited in claim 1 wherein the outer peripheral edge of the cover is magnetically detected by locating a plurality of marks relative to the outer peripheral edge of the cover through the use of a magnetic detection apparatus, and wherein the magnetic detection apparatus employed includes an inductive coil which changes inductance as a function of the proximity and mass of the cover, oscillator means including the coil which changes its amplitude of oscillation whenever the iNductance of the coil increases due to the detection of the cover, and alert means operated by the oscillator means for indicating the detection of the cover.
Claim 4
Dependent Claim
57 words
The method recited in claim 2 wherein the marks are located by moving the inductive coil relative to the manhole cover so as to activate and deactivate the alert means and the marks are marked relative to the positioning of the coil in a consistent manner to establish the shape of the outer edge of the cover.
Claim 5
Dependent Claim
63 words
The method recited in claim 3 wherein the steps of magnetically detecting the approximate depth of the asphalt layer over the cover includes employing a heating element beneath the layer of insulating material to melt through the asphalt layer, and controlling the duration the heating element is energized and the rate it generates heat energy according to the thickness of the asphalt layer.
Claim 6
Dependent Claim
96 words
The method recited in claim 4, wherein the depth of the asphalt layer is determined by moving the coil of the magnetic detection apparatus upward vertically from the portion of asphalt situated over the located center of the cover to the position where the inductance of the coil decreases to the value at which the alert means is deactivated by the oscillator means, and the insulating material is an asbestos blanket which is secured over the heating element during its energization to prevent the loss of heat energy and direct the heat generated into the asphalt.
Claim 7
Dependent Claim
17 words
The method recited in claim 5 wherein the general location of the manhole cover is magnetically sensed.
Claim 8
Dependent Claim
19 words
The method recited in claim 6, including the step of replacing and resealing the removed manhole cover in place.
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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) | 1976-10-08 | 1977-04-09 | 1977-10-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-10-08 | 1981-04-09 | 1981-10-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-10-08 | 1985-04-09 | 1985-10-09 | $7700.00 | Window Closed / Lapsed |