Patent US4297179A successfully refreshed from Google Patents.
Patent US3571909A successfully refreshed from Google Patents.
US3571909A
Expired / Lapsed
US
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Method of joining structural members of a ladder
Assignee: CROFT METAL PRODUCTS Inc
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Filing: 1968-12-30
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Granted: 1971-03-23
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Expires: 1988-12-30
Abstract
Abstract Exceptional rigidity is imparted to a metal ladder by roll forging tabs at the ends of the steps and which project through the side rails. The roots of the tabs are expanded to fit tightly in the side rail openings and an enlarged head is formed on each tab which bears against the side rail and securely locks the step in place. The enlarged heads are confined between ribs on the side rails, the ribs having mutually divergent opposed faces serving to wedge the parts together.
Inventors
- 👤 Melvin J Stern
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 13:27
CPC Classifications
E; E06; E06C; E06C7/00; E06C7/08; E06C7/082; E06C7/084; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49826; Y10T29/49908; Y10T29/49915; Y10T29/49938; Y10T29/49943; Y10T29/53; Y10T29/53709; Y10T29/5377
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
163 words
The method of making a metal ladder which comprises: the steps of: a. forming a plurality of metal steps each having a plurality of projecting tabs at its opposite ends, b. forming a pair of side rails, each having tab-receiving openings at spaced points therealong, said rails being formed with outwardly diverging ribs adjoining opposite sides of said openings and extending in a direction longitudinal of said side rails, c. assembling the side rails and steps with the ribs facing outwardly and with the tabs of the steps projecting through and beyond the tab-receiving openings, and d. roll forging the tabs to such an extent that the portions of the tabs lying within the tab-receiving openings are expanded into tight filling engagement with said openings while the portions of the tabs projecting beyond said openings are rolled down to form enlarged heads bearing firmly against the divergent rib surfaces thus assuring a rigid and firm connection between the steps and the side rails.
Claim 2
Independent Claim
163 words
The method of making a metal ladder which comprises: the steps of: a. forming a plurality of metal steps each having a plurality of projecting tabs at its opposite ends, b. forming a pair of side rails, each having tab-receiving openings at spaced points therealong, said rails being formed with outwardly diverging ribs adjoining opposite sides of said openings and extending in a direction longitudinal of said side rails, c. assembling the side rails and steps with the ribs facing outwardly and with the tabs of the steps projecting through and beyond the tab-receiving openings, and d. roll forging the tabs to such an extent that the portions of the tabs lying within the tab-receiving openings are expanded into tight filling engagement with said openings while the portions of the tabs projecting beyond said openings are rolled down to form enlarged heads bearing firmly against the divergent rib surfaces thus assuring a rigid and firm connection between the steps and the side rails.
Claim 3
Dependent Claim
23 words
The method of claim 1 wherein the steps are provided with depending flanges and the tabs are formed as projections on said flanges.
Claim 4
Dependent Claim
46 words
The method of claim 2 in which there are three such flanges, one centrally located and one along each edge of the steps and in which the tabs are formed on the inner surfaces of the edge flanges and on both surfaces of the central flange.
Claim 5
Dependent Claim
24 words
The method of claim 1 in which the ribs of the side members are continuous and extend along the entire length of such members.
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) | 1974-03-22 | 1974-09-21 | 1975-03-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-03-22 | 1978-09-21 | 1979-03-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-03-22 | 1982-09-21 | 1983-03-23 | $7700.00 | Window Closed / Lapsed |