Road structure – process – or apparatus – Pavement – Anti-slip surface
Reexamination Certificate
1998-04-16
2001-10-16
Will, Thomas B. (Department: 3673)
Road structure, process, or apparatus
Pavement
Anti-slip surface
C182S090000, C182S092000
Reexamination Certificate
active
06302618
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a foothold of a manhole, a quay, etc., comprising a tread and side portions continued from and positioned at both sides of the tread.
2. Prior Art
A conventional foothold of a manhole, a quay, etc., of this type is disclosed, for example, in JP-Y 4-4040 in which a tread and side portions continued and positioned at both sides of the tread and they are positioned to be flush with each other when viewed from the side thereof, and the upper surface of the tread is linear and flat.
However the conventional foothold of a manhole has the following problem. That is, when operators move up and down in the manhole by use of a plurality of footholds arranged in the manhole, a quay, etc., they move up and down in an unstable condition where they are liable to miss their footing from the tread and also they are fatigued with their feet or knees since the upper surface of each tread is linear and flat.
SUMMARY OF THE INVENTION
The present invention has been made to solve the aforementioned problem and it is an object of the invention to provide a foothold of a manhole which enables operators to put their feet on the tread in a natural state under a stable condition, and to reduce their fatigue with their feet or knees when they move up and down in the manhole by use of the foothold.
To achieve the above object, a foothold of a manhole, a quay, etc., according to a first aspect of the present invention is characterized in that at least an upper surface of a tread is inclined upward from a central portion of the tread toward side portions of the tread at an angle ranging from 1 to 5 degrees.
A foothold of a first modification of the first aspect of the invention is characterized in that the tread comprises a core and synthetic resin for covering the core, wherein the core is linear and disposed horizontally, while a thickness of the synthetic resin for covering the core is inclined upward from a central portion toward the side portions thereof at an angle ranging from 1 to 5 degrees.
A foothold of a second modification of the first aspect of the invention is characterized in that the tread comprises a core and synthetic resin for covering the core, wherein the core is inclined upward from a central portion toward the side portions thereof at an angle ranging from 1 to 5 degrees, while a thickness of the synthetic resin is uniform at the upper surface thereof.
A foothold of a manhole, a quay, etc., adapted for one foot according to a second aspect of the present invention is characterized in that at least an upper surface of a tread is inclined upward from one side portion toward the other side portion at an angle ranging from 1 to 5 degrees.
Ambulatory physiology acknowledges that unstable walking posture causes people to fatigue or injure their feet or knees if the surface to which they contact is flat when they continue walking while standing for a long time. They can walk stably if the surface to which the feet contact is inclined subtly at an angle of 3 degrees or an angle which is slightly greater or less than 3 degrees.
Since at least the upper surface of the tread is inclined upward from the central portion of the tread toward the side portions thereof at an angle ranging from 1 to 5 degrees, operators hardly miss their footing from the tread and can move up and down in the manhole in a stable condition when they move up and down utilizing many footholds which are installed vertically in the manhole, a quay, etc.
Since at least the upper surface of the tread is inclined upward from one side portion toward the other side portion of the tread at the angle ranging from 1 to 5 degrees in the case of the foothold adapted for one foot, namely, in the case of the foothold on which they keep their footing on the foothold with their foot, each foot contacts the tread of the foothold at a desired angle so that they do not lose or miss their footing from the tread as frequently and can move up and down in the manhole under a stable condition when they move up and down.
REFERENCES:
patent: 601849 (1898-04-01), Aiken
patent: 2064803 (1936-12-01), Grove
patent: 4100997 (1978-07-01), Peacock
patent: 4241543 (1980-12-01), Foscarini et al.
patent: 4610330 (1986-09-01), Borst
patent: 4655318 (1987-04-01), Bowen
patent: 4660681 (1987-04-01), Zenhausern
patent: 4702349 (1987-10-01), Zenhausern
patent: 4771861 (1988-09-01), Zenhausern et al.
patent: 4778032 (1988-10-01), Takahashi
patent: 4869342 (1989-09-01), Borst
patent: 0 173 227 (1986-03-01), None
patent: 470 919 (1937-08-01), None
patent: 4-4040 (1992-02-01), None
Flynn ,Thiel, Boutell & Tanis, P.C.
Hartmann Gary S.
Miyama Kogyo Kabushiki Kaisha
Will Thomas B.
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