Land vehicles – Wheeled – Tiltable vehicles – stabilized by attendant or article
Reexamination Certificate
1999-08-05
2001-08-14
Vanaman, Frank (Department: 3611)
Land vehicles
Wheeled
Tiltable vehicles, stabilized by attendant or article
C280S047200, C280S047290, C280S641000
Reexamination Certificate
active
06273438
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a hand truck for carrying boxes, parcels, furniture and other heavy items.
A conventional hand truck comprises an elongate upright chassis having a handle at the upper end and having a load lifting platform (toe plate or fork) at the opposite, lower end. The platform extends outward from the bottom of the chassis at an angle of approximately 90°.
The chassis and platform are carried by a pair of rugged wheels, one on each side of the lower end of the chassis. The wheels are rotatable about individual axles on opposite sides of the chassis or about a single, common axle which extends across the width of the chassis. In either case, the wheels rotate about a common wheel axis which extends transversely to the longitudinal axis of the chassis.
A hand truck of this type is extremely useful, but it suffers from the drawback that it is inherently unstable. When carrying heavy loads (e.g., 200-700 pound loads) the hand truck has a tendency to either tip forward to its upright position, to where the load-bearing surface of the platform is horizontal, or tip backward to where the longitudinal axis of the chassis is essentially horizontal. With such heavy loads, a hand truck operator must be careful to maintain the hand truck in a balanced position with both the longitudinal axis of the chassis and the plane of the platform at an angle of about 45° with respect to the vertical (and horizontal).
SUMMARY OF THE INVENTION
A principal object of the present invention is to provide a hand truck having increased stability and safety as compared to hand trucks known heretofore.
This object, as well as other objects which will become apparent from the discussion that follows, are achieved, in accordance with the present invention, by providing a hand truck which comprises the following essential elements:
(a) an elongate chassis having upper and lower ends and a first longitudinal axis between them;
(b) a handle portion arranged at the upper end of the chassis;
(c) load lifting platform arranged at the lower end of the chassis, the load lifting platform extending outward from the chassis along a second longitudinal axis which is substantially perpendicular to the first longitudinal axis;
(d) a pair of truck wheels disposed on opposite sides of the chassis adjacent the lower end, the truck wheels being rotatable about a common wheel axis which extends transversely to both the first and the second longitudinal axes; and
(e) a wheel axle carriage for supporting the wheels and for moving the wheel axis between a first position above the second longitudinal axis and a second position below the second longitudinal axis.
According to a particular feature of the present invention, the hand truck is also provided with a rear support structure, connected between the axle carriage and the chassis on the side of the longitudinal axis opposite to the platform, partially supporting the weight of the chassis and the load carried by the hand truck. When the chassis is tilted backward about its wheel axis, in a direction opposite to the direction of extension of the platform, the rear support structure contacts the ground and, together with the hand truck wheels, supports the weight of the chassis and its load. Preferably, the rear support structure has at least one caster wheel arranged to make contact with the ground so that the hand truck, together with its load, can be moved about when in the load supporting position.
For a full understanding of the present invention, reference should now be made to the following detailed description of the preferred embodiments of the invention as illustrated in the accompanying drawings.
REFERENCES:
patent: Re. 28936 (1976-08-01), Talamantez
patent: 1341171 (1920-05-01), Hall
patent: 3063730 (1962-11-01), Domoradzki
patent: 3655212 (1972-04-01), Krass et al.
patent: 4762333 (1988-08-01), Mortenson
patent: 5207439 (1993-05-01), Mortenson
patent: 5779251 (1998-07-01), Meier
patent: 703231 (1965-02-01), None
patent: 734075 (1932-10-01), None
patent: 49020 (1938-10-01), None
Milde Hoffberg & Macklin, LLP
Vanaman Frank
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