Land vehicles – Wheeled – Running gear
Reexamination Certificate
1998-10-09
2001-10-16
English, Peter C. (Department: 3619)
Land vehicles
Wheeled
Running gear
C280S755000
Reexamination Certificate
active
06302419
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a rear axle swing restriction system and a rear axle swing restriction method. More specifically, the invention relates to a system and a method for swing restriction of a rear axle of an industrial vehicle, such as a fork lift truck, including a front axle of a rigid axle type and a rear axle of a swing axle type, in which the rear axle is operatively connected relative to a vehicle body at a central part thereof in a transverse direction of the vehicle, so that it is vertically swingable about the connected part relative to the vehicle body, and which has a stopper mechanism arranged between the rear axle and the vehicle body, for restricting an allowable range of the vertical swing.
There is disclosed in Japanese Patent Application Laid-Open Publication No. 6-106930 a fork lift truck as a vehicle including a front axle of a rigid axle type and a rear axle of a swing axle type.
FIG. 1
is a front view of the rear axle, partly in section. Left and right rear wheels
1
are rotatably supported on left and right knuckle spindles
3
, respectively, and the knuckle spindles
3
are operatively connected by left and right king pins
7
to both ends of steering axle
5
as the rear axle in concern.
The steering axle
5
has at a transversely central part thereof a swing shaft
9
provided therethrough in a longitudinal direction of the vehicle. The swing shaft
9
is operatively supported at its longitudinal ends with a pair of brackets
13
hung from underside of a vehicle body
11
, so that left and right portions of the steering axle
5
are vertically swingable relative to the vehicle body
11
, about a center of the swing shaft
9
as a swing center S, with effects such as a prevention of a floating of driving front wheels in travel on an undulating road or the like, permitting an improved ride feeling to be comfortable while traveling.
The vehicle body
11
has under left and right sides thereof a pair of stopper bolts
15
downardly projecting therefrom. On the other hand, the steering axle
5
has at corresponding locations thereon a pair of pads
17
for receiving lower ends of the stopper bolts
15
, as they are either brought into abutment thereon, to thereby restrict an allowable range of the swing of the steering axle
5
relative to the vehicle body
11
.
While the steering axle
5
swings within the allowable range, causing neither stopper bolt
15
to abut on pad
17
, the vehicle body
11
is supported at three points defining a reverse triangle, i.e. at the left and right front wheels and the swing shaft
9
, so that the fork lift truck usually travels like a tricycle that has a center of gravity within a triangle defined by a single front wheel and a pair of rear wheels.
In general, the fork lift truck is kept from tumbling when its body leans within a limit of floor inclination, and has “a stability against the tumbling in correspondence to an inner region of a triangular plane defined by support points of the body” (hereafter “vehicle body stability” or “stability”). The wider the region is, the greater the stability becomes.
The fork lift truck in concern however has a mast, which may have a significant lift height and may serve for carrying a heavy load lifted at a maximum height, with a significant rearward tilt, shifting a center of gravity of the vehicle body
11
toward the swingable rear axle
5
. As the center of gravity moves rearward, the reverse triangle has a decreased transverse allowance for the stability, resulting in a reduced capacity.
The fork lift truck may travel at an accelerated speed on a flat road, with a “stableness”. The stableness of travel is subjected to the three-point support system, and may be kept under a potential level. However, all the road is not flat.
SUMMARY OF THE INVENTION
The present invention has been achieved with such points in view.
It therefore is an object of the invention to provide a system and a method for swing restriction of a rear axle of a vehicle, permitting an increased vehicle body stability such as when handling a load and an enhanced stableness of travel such as at an accelerated speed, allowing for a comfortable ride feeling such as on an undulating road.
To achieve the object, an aspect of the invention provides a system for swing restriction of a rear axle of a vehicle in which the rear axle is operatively connected at a transversely central part thereof to a vehicle body and vertically swingable about the connected part relative to the vehicle body and which has a stopper mechanism interposed between the rear axle and the vehicle body for restricting a range of the vertical swing, wherein the system comprises the stopper mechanism adapted to be operable in a swing restricting state thereof for restricting a swing action of the rear axle relative to the vehicle body and in a swing enabling state thereof for enabling the swing action and to be normally held in the swing restricting state, and a restriction canceler for operating the stopper mechanism to cancel the swing restricting state to enter the swing enabling state.
Another aspect of the invention provides a method for swing restriction of a rear axle of a vehicle in which the rear axle is operatively connected at a transversely central part thereof to a vehicle body and vertically swingable about the connected part relative to the vehicle body and which has a stopper mechanism interposed between the rear axle and the vehicle body for restricting a range of the vertical swing, wherein the method comprises the steps of normally holding the stopper mechanism in a swing restricting state thereof for restricting a swing action of the rear axle relative to the vehicle body, and operating the stopper mechanism to have a swing enabling state thereof for enabling the swing action, as necessary.
According to those aspects of the invention, a stopper mechanism is normally kept in its swing restricting state, restricting a swing action of a rear axle relative to a vehicle body, permitting an improved stability of the vehicle body, such as for a load handling service, and an improved stableness of travel at a high speed. Further, such as when traveling an undulating road, the stopper mechanism may be operated to cancel the swing restriction, to enter its swing enabling state for enabling the swing action of the rear axle relative to the vehicle body, permitting an enhanced ride feeling due such as to an avoided lifting of front drive wheel.
REFERENCES:
patent: 3077952 (1963-02-01), Neises
patent: 3171556 (1965-03-01), Brekelbaum et al.
patent: 3976302 (1976-08-01), Hammarstrand
patent: 4152004 (1979-05-01), Schroder
patent: 4264014 (1981-04-01), Hogg et al.
patent: 4344497 (1982-08-01), Rathi et al.
patent: 5639119 (1997-06-01), Plate et al.
patent: 5947516 (1999-09-01), Ishikawa
patent: 1393215 (1975-05-01), None
patent: 58-167215 (1983-10-01), None
patent: 58-211903 (1983-12-01), None
patent: 58-214406 (1983-12-01), None
patent: 06-106930 (1994-04-01), None
English Peter C.
McDermott & Will & Emery
Nissan Motor Co,. Ltd.
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