Land vehicles – Wheeled – Wheel steering by attendant
Patent
1997-11-13
1999-10-12
Swann, J. J.
Land vehicles
Wheeled
Wheel steering by attendant
280 33991, 180408, 180409, B62B 300
Patent
active
059644710
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a steerable trolley, and more particularly but not exclusively to a castor wheeled trolley such as a supermarket trolley.
SUMMARY OF INVENTION
Supermarket trolleys are a well known article and commonly comprise a manually propelled trolley comprising some form of load holder which may be secured to a frame which is mounted on four independent castor wheels. The trolley usually has a handle bar which extends laterally adjacent to the upper part of the rear side of the load holder between two parallel arms which project rearwardly from the load holder with which the operator controls the trolley. The castor wheels allow the trolley to be moved in any direction at any time. However, the castor wheels suffer a number of disadvantages. For instance, the trolley easily runs wide and out of control when any attempt is made by the user to change the trolley's direction of travel. The operator can overcome this problem in one of two ways. Firstly, he may realign the trolley in the required direction of travel by making sideways movements in the opposite direction at his end of the trolley while the other end of the trolley remains relatively stationary. Progress by this method is very hesitant and considerable energy is expended through overcoming inertia when continually stopping and starting the trolley's movements. Alternatively, the operator may use his strength at his end of the trolley to apply a turning moment on the trolley. The other end of the trolley is pulled round in one direction while the operator's end is pushed out in the other direction and the trolley thus changes direction. Progress is much smoother by this method but it requires a good deal of strength especially with large and heavy trolleys and is considered to be responsible for back injury to the operator.
Further problems arise in the case of a trolley with a "sticking" wheel. Typically, when one wheel is reluctant to roll smoothly it acts as a brake on that wheel and the trolley is subjected to brake steering. The trolley is then dragged around to the side with the sticking wheel. The operator must then take action to overcome this problem. One possibility is to position the faulty wheel close to an imaginary line which passes through both the trolley's centre of gravity and the mid-point between the operator's two pushing hands. This causes what is commonly known as "crab-steering" and the trolley thus affected takes up more floor space than it would require normally. Alternatively, the operator may try to apply a turning moment to the trolley equal to that being applied by the faulty wheel through the braking effect. The trolley thus remains in line with the direction of travel, the floor space used remains normal but the strain on the operator is considerable.
A still further problem with this type of trolley is the tendency for the trolley, when crossing slopes, to be subjected to gravitational forces and to run downhill due to the tendency of the castor wheels to turn and follow the path of least resistance. To successfully cross a slope the operator must either create a barrier by positioning his body close to the imaginary line which passes through the trolley's centre of gravity and which points directly downhill or, again, apply a turning moment to the trolley equal to that being applied by gravity. Both methods cause inconvenience to the operator.
The yet further problem with this type of trolley is that when stopped on a slope the trolley is again subjected to gravitational forces and would run downhill unless the trolley operator provided a barrier, usually by positioning his body downhill from the trolley. This not only inconveniences the operator but makes loading or unloading the trolley very difficult indeed.
It is an object of the present invention to overcome these problems.
According to the present invention there is provided a steerable trolley comprising: vertical axis; and a corresponding driven wheel, the communication means being operable such that pivotal m
REFERENCES:
patent: 2551821 (1951-05-01), Bengtson
patent: 2834605 (1958-05-01), McCollough
patent: 3235283 (1966-02-01), Voghel
patent: 4248444 (1981-02-01), Johnson
patent: 4852679 (1989-08-01), Fry
patent: 4934726 (1990-06-01), Daenens et al.
McClellan James S.
Schindler Edwin D.
Swann J. J.
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