Patent Application
20060131089
1. Field of the Invention
The present invention relates to a speed limiting device of an electric cart, which can perform a calculation based on an angle, at which the cart is turning, to obtain a maximum allowed speed, and next make the cart move at a smaller one of the present speed and the maximum allowed speed, thus preventing the cart from moving at such a high speed as to fall over while it is turning.
2. Brief Description of the Prior Art
Electric carts are very convenient personal vehicles for leg-handicapped people and the elderly, and they are more strength saving and convenient to use than conventional wheelchairs because they are electrically actuated.
However, because common electric carts have a relatively high center of gravity, they might fall over if they move at high speed while turning. And, because common electric carts aren't equipped with any protection around the riders, the riders are prone to get injured should the carts fall over.
It is a main object of the invention to provide a device, which can limit the speed of an electric cart when the cart is turning.
The speed limiting device of the present invention includes a measuring mechanism used for measuring an angle, at which the cart is turning, a conversion mechanism, a comparer, and a switch. The conversion mechanism can perform calculation based on both an input angle value and a predetermined centrifugal speed value to obtain a maximum allowed speed. The switch is connected to a motor of the cart while first and second alternative contacts are provided for the switch to selectively touch. The first contact is connected to the output terminal of the conversion mechanism, and the present speed value is sent to the second contact and the comparer, which can make a comparison between the present speed and the maximum speed, according to the result of which comparison the switch will touch either one of the contacts, thus making the cart run at a smaller one of the two speeds when the cart is turning.
The present invention will be better understood by referring to the accompanying drawings, wherein:
Referring to
The electrical potential measuring mechanism 11 is used for measuring the angle, at which the electric cart is turning. The soft constraint 12 is connected to an output terminal of the electrical potential measuring mechanism 11 at an input terminal thereof, and it is set such that if an input angle value is smaller than the absolute value of predetermined angle values, e.g. ±5°, the input angle value will be considered to be the result of slight shaking of the cart, and neglected.
The speed conversion mechanism 13 is connected to an output terminal of the soft constraint 12 at an input terminal thereof, and a predetermined centrifugal speed value has been already input in the speed conversion mechanism 13 before the device 1 is put into use. The speed conversion mechanism 13 will perform a calculation based on an input angle value (θ), at which the electric cart is turning, and the predetermined centrifugal speed value (αL) as well as a formula: the maximum allowed speed=√(αL/θ), i.e. √ (the predetermined centrifugal speed value/ the input angle value). Consequently, the maximum allowed speed is obtained through the above calculation.
The comparer 14 is connected to an output terminal of the speed conversion mechanism 13 at an input terminal thereof. And, the output terminal of the speed conversion mechanism 13 is connected to a first one of two alternative contacts for the switch 15. The comparer 14 is connected to the switch 15 at an output terminal thereof for controlling the switch 15. The switch 15 is connected to a motor 2 of the electric cart at an output terminal thereof. Furthermore, the current speed value of the cart will be sent to a second one of the two alternative contacts for the switch 15.
The present speed value of the cart is sent to the comparer 14, and the comparer 14 will make a comparison between the current speed of the cart and the input maximum allowed speed. If the input maximum allowed speed is greater than the current speed, the comparer 14 will make the switch 15 touch the second one of the two alternative contacts; thus, the motor 2 won't change the speed, and the cart will still move at the current speed while turning. If the input maximum allowed speed is smaller than the current speed, the comparer 14 will make the switch 15 touch the first one of the two alternative contacts; thus, the motor 2 will change the speed so that the cart moves at the maximum allowed speed instead of the current speed while turning.
Therefore, when the electric cart is turning at a certain angle that is greater than 5°, the present speed limiting device will perform a calculation base on said certain angle as well as the predetermined centrifugal speed value to obtain a maximum allowed speed, and next the device will make the cart move at the maximum allowed speed instead if the current speed is greater than the maximum allowed speed; thus, the cart will move at such a speed as not to fall over while turning.
From the above description, it can be easily understood that because of the speed limiting device of the invention, while turning, the cart won't move so fast as to cause discomfort to the rider, and the risk of the electric cart falling over while turning is eliminated, and the cart is safer to ride on.
