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Why Can The Wheels Of Supermarket Shopping Carts Turn Freely?

Jan. 13, 2020

Every holiday, people will go to the supermarket to buy some daily necessities, go to the supermarket and push a shopping cart, walk around and see what they need. But have you ever noticed carefully that the wheels of the supermarket trolley can turn freely, and in which direction we want to go, the shopping cart can easily change.

Supermarket Cart

Supermarket Cart

Why ? ‍

Supermarket trolley manufacturer will share with you, let's first understand the history of the development of wheels. Throughout the history of human development, people have created many great inventions, and these inventions have greatly changed our lives. Wheels are one of them. The vehicles we use to travel every day rely on wheels to achieve transportation. Now it is difficult to verify who invented the wheel, but one thing is certain, the invention of the wheel is a slow and long evolution process. Initially it was found that scrolling is much less labor-intensive than sliding.

People put logs under heavy loads, transported them through the rolling of the logs, and later inspired the logs to invent the wheels. ‍The wheels should appear at the same time as the car. Because a single wheel is useless, combining several wheels with axles can make the most of its effect. It is difficult to assume that human beings have not invented the wheel, whether ancient or modern, what our society will look like. The emergence of wheels has made it possible for human beings not only to travel long distances, but also to transport heavier objects to further places. Through commercial activities, large-scale cities have been developed. During the development of wheels, people found that the wheels can only run in a straight line, and it is difficult to change the direction when carrying heavy objects.

So people invented a wheel with a steering structure, that is, a caster. The invention of casters has greatly improved the handling efficiency. With the development of industry, it has become more and more widely used, becoming one of the indispensable parts. ‍ Casters include casters, fixed casters and casters with brakes. The movable caster is what we call a universal wheel, which can rotate 360°. Usually two casters are used together.

There are four casters underneath a supermarket cart or a trolley for luggage at the airport. All four casters are casters. ‍If you observe carefully, you can find that the axle and the car body of the universal caster are not fixed, but can rotate freely about the vertical axis. If the axle is fixed to the car body, the casters can only go straight forward, and the car cannot turn. In addition, you can find that when you push the cart, the wheels of the caster always follow the rotation axis. If you change from forward to backward, the wheels of the caster will suddenly turn 180 ° around the vertical axis, or the wheels are still following the rotation axis. Generally, the rolling direction of the caster must be consistent with the forward direction to make the shopping cart move smoothly. Once the rolling direction of the caster is inconsistent with the forward direction of the vehicle body, the friction on the ground will generate a torque on the vertical rotation axis in front and push the caster Go to a position that matches the walking direction. ‍

Although the casters look simple, the manufacturing process is not very simple. First, press the steel sheet into a sheet on the punch according to the size, and at the same time, punch a round hole in the sheet. ‍Put the stamped sheet on the punch die, and press the bracket and brake sheet to form. In a circle of the stamped bowl, put the lubricant first and put the steel balls. The number of steel balls is indispensable. Then mount the rack on the bowl and put the lubricant and steel balls on the bracket. After the steel balls are installed, the baffles and washers are installed. The cylinder in the bowl-shaped plate is fractured by a hydraulic press, and the small bowl and the bracket are riveted together.

Put the rubber into the machine to melt it, and press it into a rubber wheel through the mold. The burr at the clamping line of the rubber wheel must be polished smoothly.

Install the shaft ring in the center hole of the rubber wheel, connect the rubber wheel to the bracket with a screw, install the nut, and finally test the caster, and the caster is ready.

Did you know that the cycling principle also uses the universal wheel. If the rotation axis of the bicycle front fork is extended to the ground, its intersection with the ground is always in front of the contact point between the front wheel and the ground. When you push the cushion forward, the front wheel obeys the forward direction very obediently. If you push the cart backwards, the relative positions of the front wheels and the forks are exactly opposite, and the pushing direction of the lateral friction force is also opposite, and the front wheels will shake left and right. The relative position of the front fork rotation shaft of the bicycle and the contact point between the front wheel and the ground is very important for ensuring the stability of the bicycle. This is even more important than the effect of inertia as the wheels rotate. ‍

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