Chalk sheath

Abstract

The invention relates to teaching assisting tools, in particular to a chalk sheath. The chalk sheath is characterized by comprising a cylindrical sleeve with one end provided with an opening and a hollow cylindrical tube; one end of the tube is sleeved in the sleeve, and the tube matches with the sleeve in a threaded manner; the bottom of the sleeve is connected to a piston through a spring, and the piston is sleeved in a cavity of the tube. Compared with the prior art, the chalk sheath has the advantages that a hand cannot contact with the chalk when writing, chalk dust cannot cling to the hand, and corresponding contamination can be avoided; meanwhile, the chalk in the sheath can be controlled to get in and out conveniently, the appropriate length of the part of the chalk extending out of the sheath is maintained constantly, and the chalk is not easy to break when being used for writing; the entire chalk sheath is easy to produce and low in cost.

Description

technical field [0001] The invention relates to teaching aids, in particular to a chalk sheath. Background technique [0002] The mode that the mode that the school of my country most areas adopts chalk to write on blackboard comes class at present, and the method that teacher uses chalk is that hand directly holds chalk and rubs on blackboard always for a long time. Now, the chalk of domestic use mainly contains two kinds of common chalk and dust-free chalk, and its main component is calcium carbonate (limestone) and calcium sulfate (gypsum), and contains a small amount of calcium oxide (quicklime). Because calcium oxide is corrosive, long-term contact will cause skin keratosis and chapping on the palms. Moreover, teachers need to turn over textbooks and lesson plans after taking the chalk, and the chalk powder on their fingers will stain it. And because the chalk is too brittle, the chalk is easily broken during writing, which not only wastes the chalk, but also causes in...

AI Technical Summary

Problems solved by technology

Due to the corrosiveness of calcium oxide, long-term contact will cause skin keratosis and chapping on the palm of the hand, and teachers need to turn over textbooks and lesson plans after taking the chalk. The chalk powder on the fingers will stain it

And because the chalk is too brittle, the chalk is easily broken when writing, which not only wastes the chalk, but also brings inconvenience to writing.

The use of chalk has not been improved so far

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