Counter balance for middle school teaching

Abstract

The invention discloses a counter balance for middle school teaching. The counter balance comprises a base and vertical support arms. Insert holes are formed in the upper surface of the base. The bottom portion of each vertical support arm is provided with a first magnet. A rotating disk fixedly inserted to a fulcrum shaft is arranged under each insert hole. The outer circle side wall of each rotating disk is provided with a plurality of convex teeth. Second magnets and third magnets are arranged alternately on the plurality of convex teeth. The second magnet and one end of a first magnet areopposite poles, and the third magnet and one end of the first magnet are same poles. A through hole is formed in the bottom portion of the insert hole. An external thread is formed on the outer wall of each vertical support arm. An adjusting gear pressed against the upper surface of the base is screwed in each vertical support arm. One side of each adjusting gear is engaged with a horizontal toothbar. The two adjusting gears at the two sides of the base are engaged to the two sides of the tooth bar respectively. A placement groove is formed in the upper surface of the base. The tooth bars areinserted into the placement groove. The two-end inner walls of the placement groove are respectively provided with a magnet layer. The two ends of the tooth bar are respectively provided with an ironlayer. The counter balance can effectively protect edges when placed.

Description

Technical field: [0001] The invention relates to the technical field of middle school teaching instruments, in particular to a tray balance used in middle school teaching. Background technique: [0002] The tray balance is one of the necessary instruments in the laboratory in middle school teaching. It is made by the principle of Roberwell. The weighing pan is stressed on the bottom plane and can automatically move to the center position in the non-center position to form a balance. The tray balance mainly includes a base, a middle tool rest, a vernier, a lever with a scale, and a tray. The tray is installed at both ends of the lever through a hanger. In the hole, the outer periphery of the vertical support arm under the tray is provided with a rubber sleeve for protecting the knife holder, which is fixed in the corresponding fixing hole on the base through the rubber sleeve. Before the existing pallet balance is used, the protective rubber sleeves under the two pallets nee...

AI Technical Summary

Problems solved by technology

After use, in order to protect the knife edge and prevent the knife edge from being in working condition, the rubber sleeve must be reinstalled, so that it can be placed in the cabinet. This method is time-consuming and laborious to install and remove the rubber sleeve, and the rubber sleeve is easy to be lost or damaged, causing the balance of the pallet. If it is placed in a working state, it is easy to damage the knife edge, and the accuracy of the tray balance is greatly reduced, which will also seriously affect the effect of teaching experiments

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