Counter balance for teaching of middle school

Abstract

The invention discloses a counter balance for teaching of the middle school. The counter balance comprises a pedestal, a middle knife rest, a lever with scales and pallets, the pallets are mounted atthe two ends of the lever via hangers respectively, vertical support arms are arranged in the lower ends of the hangers respectively, jacks are formed in the upper end surface of the pedestal, the lower ends of the vertical support arms extend into the jacks respectively, the bottom of each vertical support arm is provided with a first magnet, rotating discs are arranged under the jacks respectively, multiple protruded teeth are formed in the excircle sidewall of each rotating disc, second and third magnet are arranged on the protruded teeth at interval, the end, close to the first magnet, ofeach second magnet and the first magnet are heteropolar, the end, close to the first magnet, of each third magnet and the first magnet are homopolar, a through hole is formed in the bottom of each jack, the second and third magnets can be inserted into the through hole, a connecting groove communicated with the rotating disc is formed in the bottom of the jack at one side of the through hole, a limiting plate is inserted into the connecting groove, a spring sleeves the limiting plate, and the two ends of the spring are fixed to the inner wall and limiting plate of the connecting groove respectively. A knife edge can be protected effectively when the counter balance is disposed.

Description

Technical field: [0001] The invention relates to the technical field of middle school teaching instruments, in particular to a pallet balance used for 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 ...

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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