Sheet mass measuring unit

Abstract

A mass measuring unit includes two driving rollers vertically separate from each other and intersecting the direction of conveyance of a mail matter. Servo motors for driving the driving rollers are connected to torque detection units. A control unit controls motor control units to cause them to impart a rate difference between the driving rollers to rotate the mail matter during its conveyance, and to cause the torque detection units to detect the torque values of the servo motors. The control unit compares the thus detected torque values with the torque values of the servo motors detected when the servo motors are idling without rotating the mail matter, thereby measuring the mass of the mail matter using a calculation unit.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2009-185952, filed Aug. 10, 2009, the entire contents of which are incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to an apparatus for measuring the mass of a paper sheet, such as a mail matter, and more particularly, to an apparatus for measuring the mass of a paper sheet conveyed at a relatively high rate, without stopping the conveyance of the sheet.[0004]2. Description of the Related Art[0005]Jpn. Pat. Appln. KOKAI Publication No. 2005-162407 (hereinafter, patent document 1), for example, discloses a mass detection apparatus as an apparatus for measuring the mass of a paper sheet during conveyance of the same. In the apparatus disclosed in patent document 1, the rotational rate of a driving roller provided along a conveyor path is varied to gradually...

AI Technical Summary

Benefits of technology

[0008]It is an object of the invention to provide a paper sheet mass measuring unit capable of highly accurately measuring mass of a paper sheet and enhancing the throughput.

[0012]In the above-described invention, a sheet of paper is rotated during its conveyance, and the torque of the rotation mechanism is detected, and is compared with the torque of the driving system beforehand measured under the same conditions but without rotating any sheet of paper, thereby measuring the mass of the sheet of paper. By virtue of this structure, the mass of each sheet of paper can be measured while sheets of paper are successively conveyed at high rate, and hence the conveyance throughput can be enhanced, compared to the conventional case where the mass of each sheet of paper is measured based on a change in torque detected when each sheet of paper is accelerated and decelerated along the conveyor path.

[0013]Further, in the above-described invention, since the mass of each sheet of paper is measured based on a change in the torque of the rotation mechanism detected when each sheet of paper is rotated by the rotation mechanism, a relatively high torque due to a relatively high rotation moment can be generated, and hence the mass of each mail matter M can be measured at high accuracy, compared to the conventional case where each sheet of paper is accelerated and decelerated along the conveyor path.

Problems solved by technology

However, in the mass detection apparatus disclosed in patent document 1, it is necessary to change the conveyance rate of each paper sheet during conveyance thereof, and hence it is necessary to provide a sufficient gap between successive paper sheets, which inevitably reduces the throughput.

Furthermore, in this apparatus, the ratio of an increase in the inertia moment of the driving mechanism comprising the driving roller itself subjected to acceleration / deceleration control, the driving shaft of the driving roller, and / or the rotor of a motor for driving the driving roller, which inertia moment occurs when the driving mechanism conveys a paper sheet, to the inertia moment of the mechanism when it conveys no sheet, is extremely low.

This inevitably reduces the mass detection accuracy.

Images