JPS59102737A - Double feed preventive mechanism of sheet feeding device - Google Patents

Abstract

PURPOSE:To have always stable paper feeding performance, in an arrangement in which double feed is prevented by means of cooperation of a feed roller and a reverse roller, by furnishing a drive transmission means to change the torque of reverse roller and by controlling said means according to the format and type of the sheets of paper as well as the humidity condition etc. CONSTITUTION:A reverse roller 5 installed in the understream of a sheets feeder roller, not illustrated, which is to send off the sheets in stack one after another and which constitutes a distribution roller couple 3 together with a feed roller 4, is rotated by a chain 9 with the aid of a hysteresis clutch 7 as drive transmission means and an output sheet 7e. This hysteresis clutch 7 is so constructed that the torque borne increases proportional to the exciting current for an excitor coil 7h, so as to put the clutch 7 in engagement by the current from a rectifier 11 in compliance with a clutch-on signal S. Torque corresponding to this exciting current shall be generated by controlling a variable resistor 10 and thereby increasing or decreasing the exciting current.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a paper feeding device for a copying machine, a printing machine, etc., and more particularly to a mechanism for preventing double feeding of stacked papers that are fed out one by one.

BACKGROUND ART Conventionally, it has been known to provide a pair of separating rollers consisting of a feeding roller and a reversing roller on the downstream side of a paper feeding roller that sends out stacked sheets.

This reversing roller is also always in reverse during paper feeding operation, or during normal feeding (feeding one sheet), due to the pressure contact force with the feed roller, the torque in the reverse direction of the reversing roller is tangential to the normal rotation direction. The force is overcome and the reversing roller is driven in the forward rotation direction, but during double feeding, the reversing roller rotates in the reverse direction and sometimes separates the second and subsequent sheets of paper.

In any of these mechanisms, conventionally, the separation force (torque of the reversing roller) differs depending on the type of paper, or the friction coefficient between the sheets differs due to changes in the loaded paper, the humidity conditions around the separation roller, etc. etc. were not taken into account.

That is, in addition to so-called plain paper, paper used in copying machines includes rough paper, second original drawing paper, film/base paper for OHP (overhead projector), and the like.

Since the coefficient of friction between these sheets differs under the same outside air conditions, it is difficult to say that all types of paper will be completely separated by a certain set torque of the reversing roller. Incidentally, the coefficient of friction increases in the order of cardboard, OHP film, plain paper, second original paper, and rough paper. Therefore, for example, if the reverse torque value is the best for thick paper, it is possible that rough paper will not be sorted and will be fed twice, and conversely, if the reverse torque value is the best for rough paper, then the reverse torque value for thick paper There was a risk that the paper would not be fed downstream from the pair of separating rollers, that is, a state of non-feeding would occur.

On the other hand, even if the paper is of the same type, the coefficient of friction between the papers varies greatly depending on the external humidity conditions.

That is, the higher the humidity, the higher the coefficient of friction.

Purpose The present invention has been made based on the above background, and is capable of stably feeding paper (feeding sheets one by one) for many types of paper or under various external humidity conditions. The purpose of this is to provide a mechanism for preventing double feeding.

composition The configuration of the present invention will be explained below based on the illustrated embodiments.

FIG. 1 is a mechanical explanatory diagram of a paper feeding device according to the present invention.

In the figure, reference numeral 1 denotes stacked sheets, and 2 denotes a paper feed roller that feeds the stacked sheets 1 one by one starting from the topmost sheet. Reference numeral 3 denotes a pair of separating rollers, which consists of a feed roller 4 and a reversing roller 5 that presses against the feed roller 4.

As described above, this reversing roller 5 is capable of reversing at all times or during double feeding, and is provided with a hysteresis clutch (drive transmission means) described later. Reference numeral 6 denotes a pair of range strollers for synchronously conveying paper to a photoreceptor (not shown).

FIG. 2 is a plan view of the crest of the hysteresis clutch portion.

The hysteresis clutch 7 includes a rotor 7& on the input side, an outer magnetic pole 7b, a cup 7e on the output side, and a ball bearing 7d.

Output shaft 7e, flange 7f, inner magnetic pole 7gs excitation coil 7
h, field 71. Installation 7 lunge 7j.

It consists of an input shaft 7k. This hysteresis clutch 7 is well known and has characteristics as shown in FIG. That is, the torque increases in proportion to the excitation current. Returning to FIG. 2 again, 8 is a linear rocket which is driven from the outside by a chain 9, and is fixed to the input shaft 7k. When the hysteresis clutch 7 is turned on, the torque on the input shaft 7 is applied to the output shaft 7e.
As a result, the torque of the reversing roller 5 attached to the output shaft 7e becomes variable.

Figure 4 shows the hysteresis clutch 7 configured in this way.
This figure shows an example of a circuit that makes the torque of the motor variable.

In the figure, 10 is a slider, 11 is a rectifier, 12 is a transistor, and S is a clutch-on signal. This clutch-on signal S and the current of the rectifier 11 turn on the hysteresis clutch 7 and generate a predetermined driving torque. I will do it.

In this circuit, if the slider 10 is moved to increase or decrease the excitation current, the hysteresis clutch 7 will become
A torque corresponding to this exciting current is generated. Not only the hysteresis clutch 7, but also the A clutch has such characteristics.

FIG. 5 is a plan view showing the adjustment knob of this slide duck 10. On the index plate 13, pl l Pl +P3
It is equipped with a five-level index section of 1 pn + P5, which corresponds to rough paper, second original paper, plain paper, OHP film, and cardboard. The adjustment knob 14 moves between these positions. For example, when using plain paper, set it to the ps position, and when using a second original, set it to the p! position.
It will be set in position. Then, the excitation current is adjusted by the slider 10, and a torque corresponding to each paper is generated.

As described above, the exciting current increases in the direction P5→P, increasing the torque.

Figure 6 shows that considering the external pressure humidity data of the paper type data,
2 is a block diagram of a circuit configured to set the torque of the hysteresis clutch 7. FIG.

In the figure, 15 is a humidity sensor, 16 is an A/D converter for digitally converting the signal from this humidity sensor 15, and 17 is a switch for inputting selection data of special cassettes (not shown) for various types of paper. group, 1
8 is a CPU that takes in the humidity signal from the A/D converter 16 and paper type information from the switch group 17 and outputs an appropriate torque signal, and 19 is a D/A that converts the signal from this CPU 8 into analog. The hysteresis clutch 7 is finally driven by a signal from the D/A converter 19.

Effects As described above, in the present invention, the optimal torque value of the reversing roller is set depending on the type of paper, humidity conditions, etc., so that stable paper feeding performance can always be obtained under any circumstances.

[Brief explanation of drawings]

Fig. 1 is a simplified mechanical diagram of the paper feeding device that is the premise of the present invention, Fig. 2 is a longitudinal cross-sectional view of the drive transmission means according to one embodiment, Fig. 3 is its characteristic diagram, and Fig. 4 is a schematic diagram of the paper feeding device. Circuit diagram according to the embodiment, Figure 5 is a plan view of the operating section, and Figure 6 is a block diagram according to another embodiment. DESCRIPTION OF SYMBOLS 1... Loaded paper, 2... Paper feed roller, 4... Feed roller, 5... Reverse roller, 7... Drive transmission means. Na 1 z Gnat diagram μ) 1 stone 1 Hishi EL (Rin 7, <Kuni Sai 5 1986

Claims (1)

[Claims] In a paper feeding device equipped with a paper feed roller that sends out stacked paper, a feed roller provided downstream of this paper feed roller, and a reversing roller that presses against this feeding roller to prevent double feeding, the torque roller of this reversing roller is variable. A drive transmission means is provided,
A double-feed prevention mechanism for a paper feeding device, characterized in that torque compensation of the reversing roller is controlled by controlling the drive transmission means according to the type of paper, humidity conditions, etc.