Electrophotographic Apparatus

Abstract

A device for detecting the jamming of copy material in a photocopying machine or the like is provided which can detect not only jamming of copy material occured at any portion of the whole path thereof but also jamming occured in a particular device or station where the jamming tends to occur or causes a serious dangerous condition. The actual time intervals required for copy material to pass through the whole path and through the particular station are compared with the reference time intervals respectively so that when the actual time intervals are longer than the reference time intervals, a warning signal is generated. The warning signal may be used to automatically stop the operation of the photocopying machine or its particular station such as a fixing station in order to prevent a fire hazard.

Description

BACKGROUND OF THE INVENTION

The present invention relates to generally a device for detecting the jamming of a copy material in a photocopying machine or the like and more particularly a device for detecting the jamming of copy material in a photocopying machine or the like capable of automatically detecting the jamming occured in the path of copy material, thereby preventing a fire hazard of and damage to the photocopying machine or the like.

In the prior art device for detecting the jamming of copy material, at least two detecting means are arrayed in spaced-apart relation with each other by a predetermined distance so that a reference time interval required for the copy material to pass over the distance between the two detecting means under the normal condition may be compared with an actual time interval required for the copy material to pass over the distance between the two detecting means so as to detect the jamming by the difference between the reference and actual time intervals. The prior art device of the type described has the defects that it requires a large number of component parts, a large installation space and it is complex in construction, which tends to lead to the difficulty in maintenance and repair and to a false operation.

The jamming of copy material in the photocopying machines or the like tends to occur in the following devices or portions:

I. IN A COPY MATERIAL FEEDING DEVICE WHERE THE JAMMING OCCURS DUE TO THE FALSE OPERATION OF THE FEEDING DEVICE;

II. AT A SEPARATOR IN CASE OF AN IMAGE-TRANSFER TYPE PHOTOCOPYING MACHINE WHERE THE JAMMING OCCURS WHEN THE COPY MATERIAL DOES NOT COMPLETELY SEPARATED FROM AN ELECTROPHOTOGRAPHIC PHOTOSENSITIVE MEMBER OR THE LIKE AFTER IMAGE TRANSFER; AND

III. IN A FIXING STATION WHERE A CONVEYOR BELT FOR TRANSPORTING THE COPY MATERIAL THROUGH THE FIXING STATION IS UNIVERSALLY OF THE WIRE SCREEN TYPE BECAUSE THE SURFACE OF THE COPY MATERIAL IS SUBJECTED TO AN ELEVATED TEMPERATURE BETWEEN 150.degree.-250.degree.C in order to fuse and pass the toner to the copy material, so that the copy material tends to be caught or jammed by the screen.

The jamming of copy material will cause a fire of and a damage to the photocopying machine or the like.

SUMMARY OF THE INVENTION

One of the objects of the present invention is therefore to provide a device for detecting the jamming of copy material in a photocopying machine or the like capable of giving a warning signal upon the occurrence of jamming in the whole path of the copy material through the photocopying machine or the like by detecting a difference between a reference time interval required for the copy material to pass through the whole path and an actual time interval required.

Another object of the present invention is to provide a device for detecting the jamming of copy material in a device or portion where the jamming tends to occur very often.

Another object of the present invention is to provide a device for detecting the jamming of copy material not only in the whole path of copy material but also in a particular device or portion in the photocopying machine or the like, that is the jamming detecting device capable of accomplishing the above two objects of the present invention simultaneously so as to detect the jamming occured from the time when the copy material feed or transportation is initiated to the time when the copy material is completely discharged out of the fixing station.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic view illustrating the path of copy material in a photocopying machine provided with a jamming detecting device of the first embodiment of the present invention;

FIG. 2 is a block diagram for explanation of the mode of operation of the first embodiment;

FIG. 3 is an electric circuit diagram of the embodiment of the present invention;

FIG. 4 is schematic view illustrating the arrangement of a second embodiment of the present invention;

FIG. 5 is a block diagram for explanation of the mode of operation thereof;

FIG. 6 is a time chart for explanation of the mode of operation of the embodiment of the present invention; and

FIG. 7 is an electric circuit diagram of a third embodiment of the present invention, which is the combination of the first and second embodiments of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a switch 3 is actuated by a cam 6 carried by a control roller 2 which is rotated in synchronism with a feed roller 10 for feeding copy papers 1 one by one. Another switch 4 is disposed at the discharge end of a fixing station 11 so as to detect the arrival of a processed copy paper 1. The device for detecting the jamming of copy paper in a photocopying machine in accordance with the present invention is characterized by the fact that the difference between a reference time interval counted by a timer 5 (See FIG. 2) which is actuated in synchronism with the actuation of the switch 3 and an actual time interval from the time when the switch 3 is actuated to the time when the switch 4 is actuated is used to detect whether the jamming of copy paper exists or not in the photocopying machine.

Upon depression of a copy button (not shown), the control roller 2 starts rotation so that the cam 6 closes the switch 3, thereby actuating a relay 7 (See FIG. 2). In consequence, the relay 7 is self-held for a reference time interval Ts as the timer 5 is actuated simultaneously. A gate 8 is so arranged as to remain opened when the following relation is held:

Ts > To

where To is an actual time interval from the time when the feeding of copy paper 1 is started to the time when the copy paper 1 reaches the discharge end of the fixing station 11 after having been transported through the photocopying machine under the normal condition without jamming.

When the jamming of copy paper 1 occurs, the actual time interval To will become longer so that the time interval relation becomes

Ts > To

In this case the gate 8 is opened so that the output from the gate 8 actuates an alarm system through a control circuit 9 thereby giving the signal of jamming condition.

In the first embodiment described above, two detectors or switches 3 and 4 are disposed at the feeding and discharge ends of the passage of the copy papers 1 so that the actual time interval To required for the copy paper 1 to be transported through the path in the photocopying machine may be compared with the reference time interval Ts required for the copy paper 1 to pass through the path under normal conditions, that is without jamming. The difference between the actual and reference time intervals To and Ts is used for detecting the jamming of copy paper. The first embodiment has an advantage that the whole passage of copy papers may be monitored. In the first embodiment, the leading edge of the copy paper 1 actuates the detector or switch 4 at the discharge end, but jamming will occur when the copy paper has not passed yet through the detector or switch 4 even though the detector or switch 4 has been actuated, giving the signal of normal transportation or passage of the copy paper. This type of jamming cannot be detected by the first embodiment. In addition in case of the occurrence of this type of jamming the copy paper is generally jammed in the fixing station 11 and is overheated by a heater (not shown) in the fixing station, thus causing a fire hazard condition.

Another embodiment to be described hereinafter is to eliminate this defect of the first embodiment and is characterized in that the jamming signal is generated when

T > Ts'

where T is a time interval required for copy paper 1 to pass through a device or station in which jamming tends to occur very often; and

Ts' is a reference time interval set by a timer, that is a time interval required for the copy paper to pass through the device or station under the normal conditions.

The first embodiment will be described in more detail with reference to FIG. 3. When the transportation or feed of the copy paper 1 is started, the first switch 3 is actuated or closed so as to energize a relay 22 closing its contact 22a. In consequence the relay 22 is self-held. Since the copy paper 1 has not arrived yet at the second switch 4, a transistor 30 is turned off while a transistor 32 is turned on so that a relay 33 is energized to open its contact 33a and to switch its movable contact 33b from a fixed contact A to B. A capacitor 37 is charged with a time constant determined in conjunction with a resistor 36. When the copy paper 1 reaches the second switch before the capacitor 37 is charged to a voltage sufficient enough to turn on a double-base diode 25, the transistor 30 is turned on by the energization of the switch 4 while the transistor 32 is turned off thereby de-energizing the relay 33. The movable contact 33b is switched back to the fixed contact A and the contact 33a is reset or closed. However, when the copy paper 1 does not reach the second switch, the voltage across the capacitor 37 reaches a level to turn on the double-base diode 25 and also a silicon-controlled rectifier 26 thereby energizing a relay 27. In consequence a contact 27a is closed to thereby turn on a warning lamp 35.

Next, further embodiment will be described with reference to FIGS. 4 and 5. FIG. 4 illustrates a fixing station having fixing means 11 and 11' disposed in the vicinity of the discharge end of the photocopying machine. A jamming detector consisting of a light source 12 and a photoconductive element 13 is disposed at the discharge end of the fixing station. The light beam from the light source 12 to the photoconductive element 13 will be interrupted when the copy paper 1 reaches the jamming detector so that the resistance of the photoconductive element 13 is varied accordingly. In response to the variation in resistance of the element 13 both of an amplifier 17 and a timer 18 in a switching circuit shown in block diagram in FIG. 5 are simultaneously actuated and a comparator 19 compares the reference time interval Ts' (See FIG. 6) of the timer 18 with the actual time interval T required for the copy paper 1 to pass through the jamming detector. When the copy paper 1 is transported under the normal condition, the condition

T < Ts'

is satisfied. On the other hand, when the jamming occurs, the time interval relation will become

T > Ts'

That is, there is a time difference .DELTA.t as shown in FIG. 6. In this case, the output is derived from the comparator 19 to actuate an alarm system 20.

In summary, in the first and second embodiments, the detector or monitor is disposed in a device or station in the path of the copy paper where the jamming tends to occur often so that the actual time interval for the copy paper to pass this detector is compared with the reference time interval for detecting the occurrence of jamming. Therefore, the sensitivity for detecting the jamming may be much improved as compared with the system in which the actual time interval required for the copy paper to pass between two points is compared with a reference time interval.

Next with reference to FIG. 7 the third embodiment of the present invention will be described which is the combination of the first embodiment with the second embodiment. Upon initiation of the feeding of copy paper, a switch 21 is closed to energize the relay 22 to close the contact 22a thereby self-holding the relay 22. The movable contact 22b is switched from the fixed contact A to B so that the capacitor 24 is charged through a variable resistor 23 to a predetermined voltage after a time interval determined by a CR time constant. When the copy paper 1 reaches the detector as shown in FIG. 4 under the normal condition without jamming, the beam from the light source 12 to the photoconductive element 13 is interrupted so that the resistance of the element 13 is increased. The voltage across the element 13 becomes higher than the emitter potential of the transistor 30 applied through the Zener diode 29 to thereby turn on the transistor 30. The voltage across the collector resistor 31 drops so that the transistor 32 is turned on to energize the relay 33. The contact 33a is opened to de-energize the relay 22. The movable contact 22b is switched to the fixed contact A and the capacitor 24 is discharged through the resistor 34. Thus, the double-base diode 25 and also the thyristor 26 are not turned on.

If the copy paper 1 fails to reach the detector within the reference time interval, the double-base diode 25 is turned on so that the thyristor 26 is turned on to energize the relay 27 to close its contact 27a to thereby turn on the warning lamp 35 as in the manner described above.

Once the copy paper 1 has reached the detector the relay 33 is energized so as to switch the movable contact from the fixed contact A to the fixed contact B so that the capacitor 37 is charged through the variable resistor 36. When the copy paper 1 passes through the detector before the voltage across the capacitor 37 reaches a predetermined value, the relay 27 is not energized. However, when the jamming occurs when the copy paper 1 is still passing through the detector, the copy paper cannot pass through the detector within the reference time interval so that the relay 27 is energized to thereby turn on the warning lamp 35.

Claims

We claim:

1. A device for detecting the jamming of copy material in a photocopying machine or the like comprising

means for transporting copy material along a predetermined path through said machine,

sensing means disposed in the path of said copy material,

timer means for counting a reference time interval required for said copy material to pass through said sensing means under normal conditions, said timer means including means for initiating said reference time interval as a leading edge of said copy material passes through said sensing means, and

means for generating an output signal when the actual time interval required by said copy material to pass through said sensing means is longer than said reference time interval.

2. A device for detecting the jamming of copy material in a photocopying machine or the like comprising

means for transporting copy material along a predetermined path through said machine,

means for feeding said copy material to said transporting means,

a first switching means,

control means for actuating said first switching means in response to actuation of said feeding means,

timer means actuated in response to the actuation of said first switching means for counting a reference time interval Ts required for said copy material to pass along the whole length of said predetermined path,

second switching means disposed at the end of said predetermined path of said copy material, and

means for generating an output signal when a time interval from the time when said first switching means is actuated to the time when said copy material actuates said second switching means is longer than said reference time interval Ts.

3. The device according to claim 1, wherein said sensing means comprises a light source, and a photo-responsive element opposed to said light source and connected to said timer means.

4. The device according to claim 1, wherein said machine includes means for fixing an image produced on said copy paper, and wherein said sensing means is disposed in the vicinity of a discharge end of said fixing means.

5. A device for detecting the jamming of copy material for use in a photocopying machine or the like comprising means for transporting copy material along a predetermined path through said machine,

means for feeding said copy material to said transporting means,

first switching means,

control means for actuating said first switching means in response to actuation of said feeding means,

first timer means actuated in response to the actuation of said first switching means for counting a reference time interval Ts required for said copy material to pass along the whole length of said predetermined path,

second switching means disposed at the end of said predetermined path of said copy material,

first output generating means for generating a first output signal when a time interval To from the time when said first switching means is actuated to the time when said copy material actuates said second switching means is longer than said reference time interval Ts,

sensing means disposed adjacent the end of said predetermined path of said copy material,

second timer means for counting a reference time interval Ts' required for said copy material to pass through said sensing means under normal conditions,

second output generating means for generating a second output signal when a time interval T required for said copy material to pass through said sensing means is longer than said second reference time interval Ts', and

means for generating a warning signal when either of said first or second output generating means generates a said output.