Abstract:
According to the present invention, there is provided an automatic carriage-returning device for a facsimile apparatus comprising a rotary drum for performing the main scanning, a carriage for performing the sub-scanning along the axis of the drum, a belt for moving the carriage in the sub-scanning direction, a coupling means for connecting the belt with the carriage, and spring means operative to return the carriage toward the initial position, said carriage being returned to the initial position by means of repeating actuation and release of the coupling means to the belt.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a facsimile apparatus and, more particularly, to a mechanism for automatically returning the sub-scanning carriage of a facsimile appratus. 
     In a facsimile apparatus, of a rotary drum scanning type, comprises a scanning drum which is rotatable about its axis for sub-scanning and an optical sensing device or recording stylus disposed opposite the drum surface to move in a direction normal to the main scanning. It is necessary that the sub-scanning carriage comprising the optical sensing device or recording stylus (hereunder referred to simply as a &#34;carriage&#34;) be returned to the initial position after it has completed a sub-scanning in forward direction. While such returning is effected manually in most prior art systems, several systems have been proposed to simplify the returning operation by providing the carriage with a mechanism for giving an automatic carriage return. Japanese Patent Publication No. 372/72 and Japanese Utility Model Public Disclosure No. 65732/76 describe a method of buffering the return impact by the application of a braking force onto a disc through which eddy currents flow, and method of temporarily stopping the carriage just before it reaches the initial position, respectively. However, these and other conventional methods of automatically returning the carriage have a disadvantage because they require a complex control mechanism. 
     SUMMARY OF THE INVENTION 
     It is therefore a primary object of this invention to provide a mechanism of returning the carriage of a facsimile apparatus, free from the disadvantage of the conventionel technique and effectively achieving the intended returning operation by means of a simple control and with a small impact resulting from the carriage impinging on the initial position. 
     Other objects, features and advantages of this invention will be apparent by reading the following detailed description of the invention in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a perspective view illustrating one embodiment of the receiver of the facsimile apparatus according to this invention; 
     FIG. 2 is a cross section of the receiver taken along line 2--2 of FIG. 1, which includes a motor, drum and a carriage; 
     FIG. 3 is a block diagram of the control circuit used to control the automatic carriage returning mechanism of this invention; and 
     FIG. 4 is a timing diagram illustrating the operation of the control circuit shown in FIG. 3. 
    
    
     According to the present invention, an automatic carriage returning device for a facsimile apparatus comprises a rotary drum for performing the main scanning, a carriage for performing the sub-scanning along the axis of the drum, a belt for moving the carriage in the sub-scanning direction, a coupling means for connecting the belt with the carriage, and spring means operative to return the carriage toward the initial position. The carriage is returned to the initial position by means of a repeated actuation and release of the coupling means to the belt. 
     Since a simple mechanism is used to repeatedly couple the carriage with and disconnect it from the belt, only a very small impact will result when the carriage returns to the initial position. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In FIGS. 1 and 2, paper-holding bars 5 and 5&#39; hold a recording paper against the surface of a drum 3, which is rotatably supported by support frames 1 and 2. A timing belt 11 is supported under tension between the drum 3 and a pulley 8 mounted on the shaft 7 of a drum drive motor 6, to rotate the drum in a direction C for main scanning. Under the bottom side of the carriage 12 is disposed a recording stylus 27 which is brought into contact with the surface of the recording paper 4 in a receive mode of the facsimile. 
     The sub-scanning mechanism incorporating the automatic carriage returning device comprises the carriage 12 which is guided by guide shafts 33 and 34 each supported by the frames 1 and 2, so as to be moved both in a foward B direction and in a return A direction. A boss 13, integrally mounted on the carriage 12, is coupled with a plunger 15 of a solenoid 14 biased by a compressive spring 16, to captivate an endless belt 19 between the boss 13 and the plunger 15. Belt 19 is supported under tension by a drive pulley 17 and an idler pulley 18. To supply a predetermined tension, a spiral spring 20 made of stainless steel is supported on one end by a bracket 21 (attached to the frame 1) by means of a shaft 22, whereas the other end of the spring is connected to the carriage 12 by a screw 23. A microswitch 24 is disposed in such a position that it acts as a stopper for the carriage 12. A microswitch 25 is a sub-scanning end indicating switch which is operated when actuated by the carriage 12 moving in the forward B direction. 
     FIG. 3 shows a control circuit 26 for controlling the solenoid 14, the circuit microswitches 24 and 25, comprising an S-R flip-flop 35, an AND gate 37, and a transistor 38. The terminals a and a&#39; of the microswitches 24 and 25, respectively, are connected to a common power source. The respective contacts b and c&#39; of the microswitches 24 and 25 are connected to terminals R and S of the flip-flop 35, respectively. The output of the flip-flop 35 and a clock pulse are supplied to different inputs of the AND gate 37. The output of the AND gate is connected to the base of the transistor 38. The transistor 38 responds to the base voltage, to supply the solenoid 14 with a current from a solenoid power source 39. When the microswitch 25 is actuated by the carriage 12, contacts a&#39; and c&#39; are closed temporarily, and when the microswitch 24 is actuated by the carriage 12, movable contact a and contact c close. For other conditions, the microswitch 25 is actuated to interconnect contact a&#39; and contact b&#39;, to provide a voltage across a control circuit 40 which switches on or off a sub-scanning drive motor 28 (FIG. 1). 
     The operation of the control circuit shown in FIG. 3 will now be explained, by reference to the timing diagram of FIG. 4. When a starter switch (not shown) is turned on, the sub-scanning drive motor 28 is driven responsive to a signal M (FIG. 4) to rotate the drive pulley 17 in a direction indicated by the arrow D (FIG. 1). The microswitch 24 is opened to apply a low level input signal F (FIG. 4) to the terminal R of the flip-flop 35. The carriage 12, located at the initial position, is engaged with the endless belt 19 which is held between the boss 13 and plunger 15 under such a pressure that it overcomes the tension of the spring 20 thereby enabling the carriage to be moved in the direction B. The carriages 12 makes a further advance until the spring of microswitch 25 is temporarily placed in the position c&#39; (FIG. 3). The supply of the input signal M to the sub-scanning motor 28 is stopped when the contacts a&#39;, b&#39; open, while at the same time, a temporarily high level of input signal G is delivered through closed contacts a&#39;, c&#39; to the S terminal of the flip-flop 35 which then provides a high level output signal I. 
     The logical product of the flip-flop output signal I and a clock pulse H having a pulse repetition rate of 200 ms causes the AND gates 37 to provide a pulsed output signal J of a waveform having the pulse repetition rate of the clock pulse. The transistor 38 responsively operates to supply the solenoid 14 with a pulse current which operated the plunger 15 (FIG. 1). Since the tension of the spring 20 continuously pulls the carriage 12 in the direction A, it is returned in the direction A only during the period while the solenoid 14 is operated and the carriage 12 is released from engagement with the endless belt 19. When the sub-scanning drive motor 28 is in a stop mode, the torque required to turn the rotary shaft of the sub-scanning motor 28 is return far greater than the torque provided by the tension of the spring 20. Therefore, so long as the carriage 12 is coupled with the endless belt 19, it remains stationary in the position where it is engaged with the belt 19. Hence, the carriage 12 moves toward its initial position by repeating an incremental return operation responsive to pulses supplied from the solenoid 14 until it abutts against the microswitch 24. 
     When the carriage 12 stops at the initial position, the input F has a high level and the flip-flop 35 is reset to stop the supply of current to the solenoid and to keep the plunger 15 in its position which holds the endless belt in place. 
     As can be seen from the foregoing description, the arrangement of this invention intermittently supplies the driving current to the solenoid 14, thereby to intermittently engage the carriage 12 with and disengage it from the endless belt 19 to the extent that the inertia force applied to the carriage 12 by the tension of the spring 20 is not great; thus, only a small impact will result when the carriage returns to the initial position. In other words, the solenoid 14 mounted on the carriage 12 functions both to engage the carriage with the belt and to buffer the resulting return impact. This invention has the advantage that it is a simple and practical automatic carriage return device which requires no other special control mechanism. 
     This invention has been described hereinabove with reference to the embodiment of a facsimile receiver apparatus wherein the sub-scanning carriage has a recording stylus. However, it will be apparent to those skilled in the art that the automatic carriage return device of this invention may be applied to a facsimile transmitter including an optical sensing device for sensing the density of an original picture supported around the rotary drum. Or, the invention could also be applied to a facsimile transceiver.