Power switching apparatus having improved power switching timing

Abstract: A power switching apparatus in accordance with present invention includes a sun gear 15 which can be driven to rotate in either direction, an arm 17 which can swing freely relative to the rotating axis of the sun gear, a planetary gear 19 pivotally provided at the arm for engaging with the sun gear, a pair of driven gears 13, 14 disposed a prescribed distance apart from each other in the circumferential direction of the sun gear so that each of said driven gears can engage with the planetary gear independently, and a control device 23 for controlling the position of the planetary gear so as to engage the planetary gear with one of the driven gears before the rotation of the sun gear is initiated.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates generally to a power switching apparatus and, more particularly, to a power switching apparatus for transmitting driving force created by one driving power source to two systems of gear groups by changing the direction of rotation. Description of the Background Art Unlike a facsimile machine of a separate type having separate structures for transmission and reception, a facsimile machine capable of both transmission and reception has advantages that not only the entire apparatus can be made compact and less costly but also operation noises and power consumption can be reduced, and maintenance thereof can be simplified since driving means and structures supporting the driving means can be shared for transmission and reception. Figs. 6A and 6B are views showing a rotating transmission structure which can be incorporated in such a facsimile machine, etc., which is disclosed in Japanese Patent Laying-Open JP-A-61184248. Referring to the figures, the structure and operation thereof will be briefly described. As shown in Fig. 6A, a driving motor 102 normally rotates to cause a worm 103 to rotate in the direction of arrow a, thereby rotating a sun gear 107 in the direction of arrow b. The rotation of the sun gear 107 drives a swinging arm 110 friction-coupled thereto to swing in the direction of arrow c to a first position, thereby engaging a second planetary gear 115 with a first gear 119, so that the gear 119 is rotated in the direction of arrow d. When the driving motor 102 is reversely rotated, as shown in Fig. 6B, the worm 103 is rotated in the direction of arrow e to rotate the sun gear 107 in the direction of arrow f. The rotation of the sun gear 107 then drives the swinging arm 110 friction-coupled thereto to swing in the direction of arrow g from the first position to a second position, thereby engaging a first planetary gear 113 to a second gear 121, so that the gear 121 is rotated in the direction of arrow h. The first and second gears 119 and 121 are coupled to two systems of gear groups, respectively, and, therefore, each being rotated, drive the respective gear groups to rotate. In such a structure, even with one driving power source (the driving motor 102), the transmission system of rotating movement can be changed by shifting the direction of rotation thereof, to adapt to transmission operation or reception operation by a facsimile machine, etc. In other words, a power switching apparatus is implemented by driving a sun gear to rotate by power generated by a motor, providing planetary gears to be engaged to the sun gear pivotally around an arm disposed around the rotating axis of the sun gear which can swing freely and by providing a pair of driven gears at a distance apart from each other in the circumferential direction of the sun gear. The sun gear 107 is driven to rotate in one direction in a time period W1 as shown in Fig. 7, so that one of the driven gears 119 is driven to rotate, thereby feeding an original for transmission, while at the time of reception the sun gear 107 is driven to rotate reversely in a period W2 to carry a sheet of recording paper, thereby driving the other driven gear 121 to rotate. When the sun gear 107 is driven to rotate in one direction, the driven gear 119 is driven to rotate with a time delay of ΔW1, shown in Fig. 6. The time ΔW1 is time required for the planetary gear 115 to be engaged with the driven gear 119. When the sun gear 107 is rotated reversely, the other driven gear 121 is driven to rotate with a time delay of ΔW2. The time delays ΔW1 and ΔW2 vary in accordance with the angular position when an arm 110 stops, which varies due to frictions and so forth. The time ΔW1 and the time ΔW2 fluctuate accordingly. Such fluctuation in time delay gives rise to the following problems in a conventional power switching apparatus. In a facsimile machine capable of both transmission and reception, if, for example, an original is carried after the ΔW1 time elapse when a sun gear is driven to rotate to read the original, variation in this time delay ΔW1 causes a change in the time before the original arrives at a reading head. This causes a corresponding variation of reading initiation time. It is desired to transmit the original image accurately by advancing the reading initiation time at the tip of the original. Such time delays ΔW1 and ΔW2 in the operation of the respective driving gears are desirably constant not only in the facsimile machine both capable of transmission and reception as described above but also in any other apparatuses having such a power switching structure. For reference, CH-A-591 957 describes a device for changing over the transportation direction of a colour ribbon which is wound alternately between two reels driven by a motor, wherein there is fitted onto the shaft of the motor directly, or the shaft of a transmission unit which is driven by the motor, a rocker relative to which the shaft is capable of moving with an adjustable friction. There is also secured on the shaft a pinion which is in continual engagement with a change wheel mounted rotatably on the rocker. By reversing the direction of rotation of the motor, or the transmission unit, the change wheel is adapted to be brought into mesh with the tooth system of one of the colour ribbon reels alternately, as a result of the pivoting movement of the rocker. SUMMARY OF THE INVENTION It would be desirable to achieve power switching in a power switching apparatus at a high accuracy. It would also be desirable to achieve power switching in a power switching apparatus in accurate timings. The present invention is defined in the claims. A power switching apparatus in accordance with a preferred embodiment includes a sun gear which can be driven to rotate in either direction; an arm which can swing freely relative to the rotating axis of the sun gear; a planetary gear rotatably provided at the arm for engaging with the sun gear; a pair of driving gears disposed a prescribed distance apart from each other in the circumferential direction of the sun gear so that each of the driven gears can engage with the sun gear independently; and control means for controlling the position of the planetary gear so that the planetary gear engages with a predetermined one of the driven gears before the initiation of the rotation of the sun gear. The power switching apparatus having such a structure as described above can achieve the power switching in an accurate timing because the planetary gear is engaged with a prescribed driven gear before the rotation of the sun gear. The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing an electrical structure of a facsimile machine in accordance with one embodiment of the present invention; Fig. 2 is a sectional view showing a structure of a power switching apparatus incorporated in the facsimile machine shown in Fig. 1; Fig. 3 is a view showing a part of the structure shown in Fig. 2 by way of simplification; Fig. 4 is a flow chart showing the control of a processing circuit 23 shown in Fig. 1; Fig. 5 is a waveform chart showing the operation of a sun gear and, driven gears A and B for explaining the control operation by the processing circuit shown in Fig. 1; Fig. 6A and 6B are views showing a structure of a conventionalpower switching apparatus; and Fig. 7 is a waveform chart showing the operation of each gears for explaining the operation of the conventional power switching apparatus. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 is a block diagram showing an electrical structure of a facsimile machine in accordance with one embodiment of the present invention. A processing circuit 23 implemented by microcomputer, etc. is connected to a telephone line 24a. A reception detection device 24 detects facsimile reception, and a recording head 10 is operated upon reception. An original is facsimile-transmitted by operating a transmitting button 25, and a reading head 7 is operated upon transmission. Both in transmission and reception, a pulse motor 30 is driven. Fig. 2 is a sectional view showing a structure of a power switching apparatus incorporated in the facsimile machine capable of both transmission and reception shown in Fig. 1. In Fig. 2, upon transmission, an original 1 is fed interposed between a pair of rollers 3 and 4 through a guide member 2, to be fed in the direction of arrow 6 through a guide member 5. The contents of the original are read by the reading head 7, e.g. a line image sensor. The data on the original image read by the reading head 7 is transmitted through the telephone line 24a, etc. shown in Fig. 1. Upon reception, a received image received through the telephone line 24a is recorded by the recording head 10 intermittently pressure-contacted to a platen roller 9 into a sheet of heat sensitive recording paper which is stored in a rolled manner and taken out sequentially. Thus recorded paper is discharged through a guide member 11 as shown by arrow 12. To the roller 3 and the platen roller 9 fixed are driven gears 13 and 14. The sun gear 15 is fixed to a rotating axis 16, and is driven to rotate by the pulse motor 30 capable of rotating normally and reversely. The rotating axis 16 is inserted through the sleeve 18 of the arm 17, and, therefore, the arm 17 can swing around the rotating axis 16 of the sun gear 15. The planetary gear 19 to be engaged with the sun gear 15 is pivotally provided at the tip of the arm 17. The driven gears 13 and 14 are disposed a prescribed distance apart from each other in the circumferential direction of the sun gear 15 so that the planetary gear 19 can engage with the driven gear 13 and 14 selectively depending upon its position. Fig. 3 is a view showing the sun gear 15, the arm 17, the planetary gear 19, and the driven gears 13 and 14 shown in Fig. 2 by way of simplification. The sun gear 15 rotates clockwise to cause the line along the axis of the arm 17 to move to a position represented by reference numeral 21, and the planetary gear 19 engages with the driven gear A 13, thereby performing reading operation. On the other hand, the sun gear 15 rotates anti-clockwise to cause the axis line of the arm 17 to move to a position represented by reference numeral 22, so that the planetary gear 19 engages with the driven gear B 14, thereby performing recording operation. Fig. 4 is a flow chart showing the operation of the processing circuit 23 shown in Fig. 1, and Fig. 5 is a waveform chart of the sun gear, the driven gears A and B for clarifying the operation of the processing circuit 23. In step S1, the switch for power supply is turned on to start the process flow. In step S2, initialization is executed. In other words, the sun gear 15 is rotated clockwise as shown by reference numeral 27 in Fig. 2 in a time period from t1 to t3 in Fig. 5, thereby executing initialisation. The planetary gear 19 thus moves to the direction of the driven gear A 13 to engage therewith, and the driven gear A 13 rotates slightly in a time period from t2 to t3 as shown in Fig. 5. In step S3, the engagement state is maintained as in a stand-by state. In step S4, it is determined whether a transmission button 25 is pressed or not. If the transmission button 25 is pressed, the flow proceeds to step S5 for transmission operation, and the sun gear 15 is driven to rotate in the direction of arrow 27 by a pulse motor 30 in time t4. Power from the sun gear 15 immediately drives the roller 3 through the planetary gear 19 and the driven gear A 13 in a time period t4 - t5, because the planetary gear 19 is already engaged with the driven gear A 13. Also, the rotation of the roller 3 drives the roller 4 in contact with the roller 3 so that the original 1 interposed between these rollers is fed in the direction of arrow 6. The fed original image is read by the reading head 7 to perform the facsimile transmission. In step S6, the initialization state, i.e. the state in which planetary gear 19 is engaged with the driven gear 13 is maintained by the rotation of the sun gear 15 in the direction of arrow 27 as described above. In step S4, it is determined that the apparatus is not in transmission operation, in other words a facsimile reception state is detected by the reception detection device 24, the pulse motor 30 drives the sun gear 15 to rotate reversely to the direction of arrow 27. The planetary gear 19 therefore moves in accordance with the anticlockwise rotation of the sun gear from the axis line position 21 (see Fig. 3) to the axis line position 22, so that planetary gear 19 engages with the driven gear B 14 in time t7. The driven gear 14 is thus driven to rotate by the sun gear 15 during a time period from t7 to t8, the sheet of recording paper 8 on which the received data is recorded by the recording head 10 is discharged in the direction of arrow 12. The reception operation being completed, the pulse motor 30 drives the sun gear 15 to rotate in the direction of arrow 27 in a time period t9 - t11 in initialization operation. The planetary gear 19 therefore moves to the axis line position 21 from the axis line position 22, to engage with the driven gears A 13. The driven gear A 13 rotates slightly in a time period from t10 - t11 as shown in Fig. 5. In this embodiment, when the sun gear 15 is not driven, the planetary gear 19 and the arm 17 spontaneously return to the position 21 by their own weights so that the initialization operation is achieved in a stable manner. In this embodiment, the planetary gear 19 returns to the side of the driven gear by its own weight, but springs, etc. may be used to constantly energize the planetary gear to the side of one of the driven gears. Thus, upon the transmission, the power of sun gear 15 is immediately transmitted to the driven gear 13 through the planetary gear 19 by the pulse motor 30 in time t4. In other words, the driving force of the pulse motor 30 is immediately transmitted to the rollers 3 and 4. Also, upon the reception, when the sun gear 15 is rotated at a constant rotating speed by the pulse motor 30, the planetary gear 19 engages with the driven gear B 14 after a constant time W0 from t6 to t7. Thus, both in the transmission operation and the reception operation, the original 1 and the sheet of recording paper 8 can be fed in accurate timing. Although in the above described embodiment, the planetary gear 19 is positioned on the side of the driven gear A as in a stand-by state, it goes without saying that similar effect can be obtained if the planetary gear 19 is positioned on the side of the driven gear B in the stand-by state. In an alternative embodiment, an electromagnetic solenoid may be provided to shift the arm 17 angularly in the clockwise direction shown in Fig. 2 to initialize the position of the planetary gear 19 always in a constant position. Although in the above described embodiment, the present invention is applied to a facsimile machine, the present invention can be applied similarly to power switching apparatuses in other fields having similar structures. Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being defined by the appended claims.

Claims: Apparatus for selectively driving one of a pair of rotatable elements (3,9), said apparatus comprising a rotary drive means (15) arranged to be selectively driven in opposite rotational directions, a pair of rotary driven means (13,14) coupled to respective ones of said rotatable elements (3,9) and disposed in spaced apart positions about the rotational axis of said drive means, and rotary intermediate engagement means (19) for engaging the drive means and being movable between first and second positions which are circumferentially spaced about the axis of the drive means and in which the intermediate engagement means couples the drive means to respective ones of said pair of driven means, characterised by means (23,30;17,18) for setting the intermediate engagement means (19) at a predetermined circumferential position in advance of the drive means being operated for driving a selected element. Apparatus according to claim 1, wherein said means for setting the position of said intermediate engagement means comprises means for setting the intermediate engagement means in engagement with a predetermined one of said pair of driven means (13,14). Apparatus according to claim 2 wherein said means for setting the position of the intermediate engagement means (19) comprises means for rotating said drive means (15) in a prescribed direction for a prescribed time period. Apparatus according to claim 3, wherein said means for rotating said drive means rotates said drive means (15) for said prescribed time period when the driving of the drive means (15) is completed. Apparatus according to claim 1, 2, 3 or 4, wherein said drive means (15) comprises a sun gear, and said intermediate engagement means (19) comprises a planet gear. Apparatus according to claim 5, wherein said planet gear (19) is mounted pivotally on an arm (17) capable of swinging relative to the rotational axis of said sun gear (15). Apparatus according to claim 6, wherein one end of said arm (17) is rotatably attached to the axis of said sun gear (15) to be freely rotatable relative thereto, and said planetary gear (19) is attached to the other end of said arm. Apparatus according to any preceding claim, wherein said means for setting the position of the intermediate engagement means comprises the arrangement of the intermediate engagement means (19), said intermediate engagement means (19) being moveable under its own weight to said predetermined circumferential position when said drive means (15) is not driven to rotate. Apparatus according to any preceding claim, further comprising a pulse motor (30) operable in a forward direction and in a reverse direction for driving said drive means (15). A facsimile machine incorporating apparatus as defined in any of claims 1 to 9. A facsimile machine according to claim 10, wherein one of said driven means (13) is driven during a transmission operation, and the other of said drive means (14) is driven during a reception operation. A facsimile machine according to claim 11, further comprising determining means (23) for determining whether the machine is in a transmission state or a reception state, wherein a pulse motor is operated to rotate the drive means (15) in a prescribed direction in response to the output of said determining means. A facsimile machine according to claim 11 or 12, wherein said driven means (13) driven during a transmission operation drives a feed roller means (3) for feeding an original (1) during transmission, and said driven means (14) driven during a reception operation drives a platen roller (9) for supporting a recording sheet material during reception.

Inventors: KIDA SHIGERU, SAKAI KATSUYUKI, KIDA, SHIGERU, SAKAI, KATSUYUKI
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1991
Main classification: H04N1
IPC codes: H04N1, F16H1, F16H3, F16H37