Patent Publication Number: US-3881144-A

Title: Device for intermittently driving an electromagnetic device

Description:
United States Patent [1 1 Kikuchi 1 Apr. 29, 1975 1 DEVICE FOR INTERMITTENTLY DRIVING AN ELECTROMAGNETIC DEVICE [75] Inventor: Tomio Kikuchi, Tokorozawa. Japan [73] Assignee: Kabushikikaisha Copal, Tokyo,  
 Japan 22 Filed: Sept. 4. 1973 211 Appl. No.: 394.261  
 [30] Foreign Application Priority Data Sept. 8. 1973 Japan 48-10479) Sept. 8. 1973 Japan 48-104800 [52] US. Cl 318/466; 318/467 [51] Int. Cl. H02p 3/00 [58] Field of Search 318/466. 467  
 [56] References Cited UNITED STATES PATENTS 3.520.391 7/1970 Graham et al 318/470 X 3.668.496 6/1972 Markowitz et al 318/466 -l[]l--F-F FF ----1 PF Prinmry Examiner-T. E. Lynch [57] ABSTRACT A control system is disclosed for intermittentlydriving an electromagnetic device by controlling a switching circuit actuated by periodically generated pulses applied thereto. The system has a member coupled with the electromagnetic device so as to be moved thereby and a normally opened switch connected between the electromagnetic device and an electric power source. The member is operably coupled with the switch such that, when the electromagnetic device is driven by the actuation of the switching circuit the switch is closed by the member to directly connect the electromagnetic device to the electric power source through the switch for the time period determined by the actuation of the member which is related to the electromagnetic device for the determined amount of the actuation thereof 2 Claims, 2 Drawing Figures PATENTEUAPR29i97s lm t B Ii! 1 I DEVICE FOR INTERMITTENTLY DRIVING AN ELECTROMAGNETIC DEVICE BACKGROUND OF THE INVENTION The present invention relates to a system for intermittently driving an electromagnetic device, and, more particularly, to such a system by controlling a switching circuit connected to the electromagnetic device by means of periodically generated pulses.  
  An example of the electromagnetic device is an electric motor which is utilized in a digital clock in which indicating symbol bearing members are intermittently actuated by the motor periodically actuated at the time intervals of one minute. The periodically generated pulses for actuating the motor are generated by a quartz oscillator, for example, having the frequency of 279,609 KHz as the reference frequency which frequency is reduced by /2 by 24 flip-flop circuits connected in series to provide a frequency of 1/60 Hz, i.e., one per 1 minute. The time period in which the motor is energized is determined by the width of the pulse.  
  Determination of the time period for energizing the motor by the width of the pulse is disadvantageous in that the control of the load of the motor can not be properly effected because the amount of rotation or work done by the motor varies depending upon the fluctuation of the voltage of the motor driving circuit and/or the load given to the motor.  
  The present invention aims at avoiding the above described disadvantages.  
 SUMMARY OF THE INVENTION The object of the present invention is to provide a novel and useful system for intermittently driving an electromagnetic device which avoids the above described disadvantages.  
  The above object is achieved in accordance with the present invention by providing a system for intermittently driving an electromagnetic device energized by an electric power source by controlling a switching circuit connected thereto by means of pulses applied thereto which are periodically generated by a pulse generating circuit, which system is characterized by a member coupled with the electromagnetic device and a normally opened switch connected between the electric power source and the electromagnetic device, the member being so constructed and arranged in relation to the switch that the latter is closed by the member after the electromagnetic device is energized by the actuation of the switching circuit thereby permitting the electromagnetic device to be directly connected to the electric power source through the switch and, upon completion of the actuation of the electromagnetic device, the switch is opened by the member so as to deenergize the electromagnetic device.  
  By the above described arrangement of the system of the present invention, since the electromagnetic device is energized directly through the switch by the electric power source and not through the switching circuit for the determined period of time for the actuation of the electromagnetic device, influence of voltage fluctuation and/or load fluctuation given to the electromagnetic device are reduced to the minimum thereby insuring accurate and stable operation of the device.  
  In accordance with another feature of the present invention, the system is provided with a resettable flipflop circuit in the pulse generating circuit as the final stage thereof and a reset signal generating circuit incorporated in the switch and connected to the resettable flip-flop circuit, the reset signal generating circuit being actuated by the member coupled with the electromagnetic device at the end of the actuation thereof so as to generate the reset switch thereby deenergizing the resettable flip-flop circuit.  
  By this arrangement, the width of the pulse for actuating the device can be enlarged to the half of the period ofthe pulses, for example, to insure positive operation of the electromagnetic device. while the actuation of the electromagnetic device is positively stopped within the period of the cycle of operation to insure stable and accurate operation of the system.  
 BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic diagram showing the electric circuit of an embodiment of the system of the present invention; and  
  FIG. 2 is a schematic diagram showing the electric circuit of another embodiment of the system of the present invention.  
 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. I, a crystal oscillator 0 having the reference frequency of 279,609 KHz is connected to a series of flip-flop circuits F.F comprising 24 flipflop circuits so as to reduce the frequency by /1 to provide pulses P occurring each seconds. The output of the flip-flop circuit is connected to the base of a transistor T constituting a switching circuit.  
  The collector of the transistor T is connected to one terminal of an electric motor M. The other terminal of the motor M is connected to the plus terminal of an electric power source while the emitter of the transistor T is connected to the minus terminal of the electric power source.  
  Thus, each time the pulse P is applied to the base of the transistor T, the same is rendered conductive so that the motor M is energized by the electric power source to drive the load.  
  The motor M is coupled with a load L for actuating the same for the purpose intended for the operation of the device.  
  In accordance with the present invention, a normally opened switch S is provided, the movable contact of which is connected to the junction of the collector of the transistor T and the one terminal of the motor M, while the other contact is connected to the minus terminal of the electric power source. A cam C having a recessed portion of predetermined circumferential length is operatively coupled with the motor M directly or through reduction gearing (not shown). The cam C is so located in relation to the movable contact of the switch S that the movable contact is urged to contact with the circumference of the cam C so that, when the movable contact moves out of the recessed portion of the cam C as the same is rotated, the switch is closed so as to directly connect the motor M to the electric power source through the switch S for the time period defined by the speed of rotation of the cam C and the circumferential length of the land or raised portion of the cam C. The rotational speed of the cam C and the configuration of the cam C are selected so as to close the switch S for the time required for the actuation of the load L by the motor M. The relative position between the recessed portion of the cam C and the movable contact of the switch S is so set that the switch S is closed after the motor M is energized through the transistor T but before the pulse P becomes null. In other words, the width Pw of the pulse P is so selected that the switch S is closed to positively drive the motor M therethrough before the pulse P vanishes.  
  It is apparent that the transistor T may be replaced by a SC R.  
  The operation of the device as described above is as follows.  
  When a plus pulse P is applied to the base of the transistor T by the oscillator through the flip-flop circuits F.F, the transistor T is rendered to be conductive so that the motor M is energized. The cam C is also rotated by the motor M so that the movable contact of the switch S comes out of the recessed portion of the cam C thereby closing the switch S. Thus, the motor M is directly connected to the electric power source thereby permitting the motor M to be driven for the time period determined by the cam C even after the pulse P vanishes. The motor M is deenergized when the cam C has been rotated by the determined amount for the cycle.  
  The cam C is shown as having a single recessed portion, however, it is apparent that a plurality of recessed portions may be provided at determined intervals to effect the same operation.  
  As described above, since the rotation of the motor M is controlled solely by the rotation of the cam C with respect to the switch S, the motor M is not influenced by the voltage variation and/or load variation so that positive and accurate] operation of the device is insured.  
  Further, since the motor M is energized directly through the switch S and not through the switching circuit, the voltage drop caused by the switching circuit is avoided so that the source voltage is effectively applied to the motor M.  
  FIG. 2 shows a second embodiment of the device of the present invention. The device shown in FIG. 2 is substantially similar to that shown in FIG. 1, except that a resettableflip-flop circuit R.S.F.F. is replaced by the flip-flop F.F at the final stage of series of flip-flop circuits F.F. shown in FIG. 1, and a switch S is used in place of the switch S of FIG. I. The switch S includes a movable contact cooperating with the cam C and connected to the minus terminal of the electric power source and two contacts 8,, S the contact S being connected to the junction of the motor M and the collector of the transistor T and normally kept opened from the movable contact thereby serving as the switch S of FIG. 1, while the contact 8, is connected to the plus terminal of the electric power source through a resistor r as well as to the reset terminal R of the resettable flip-flop circuit R.S.F.F. through a terminal X and is normally kept closed to the movable contact to apply minus voltage to the reset terminal R of the resettable flip-flop circuit R.S.F.F.  
  Thus, when pulse P is applied to the transistor T and the motor M is energized through the switching circuit constituted by the transistor T, the contact S contacts with the movable contact so as to directly connect the motor M to the electric power source and the contact S is opened fromthemovable contact so as to apply plus voltage to the reset terminal R of the resettable flip-flop circuit R.S.F.F. by the action of the cam C rotated by the motor M.  
  When the cam C has been rotated by the determined amount for the cycle, i.e., when the movable contact falls in the recessed portion of the cam C, the contact S &#39;is again opened to deenergize the motor M and the contact S is closed to apply minus voltage to the reset terminal R through the terminal X thereby resetting the resettable flip-flop circuit R.S.F.F. to nullify the pulse P so that the switching circuit is positively made inoperative.  
  Since the switching circuit is positively made inoperative at the end of the cycle of operation by the reset signal supplied to the resettable flip-flop circuit R.S.F.F. from the switch S, the duration or width of the pulse P can be prolonged to the half of the period of the pulses P thereby permitting the motor M to be positively rotated until the cam C closes the contact S to the movable contact of the switch S regardless of the voltage drop and/or overload of the motor M. Therefore, positive and accurate operation of the device is insured.  
  In the above embodiment, the motor M is shown as the electromagnetic devices. Other device such as an electromagnetically operable plunger or reciprocally actuated electromagnetic device may be applicable.  
  In case a plunger is used, a circuit for directly connecting the electromagnetic device to the electric power source, i.e., the contact S of the switch 8&#39; is dispensed with, and only the reset signal generating circuit, i.e., the contact 8, and the movable contact of the switch S are required. In this case, the switch is opened when the plunger is under the inoperable condition, and it is closed at the end of the operation of the plunger so as to reset the resettable flip-flop circuit R.S.F.F.  
 I claim:  
  1. A control system for intermittently driving an electric motor energized by an electric power source by controlling a switching circuit connected thereto by means of pulses applied thereto which are periodically generated by a pulse generating circuit having a reference frequency generating element and a multi-stage flip-flop circuit connected as a counting circuit for reducing the frequency generated by said reference frequency generating element, wherein the improvement comprises a resettable flip-flop circuit incorporated in said multi-stage flip-flop circuit at the final stage thereof, a reset signal generating circuit connected to said resettable flip-flop circuit and having a mechanical switch for actuating said reset signal generating circuit so as to generate a reset signal upon actuation thereof, and a cam member coupled with said electric motor so as to be actuated at the end of the actuation thereof, said cam member being so coupled with said mechanical switch that the latter is actuated to thereby reset said resettable flip-flop circuit by the reset signal applied thereto from said reset signal generating circuit.  
  2. A control system in which an oscillator provides timing pulses for application to a semiconductor switch connected to complete a series circuit with an electric motor as the switch is gated on to intermittently drive a load coupled to the motor, which series circuit is completed between a pair of conductors to which an energizing potential difference is applied, comprising:  
 a plurality of flip-flop circuits connected in a counting chain and &#34;coupled to the oscillator, to provide gating pulses at a frequency different than the oscillator frequency;  
 a resettable flip-flop circuit having a set input connection coupled to the last flip-flop circuit in the counting chain, a reset input connection, and an output connection coupled to the semiconductor switch to gate the switch on when the resettable flip-flop provides a turn-on pulse in response to receipt of a set signal from the counting chain;  
 an electric switch having a movable contact normally a cam positioned to operate the electric switch,  
 which cam is mechanically coupled to said motor and has a recessed portion in which said movable contact is normally received to allow said movable contact to engage the first fixed contact and apply the potential received from the other of said conductors to the reset connection of the resettable flip-flop, and which cam has a raised portion to displace said movable contact to engage the second fixed contact and complete a circuit which shunts said semiconductor switch to provide an energizing circuit for the motor after the initial energization of the motor through the circuit including the semiconductor switch, such that the motor drives its load until the cam rotates so that the movable contact again rests in the recessed portion to interrupt the shunt energizing circuit for the motor and reset the resettable flip-flop.