US3711741A

US3711741A - Electronic flash device

Info

Publication number: US3711741A
Application number: US00122576A
Authority: US
Inventors: H Akiyama; S Ando
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 1971-03-01
Filing date: 1971-03-01
Publication date: 1973-01-16
Anticipated expiration: 1990-01-16

Abstract

A completely water- and airtight electronic flash device is provided. The device is provided with casing molded of plastic, a rechargeable secondary battery having a voltage not higher than 30 volts, a diode in a charging circuit of the battery preventing the discharge of the battery when the charging circuit is shortcircuited by water or the like, and a trigger actuable by a signal generated by an electromagnetic trigger inductor for operating the flash device.

Description

United States Patent Akiyama et al.

ELECTRONIC FLASH DEVICE Inventors: l-lideakl Aklyama; Sadanao Ando,

both of Tokyo, Japan Kabushiki Kaisha Ricoh, Tokyo, Japan Filed: March 1, 1971 Appl. No.: 122,576

[73] Assignee:

US. Cl ..31S/241 P, 315/241 R, 315/362 Int. Cl. ..l-l05b 31/04, H05b 37/00 Field of Search....3l5/241 P, 151, 219; 240/2 C, 240/6.4 R, 10.6 R, 10.6 CH, 11.4 R, 1.3;

[56] References Cited UNlTED STATES PATENTS Nessel ..3l5/241 P Carter.... .....3l5/241 P Murata ..315/151 Edgerton ..315/157 Jan. 16, 1973 OTHER PU BLlCATlONS Cross-Underwater Photography and Television" Exposition Press New York 1954 TR800 C7; Title Page & pp. 48-53.

Primary Examiner-Herman Karl Saalbach Assistant ExaminerMarvin Nussbaum Attorney-Burgess, Ryan and Wayne [57] ABSTRACT 9 Claims, 5 Drawing Figures PATENTEU JAN 16 I975 FIG.1

FIG.3

ELECTRONIC FLASH DEVICE BACKGROUND OF THE INVENTION The present invention relates to an electronic flash device which may be used safely in underwater photography and in an extremely inflammable environment.

In general, an electronic flash device is flashed by first applying a voltage of from 200 to 500 volts across an xenon gas-filled lamp and then applying a trigger voltage of l 1.8 K volts. When the electronic flash device of the type described is used in underwater photography, the high voltage frequently leaks outside the casing, thus causing injuries to an operator. A spark tends to be produced in the high voltage circuit of the electronic flash device so that the device cannot safely be used in an extremely inflammable environment.

SUMMARY OF THE INVENTION According to the present invention, a completely waterand airtight electronic flash device is provided, which uses as a power source a rechargeable secondary battery having a voltage not higher than 30 volts. When water is between the terminals of the power source, a drain on the battery may be prevented by a diode circuit and the lack of a triggering. For a fire-proofed electronic flash device, in accordance with the present invention, a reed relay is used which is housed within the airtight casing and a power source switch is utilized which is actuated by displacement by a magnet. Therefore, no spark is produced which can leak to the atmosphere, and the electronic flash device of the present invention may be used safely in dangerous environmental conditions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of an electronic flash device for underwater photography in accordance with the present invention;

FIG. 2 is a perspective view of a casing used therewith;

FIG. 3 is a schematic diagram of an alternative embodiment of a power source switch thereof in accordance with the present invention;

FIG. 4 is a perspective fragmentary view of a casing when the switch shown in FIG. 3 is used; and

FIG. 5 is. a schematic diagram of an alternative embodiment of a trigger of an electronic flash device in accordance with the present invention.

DESCRIPTIONOF THE PREFERRED EMBODIMENT Referring to FIG. 1 illustrating a schematic diagram of an exemplanary embodiment of the present invention, there is shown a pair of terminals 1 connected across a secondary rechargeable battery 6 through a diode 3. In particular, one of the electrodes of the battery is connected to the anode of diode 3 while the cathode thereof is connected to the positive side of battery 6. The negative electrode or side of battery 6 is directly connected to the other of two terminals 1. As can be clearly seen, when water is between the two terminals 1, as would be the case underwater, the diode 3 is back-biased while the terminals are :short-circuited. In this manner, the battery 6 can not discharge and is preserved for use with the flashing unit.

A switch 2 is provided for connecting the battery 6 to the remainder of the flashing unit circuitry. The switch 2 is closed when the flashing unit is to be actuated. One side of switch 2 serves as a common bus line while the other is directly connected to the positive side of battery 6. The negative side of battery 6 is connected through a resistor 30 and through a capacitor 7 to the bus side of switch 2 and to the emitter of a transistor 16. The negative side of battery 6 is also connected through one primary winding 31 of a step-up transformer 11 to the collector of transistor 10. In addition, the negative side of battery 6 is connected through resistor 30 and through a second primary winding 32 of transformer 11 to the base of transistor 10 and to one side end of the secondary winding 33 of step-up transformer 11 while the other end of winding 33 is connected to the negative side of battery 6 and through one or a plurality of series diodes 4 to one side of a capacitor 8 and a resistor 34. The other side of capacitor 8 is connected to the bus bar side of switch 2 while the other side of resistor 34 is connected through a resistor 35 to the negative bus bar and through a device 36 to the negative bus bar.

The actuating or energizing circuit for the flashing element 14, such as a discharge tube is described hereinafter. The body of the camera is indicated by numeral 37 and includes a second battery 18, the positive side of which is connected through a resistor 19 and a manually operated switch 16, held in the normally open position to one side of an inductor 15. The negative side of battery 18 is connected through a capacitor 17 to the connection between resistor 19 and switch 16 and is directly connected to the other side of inductor 15. When switch 16 is closed, a trigger pulse appears across inductor 15.

An electromagnetic trigger inductor 13 is magnetically coupled to inductor 15 and has one end thereof connected to a trigger electrode of a silicon controlled rectifier (SCR) 5. The cathode of SCR 5 is connected to the common bus line while the anode thereof is connected through one end of a primary winding 38 of a step-up transformer 12 and through resistor 39 to one side of tube 14. A capacitor 9 is connected between the cathode of SCR 5 and the other side of winding 38. The secondary winding 40 of step up transformer 12 is directly coupled to the flash tube 14 enabling it to be actuated. The working voltage of the capacitor 9 is 400 volts and its capacitance 0.02 LP. The electromagnetic trigger inductor 13 consists of a U-shaped core which, for instance, consists of three laminations of pure iron having a thickness of 0.8 mm and carries a coil of 500 turns of wire having a diameter of 0.15 mm.

The inductor 15 consists of a U-shaped core similar to that of the inductor 13 and, for instance, a coil of 300 turns of wire having a diameter of 0.2 mm. The spacing between the cores of the

inductor

13 and 15 is,

' preferably, 2 mm when a flash lamp attachment is mounted upon the camera. The capacitor 17 has a capacitance of 30 uF; the battery 18 is 3 volts; and the resistance of the resistor 19 is 200 ohms.

Next referring to FIG. 2, the terminals 1 and the electrical conducting members of switch 2 are extended from a casing 20 which may be made of plastic as by molding or any other suitable method. The diode 3 is connected to one of the pair of terminals 1 so that the current for recharging the battery 6 may flow through the diode 3 when forward biased but the discharge current is blocked when water enters between the terminals 1 so that no electric power is dissipated into the water. Since the electronic flash device operates on less than 30 volts, the switch 2 may safely be closed by directly shortcircuiting the contacts or terminals 2 by means of a contact element 21 without fear of a significant spark.

FIG. 3 illustrates an electric circuit for another embodiment of a power switch in accordance with the present invention. A reed relay 22 is placed in the circuit to replace switch 2 in such a way that the relay 22 together with iron elements 23 thereof are embedded in the casing 20 close to the surface as shown in FIG. 4 and that the reed switch 22 is closed by use of a suitable magnet. One side of the relay 22 is connected to the positive side of battery 6, while the other side is connected to the negative bus bar. This arrangement is particularly adapted to permit the use of the electronic flash device in an extremely inflammable atmosphere thus completely preventing a spark.

Another embodiment of the trigger or actuating circuit is shown in FIG. 5. In this circuit, instead of the SCR 5, a reed relay 24 is used, which consists of a miniature reed carrying a coil of, for instance, 300 turns of enameled wire having a diameter of 0.15 mm. When a pulse of 30 mA is applied to the relay 24, along line X, a time delay of about 0.1 microsecond will result which will not prevent the relay 24 from being satisfactorily used for triggering.

As described hereinabove, the casing of the flash device is airtightly and watertightly made of a plastics as by molding and the discharge of current is prevented by the charging diode when water enters between the terminals. The power source having a voltage not higher than 30 volts is used so that, in case of the underwater photography, the power source switch may be closed by shortcircuiting the terminals. This makes it possible to provide an electronic flash device simple in construction.

For using the electronic flash device andpreventing fire or explosion, the airtight reed relay 22 may be actuated by a magnet to connect the battery 6 to the remainder of the flashing unit. The trigger signal is not directly applied to the device because an induced signal is used as the trigger, so that the electronic flash device can be made completely safe.

What is claimed is:

1. An electronic flash device comprising a plastic casing, a rechargeable battery having a pair of electrodes, a pair of terminals, one of said pair of terminals connected to one of said electrodes, a diode connected between said other. of said pair of terminals and the other of said electrodes, said diode permitting current to pass to recharge said battery and blocking current from flowing through said battery when said terminals are shortcircuited, said flash device supplied by said battery, and a trigger means coupled to said flash device for operating said electronic flash device, said diode, said battery and said trigger means being housed within said casing.

2. An electronic flash device according to claim 1, further comprising a switch means connected between said batter and said electronic flash device.

3. An e ectronrc flash device according to claim 2,

wherein said switch means comprises a pair of electrically conducting members projecting from said casing, one of said conducting members being connected to said battery and the other of said conducting members being connected to said flash device.

4. An electronic flash device according to claim 2, wherein said switch means comprises a magnetically actuated reed relay.

5. An electronic flash device according to claim 4, wherein said reed relay comprises elements capable of being electrically coupled together, said elements being embedded within said casing.

6. An electronic flash device according to claim 1, wherein said trigger means comprises electromagnetic trigger inductor means and a silicon controlled rectifier, said inductor means triggering said silicon controlled rectifier operating said flash unit.

7. An electronic flash device according to claim 1, wherein said trigger means comprises a reed relay and an actuating signal for closing said reed relay.

8. An electronic flash device according to claim 1, wherein the voltage of said battery is no greater than 30 volts.

9. An electronic flash device according to claim 1, wherein said casing is formed by molding'said plastic.

Claims

1. An electronic flash device comprising a plastic casing, a rechargeable battery having a pair of electrodes, a pair of terminals, one of said pair of terminals connected to one of said electrodes, a diode connected between said other of said pair of terminals and the other of said electrodes, said diode permitting current to pass to recharge said battery and blocking current from flowing through said battery when said terminals are shortcircuited, said flash device supplied by said battery, and a trigger means coupled to said flash device for operating said electronic flash device, said diode, said battery and said trigger means being housed within said casing.

2. An electronic flash device according to claim 1, further comprising a switch means connected between said battery and said electronic flash device.

3. An electronic flash device according to claim 2, wherein said switch means comprises a pair of electrically conducting members projecting from said casing, one of said conducting members being connected to said battery and the other of said conducting members being connected to said flash device.

9. An electronic flash device according to claim 1, wherein said casing is formed by molding said plastic.