US3895257A - Photographic enlarger with electronic light control - Google Patents

Photographic enlarger with electronic light control Download PDF

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Publication number
US3895257A
US3895257A US44148474A US3895257A US 3895257 A US3895257 A US 3895257A US 44148474 A US44148474 A US 44148474A US 3895257 A US3895257 A US 3895257A
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US
United States
Prior art keywords
switch
lamp
thyristor
current
circuit
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Expired - Lifetime
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English (en)
Inventor
Armin Stiller
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rollei Werke Franke und Heidecke GmbH and Co KG
Original Assignee
Rollei Werke Franke und Heidecke GmbH and Co KG
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B27/00—Photographic printing apparatus
    • G03B27/72—Controlling or varying light intensity, spectral composition, or exposure time in photographic printing apparatus

Definitions

  • control switches which may be at a control 317/135 A, 141 S, 148.5 B; 355/69 desk or console, are in electronic circuits which may I operate at a lower voltage than the main enlarger [56] References Cit d lamp, so that these control switches and the conduc- UNITED STATES PATENTS tors leading to them do not have to withstand the 3,555,390 1/1971 Peffer et al 317/1485 B x "wage of the enlarger lamp' 3,571,612 3/1971 Ukai et a1.
  • Another object is the provision of an arrangement whereby the control switches, placed at a desk or console, are in circuits operating at lower voltage than the main line voltage of the illumination lamp, so that the switches themselves and the wiring circuits relating thereto do not have to withstand the full voltage of the lamp and therefore can be made of lower quality and less expensive materials.
  • the illumination lamp of a photographic enlarger is in the lamp head at the top of the enlarger, which is at some distance, at least a few feet, from the operating desk or console where the control switches are conveniently grouped. It is another object of the invention to provide control circuits so designed and arranged that only conductors carrying lower voltages need to run from the operating desk or console to the enlarger head containing the lamp, thus enabling the control to be accomplished in a very simple and inexpensive way, without the necessity of running special cables or leads from the console to the enlarger head, of sufficiently heavy capacity to carry the mains or line voltage at which the illumination lamp operates.
  • a relay switch which controls the supply of current to the illumination lamp, and a thyristor in the circuit of the relay.
  • a control switch by the closing of which it is possible to apply to the ignition section or control gate of the thyristor, for a short time, a voltage which causes the thyristor to be driven hard.
  • this switch is connected to the cathode of the thyristor bridged with a resistor, while a series circuit consisting of a resistor and a capacitor is arranged in parallel with the switch, and the resistor of the ignition section or control gate of the thyristor is connected in parallel.
  • the thyristor can not immediately ignite as soon as it receives a control impulse from the timing circuit, and that it will only ignite after the switch situated in its current circuit has been closed.
  • This enables the exposure lamp to be kept on as long as desired, to enable as much preparatory or preliminary work as desired to be accomplished, without having the lamp prematurely turned off.
  • the switch in the current circuit of the thyristor is closed, so that the latter cuts through and the illumination lamp is extinguished. Then the exposure process can take place in the conventional manner, with the aid of a timing switch.
  • the terminals 1 and 2 of the switching arrangement or control arrangement of the present invention are connected to any suitable source of direct current, schematically indicated at 30, which may be a conventional converter having an output of direct current, from an input of alternating current received from the conventional supply line or mains 4.
  • the enlarger exposure lamp 3 also receives its current from the mains 4.
  • a main on-andoff switch 4a is provided, which turns off both the lamp 3 and the converter 30 when this switch is open.
  • the lamp 3 is situated, as usual, in the head of the enlarger, and the current to the lamp is controlled by a relay switching contact 5 which is opened when the relay coil or winding 6 is energized, and is normally closed when no current flows through the relay 6.
  • This relay 6 is part of the electronic control circuit which will now be described.
  • a series connection including the exciter winding or coil of the relay 6, a thyristor 7, and a single pole switch 8.
  • the thyristor is bridged by a resistor 9 in parallel with the thyristor as shown.
  • a series circuit having a resistor 10 and capacitor 11 is in parallel with the switch 8.
  • This resistor 10 is also connected in parallel with a compensating resistor 28 in the ignition section or gate circuit of the thyristor.
  • a series connection of a further resistor 12 and a time switch 13 extends from the terminal 1 to the terminal 2, that is, in parallel with the above described circuit having the elements 6, 7, and 8.
  • a quenching capacitor 14 is connected as illustrated, from a point between the resistor 12 and the switch 13, to the anode of the thyristor 7.
  • a Zener diode 15 is connected in the manner illustrated in the wiring diagram. With the thyristor 7 blocked and the switch 8 closed, the timing circuit is subjected, by means of this Zener diode 15, to a constant direct voltage, inasmuch as the Zener diode is parallel to the series circuit comprising the thyristor 7 and the switch 8, or the resistor 9 and the switch 8.
  • the timing circuit comprises, in known manner, a a programmable unijunction transistor 16, the timing elements 17, 18, 19, 20, 21, 22, and 23, and a voltage divider circuit having resistors 24 and 25, this voltage divider circuit being connected with the terminals 1 and 2 in the manner illustrated.
  • the central tap of the voltage divider circuit is connected to the control grid or gate of the programmable unijunction transistor or PUT 16.
  • the timing circuit further comprises a resistor 26 which is connected with the cathode of the PUT and in parallel with the.QQUlrQl-se EiQmQf the thyristor 7,
  • control 's'ect'ion is provided for this-purpose, withlij a series resistor 29.
  • the voltage divider circuit 24, 25 is subjected. by means of another Zener diode 27, to a constant voltage.
  • the circuit operates as follows:
  • the switches 8 and 13 are open, and the switch is closed. this being the normal position of the switch 5 when no current is flowing through the relay 6.
  • the enlarger lamp 3 is directly connected to the alternating current mains 4, at the normal line voltage (say for example l volts) while the terminals 1 and 2 of the timing or control circuit are subjected, through the converter 30, to a direct current voltage which is preferably considerably less than the mains or line voltage in the line 4.
  • the exposure lamp 3 is lit, and the photographic enlarger is illuminated so that the operator can perform the preliminary or preparatory work.
  • the switch 8 When the preparatory work is completed and the user is ready to make the exposure, the switch 8 is closed.
  • the ignition section or gate of the thyristor 7 thus receives an ignition voltage, and the thyristor, which is subjected to the voltage across the terminals 1 and 2 when the switch 8 is closed, is driven hard. A current thus flows through the winding of the relay 6, and this opens the switch 5, so that the enlarger illumination lamp 3 is extinguished.
  • the capacitor 14 now charges up, through the resistor 12, to the terminal voltage.
  • the timing circuit is subjected to a constant direct voltage corresponding to the breakdown voltage of the Zener diode 15.
  • the capacitors 22 and 23 charge up with a time constant adjustable by means of the adjustable resistors 18, 20, and 21.
  • the hump voltage of the PUT 16 When the hump voltage of the PUT 16 is reached, the latter becomes conductive and the capacitors 22 and 23 discharge via the PUT 16, in which process a voltage impulse is generated in the resistor 26, This voltage impulse is fed to the gate of the thyristor 7 and causes the thyristor to cut through or become conductive.
  • the timing circuit is short circuited at the moment when the thyristor 7 is driven hard.
  • the switch 8 is not opened until the operator has removed the sensitized paper on which the exposure has just been made, and put it in a safe place such as a developer bath, because the opening of the switch 8 will or might cause the relay switch 5 to close and light the lamp 3.
  • the opening of the switch 13 may be postponed, if desired, until the operator is ready to open the switch 8 also.
  • the apparatus is then ready for the next cycle of operation, closing the switch 8 serving to put out the lamp 3 so that the sensitized paper may be placed in exposure position, and the subsequent closing the switch 13 serving to turn on the lamp 3 to make the exposure, for the exposure time interval determined by the timing portion of the circuit.
  • a photographic enlarger comprising a lamp circuit, a lamp in said circuit, a first switch in said lamp circuit in series with said lamp, said first switch being normally closed, means for supplying current of one voltage to said lamp circuit to cause said lamp to be lit while said first switch is closed, and an electronic control circuit for controlling the respective lit and unlit conditions of said lamp by operation of said first switch from a location remote from said first switch, said control circuit comprising a source of direct current at a voltage less than the voltage supplied to said lamp circuit, a relay coil (6) for operating said first switch, said first switch being closed while no current is flowing in said relay coil and being open while current is flowing therein, a thyristor (7) in series with said relay coil, a second switch (8) in series with said relay coil and thyristor, said relay coil, thyristor, and second switch being connected in series across said source of direct current, means responsive to the closing of said second switch for rendering said thyristor conductive so that current will flow in said relay coil to open said first

Landscapes

  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • General Physics & Mathematics (AREA)
  • Light Sources And Details Of Projection-Printing Devices (AREA)
  • Control Of Exposure In Printing And Copying (AREA)
  • Discharge-Lamp Control Circuits And Pulse- Feed Circuits (AREA)
US44148474 1973-02-14 1974-02-11 Photographic enlarger with electronic light control Expired - Lifetime US3895257A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19732307200 DE2307200B2 (de) 1973-02-14 1973-02-14 Fotografischer vergroesserungsapparat

Publications (1)

Publication Number Publication Date
US3895257A true US3895257A (en) 1975-07-15

Family

ID=5871870

Family Applications (1)

Application Number Title Priority Date Filing Date
US44148474 Expired - Lifetime US3895257A (en) 1973-02-14 1974-02-11 Photographic enlarger with electronic light control

Country Status (6)

Country Link
US (1) US3895257A (it)
JP (1) JPS49114925A (it)
DE (1) DE2307200B2 (it)
FR (1) FR2218029A5 (it)
GB (1) GB1412370A (it)
IT (1) IT999832B (it)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3403736A1 (de) 2017-05-17 2018-11-21 Primetals Technologies Austria GmbH Führen metallischer bänder in einer bandbearbeitungsanlage

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3555390A (en) * 1968-10-07 1971-01-12 Sylvania Electric Prod Switching circuit for motor control in slide scanning systems
US3571612A (en) * 1967-12-20 1971-03-23 Ricoh Kk Safety device for an exposure lamp in a reproduction apparatus
US3611049A (en) * 1970-06-29 1971-10-05 Dick Co Ab Automatic power control circuit
US3697821A (en) * 1971-07-30 1972-10-10 Hunt Electronics Co Light dimming system having multiple control units
US3737734A (en) * 1968-10-25 1973-06-05 Minolta Camera Kk Copying machine
US3742295A (en) * 1970-03-30 1973-06-26 Minolta Camera Kk Lighting system in copying apparatus
US3754165A (en) * 1970-08-29 1973-08-21 Siemens Ag Electromagnetically actuated switching device having delayed dropout
US3808456A (en) * 1971-09-27 1974-04-30 Switchpack Systems Remote control switching system

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3571612A (en) * 1967-12-20 1971-03-23 Ricoh Kk Safety device for an exposure lamp in a reproduction apparatus
US3555390A (en) * 1968-10-07 1971-01-12 Sylvania Electric Prod Switching circuit for motor control in slide scanning systems
US3737734A (en) * 1968-10-25 1973-06-05 Minolta Camera Kk Copying machine
US3742295A (en) * 1970-03-30 1973-06-26 Minolta Camera Kk Lighting system in copying apparatus
US3611049A (en) * 1970-06-29 1971-10-05 Dick Co Ab Automatic power control circuit
US3754165A (en) * 1970-08-29 1973-08-21 Siemens Ag Electromagnetically actuated switching device having delayed dropout
US3697821A (en) * 1971-07-30 1972-10-10 Hunt Electronics Co Light dimming system having multiple control units
US3808456A (en) * 1971-09-27 1974-04-30 Switchpack Systems Remote control switching system

Also Published As

Publication number Publication date
DE2307200B2 (de) 1976-08-05
FR2218029A5 (it) 1974-09-06
JPS49114925A (it) 1974-11-01
DE2307200A1 (de) 1974-08-22
IT999832B (it) 1976-03-10
GB1412370A (en) 1975-11-05

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