Compact accessory strobe for cameras with battery enclosed film pack

A compact strobe is adapted for direct connection to a Polaroid SX-70 Land Camera or the like. Once the strobe is connected to a film laden camera, it is provided with a steady state input voltage which can be utilized by the strobe to charge a storage capacitor. The storage capacitor may thereafter be triggered at an appropriate time during the camera exposure interval by a select trigger signal, also furnished from the camera, to discharge through a flash tube thereby providing a source of artificial illumination. Connection from the camera to the strobe is made from the flash array receiving socket on top of the camera exposure housing as well as from the remote actuator button socket on the side of the camera exposure housing. To accommodate this connection, the strobe is provided with both a blade connector similar to that utilized on a conventional multilamp flash array and a flexible electrical connecting member for connecting directly to the remote actuator button socket.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a strobe arrangement for use with Polaroid 
SX-70 type Land Cameras and more particularly to a strobe arrangement 
which is both powered and triggered from an SX-70 type camera upon 
attachment thereto. 
2. Description of the Prior Art 
The Polaroid SX-70 Land Camera, made and sold by the Polaroid Corporation 
of Cambridge, Massachusetts, U.S.A., is adapted to make photographs 
automatically either by ambient light or with the aid of a flash lamp 
array. For this purpose, the camera is provided with an accessory socket 
in the shutter and lens board housing which will accept a part from a 
flash lamp array. The flash lamp array includes five flash lamps in one 
array and five in another so that five sequential exposures can be made, 
each with a different bulb, when the array is inserted in the socket in 
either position. The remaining five lamps can be sequentially used by 
removing the flash array, and putting it back in facing the opposite 
direction. 
The camera is provided with a sequencing circuit to select the next unfired 
bulb for energization, and to sequence the camera circuits which operate 
the shutter, control the mirror and operate the processing rolls. 
It would be highly desirable to extend the capabilities of the Polaroid 
SX-70 Land Camera, and other cameras such as the new Polaroid Pronto 
Camera, for use with electronic flash. One type of strobe suitable for use 
with Polaroid's SX-70 Land Cameras as disclosed in a U.S. Pat. No. 
3,943,532 entitled "Flash Attachment for Self Developing Collapsible 
Cameras", issued Mar. 9, 1976 teaches the use of a flash lamp attachment 
having a flash tube and reflector assembly connected to a separate power 
pack unit which is removable from the camera body. The power required for 
igniting the flash lamp is provided by a separate disposable battery 
contained within a large auxiliary power pack unit that releasably 
attaches to the bottom of the SX-70 camera. However, such an auxiliary 
power pack unit is bulky and heavy and not particularly compatible with 
the SX-70 camera's compact design features. 
Thus it is a primary object of this invention to provide a compact strobe 
arrangement for use with Polaroid's SX-70 Land type cameras wherein the 
strobe receives both a trigger pulse signal and a charging current 
directly from the camera furnished by way of the SX-70 film pack battery. 
It is a further object of this invention to provide a compact strobe 
adapted for connection to conventional SX-70 Land Cameras so as to receive 
both a charging current and a trigger signal from the SX-70 camera without 
requiring modification to the camera. 
Other objects of the invention will in part be obvious and will in part 
appear hereinafter. The invention accordingly comprises the mechanism and 
system possessing the construction, the combination of elements and 
arrangement of parts which are exemplified in the following detailed 
disclosure. 
SUMMARY OF THE INVENTION 
The invention relates to an electronic flash unit for use with a camera of 
the type having a flash socket assembly adapted for receipt of a 
conventional multiple flash lamp array together with an electrical 
receiving socket spaced apart from the flash socket for accommodating the 
connection of a conventional remote actuator button. The flash unit 
comprises a housing, a storage capacitor and means responsive to an 
applied voltage for charging the capacitor. Circuit means are also 
provided to respond to an applied trigger signal for discharging the 
capacitor through the discharge tube to produce an illuminating flash of 
light. A connector blade extends outward from the strobe housing and is 
adapted for receipt within the camera flash socket assembly. The connector 
blade includes at least three spaced apart terminal elements of which two 
terminal elements are arranged to receive an applied trigger signal from 
the camera and of which the third terminal element is arranged to receive 
one side of an applied voltage from the camera for charging the capacitor. 
Means are provided for respectively electrically connecting the trigger 
signal receiving terminal elements to the means for discharging the 
capacitor and for electrically connecting the applied voltage receiving 
terminal element to the means for charging the capacitor. A flexible 
electrical connecting member extends outward from the strobe housing and 
connects to an electrical insertion jack adapted for receipt within the 
camera receiving socket to receive the other side of the applied voltage 
from the camera for charging the capacitor. Means are also provided within 
the housing for electrically connecting the flexible member to the means 
for charging the capacitor.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIG. 1 there is shown a front portion of a folding 
Polaroid SX-70 Land camera 10 of the type more fully shown and described 
in U.S. Pat. Ser. No. 3,820,128 by J. Burgarella et al. entitled "Flat 
Photographic Control System" issued June 25, 1974 and assigned in common 
herewith. Camera 10 is illustrated as including a shutter housing section 
12 mounted to pivot into a face down position on a housing section 14 when 
the camera is folded for storage. Housing section 12 includes a lens and 
shutter assembly 16 which may be of the type shown in U.S. Pat. No. 
3,200,723 having a picture taking axis 18, a focus wheel 20 for focusing 
the lens and an actuator button S1 for initiating the exposure cycle of 
the camera. Housing section 12 further includes a flash socket assembly 24 
having a boss 26 which extends through a wall 28 of shutter housing 
section 12 and defines an entrance slot 30 which is orthogonal to picture 
taking axis 18 for receiving the connector blade 72 of either a disposable 
multilamp flash assembly as shown generally at 68 in FIG. 3, or 
alternatively the connector blade 88 of a strobe unit 11 shown in FIG. 1. 
Referring now to FIG. 2, the flash socket assembly 24 is shown to include a 
first set of contacts or terminal strips 32, 34, 36, 38, 40 and 42 and a 
second set of contacts or terminal strips 44 and 46. Each of the contacts 
is preferably composed of a spring material having high electrical 
conductivity and high tensile strength such as certain berryllium copper 
alloys. A nickel silver coating is preferably applied to the contact to 
minimize contact resistance. Each of the contacts includes a base section 
48 for connection to leads on a printed circuit substrates 50, a spine 52, 
and a reverse bent section including an entrance ramp portion 54, a 
contact portion 56, and an exit ramp portion 58. The entrance and exit 
ramp portions 54 and 58 assure a smooth insertion and withdrawal of the 
connector blade. The contact portions 56 apply a loading force on the 
contiguous surface of the connector blade in a direction normal to the 
plane of the connector blade from either a multilamp flash assembly or 
strobe unit so as to retain the blade in the socket assembly, and so as 
not to introduce any lifting force component which might tend to raise the 
connector blade from the socket assembly. Spacing means 60 are 
interdigitated with the contacts to maintain the parallel relationship 
between the contacts and to prevent a contact from moving into electrical 
engagement with an adjacent contact. Socket assembly 24 also includes an 
outwardly beveled mouth 62 surrounding slot 30 and walls 64 which guide 
the connector blade into its operative position within the socket 
assembly. 
As schematically indicated in FIG. 3, the conventional multilamp flash 
assembly or array 68 may comprise an insulating block or support section 
74 supporting 5 reflectors 69 comprising reflective recesses in which each 
of a series of 5 flashlamps 70 is mounted. Five additional flash lamps are 
similarly disposed on the opposite side of the flash assembly 68. Each of 
the flashlamps 70 has one terminal connected to a common terminal 76 
formed as a conductive strip on connector blade 72 of insulated material 
that is adapted to fit into the socket of assembly 24. Each of the 
flashlamps 70 has a second terminal connected to a different one of a set 
of 5 output terminals 78, also formed as conductive strips on the 
connector blade 72. 
Upon insertion of the connector blade 72 of the flash array 68 within the 
flash socket assembly 24 of FIG. 1, the second terminals 78 make 
respective electrical contact with the socket terminal strips 32 through 
42. The terminal strips 32 through 42, in turn, are connected to a 
distributor or flash sequencing circuit schematically indicated at 82. 
Generally, in response to an input trigger signal supplied to the 
distributor circuit 82 in a manner to be subsequently described in greater 
detail, the distributor circuit operates to effectively connect one of the 
terminals 78 selected in a predetermined sequence to a ground terminal. 
The common terminal 76 is also connected to the positive supply terminal 
of a battery shown schematically at 84 in a manner to be subsequently 
described. The battery 84 is preferably insertable within the folding 
camera 10 in correspondence with the film pack or cassette in a manner as 
is well known in the art for Polaroid SX-70 type film cassettes and 
cameras. The distributor circuit 82 operates in a manner to be 
subsequently described to selectively ground the terminal 78 connected to 
the first unfired flashbulb 70 in an ordered sequence in the array so that 
when one of the terminals 78 is grounded current flows through the 
associated flashlamp 70. 
The connector blade 72 is provided with a relatively wide terminal 80 that 
bridges the pair of terminal strips 44 and 46 upon insertion of the 
connector blade 72 within the socket assembly 24. Electrically shorting 
terminal strips 44 and 46 operate to signal the camera circuit that the 
flash array is in position in the camera and ready to be used. 
Referring now to FIG. 4 there are shown the details of the strobe unit 11 
adapted to cooperate with the camera of FIG. 1, together with a particular 
form of distributor network 82 adapted to cooperate with an electronic 
control module (ECM) 130, the details of which may be more readily 
understood from U.S. Patent Ser. No. 3,820,128, supra, together with U.S. 
Patent Ser. No. 3,930,184 entitled "Electronic Flash Coupling System For 
Sequential Flashbulb Firing Circuit" by C. Biber issued Dec. 30, 1975 and 
assigned in common herewith. More specifically, strobe unit 11 includes 
connector blade 88 on which there is provided a wide terminal 90, 
corresponding to the terminal 80 in FIG. 3. Five terminals 92 are also 
provided corresponding to the terminals 78 in FIG. 3 and one terminal 92' 
is provided corresponding to the common terminal 76 in FIG. 3. As will be 
readily apparent, only one of the five terminals 92 is electrically 
necessary and the other terminals may be omitted if desired. The wide 
terminal 90 of the strobe connector blade 88 is adapted to electrically 
connect the terminal strips 44 and 46 thereby enabling the electronic 
control module 130 by providing its sole connection to the ground terminal 
of battery 84 through lines 89 and 91 which are electrically connected in 
serial relation through terminal strips 44 and 46 and wide terminal 90. 
One of the terminals 92, here shown as the one adjacent wide terminal 90, 
is connected to the common terminal 92' by way of a resistor R3 which 
corresponds to the impedance of an unfired flashlamp for reasons which are 
more fully apparent in U.S. Patent Ser. No. 3,858,227 entitled "Adaptor 
Apparatus For Flash Firing System" by S. Ellin et al. issued Dec. 31, 1974 
and assigned in common herewith. Thus, the resistor R3 preferably has a 
value in the order of 4 ohms, approximately the resistance of a flashlamp 
before it is fired. Connected in parallel with the resistor R3 is a 
current limiting resistor R4 in serial connection to a gate resistor R2. 
The strobe unit 11 is also adapted to receive an external substantially 
steady state DC battery voltage from the lines 96 and 106 for powering a 
conventional voltage converter 108. There may also be provided an on-off 
switch 94 by which the user may control the power connection to the 
voltage converter 108. The voltage converter 108 operates in a 
conventional manner to convert the DC voltage, as may be derived from 
battery 84 which is preferably 6 volts, to a suitable strobe operating 
voltage such as 350 volts. This voltage appears on a pair of output 
terminals or lines 110 and 112 from the voltage converter 108. 
The first circuit path across the output terminals 110 and 112 includes a 
series ready-light 114, and a resistor R5 in series therewith. The 
ready-lamp 114 may be a conventional gas discharge lamp of any suitable 
design. The resistor R5 is selected to limit the current flowing through 
the lamp 114 to a suitable value. A second path across the leads 110 and 
112 comprises a storage capacitor C3 in a suitable size for storage of the 
energy necessary to fire a gas tube 116. The gas tube 116 has electrodes 
connected across the leads 110 and 112 in the third path. The tube 116 is 
triggered to produce a flash of light when the capacitor C3 is 
sufficiently charged to allow the lamp 114 to glow and a relative high 
voltage spike, such as 5,000 volts is applied to the grid terminal 118 of 
the tube 116. 
The grid 118 is connected to the lead 112 through the high voltage 
secondary winding 120 of a pulse transformer generally designated at 122. 
The low voltage primary winding 124 of the transformer 122 has one 
terminal connected to the lead 112 and a second terminal connected through 
a capacitor C4, in series with a resistor R7, to the lead 110. A silicon 
controlled rectifier SCR1 has its anode terminal connected to the junction 
of the resistor R7 and the capacitor C4 and its cathode connected to the 
lead 112. Resistor R2 is connected between the gate and the cathode of the 
silicon controlled rectified SCR1 to prevent false triggering of the 
controlled rectifier. 
In order that the strobe unit 11 be made as compact as possible, it is 
desired that the voltage converter 108 be powered directly from the camera 
battery 84. It is toward this end that the instant invention is directed 
as will become more readily apparent from the following discussion. During 
operation of the strobe unit 11 when the switch 94 is closed, the 
capacitors C3 and C4 will be charged. When the charge is adequate to 
develop a suitable flash of light for exposure, the ready lamp 114 will 
discharge and glow, indicating that the strobe unit is ready for use. 
Thereafter an appropriate input signal applied to the terminals 92 and 92' 
by the distributor circuit 82 will operate to gate the silicon controlled 
rectifier SCR1 into conduction, causing discharge of the capacitor C4 
through the primary winding 124 of the transformer 122, resulting in a 
triggering spike being applied to the grid 118 of the flashtube 116 to 
cause it to discharge and produce a flash. Discharge of the capacitor C3 
through the tube 116 will cause the ready light 114 to be extinguished. 
With the discharge of the capacitor C4, ringing in the discharge circuit 
will cause a momentary reversal of voltage sufficient to cutoff the 
silicon controlled rectifier SCR1. 
The distributor circuit 82 comprises 5 electronic switches, hereshown as an 
ordered array of silicon controlled rectifiers SCR2 through SCR6. Of 
these, only the first silicon controlled rectifier SCR2 in the sequence, 
the second SCR3, in the last SCR6, are shown. The stage comprising the 
switch SCR3 is typical of the storage stages comprising the receifiers 
SCR4 and SCR5, not shown. 
The anode terminals of the silicon controlled receifiers SCR2 through SCR6 
connect respectfully to the terminal strips 32 through 42 with all the 
cathode terminals connecting to ground. Each of the gates of the 
controlled rectifiers SCR2 through SCR6 is connected to ground through a 
different one of a set of resistors R10 through R14 of which only the 
resistors R10, R11 and R14 are shown. Each of the controlled rectifiers 
SCR2 through SCR6 has its anode connected to the collector of a different 
one of a set of 5 gate control NPN transistors Q1 through Q5. The emitter 
of each of the transistors Q1 through Q5 is connected to the gate of a 
different one of the controlled rectifiers SCR2 through SCR6. The base of 
each of the transistors Q1 through Q5 is connected to the collector of a 
different one of a set of 5 inhibit NPN transistors Q6 through Q10. The 
emitter of each of the transistors Q6 through Q10 is grounded with respect 
to the battery 84. The base terminals of transistors Q6 through Q10 are 
each connected through a different one of a series of current distributing 
resistors R15 through R19 to an output terminal 126 from the electronic 
control module 130. When the electronic control module 130 provides a 
positive voltage signal corresponding to a logic 1 at output terminal line 
126, each of the transistors Q6 through Q10 is gated into conduction 
thereby preventing any of the transistors Q1 through Q5 from being biased 
into conduction. The electronic control module 130 also provides a trigger 
signal at output terminal line 128 to the base of a PNP transistor Q11. 
The emitter terminal of transistor Q11 is connected to the positive 
voltage side of the battery 84 by way of a resistor R1 and the actuator 
button S1. Thus, the emitter terminal of transistor Q11 receives a 
positive potential from the battery 84 when the button S1 is depressed. 
The collector of transistor Q11 is returned to ground through a resistor 
R20. The collector of transistor Q11 also connects to a lead 132 through a 
pair of diodes D4 and D5 in series. 
The lead 132 is connected to the base terminal of the transistor Q1 through 
a resistor R21. The lead 132 is also connected to the emitters of a group 
of 4 logic PNP transistors Q12 through Q15, of which only the transistors 
Q12 and Q15 are shown. The collectors of the transistors Q12 through Q15 
are connected to the bases of the transistors Q2 through Q5, respectively. 
The base of the transistor Q12 is connected to the anode of the controlled 
rectifier SCR2 through a resistor R22. A similar resistor R23 connects the 
anode of the controlled rectifier SCR3 to the next stage transistor Q13, 
not shown. Other stages are similarly connected, e.g., the base of the 
transistor Q15 is connected to one terminal of a resistor R26, and the 
other terminal of the resistor R26 is connected to the anode of the 
controlled rectifier SCR5, not shown. 
Referring now to FIG. 3 in conjunction with FIG. 4 it can be seen that the 
distributor circuit 82 is designed to fire each lamp in order from first 
to last. This is accomplished by having each switching circuit receive a 
trigger signal only when the preceding flash lamp is open circuited. 
Assuming that none of the flashlamps have been fired and that the 
distributor circuit 82 is triggered at the appropriate time by the 
electronic control module 130, which appropriate time is generally 
programmed to occur when the shutter is fully open in response to 
depression of actuator button S1 as fully disclosed in U.S. Patents Ser. 
Nos. 3,930,184 and 3,820,128, supra. The appropriate trigger signal from 
the electronic control module 130 provides a zero or negative potential 
signal at output terminal line 126 so as to maintain the inhibit 
transistors Q6 through Q10 in a nonconducting state while a negative going 
pulse is provided at the output terminal line 128 to gate transistor Q11 
into conduction. Turning on transistor Q11 operates to render gate control 
transistor Q1 conductive so as to switch on SCR2 thereby effectively 
coupling the first lamp 70 across the battery 84 supplied voltage so as to 
fire the lamp. As the lamp 70 is initially supplied with current and 
begins to flash, SCR3 will not turn on because its gate control transistor 
Q2 remains in a nonconductive state. The latter falls from the fact that 
its associated logic transistor Q12 is not rendered conductive. That is, 
the voltage across the emitter-base junction of the transistor Q12 is 
substantially identical to the voltage across the flashing lamp and the 
latter voltage is low in as much as the initial filament resistance is 
also very low. It should be readily appreciated, however, that if the lamp 
filament heats up, its resistance increases (just prior to opening of the 
filament) and the voltage across the lamp will accordingly increase. 
However, the electronic control module 130 operates to turn on inhibit 
transistors Q6 through Q10 so that subsequent circuits cannot turn on at 
this latter time during flashing of a preceding lamp. Thus, once the 
firing of a particular bulb is initiated, a high level in each signal is 
provided from the distributor circuit 82 for feedback through the 
electronic control module 130 so that the distributor circuit 82 is 
clamped off so as to prevent additional lamp firing at that time as is 
more fully described in U.S. Patent Ser. No. 3,930,184, supra. 
Following the firing of the first lamp, when a subsequent trigger signal is 
received from the electronic control module 130 the first SCR2 will be in 
a conductive state and the voltage across the first open lamp is high so 
that the voltage across the transistor Q12 will exceed the threshold 
voltage necessary to turn on this transistor. The latter, in turn, 
provides a suitable gating signal to the second SCR3 through gate 
transistor Q12 so as to draw ignition current through the second lamp. 
However, during initiation of current through the second lamp, the 
following SCRs will not be turned on in as much as transistor Q13 (not 
shown) is in parallel with the conducting line, and hence, is not biased 
for conduction. 
Assuming now that the strobe unit 11 of FIG. 4 is inserted into the flash 
socket assembly 24, camera operation will procede in like manner with the 
electronic control module 130 providing a negative trigger signal at 
terminal line 128 threrby forward biasing the emitter-base junction of 
transistor Q11. At the same time, a zero potential or negative potential 
signal is provided at output terminal line 126 to simultaneously turn off 
transistors Q6 through Q10. The diodes D4 and D5 operate to drop the 
voltage to the emitters of transistors Q12 through Q15 so that they are 
below the potential at their associated base terminals when the controlled 
rectifier SCR2 is nonconducting. This effect, however, is not important to 
the operation of the strobe unit 11 but, however, is significant to the 
operation of the linear flash lamp array 68 as previously discussed. The 
pulse of increased potential across the lead 132 will operate to bias the 
transistor Q1 into conduction causing the potential across the resistor 
R10 to rise, and supply gate current to turn on the controlled rectifier 
SCR2, which will then go into avalanche conduction. Current will now flow 
through the resistors R3 in parallel with R2 and R4 thereby gating the 
controlled rectifier SCR1 into conduction. Assuming that the capacitors C3 
and C4 are charged, with the SCR1 conducting, the capacitor C4 will 
discharge, causing the pulse transformer 122 to gate the gas tube 116 into 
conduction to produce a light flash. 
As previously discussed strobe unit 11 is adapted to receive charging 
current from the battery 84 situated within the folding camera 10 as shown 
in FIG. 1. The battery 84 is preferably of a type, which is carried in a 
Polaroid SX-70 Land Film Pack as manufactured and sold for use in the 
Polaroid SX-70 Land Camera. Once the battery 84 is inserted within the 
SX-70 camera, the positive and negative terminals are automatically 
contacted to power circuitry and equipment within the camera 10. Such an 
arrangement was neither designed nor intended for use with the type of 
compact strobe unit as shown in FIG. 4. Fortunately, the ground terminal 
from the battery is in direct electrical connection with the line 91 so as 
to provide a direct ground connection to terminal element 44. Thus, line 
106 from voltage converter 108 in strobe 11 connects directly to the wide 
terminal 90 thereby accommodating a direct electrical connection from the 
strobe unit 11 to the battery ground terminal when the connector blade 88 
is inserted within the flash socket assembly 24. Connection from the 
voltage converter 108 to the positive terminal of the battery 84, however, 
is more difficult because as is readily apparent none of the terminal 
strips 32 through 46 connect directly to the positive voltage side of the 
battery 84. Terminal strip 36 may be indirectly connected to the positive 
side of the battery 84 by way of the resistor R1 and button S2, however, 
this arrangement has proved unsatisfactory due to the high current drawn 
by the voltage converter 108 which may damage resistor R1. 
Referring now to FIGS. 4 and 1 there is shown an electrical receiving 
socket 136 having two spaced apart female type receiving chambers 138 and 
140 in the side of shutter housing section 12. The electrical receiving 
socket 136 is in parallel electrical connection with respect to the 
actuator button S1 and accommodates the insertion of a complementary jack 
connecting to a remote actuator button S1 so that the camera may be 
remotely operated in a known manner. 
The voltage converter 108 of the strobe unit 11 may thus be connected to 
the positive terminal of the battery 84 by way of the line 96 which 
serially connects to a flexible electrical connecting member 98. The 
outside end of the flexible member 98 terminating in an electrical 
insertion jack 100 having two spaced apart male prong members 102 and 104 
which are adapted for insertion within the electrical receiving socket 136 
in the side of the shutter housing section 12. As is readily apparent, the 
electrical connecting member 98 connects to only one of the prong members 
102 or 104 of the jack 100 so as not to short out the button S1 and 
thereby actuate the camera. Thus, in this manner is the strobe unit 11 
arranged to provide a direct connection to the positive and negative 
terminals of the battery 84 within the folding camera 10 while also 
receiving a synchronizing signal also generated within the camera 1o to 
fire the flash tube 16. Connecting member 98 is preferably made 
sufficiently short and integrally molded with jack 100 so as to require a 
substantial twist of the member 98 by the user in order to insert the jack 
100 with the prongs 102, 104 improperly reversed. 
Whereas the camera 10 is herein described as being a Polaroid SX-70 Land 
Camera, it will be readily understood that the invention is by no means so 
limited and may be applicable to other cameras such as Polaroid's most 
recently introduced Pronto Land Camera which also utilizes Polaroid's 
SX-70 type film. 
Since certain changes may be made in the above described system and 
apparatus without departing from the scope of the invention herein 
involved, it is intended that all matter contained in the description 
thereof or shown in the accompanying drawings shall be interpreted as 
illustrative and not in a limiting sense.