Electronic flash apparatus with extendable on/off switch control apparatus

An electronic flash unit attachable to the top of a camera shutter housing is provided with switch control apparatus which may be selectively extended into position so as to be engaged by the photographer when holding the camera in its normally expected manner. Engagement of the switch control apparatus by the photographer causes it to effect the closing of an ON-OFF switch thereby applying power to the flash unit whereas subsequent disengagement of the switch control apparatus causes it to automatically effect the opening of the ON-OFF switch.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an electronic flash apparatus with 
extendable on/off switch control apparatus and more particularly to an 
electronic flash apparatus having extendable on/off switch control 
apparatus and adapted for use with cameras wherein the switch control 
apparatus when extended, is in position to be engaged by the camera user's 
hand when holding the camera in its normally expected manner. 
2. Description of the Prior Art 
Electronic flash units for providing artificial illumination during 
photographic exposures occurring under conditions of low ambient scene 
light intensity are well known in the art. Such electronic flash units are 
generally adapted to receive an external, substantially steady state, d-c 
battery voltage which powers a voltage converter in a conventional manner 
to convert the d-c voltage which may be in the order of 6 volts, to a 
suitable flash operating voltage. A charging current from the voltage 
converter is directed to a storage capacitor so as to gradually charge the 
storage capacitor to a d-c voltage which may be in the order of 350 volts. 
Means are also provided for selectively discharging the storage capacitor 
through a flash discharge tube to produce the photographic illuminating 
flash of light. An on/off switch may also be provided to control the power 
connection from the battery to the voltage converter. Thus, when a 
photographer anticipates using the electronic flash, he must initially 
turn on the on/off switch to power the voltage converter and thereafter 
wait a short period of time for the storage capacitor to become fully 
charged. After the storage capacitor in the electronic flash is discharged 
through the flash tube during a photographic exposure operation of the 
camera, the voltage converter will automatically operate to recharge the 
storage capacitor in anticipation of a subsequent photographic exposure 
unless the operator consciously remembers to turn off the on/off switch. 
Should the operator fail to consciously turn off the on/off switch and let 
the camera sit idle for a period of time, the voltage converter will 
continue to operate to maintain the charged condition of the storage 
capacitor thereby providing a constant current drain on the battery. A 
prolonged period of idleness with the on/off switch remaining on may 
ultimately result in the complete drainage of the battery so as to render 
the battery inoperative. 
One approach to solving this problem has involved the use of a time-out 
circuit within the electronic flash so as to automatically disconnect the 
battery from the voltage converter if the flash is not fired within a 
prescribed time period. However, such a time-out circuit generally 
involves the use of a power transistor in series connection between the 
battery and voltage converter which decreases the actual power input to 
the voltage converter as a result of the high power losses inherent to the 
power transistor. 
A so called "two-button camera" having an integral flash unit built therein 
has been disclosed in a copending application for U.S. patent Ser. No. 
570,165 entitled "Photographic Apparatus", by E. H. Land, filed Apr. 21, 
1975 now U.S. Pat. No. 4,007,469 in common assignment herewith. This 
two-button camera embodies a so called "grip switch" in the base portion 
thereof to turn on the electronic control circuit associated with both the 
camera and the electronic flash when the camera is held by the user. 
However, electronic flash units are generally configured to be detachable 
from the top of the lens housing portion of the camera thereby making it 
inconvenient for a grip switch, which constitutes an integral part of the 
camera, to control the detachable electronic flash unit. Since the 
electronic flash unit is normally connected above the shutter housing of 
the camera, it has also heretofore been inconvenient to provide the 
electronic flash unit with its own grip switch since most cameras are not 
normally held above their shutter housings. 
It is therefore a primary object of this invention to provide means for 
automatically turning on and off an electronic flash unit as a function of 
whether the camera to which the electronic flash unit is attached is held 
in position in anticipation of taking a photographic picture. 
It is also an object of this invention to provide an electronic flash unit 
with extendable on/off switch control apparatus for automatically 
controlling the electrical connection between the electronic flash and its 
associated battery as a function of whether the camera to which the 
electronic flash is connected is held in its normally expected position in 
anticipation to taking a photographic picture. 
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 the 
arrangement of parts which are exemplified in the following detailed 
disclosure. 
SUMMARY OF THE INVENTION 
An electronic flash unit is provided for use with a camera of the type 
which may be held by a user in a normally expected manner and which 
includes means for providing a flash fire trigger signal at an appropriate 
time during a photographic exposure interval together with connecting 
apparatus for accommodating the removable connection of the flash unit to 
the camera. The flash unit comprises a housing within which there is 
disposed a storage capacitor, a flash discharge tube and means responsive 
to an applied voltage for charging the capacitor. Circuit means are also 
provided to respond to the trigger signal in order to discharge the 
capacitor through the discharge tube to produce an illuminating flash of 
light. In addition, electrical connecting means facilitate the electrical 
connection of the circuit means to the trigger signal providing means of 
the camera. Physical connecting means on the strobe housing are 
complementary to the camera connecting apparatus for facilitating the 
releasable, fixed, connection of the flash unit housing to the camera. 
Switch means which are connectable to a source of voltage, control the 
application of the voltage to the capacitor charging means. Means which 
are selectively extendable from the flash housing and operatively 
associated with the switch means operate to control the switch means. The 
control means are extendable subsequent to the fixed connection of the 
flash housing to the camera into interferring relation with at least a 
portion of the area otherwise expected to be occupied by a user's hand 
when holding the camera in its normal manner. The control means are thus 
extendable into position to be engaged by the user's hand when holding the 
camera and are also responsive to such engagement by the user's hand so as 
to cause the switch means to apply voltage to the capacitor charging means 
.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to FIG. 1, there is shown a front of a folding Polaroid SX-70 
Land Camera 10 of the type more fully shown and described in U.S. Pat. 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 
shown as including a shutter housing section 12 mounted to pivot into a 
face down position on a base 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. 3,820,128 supra, 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, the details of which are more 
fully described in a U.S. Pat. No. 3,757,643 entitled "Photoflash 
Apparatus" by J. Burgarella, issued Sept. 11, 1973 in common assignment 
herewith. The flash socket assembly 24 functions in a well known manner as 
connecting apparatus for accommodating the removable fixed connection of 
an electronic flash unit as shown generally at 11 with respect to the 
camera 10. The flash socket assembly 24 in its preferred mode includes a 
boss 26 which extends from a wall 28 of the shutter housing section 12 and 
defines an entrance slot 30 which is generally orthogonal to picture 
taking axis 18 for accommodating receipt of a connector blade 31 from the 
strobe unit 11 as shown in FIG. 2. In the preferred mode, wall 28 further 
includes overhanging side portions 27 and 29 at the opposite ends thereof 
for reasons which will become more apparent from the following discussion. 
Referring now to the schematic diagram of FIG. 3, the flash socket assembly 
24 is shown to include a first set of spaced apart contacts or terminal 
strips 32, 34, 36, 38, 40 and 42, and a second set of spaced apart 
contacts or terminal strips 44 and 46. The terminal strips 32-42, in turn, 
are connected to a flash fire circuit shown generally at 45 as is more 
fully described in U.S. Pat. No. 3,858,227 entitled "Adapter Apparatus for 
Flash Firing System", by S. Ellen et al., issued Dec. 31, 1974 in common 
assignment herewith. 
Referring now to FIG. 1, there is shown the flash unit 11 comprising a 
parallelepiped housing 47 having a generally planar front wall member 48 
in spaced apart generally parallel relation to a back wall member 50. The 
front and back wall members 48 and 50 are peripherally connected 
respectively by generally planar, spaced apart, parallel top and bottom 
wall members 52 and 54 together with generally planar, spaced apart, 
parallel side wall members 56 and 58. Front wall member 48 includes a 
transparent window 60 behind which is stationed an electronic flashtube 62 
which functions in a well known manner. The connector blade 31 extends 
downwardly from the bottom wall member 54 to provide means for physically 
connecting to the flash socket assembly 24. Thus insertion of the 
connector blade 31 into the flash socket assembly 24 provides for the 
releasable fixed connection of the flash unit 11 to the camera 10. 
The connector blade 31 is provided with a relatively wide terminal 66 that 
bridges the pair of terminal strips 44 and 46 upon insertion of the 
connector blade 31 within the socket assembly 24. Electrically shorting 
terminal strips 44 and 46 operates to signal a camera control circuit, as 
shown generally at 67, that the flash unit 11 is in position in the camera 
and ready to be used in a manner as is more fully described in U.S. Pat. 
No. 3,757,643 supra. Electrical connecting means comprising two additional 
terminals 68 and 70 are also provided on the connector blade 31 for making 
respective electrical contact with terminal strips 36 and 42 thereby 
facilitating receipt by the flash unit 11 of a flash fire trigger signal 
from the flash fire circuit 44 of the camera 10. 
Terminals 68 and 70 on connector blade 31 connect respectively to the 
opposite sides of a resistor R3 which corresponds to the impedance of an 
unfired flashlamp for reasons which are more fully apparent in U.S. Pat. 
No. 3,858,227 supra. Thus, resistor R3 preferably has a value on the order 
of 4 ohms, approximating the resistance of a flashlamp before it is fired. 
A current limiting resistor R4 and a gate resistor R2 are connected in 
parallel with the resistor R3. 
The flash unit 11 is also adapted to receive an external substantially 
steady state DC voltage by way of a pair of output terminals 72 and 74 for 
powering a conventional voltage converter 76. There is also provided an 
on/off switch 78 by which the user may control the power connection to the 
voltage converter 76 in the manner of this invention to be subsequently 
described in detail herein. The voltage converter 76 operates in a 
conventional manner to convert the DC voltage, as may be derived from a 
battery (not shown) which is preferably 6 volts, to a suitable flash 
operating voltage such as 350 volts. This voltage appears on a pair of 
output conductors 80 and 82 from the voltage converter 76. 
A first circuit path across the output conductors 80 and 82 includes a 
ready light 84 and a resistor R5 in series therewith. The ready light 84 
may be a conventional gas discharge lamp of any suitable design. The 
resistor R5 is selected to limit the current flowing through the lamp 84 
to a suitable value. A second path across the conductors 80 and 82 
comprises a storage capacitor C3 in a suitable size for storage of the 
energy necessary to fire the flash discharge tube 62. The discharge tube 
62 has electrodes connected across the output conductors 80 and 82 in a 
third path. The tube 62 may be triggered to produce a flash of light when 
the capacitor C3 is sufficiently charged to allow the lamp 84 to glow and 
a relatively high voltage spike, such as 5,000 volts, is applied to the 
grid terminal 86 of the tube 62. 
The grid 86 is connected to the output conductor 82 through the high 
voltage secondary winding 90 of a pulse transformer generally designated 
at 92. The low voltage primary winding 94 of the transformer 92 has one 
terminal connected to the conductor 82 and a second terminal connecting 
through a capacitor C4, in series with a resistor R7, to the conductor 80. 
A silicon controlled rectifier SCR1 has its anode terminal connected to 
the junction of the resistor R7 and the capacitor C4 and its cathode 
terminal connected to the conductor 82. Resistor R2 is connected between 
the gate and the cathode of the silicon controlled rectifier SCR1 to 
prevent false triggering of the controlled rectifier. 
In order that the strobe unit be made as compact as possible, it may be 
desired that the voltage converter 76 be powered directly from a battery 
within the camera 10 in a manner as is more fully described in a copending 
application for U.S. patent Ser. No. 679,698 entitled "Compact Accessor 
Strobe For A Camera With Battery Enclosed Film Pack" by R. Kee filed Apr. 
23, 1976 in common assignment herewith. 
Referring now to FIGS. 2 and 4, it can be seen that the flash unit 11 is 
provided with switch control means as shown generally at 96 for 
selectively controlling the on/off condition of switch 78 in the manner of 
this invention as will now be described. The switch control means includes 
a first elongated member 98 pivotally connected at one end thereof along 
an axis as shown at 102, to one end of a second elongated member 100. An 
interior, generally planar, wall member 108 is provided in generally 
parallel, spaced apart, relation inward of the side wall member 56 with 
the space therebetween being of sufficient width to accommodate limited 
lateral displacement of the elongated member 100 therebetween. The other 
end of the elongated member 100 is folded into two right angle bends as 
shown at 104 and 106 to provide a portion 110 thereof in overhanging 
relation with respect to the top edge of the interior wall member 108 to 
accommodate limited lateral pivotal movement of the elongated members 98 
and 100 thereabout in directions generally orthogonal to the wall members 
56 and 108 and generally coincident to the axis 102 about which the 
elongated members 100 and 98 are pivotally connected at 102. The right 
angle bend 106 of member 100 also engages an abutment face 111 in a manner 
operating to secure the pivot point and inhibit the overhanging portion 
110 from wandering off the top edge of wall member 108. 
The switch control means 96 additionally includes control apparatus as 
shown generally at 114 comprising a housing 115 through which there is 
provided a central bore 117 to accommodate reciprocal motion of a plunger 
116 disposed therein. One end of the plunger 116 as shown at 119 is 
engaged by the elongated member 100 so as to translate inwardly into the 
housing 115 upon the lateral pivotal movement of the elongated members 100 
and 98 toward the interior wall member 108. The plunger 116 preferably 
includes a truncated frustoconical surface 118 which cooperatively engages 
a spring loaded reciprocating ball 120 in the usual manner to provide a 
positive snap-action upon translation of the plunger 116 into the housing 
115. The other end of the plunger 116, as shown at 121, is arranged to 
engage a resilient leaf member 124 of the on/off switch 78 in a manner 
operating to deflect the leaf member 124 into engagement with a contact 
126 so as to close the on-off switch 78 upon translation of the plunger 
116 into the housing 115. There is also provided a helical compression 
spring 127 around the plunger 116 in engagement with a raised peripheral 
edge 134 thereof to continuously urge the plunger 116 into translation 
outward of the housing 115 toward the side wall 56. 
The outward end of the elongated member 98 includes a raised grip portion 
112 which may be engaged by the hand of a user in the manner of this 
invention to be subsequently described. The end wall 56 may also include a 
cut-away or recessed portion 136 complementary to the raised grip portion 
112 thereby accommodating receipt of the raised grip portion 112 therein 
upon counterclockwise rotation of the elongated member 98 into its stowed 
position as shown in FIG. 5. 
The strobe unit 11 may be used in conjunction with the camera 10 in the 
following manner. The connector blade 31 from strobe 11 is first inserted 
in the usual manner within the flash socket assembly 24 thereby 
establishing a removable fixed connection between the flash unit 11 and 
camera 10. The elongated member 98 may thereafter be rotated in a 
clockwise direction as viewed from FIG. 1 from its stowed position 
adjacent the cutaway portion 136 to its fully extended position as shown 
in FIG. 1 with the raised grip portion 112 in spaced apart relation aside 
the base housing section 14 of the camera. 
Polaroid SX-70 type Land cameras are held in a normally expected manner by 
the user who grasps the underlying surface of the base housing section 14 
in the palm of his hand while engaging the opposed sides of the base 
housing section 14 with his thumb and fingers respectively as shown in 
FIG. 1. As is now readily apparent, extension of the elongated member 98 
in the aforementioned manner operates to move the raised grip portion 112 
into interfering relation with that portion of the camera base housing 
section 14 that would otherwise be occupied by the user's thumb when 
grasping the camera in the normally expected manner. 
Thus, the user upon pivotally extending the elongated member 98, will 
thereafter when attempting to grasp the camera in the usual manner engage 
the raised grip portion 112 with his thumb so as to laterally pivot the 
elongated members 98 and 100 toward the interior wall member 108. As is 
readily apparent, such lateral pivoting of the elongated members 98 and 
100 operates to translate the plunger 116 into the housing 115 so as to 
compress the spring 127 while simultaneously displacing the reciprocating 
ball 120 radially outward. At the same time, the other end of the plunger 
at 121 engages the resilient leaf 124 of the on-off switch 78 so as to 
deflect the leaf 124 into electrical connection with the contact 126. In 
this manner, charging current from the battery is selectively applied to 
the voltage converter 76 only when the camera is grasped by the user in 
anticipation of photographing a particular scene. 
Once the camera is grasped and the switch 78 closed in the aforementioned 
manner, the user must wait for the voltage converter 76 to charge the 
capacitor C3 to its prescribed value as indicated by the ready light 84 
being lit. The user may thereafter implement a photographic exposure cycle 
in the usual manner by depressing the actuator button S1. During the 
exposure interval, the flash fire circuit 45 provides an appropriate flash 
fire trigger signal to the terminals 68 and 70 which causes a current to 
flow through the resistors R3 in parallel with R2 and R4 so as to gate the 
silicon controlled rectifier SCR1 into condition. Assuming that the 
capacitors C3 and C4 are charged as previously discussed, with the SCR1 
conducting, the capacitor C4 will discharge, causing the pulse transformer 
92 to gate the flash tube 62 into conduction to produce a light flash. 
Should the user thereafter decide to leave the camera in its erect position 
with the flash unit still attached, he may do so without worry as to 
whether he has turned off the strobe since his release of the raised grip 
portion 112 will automatically operate to open the on-off switch 78. The 
plunger 116 is automatically translated to its terminal position outside 
the housing 115 by virtue of the spring 127. In this manner, resilient 
leaf 124 of switch 78 is allowed to deflect to its normally open condition 
so as to block the flow of charging current from the battery to the 
voltage converter 76. In addition, the elongated arm members 98 and 100 
are translated laterally outward toward the sidewall 56 in a direction 
generally orthogonal thereto. 
Thus, unnecessary drainage of the battery which might otherwise occur from 
prolonged idle periods with the voltage converter 76 connected to the 
battery are automatically prevented regardless of whether the user 
consciously remembers to turn off the strobe. Prevention of such 
unnecessary battery discharge is particularly critical when the strobe 
unit 11 is adapted to receive charging current from a battery situated 
within the folding camera 10 as more fully discussed in an application for 
U.S. patent Ser. No. 679,698 supra. Such a battery would be of the 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. 
In the preferred embodiment, the means for physically connecting the flash 
unit 11 to the camera 10 in a releasable manner may additionally include a 
pair of spaced apart, resilient, C-type clips 128, 130 which are adapted 
to resiliently engage respective overhanging side portions 27 and 29 of 
the wall member 28. Resilient clip 128 may additionally include a 
cantilevered portion 132 extending laterally outward therefrom to 
accommodate engagement by a user in an upward direction in a manner 
operating to deflect the C-type clip 128 out of engagement with the 
overhanging side portion 27. The overhanging side portions 27 and 29 may 
thus form part of the connecting apparatus which permits the removable 
fixed connection of the flash unit 11 with respect to the camera 10. 
Wherein the camera 10 is herein described as being a Polaroid SX-70 Land 
Camera 10, 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 Camera which also utilizes Polaroid's SX-70 
type film. In addition, it is by no means necessary that the flash unit 11 
be made detachable from the camera 10 in the aforementioned manner and may 
instead be made integral to the shutter housing 12 while still embodying 
the switch control means 96 of this invention. Therefore, 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.