Note: Descriptions are shown in the official language in which they were submitted.
~ ~77521
1 LD-8546
FLASH LAMP ARRAY HAVING PRINTED CIRCUIT
Background of'the Inv'ention
The invention is in the field of photo flash
lamp arrays, such as -the Flip Flash type of array.
U.S. Patent No. 4,133',023, issued January 2, 1979,
to ~anson discloses a Flip Flash type of array having a
plurality of high-voltage flash lamps and their reflectors
positioned in front of a circuit board. The circuit
board is shaped to provide connector tabs Eor connection
to a camera socket. Each connector tab carries a
plurality of connection terminals which include an
electrical ground or "common" terminal. Circuit runs
carried on the board connect the terminals to the lamps
and to circuitry whereby a lamp is flashed each time a
firing voltage pulse is applied to the terminals. 'ICommon''
circuit runs on the board co~nect a lead-in wire o each
flash lamp to the common connection terminals. A metal
foil shield is positioned behind and parallel to the
circuit board and is electrically connected to the
common circuit runs and terminals by suitable conductive
means such as a wire staple through the center of the
circuit board.
' .! 775~1
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The circuit runs on Flip Flash circuit
boards are formed with a conductive ink containiny
silver. Given the high cost of silver, multiplied
by the tens of millions of Flip Flash arrays
manufactured per year, the cost of the circuit
run material is considerable and it would be desirable
to reduce this cost.
Canadian Application Serial Number 391,068,
Suster et al, filed November 27, 1981 discloses a
flash array having a circuit board on which the
circuit runs are made from an inexpensive material
comprising carbon particles applied to the board
in a liquid binder which is then dried and evaporated.
These circuit runs have a considerably higher
resistance (generally 30 or 40 times, or more~ than
the previously employed silver-containing conductive
ink. Flash arrays having the high-resistance
circuit runs have an increased tendency for lamps
to accidentally flash due to electrostatic
electricity, for example when a "charged" person handles
the array or touches its connector terminals. It
has been ascertained that this is due to the high
resistivity of the connection between the shield
and the "common" connector terminals. The referenced
patent application solves the problem by reducing
the resistance between the shield and the "common"
connector terminals.
Summary of the Inven~ion
Objects of the invention are to provide
an improved flash array construction, to reduce the
cost of circuit run material on the circuit board and
to prevent accidental flashing of lamps by electrostatic
voltage.
I ~ 77~2 t
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The invention comprises, briefly and in a
preferred embodiment r a photo flash lamp array having a
plurality of flash lamps and th~ir reElectors positioned
in front of a circuit board which is provided with
connector terminals for being connected to a camera
socket and for receiving firing voltage pulses for
causing the lamps to flash. Circuit runs of high
resistance inexpensive material, such as carbon
particles, are carried on the board to connect the
terminals to sequential lamp-flashing circuitry~ One of
the connector terminals is connected in co~non to a
lead-in wire of each of a plurality of lamps by means of
the circuit run material and this common circuit run is
made considerably wider than the other circuit runs. A
wire staple or other connecting means electrically
connects the center region of the common circuit run to
a shield behind the circuit board.
BRIEF DESCRIPTIO~ OF THE DRAWING
-
FIGURE 1 is a perspective view of a multiple
flash lamp array in accordance with the prior art.
FIGURE 2 is a cross-sectional view of FIGURE 1,
taken on the line 2-2 thereof.
FIGURE 3 is a perspective rear view of part of
the prior-art flash array.
FIGURE 4 is an exploded perspective view of the
prior-art flash array.
FIGURE 5 is a perspective view of a flash array
circuit board in accordance with a preferred embodiment
of the invention.
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DESCRIPTION OF THE PREFERRED EMBODIMENT
In Figs. 1 through 4, which show a prior-art
flash array as disclosed in the above-referenced Hanson
patent, a vertically elongated multiple flash lamp unit
17 of ~he planar array type and containing a plurality
of electrically fired fla~h lamps is provided with a
plug-in connector tab 18 at the lower end thereof,
adapted to fit into a socket of a camera or flash
adapter. The lamp array 17 is provided with a second
plug-in connector tab 18' at the top end thereof,
whereby the array 17 is adapted to be attached to the
camera socket in either of two orientations, i.e., with
either the tab 18 or the tab 18' plugged into the
socket. The array 17 is provided with an upper group 21
t5 of elongated flash lamps 22, 23, 24, and 25, lying
horizontally and stacked vertically, and a lower group
26 of flash lamps 27, 28, 29, and 3n, lying horizontally
and stacked vertically, all o-f the lamps being arranyed
in a planar configuration. Reflectors 22', etc~, are
disposed behind and partly around the respective flash
lamps, so tha~ as each lamp is flashed its light is
projected forwardly of the array 17. The lamps are
arranged and connected so that when the array is
connected to a camera by the connector 18, only the
upper group 21 of the lamps will be flashed, and when
the array i5 turned end for end and connected to the
camera by the other connector 18l~ only the then upper
group 26 of lamps w}ll be f}ashed. By this arrangement J
only lamps relatively far from the lens axis are
flashable, thus reducing the well-known undesirable
red-eye effect.
ThP general construction of the array comprises
front and back housing members 36 and 37, which
preferably are made of plastic. In the pre~erred
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embodiment shown, the front and back housing members are
joined together at their sides as indicated by the seam
line 38, and the back housing member 37 includes
integral extensions 39 and 39' at the ends thereof which
partly surround and protec~ the connector tabs 18 and
18' and also ~unction to facili~ate mechanical
attachment to the cam~ra socket. Sandwiched between the
front and back of the housing members 36 and 37, in the
order named, are the flash lamps 22, etc., a unitary
reflector and barrier member 41 (preferably of white
plastic) shaped to provide the inaividual reElectors
22', etc. and barriers 41' between adjacent lamps to
prevent sympathetic flashing of a lamp when an adjacent
lamp is flashed, a printed circuit board 42 provided
with integral connector tabs 18 and 18', and a combined
shield and indicia sheet 43 which may be provided with
instructions~ information, and other indicia such as
flash indicators 47 located behind the respective lamps
and which change color due to heat and/or light
radiation from a flashing lamp, thus indicating at a
glance which of ~he lamps have been flashed and not.
flashed.
The indicia sheet 43 may be of paper or thin
cardboard 44 coated with a layer of metal 45, such as
aluminum, on its ront or inner surface, and provided
with openings where the flash indicators 47 are desired,
and flash indicator material 48, such as a sheet-like
heat sensitive plastic material, for example biaxially
oriented polypropylene, which shrinks or melts when
subjected to heat or radiant energy from an adjacent
fla~hing lamp, is positioned over the o~enings for the
flash indicators 47 thus effectiYely changing the color
at these openings when the adjacent lamps are flashed.
For example, the plastic material can be colored green
7752 1
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on its back side ~y ink or other suitable means r and the
green disappears when the opening becomes a di-fferent
color (dark, for example) when the plastic shrinks or
melts away due to heat from an adjacent flashing lamp.
The front of the plastic (toward the lamps) should be
coated with dark ink so as to absorb heat more readily.
One or more flash indicator sheets 48 may be arranged
over portions of the metal ~oating 45 to cover over all
of the flash indicator openings. Window means 51 in the
form of openings or transparent areas are provided
through the reflector and barrier unit 41 and the
circuit board 42 to facilitate radiation from flashing
lamps reaching the flash indicators 47~ The metal
coating 45 functions as a shield and extends onto
frontwardly bent side portions 49, 50 of the indicia
sheet 43 to provide shieldiny at the sides of the array
and flanking the flash lamps. The rear housing member
37 is transparent (either of clear material or provided
with window openings) to permit viewing of the indicia
on the indicia sheet 43. The front housing member 36 is
transparent at least in front o~ the lamps 22, etc~, to
permit light from flashing lamps to emerge frontwardly
of the array, and may be tinted to alter the color of
light from the flash lamps and also may be provided with
lenses or prisms for controlling the light distrlbution
pattern.
The height and width of the rectangular array are
substantially greater than its thickness, a~d the
heights and widths of the reflector and barrier member
41 and circuit board 4~ are substantially the same as
the interior height and width of the housing members, to
fa~ilitate holding the parts in place.
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The reflector and barrier member 41 is a
one-piece member, pre~erably of molded white plastic
interspersed with titanium dioxide, shaped to provide
the reflectors 22' etc. in the form of planar rear
portions behind the respective lamps, and the tapered
reflector sides 22", etc. between adjacent lamps which
also form the barriers 41' for preventing sympathetic
flashing by which a lamp adjacent to a flashing lamp
could be caused to flash du~ to heat and/or light
radiation from the flashing lamp.
The tab 18, which is integral with the circuit
board 42, is provided with a pair of electrical
terminals 31 and 32, and similarly the tab 18' is
provided with a pair of terminals 31' and 32', for
1-5 contacting terminals of a camera socket for applying
firing voltage pulses to the array. The terminals 31
and 31' are connected together and to a lead-in wire of
each lamp, a~d constitute part of the electrical ground
circuit of the array. Each tab is provided with a third
terminal 33 and 33', respectively, which is connected
respectively to the terminals 31 and 31', as disclosed
in U.S. Patent No. 4,166,287 to Atwood. Alternatively,
these third terminals can be connected to the opposite
group of lamps and circuits as disclosed in U.S. Patent
~5 NoO 3,952,320 to Blount. The terminals 31 and 31' are
- shown as having a lateral "T-bar" configuration for
temporarily shorting the socket terminals while the
array is being plugged in, to dis~harge any residual
voltage charge in the firing pulse source and also ~o
reduce the likelihood of lamps being accidentally
flashed by electrostatic voltage when the array is
handled~ as is disclosed in U.S. Patent No. 3,980,876 to
Cote.
I !77521
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The circuit board 42 has a "printed circuitn
thereon, as will now be described, for causing
sequential ~lashing of the lamps by firing voltage
pulses applied to the terminals 31, 32 or 31', 32'. The
top and bottom halves of the printed circuitry
preferably are reverse mirror images of each other. In
the preferred embodiment shown, a pair of printed
circuit pads 22a' and 22b' are provided on the circuit
board, to which the lead-in wires 22a and 22b of lamp 22
are to be connected. Similarly, circuit pads 23a' and
23b' through 25a' and 25b', and 27a' and 27b' through
30a' and 30b' are provided for connection to the lead-in
wires of the remaining lamps, the numbers and letters in
the circuit pad designations corresponding to those of
the lamp lead-in wire. The circuit pads for the group
21 of lamps are aligned in a row near one edge of the
circuit board~ and the circuit pads for the other group
26 of lamps are aligned in a row near the other edge of
the circuit board, and on the opposite half of the
board. The respective lead-in wires 22a, 22b, etc. of
the lamps may be attached to the connector pads 22a' r
22b', etc. in various ways, such as being ultrasonically
driven into the circuit board and against the
appropriate connector pads as disclosed in U.S. Patent
No. 4,028 r 798 to Bechard et al~ In this technique
openings 22a" and 22b" r etc. are provided through the
circuit board through or adjacent to the connector pads
22a' and 22b', etc. The lead-in wires 22a and 22b, etc.
of the flash lamps are placed through the respective
openings 22a~ and 22b", etc. from the front of the
circuit boardr are laid on the back of the circuit
board r and are driven by ultrasonic drivers into the
board to make electrical and mechanical contact with the
respective circuit pads 22al and 22b', etc. As shown,
~ 1l77521
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the flash lamp lead-in wires emerge from each elongated
bulb at an end thereo.f and with the lamps positioned
horizontally and stacked vertically their lead-in wires
are near a side of the array and are bent approximately
as shown in FIGURE 2 for connection to the respective
adjacent circuit pads~
In accordance with the prior art, as shown in
Fig. 4~ all of the " a"' circuit pads are connected
electrically together and to the common electrical
ground connector terminals 31 and 31', by a circuit run
52 which includes a ground pad area 53 at the center of
the circuit board. The "electrically ~ot" connector
terminal 32 is connected via a circuit run 54 to the
circuit pad 22b' and to a radiation switch terminal 56.
A radiation activated switch 57 is connected across and
between the switch terminal 56 and a switch terminal 58
which connects to the next "hot" lamp circuit pad 23b'.
Similarly, a switch terminal 59 is connected to the lamp
pad 23b', and a radiation activated switch 61 is
connected across and between the terminal 59 and a
switch terminal 62 which is connected to the lamp pad
24b'. A third radiation activated switch 63 is
connected across and between a circuit run terminal 64
connected to pad 24b' and a circuit run terminal 66
connected to the lamp pad 25b'. The radiation activated
switches 57, 61, and 63 are respectively located behind
the lamps 22, 23, and 24, and initially have a high
impedance such as several thousand ohms or over a
million ohms. Window means 71 such as transparent
sections or openings through the back of the
reflector-barrier unit 41 permit light and heat
radiation from the flash lamps, when flashed, to reach
the radiation switches and convert them to zero or low
7752~
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impedance such as a few hundred ohms so as to connect
the "hot" connector terminal 32 to the next lamp to be
flashed. A suitable material for the radiation switches
is silver ox ide dispersed in a binder such as polyvinyl
resin. Another suitable radiation switch material is
disclosed in U.S. Patent No. 3,990~832 to Smialek et al.
Each of these radiation switches, upon receiving heat
and/or light radiation from the adjacent lamp when it is
flashed, changes from an open circuit or high resistance
to a closed circuit or low resi~tance between its switch
terminals on the circuit board.
As ha~ been e~plained, the lower portion of the
circuit board contains a substantially reverse mirror
image of the same circuit shown in the upper part of the
circuit board~ and therefore will not be described in
de~ail. It will be noted that the circuit runs from the
plugged-in terminals 31 and 32 at the lower part of the
circuit board extend upwardly so as to activate the
circuitry in the upper hal of the circuit board.
Similarly, when the unit is turned around and tab 18' is
plugged into a socket, the circuit board tarminals 31'
and 32' will be connected to and activate the lamps
which then will be in the upper half of the Elash unit
17. This accomplishes r as has been stated, the desir-
able characteristic whereby only the group of lamps
relatively farthest away from the lens axis will be
flashed, thereby reducing or eliminating the undesirable
red-eye effect. For ~onvenience in laying out the
circuit board runs, the pads 22a' and 22b' of lamp group
21, and pads 27a' and 27b' Qf lamp group 26, are
relatively reversed with respect to the other pads of
the respective groups.
!~77521
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The circuit on the circuit board 42 functions as
follows. Assuming that none of the four lamps in the
upper half o the unit 17 have been flashed, upon
occurrence of a first firing pulse applied across the
terminals 31, 32, this pulse will be directly applied to
the lead-in wires of the first-connected flash lamp 22,
~hereupon the lamp 22 flashes and becomes an open
circuit between its lead-in wires. Heat and/or light
radiation from the flashing first lamp 22 causes the
adjacent radiation switch 57 to become a closed circuit
(or a low value of resistance), thereby connecting the
circuit board terminal 32 electrically to the lead-in
wire 23b of the second lamp 23. By the time this
occurs, the firing pulse has diminished to a value
insuficient to cause the second lamp 23 to flash. When
the next firing pulse occurs, it is applied to the
lead-in wires of the second lamp 23, via the now closed
radiation switch 57~ whereupon the second lamp 23
flashes, thereby causing radiation switch 61 to assume
zero or low resistance the second lamp 23 now has an
open circuit or high resistance between its lead-in
wires. When the next firing pulse occurs, it is applied
via now closed radiation switches 57 and 61 (in series)
to the third lamp 24, thereby firing the lamp which
becomes an open circuit, and the radiation from it
- causes the radiation switch 63 to become essentially a
closed circuit across its terminals. Thus, the next
firing pulse will be applied, via now closed radiation
switches 57t 610 and 63 (in series3 to the lead-in wires
of the fourth flash lamp 25~ thereupon causing the lamp
to flash. Since this lamp is the last lamp in the
active circuit, it does not matter whether its lead-in
wires are an open or closed circuit after flashing.
Additional flash lamps, radiation switches, and
electrical conductors can be employed, if desired, using
~ ~775~
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the just described principles. When the flash unit is
turned around the other connector tab 18' attached to
the camera socket, the group of lamps that then become
uppermost and r~latively farthest away from the lens
axis will be in an active circuit and will be flashed in
the same manner as has been described. In a preferred
embodiment, the lamps 22, etc., are high voltage types,
requiring about 2000 volts or example, at low current,
for flashing, and ~hey can be fired by impacting ~r
stressing a piezoelectric element in the camera.
In the prior art of FIGURE 4, a wire staple 76 i5
placed through openings 77 through ths circuit board at
the electrical ground pad 53, and its projections at the
rear of the board are curved along the rear surface of
the board and contact against the conductive shield
member 45, thus electrically connecting the shield 45 to -
the electrical ground of the cixcuit, as is disclosed in
U.S. Patent No. 4,104,705 to Levand.
The rear metal shield 45 extends frontwardly to
the front edges of the indicia sheet sides 49 and S0 and
can extend as fa~ frontwardly as permitted by the
housing, and flanks the sides of the flash lamps 22 etc.
to provide effective shielding at the sides oE the
array.
Also, the plastic flash indicator material 48 may
extend alongside the inner surface of the metal shield
45 frontwar~ly extending portions which flank the flash
lamps a sufficient distance so as to provide electrical
insulation between the flash lamp lead-in wires 22a,
22b, etc. and the metal shield 45 in order to avoid
accidental short-circuiting of the "hot" lamp lead-in
wires 22b, etc. to the metal shield 45 which would
~ ~775~1
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prevent prQper functioning o the lamps and the lamp
firing sequencing circuitry.
As can be seen in the prior art construction of
FIGU~E 4, the circuit runs require a considerable amount
5 of circuit-run ink material which preferabl~ contains
silver (which is expensive~ to provide good electrical
conductivity and which, unlike other materials,
maintains good surface contact conductivity even when
the surface becomes oxidized in time due to exposure to
air. Attempts have been made to reduce the cost of the
circuit board by substituting low-cost material, having
substantially higher resistance than metal such as
powdered carbon, for the silver circuit runs. The
carbon particles are carried i~ a liquid binder, such as
acrylic and butyrate resins and glycol ether and ketone
solvents, and applied to the circuit board by
conventional silk-screening technique. Heat may be
applied to hasten evaporation of the binder
vehicle/so1vent, which occurs in about a minute, leaving
the carbon-particle circuit runs adhered to the board
and having a thickness of about l or 2 mils. The
circuit runs are conducti~-e due to the carbon particles
touching one another, and the cost of the carbon circ~lit
run material i5 much less than that of th~ conventional
material containing silver. Although the resistance of
the carbon circuit runs is high compared to that of the
silver runs, the high-voltage types of }amps are flashed
satisfactorily by the firin~ pulses which are high
voltage (2,000 volts for example) and very low current
(not readily measurable), and therefor the resistivity
of the carbon runs does not appreciably impede the flow
of firing pulses from the connectors 18, 18' to the
lamps 22, etc. Powdered graphite, which comprises
carbon particles having flat flake-like shapes, can be
used for the circuit runs instead of or with
conventional carbon particles having spherical-like
shapes, and has lowered resistance due to better
electrical contact between the particles~
~ ~77521
--14-- LD 8546
As is explained above, the relatively high
resistance of carbon circuit runs is not a detriment to
firing the flash lamp~ with firing pulses: however, it
has been ~ound that flash arrays having carbon circuit
runs instead of silver circuit runs have a greaker
tendency for accidental flashing of lamps by
electrostatic charges, such as can occur when a charged
person touches the common connector terminal 31 or 31'.
It is the purpose of the shield 45 to reduce the
likelihood of electrostatic flashing of the lamps. As
is disclosed in U.S. patent No. 4,019,043 to Blount, the
shield 45 is electrically connected to the common
circuit run 52, and hence to the end connector terminals
31, 31', by a contact member such as an eyelet. In the
present drawing, this contact member is the wire staple
76. If an electrostatically charged person should touch
one of the terminals 31 or 31', the charge is carried to
the shield 45 and dissipates into surrounding space and
to earth ground, and thus the charge is prevented from
reaching the lamps and their sequential flashing
circuitry so as to cause lamps to flash. When carbo~ is
used for the circuit runs~ its relatively high
resistance in the ground circuit run is believed to
reduce the effectiveness of carrying electrostatic
charges to the shield, and as a result some o~ the
charge is coupled, via stray capacitance, to lamps and
firing circuitry thus increasing the chances of
accidental flashing of lamps.
In accordance with the present invention, the
circuit board 42' of FIGURE 5 is substituted for the
circuit board 42 in the array of FIGURES 1-4. The
circuit board of FIG~RE 5 is similar to that in FIGURE 4
I ~775~1
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except that the circuit runs comprise deposited carbon
particles, and the common "ground" circuit run 52, which
extends from one end to the other o~ the circuit board,
is made wider than each of the "hot" circuit runs 54,
and preferably is wide enough to cover a major portion
of the area of the circuit board. Also, at the
connector tabs 18 and 18', the carbon material fills the
spaces between the FIG. 4 terminals 31 and 33, and 31'
and 33', thus~combining these terminals into single wide
terminals. The result is a decrease in electrical
resistance between each of the common terminals 31 and
31' and the wire staple 76 or other device which
connects the common circuit run 52 to the shield 45, so
that an electrostatic charge applied to these terminals
as described above, will more readily be carried to the
shield and dissipated instead of reaching lamps and
flashing them~ The wide common circuit run 52 also
performs an additional advantagious function of acting
as a second shield behind the flash lamps, which in
combination with the shield 45, forms a double shield
behind the lamps which further reduces the liklihood of
accidental flashing of lamps when the rear plastic cover
37 becomes electrostatically charged due to handling by
a charged person.
While preferred embodiments of the invention have
been shown and described, various other embodiments and
modifications thereof will become apparent to persons
skilled in the art, and will fall within the scope of
the invention as defined in the following claims. For
example, other means connecting the common circuit run
to the shield than staples can be used, such as rivets f
eyelets, wires, conductive ink, and even direct physical
contact. It is intended to limit the present invention~
therefore, only to the scope of said following claims.
