Multilamp Photoflash Unit With Circuit Crossover

This invention relates to multilamp photoflash units and, more particularly, to an improved photoflash unit having a circuit cross-over provision for spaced apart conductor runs on a printed circuit board supporting on array of flashlamps within the unit housing.

Numerous multilamp arrangements with various types of sequencing circuits have been described in the prior art, particularly in the past few years. A currently marketed photoflash unit (described in U.S. Pat. Nos. 3,894,226 and 4,017,728 and referred to as flipflash) employs high voltage type lamps adapted to be ignited sequentially by successively applied high voltage firing pulses from a source such as a camera-shutter-actuated piezoelectric current. The flipflash unit comprises an elongated planar array of eight high voltage type flashlamps mounted on a printed circuit board with an array of respectively associated reflectors disposed therebetween. The lamps are arranged in two groups of four disposed on the upper and lower halves respectively of the rectangular-shaped circuit board. A set of terminal contacts at the lower end of the unit is provided for activation of the upper group of lamps, while a set of terminal contacts at the top of the unit is operatively associated with the lower group of lamps. The application of successive high voltage pulses (e.g. 2000 to 4000 volts from, say, a piezoelectric source controlled by the shutter of a camera in which the array is inserted) to the terminal contact at the lower end of the unit causes the four lamps at the upper half of the array to be sequentially ignited. The array may then be turned end for end and again inserted into the camera in order to flash the remaining four lamps. In this manner one group of lamps (or half of the array) functions as a flash extender for the other group of lamps so that only the group of lamps relatively farther from the camera lens axis may be flashed. The purpose of such an arrangement is to position the "active"group of flashlamps farther above the camera lens in order to reduce the possibility of a "red-dye" effect that causes the pupils of a person's eyes to appear red or pink in flash pictures taken when the flashlamp is close to a camera lens.

The flipflash circuit board comprises an insulating sheet of plastic having a pattern of conductive circuit runs, including the terminal contacts, on one surface. The flashlamp lead-in wires are electrically connected to the circuit runs by means of eyelets secured to the circuit board and crimped to the lead-in wires. The circuitry on the board includes six printed, normally open, connect switches that chemically change from high to low resistance so as to become electrically conducting after exposure to the radiant energy from an ignited flashlamp operatively associated therewith. The purpose of these switches is to provide lamp sequencing and one-at-a-time flashing. The four lamps of each group are arranged in a parallel circuit, with three of the four lamps being connected in series with respective thermal connect switches. The circuitry on the board further includes a common circuit conductor run which is connected to one lead-in wire of each of the flashlamps in both groups and extends continuously from one end of the circuit board to the other between the common terminal contact at each end of the unit. Initially, only the first of the group of four lamps is connected directly to the high voltage pulse source. When this first lamp flashes, it causes its associated thermal connect switch (which is series connected with the next or second lamp) to become permanently conductive. Because of this action, the second lamp of the group of four is connected to the pulse source. This sequence of events is repeated until all four lamps have been flashed.

The overall construction of the flipflash unit comprises front and back plastic housing members with interlocking means for providing a unitary structure. The front housing member is a rectangular concavity, and the back housing is substantially flat. Sandwiched between the front and back housing members, in the order named, are the flashlamps, a unitary member, preferably of aluminum-coated plastic, shaped to provide the eight individual reflectors of the array, an insulating sheet, a printed circuit board, and an indicia sheet, which is provided with information trademarks and flash indicators located behind the representative lamps and which change color due to heat and/or light radiation from a flashing lamp, thus indicating at a glance which of the lamps have been flashed and not flashed. Each of the individual reflectors has a concave (generally parabolic) surface with the lamps being disposed within this concavity; the rear srurface of the reflector has holes or slots to permit light and heat radiation to pass through for actuating circuit board switches and flash indicators. In order to provide electrostatic shielding for the lamps and circuitry, the reflector member is rendered electrically conductive by a reflective metalized coating thereon, and this coating is electrically connected to the common circuit conductor run on the printed circuit board. Further, a metal foil is laminated on the indicia sheet and also connected to this common conductor run of the circuit board.

U.S. Pat. No. 4,164,007 describes an improved multilamp photoflash unit which more efficiently utilizes a given housing volume and thereby reduces the cost of the unit per flashlamp contained therein. More specifically, a compact lamp arrangement is provided whereby additional lamps are contained in a given volume while maintaining light output performance requirements. In a particular embodiment described, ten lamps are provided in a housing having the same dimensions as the above-discussed eight-lamp flipflash unit. This greater compactness is provided by arranging the planar array of lamps in two parallel columns with the tubular envelopes horizontally disposed and with the lamps of one column staggered with respect to the others so that the bases are interdigitated. A pair of reflector panels are aligned with the two columns of lamps and are arranged to overlie the lamp lead-in wires and bases.

A copending patent application Ser. No. 072,251, filed Sept. 4, 1979, assigned to the present assignee, describes a more compact, cost-efficient photoflash unit construction comprising a linear array of electrically ignitable flashlamps mounted on a printed circuit board in the form of an elongated strip. The printed circuit strip is located within the longitudinal channel of an elongated housing member having reflective surfaces adjacent to the lamps. A light-transmitting cover panel is attached to the front of the housing member to enclose the flashlamps. The lamps have substantially tubular envelopes and are positioned extremely close to one another with their longitudinal axes substantially parallel to the surface of the printed circuit strip and in substantially coaxial alignment. Typically, the diameter of the lamps, the width of the printed circuit strip, and the width of the channel in the housing member are nearly equal. In order to provide protection against the red-eye effect, a double-ended linear array is described which operates in similar fashion to the aforementioned flipflash. In one specific embodiment, three lamps mounted in the upper half of the printed circuit strip are controlled by a pair of contact terminals at the lower end of the unit, while three lamps in the lower half of the unit are controlled by contact terminals at the top end of the unit. One of the contact terminals for controlling a group of lamps is connected in common to a lead-in wire of each of the lamps of the group, while the other contact is a "hot", or signal, terminal coupled through switching circuitry to the other lead-in wire of each of the lamps. Accordingly, in order to provide an interconnection between the signal terminals at each end of the unit and the respective switching circuitry controlled thereby on opposite halves of the printed circuit strip, respective signal conductor runs must be extended through the respectively inactive halves of the circuit strip. The interconnecting conductor runs from the common terminal contacts are disposed along the outer sides of the circuit-containing surface of the printed circuit board. More specifically, the common circuit run on the bottom half of the circuit strip is located on the opposite side of the circuit board surface from the common circuit run on the top half of the circuit strip. As a result, a crossover, or side-to-side connection of the common circuit run is required in order to connect the common terminal at one end of the printed circuit strip with the common circuit conductor run connected to lamp leads in the opposite half of the circuit strip. Such a problem is created by the severe crowding of the conductive paths of this extremely compact unit. The use of printed conductor runs on both sides of the circuit strip with conventional through-connections introduces undesirable cost, e.g. two circuit screening operations are needed together with eyelets, plated-through holes, or the like. A minimum inter-run spacing of about 1.5 millimeters is necessary in order to prevent failure, i.e. promoting electrical sparkover from one run to another at the high voltages used (e.g. 2,000 volts or more).

Accordingly, it is an object of the present invention to provide an improved multilamp photoflash unit which is significantly more compact and economically includes a crossover interconnection for spaced printed circuit conductor runs.

A principal object is to economically provide means for electrically interconnecting a pair of spaced apart conductor runs on a printed circuit board in a multilamp photoflash unit having a simplified, more cost-efficient construction which is significantly more compact.

These and other objects, advantages and features are attained in a multilamp photoflash unit comprising a printed circuit board having lamp firing circuitry on a surface thereof to which the lead-in wires of an array of flashlamps are connected. The circuitry on the printed circuit board includes first and second conductor runs which are spaced apart from each other. The means for electrically interconnecting the first and second conductor runs comprises a staple of conductive material having a pair of legs extending through the printed circuit board and having a center region positioned on the opposite side of the circuit board from the surface carrying the conductor runs. The staple legs are bent over the conductor-carrying surface of the circuit board so as to secure the staple to the board with each of the legs of the staple being in contact with a respective one of the first and second conductor runs. In this manner, the staple functions as an interconnecting jumper, or crossover connection, between the spaced apart first and second conductor runs.

Preferably the staple is comprised of a non-corrosive material, such as Niron (nickel-iron alloys of Wilbur B. Driver Co.), as rusting of the staple under humid conditions, or the like, can cause the loss of electrical contact between the staple and the conductor runs. The legs of the staple can be bent inwardly toward each other or outwardly away from each other and parallel to the edges of the circuit board. The latter means for securing the staple is preferred because it provides more clearance between the two circuit runs being interconnected and, also, has been found to provide better electrical contact.

In a preferred embodiment, the circuit board is in the form of an elongated strip, and the flashlamps are divided into first and second groups of two or more lamps each disposed on respectively opposite halves of the printed circuit strip over the surface containing circuitry. The circuit board and lamps are disposed within the longitudinal channel of an elongated housing member having reflective surfaces adjacent to the flashlamps. The first and second conductor runs comprise a common circuit with the first run connected electrically to one lead-in wire of each of the first group of lamps and the second common circuit run being connected electrically to one lead-in wire of each of the second group of lamps. The printed circuit strip includes first and second connector terminal means at respectively opposite ends, with the first connector-terminal being located on the half of the circuit strip containing the first group of lamps and separated thereby from the second group of lamps, and the second connector-terminal being located on the half of the circuit strip containing the second group of lamps and separated thereby from the first group of lamps. The first common circuit run extends to the first connector-terminal means. A portion of the circuitry couples the first connector-terminal means to each lamp of the second group of lamps and another portion of the circuitry couples the second connector-terminal means to each lamp of the first group of lamps. The first and second groups of lamps are disposed in a linear array, and the channel in the housing member has a cross-section which is substantially semi-rectangular. A continuous coating of conductive reflective material may cover the rear wall and opposite sidewalls of the semi-rectangular channel, and the first and second common circuit runs are respectively disposed parallel and closer to opposite edges of the printed circuit strip facing opposite sidewalls of the channel. The common circuit coupling portion of the circuitry includes the staple which is secured to the circuit board with its center region disposed between the side of the circuit board opposite that carrying the conductor runs and the rear wall of the semi-rectangular channel. In this manner, the center region of the staple can be placed in contact with the conductively coated rear wall of the channel whereby the first and second circuit runs are electrically connected to the conductive reflective coating on the channel walls.

The first and second common circuit conductor runs have respective spaced apart terminations about the midportion of the circuit strip, and the legs of the staple are bent over the conductor-carryiing surface of the circuit strip and in contact with respective ones of the terminations of the first and second runs. The circuitry further includes a third conductor run which is connected electrically to the noncommon-connected lead-in wire of one of the lamps and located between the spaced-apart terminations of the first and second runs.

Preferably the housing member is formed of an insulating material and further includes a plurality of segments of reflector cavities formed on opposite sides of the channel, and the unit further includes a light-transmitting cover panel attached to the housing member and enclosing the flashlamps therein. The required crossover connection in this compact array is effectively and inexpensively achieved by use of the conductive, non-corrosive staple as an active, current-carrying segment of the circuitry for carrying lamp-flashing current pulses from the camera socket interface to the lamps in the far end of the array. Wire staples are inexpensive and readily available and provide a simple, rapid manner of implementing circuit run jumpers on circuit boards. No soldering or other operations are required once the staple is installed on the board.

This invention will be more fully described hereinafter in conjunction with the accompanying drawings, in which:

FIG. 1 is a front elevation of a multilamp photoflash unit in accordance with the invention, with the camera on which it is mounted shown in phantom;

FIG. 2 is an exploded perspective view of the photoflash unit of FIG. 1;

FIG. 3 is an enlarged cross-sectional view taken along 3--3 of FIG. 1;

FIG. 4 is an enlarged fragmentary front view of the midportion of the printed circuit strip of the unit of FIGS. 1-3 particularly showing one embodiment of a staple attachment to the circuit strip;

FIG. 5 is a cross-sectional view taken along 5--5 of FIG. 4; and

FIG. 6 is an enlarged fragmentary front view of the midportion of the printed circuit strip of the unit of FIGS. 1-3 particularly showing an alternative embodiment of a staple attachment to the circuit strip.

FIGS. 1 and 2 illustrate a multilamp photoflash unit 10 similar to that described in the aforementioned copending application Ser. No. 072,251, filed Sept. 4, 1979. It comprises a linear array of six flashlamps 11-13 and 14-16 mounted on a printed circuit board 18 in the form of an elongated strip. Each of the lamps has a pair of lead-in wires 11a, 11b, etc. connected to the printed circuitry on strip 18. For example, the lead-in wires 11a, 11b, etc., may be soldered to respective connector pads 11a', 11b', etc., forming portions of the conductive circuit runs on strip 18. Each of the lamps 11, etc. has a tubular light-transmitting glass envelope having a press-seal base at one end through which the lead-in wires emerge, and an exhaust tip at the other end. The envelope is filled with a quantity of filamentary combustible material, such as shredded zirconium, and a combustion-supporting gas, such as oxygen. The ignition means within the lamp envelope may comprise, in the case of a low voltage source, a filament connected across the inner ends of the lead-in wires with beads of primer material disposed about the junctions of the lead-in wires and filament. In the case of a high voltage power source, for which the illustrated embodiment is particularly intended, the ignition structure may comprise a primer bridge or a spark gap type construction. For example, a particularly suitable high voltage type flashlamp suitable for use in the linear array according to the present invention is described in U.S. Pat. No. 4,059,389, wherein the ignition structure comprises a pair of spaced apart lead-in wires with spherically shaped terminations, a glass frit coating over lead-in wires and a coating of primer material over the frit-coated terminations. The primer may bridge the wire terminations or comprise separate spaced apart coatings on the respective terminations, with the filamentary combustible being in contact with both terminations to provide a conducting path therebetween.

When the flashlamps are mounted and positioned on circuit strip 18, the lead-in wires 11a, 11b, etc., are bent at a right angle, as illustrated, so that all of the tubular envelopes of the lamps are positioned with the longitudinal axes thereof substantially parallel to the surface of printed circuit strip 18 and arranged in a substantially coaxial alignment along a common longitudinal axis CA. Further, as described in copending application Ser. No. 072,526, filed Sept. 4, 1979, assigned to the present assignee, the three lamps 11-13 at the top half of the array are inverted with respect to the three lamps 14-16 at the bottom half of the array.

Referring to FIG. 2, the circuit strip 18 has a "printed circuit" thereon for causing sequential flashing of the lamps by applied firing voltage pulses. In this particular embodiment, essentially the entire printed circuit is provided on one surface of the strip 18, namely, the obverse side of the strip over which the flashlamps are positioned. The substrate of strip 18 comprises an insulating material, such as polystyrene, or phenolic, etc., and the pattern of conductor runs may be provided on the surface thereof by means such as silk screening, chemical etching of a copper cladding, etc. Each end of the circuit strip 18 functions as a connector tab, denoted as 18a and 18b respectively. The tab 18a is provided with a pair of electrical terminals 20 and 22, and similarly, the tab 18b is provided with a pair of terminals 20' and 22' for contacting terminals of a camera socket for applying firing voltage pulses to the array. As will be described in more detail hereinafter, the terminal 20 forms part of and is connected to a common circuit conductor run 24 which is disposed parallel to the right-hand edge of the circuit strip (as viewed in FIG. 2) and connected electrically to one lead-in wire of each of the flashlamps 14-16, and the terminal 20' forms part of and is connected to a common circuit conductor run 25 which is disposed parallel to the left-hand edge of the circuit strip and connected electrically to one lead-in wire of each of the flashlamps 11-13.

The terminations of conductor runs 24 and 25 are spaced apart at the midportion of circuit strip 18 because of other circuit runs crowded therebetween; in accordance with the present invention, however, the runs 24 and 25 are interconnected by a crossover, or jumper, interconnection means to be described in detail hereinafter. As a result, terminals 20 and 20' function as part of a "ground" circuit and are shown as having an enlarged configuration for reducing the likelihood of lamps being accidentally flashed by electrostatic voltage when the array is handled.

The circuit strip-lamp assembly, which forms the functional core of the unit 10, is enclosed in a comparatively simple and compact housing construction of a cost-efficient and versatile design. More specifically, the unit enclosure comprises just two components, namely, a rear housing member 26 and a light-transmitting cover panel 28. Referring also to FIG. 3, housing member 26 has an elongated configuration and includes a longitudinal channel 30 which has a cross-section which is substantially semi-rectangular. The circuit strip-lamp assembly is located within channel 30, and cover panel 28 is attached to the front of the housing 26 so as to enclose the lamps. As illustrated in FIG. 1, the ends of tabs, 18a and 18b of the circuit strip extend beyond the opposite ends of the elongated cover panel 28 to expose the terminals 20, 22 and 20', 22', thereon for connection to a camera.

The rear housing member 26 further includes outer flanges 32 and 34 which adjoin the opposite sidewalls 36 and 38, respectively, of the semi-rectangular channel. Formed in these outer flanges are a plurality of symmetrical segments of parabolic reflector cavities, with each pair of reflector cavity segments 11', 11", etc., on opposite sides of the channel 30 being associated with a respective one of the flashlamps 11, etc. Housing member 26 is molded of an insulating plastic material, such as polystyrene, but reflective surfaces are provided adjacent to all the flashlamps by covering all of the surfaces of channel 30 (i.e., sidewalls 36 and 38 and rear wall 40) and the surfaces of the outer flanges 32 and 34 which face the cover panel, including the parabolic reflector cavity segments 11', 11", etc., with a continuous coating of conductive reflective material 42. For example, the channel and front surfaces of the flanges may be metalized such as by an aluminum vacuum deposition process. In this manner, member 26 integrally functions as a compact, cost-efficient, multi-cavity reflector member in addition to functioning as a rear housing enclosure. It will be noted that the lamp-carrying terminal strip is located substantially internal to this reflector member. Further, referring particularly to FIGS. 1 and 3, it will also be noted that the common longitudinal axis CA of the linear array of flashlamps 11, etc., is substantially parallel to the longitudinal axes of printed circuit strip 18 and channel 30 and lies in a plane a-a which symmetrically intersects the parabolic reflector cavity segments 11', 11", etc., on opposite sides of the channel. Hence, portions of the reflector cavities and sidewall reflective surfaces are located behind the longitudinal center line of the lamps so that as each lamp is flashed, light is projected forwardly of the array.

The housing member further includes integral extensions 47 and 47' at the opposite ends thereof which partly surround and protect the extending connector tabs 18a and 18b of the printed circuit strip 18, exposing the terminals thereon, and also function to facilitate mechanical attachment to the camera socket. The printed circuit strip 18 may be secured in channel 30 by means such as providing an interference fit with walls 36 and 38 or by applying a cement between the back of the strip 18 and the rear channel wall 40 (FIG. 3).

The light-transmitting cover panel 28 basically comprises a planar strip of clear plastic material, such as polystyrene, and may be attached to the plastic rear housing member 26 by conventional methods, such as the use of cement or ultrasonic welding about the periphery. Improved structural rigidity and cost-efficiency, however, are provided by a preferred method of attachment described in copending application Ser. No. 072,529 filed Sept. 4, 1979, assigned to the present assignee. Referring to FIGS. 1 and 2, the cover panel molding includes four rectangular corner posts 70 which fit into corresponding slots 72 in the housing member flanges and straddle respective ends thereof. These corner posts grip the sides of housing member 26 on the outside and are ultrasonically welded thereto. This secures the ends of the panel and prevents spreading of the respective ends of the housing. Along each side of the midportion of the cover are provided four cylindrical posts 74 (a total of eight) which fit into corresponding holes 76 in the rear housing. Ultrasonically heated and pressure-formed rivet heads (not shown) are formed on the ends of these posts to secure the longitudinal edges of the cover to the housing. Further, cover panel 28 includes a transverse web 78 which projects from the center thereof and fits within slots 80 in the sidewalls 36 and 38 of the housing channel 30. Web 78 thereby bridges the housing channel to provide oppositely directed forces with respect to the four corner posts 70 so as to prevent collapse of the central portion of the cover panel and assure a snug fit. Ultrasonic welding is also employed on each side of the web 78 which engages a slot 80.

As described in copending application Ser. No. 072,534 filed, assigned to the present assignee, the integral transverse web 78 of cover 28 also provides a light-attenuating partition between the tips of lamps 11 and 14 to prevent sympathetic flashing. Additional transverse webs 82 of reduced size are also provided as integral parts of cover 28 to prevent sympathetic flashing between the remainder of the lamps.

When fully assembled, the completed photoflash unit according to the invention is provided with a plug-in connector tab 18a at the lower end thereof which is adapted to fit into a camera or flash adapter. A second plug-in connector tab 18b is provided at the top end of the unit whereby the array is adapted to be attached to the camera socket in either of two orientations, i.e. with either the tab 18a or 18b plugged into the socket. The lamps are arranged in two groups of three disposed on the upper and lower halves, respectively, of the elongated linear array. Upper group 57 comprises lamps 11-13, and lower group 58 includes lamps 14-16; the reflector cavity segments 11', 11", etc., along with the reflective channel sidewalls, are associated with the respective lamps so that as each lamp is flashed, light is projected forwardly of the array. The lamps are arranged and connected so that when the array is connected to a camera by the connector tab 18a (such as illustrated in FIG. 1 for the case of camera 60 shown in phantom) only the upper group 57 of the lamps will be flashed, and when the array is turned end for end and connected to the camera by the other connector tab 18b, only the then upper group 58 of lamps will be flashed. By this arrangement, only lamps relatively far from the camera lens axis are flashable, thus reducing the undesirable red-eye effect.

Referring to FIG. 2, the circuit board 18 has a "printed circuit" thereon for causing sequential flashing of the lamps by firing voltage pulses applied to the terminals 20, 22, 20', 22'. The top and bottom of the printed circuitry preferably are reverse mirror images of each other. The circuit located on the upper half of the circuit strip 18 and activated by the pair of terminals 20 and 22 includes three lamps 11-13 arranged in parallel across the input terminals. The circuit also includes two normally open (N/O) radiant-energy-activated connect switches 61 and 62 for providing sequential flashing of the lamps 11-13 in response to firing pulses successively applied to the input terminals 20 and 22. Each N/O connecting switch is responsive to the flashing of an associated lamp to form a closed circuit condition.

Terminal 22 is part of a "hot" or signal circuit conductor run 65 that extends upwardly through the lower half of the circuit strip 18 and terminates at a lead-in wire of lamp 11 and one terminal of the N/O switch 61 in the upper half of the circuit strip. The other side of switch 61 is connected to a lead-in wire of lamp 12 and to one terminal of N/O switch 62 via circuit run 66. Circuit run 67 then connects the other terminal or switch 62 to a lead-in wire of lamp 13.

On the other half of the circuit strip, terminal 22' is part of a signal circuit conductor run 68 that extends downwardly through the upper half of circuit strip 18 and terminates at a lead-in wire of lamp 14. The remainder of the circuitry in the lower half of the circuit strip is similar to that described above for the upper half of the circuit strip.

As described hereinbefore, the terminals 20 and 20' comprise integral portions of respective common circuit conductor runs 24 and 25. These common circuit runs respectively terminate at conductor termination pads 63 and 64, respectively, near the midportion of the circuit strip and are spaced apart thereat to provide clearance for the signal circuit conductor runs 65 and 68 to extend therebetween, as shown in FIGS. 2, 4 and 6. To enable activation of lamp group 57 by an input pulse applied across terminals 20 and 22, some means must be provided for interconnecting common run 24 with the spaced apart common run 25 (connected to a terminal of each of the lamps 11-13) without interferring with the signal conductor runs 65 and 68. The same interconnecting means is necessary to enable activation of lamp group 58 from terminals 20' and 22', one terminal of each of the lamps 14-16 being connected to run 24.

In accordance with the present invention, this common circuit crossover between the spaced-apart conductor runs 24 and 25 is accomplished by use of a common wire staple 83 as a jumper therebetween. Referring particularly to FIGS. 4 and 5, a wire staple 83, formed of electrically conductive material, is inserted through two holes 84 and 85 (FIG. 5) in circuit board 18 from the back side thereof, i.e., the side with no conductor runs, and crimped over on the conductor carrying surface. More specifically, the staple 83 has a pair of legs 83a and 83b which extend through the circuit board and a center region 83c which is positioned on the opposite side of the circuit board from the surface containing the conductor runs. The staple legs 83a and 83b are bent over the conductor-carrying surface of the circuit board so as to secure the staple to the circuit board with each of the legs being in contact with a respective one of the conductive pads 63 and 64 of the runs 24 and 25. In the embodiment of FIGS. 4 and 5, the staple legs 83a and 83b are bent inwardly toward each other with the bent over portion of leg 83a in contact with the common run termination pad 63 and leg 83b in contact with the conductor run termination pad 64.

In an alternative embodiment, illustrated in FIG. 6, the staple legs 83a and 83b are bent outwardly away from each other and parallel to the edges of the circuit strip. The legs bent in this manner continue to be disposed over the conductor-carrying surface of the circuit strip and in contact respectively with the common run termination pads 63 and 64. The configuration of FIG. 6 is particularly advantageous because it provides additional clearance between the common circuit run terminations and has also been found to provide better electrical contact.

The wire staple 83 can be installed as previously stated, or it can be force-driven through the board and the circuit if the board is made of a suitable material. In one specific implementation, the wire used to form the staple was 0.020 inch diameter Niron, a class of nickel-iron alloys obtainable from Wilber B. Driver Co. This wire is used, as can other wires with similar properties, because it is resistant to corrosion and rusting, which can cause the loss of electrical contact between the staple and the conductor pad 63 or 64. Flat wire of different dimensions can also be used.

When the circuit strip 18, with staple 83 attached, is inserted in channel 30 of the housing member 26, the center region 83c of the staple is disposed between the back of the circuit strip 18 and the conductive coating 42 on the rear wall 40 of the longitudinal channel. Accordingly, the center region 83c of the staple is in contact with the continuous coating of conductive reflective material 42 on the channel wall, whereby conductor runs 24 and 25 are electrically connected to the wall coating 42. Further, by virtue of staple 83, a "ground" circuit is provided by runs 24 and 25, and the staple, which makes contact with each of the lamps 11-16.

Returning now to the description of the printed circuit configuration, the first lamp to be fired, namely, lamp 11, is connected directly across the input terminals 20 and 22. The N/O connect switches 61 and 62 are series connected in that order with lamp 13, which is the third and last lamp to be fired, across the input terminals 20 and 22. And, the second lamp to be fired (lamp 12) is series connected with the N/O switch 61.

The radiant-energy-activated N/O connect switches 61 and 62 are in contact with and bridge across the circuit runs that are connected to them. The material for the connect switch is selected to be of the type initially having an open circuit or high resistance, the resistance thereof becoming nearly zero or a lower value when the material receives radiation in the form of heat and/or light from a respective adjacent lamp, upon the lamp being flashed. For this purpose, each of the connect switches is respectively positioned behind and near to an associated flashlamp. More specifically, switch 61 is positioned behind lamp 11, and switch 62 is positioned behind lamp 12.

The high resistance paste used to make switches 61 and 62 may comprise a known mixture of silver compound and a binder. According to a preferred embodiment, however, the material comprises a silver compound such as silver carbonate, a binder such as polystyrene resin, a large proportion of electrically non-conductive inert particulate solids, such as titanium dioxide, and a protective oxidizing agent such as barium chromate. For example, as described in a copending application Ser. No. 021,398, filed Mar. 19, 1979, and assigned to the present assignee, the dried composition of a specific silk screenable high resistance material comprises 67.43% silver carbonate, 22.48% titanium dioxide, 8.99% glass beads, 0.11% barium chromate, 0.07% lecithin as a wetting agent, and 0.91% polystyrene resin as a binder. The barium chromate was included to enhance environmental stability, as described in U.S. Pat. No. 4,087,233. This mixture is made into a paste by ball milling in a suitable solvent such as butyl cellosolve acetate. The solids content may be adjusted to suit the method of switch application. For silk screening over a circuit strip, it is preferred to adjust the solids content to about 74%.

The circuit on the circuit strip 18 functions as follows. Assuming that none of the three lamps on the upper half of the unit have been flashed, upon occurrence of the first firing pulse applied across the terminals 20 and 22, this pulse will be directly applied (via run 65 and the combination of runs 24, 25 and staple 83) to the lead-in wires of the first-connected flashlamp 11, whereupon lamp 11 flashes and becomes an open circuit between its lead-in wires. Heat and/or light radiation from the flashing first lamp 11 is operative to activate the N/O connect switch 61. As a result, the radiation causes the normally open connect switch 61 to become a closed circuit (or a low value or resistance), thereby connecting the circuit strip terminal 22 electrically to the second lamp 12 via circuit run 66. By the time this occurs, the firing pulse has diminished to a value insufficient to cause the second lamp 12 to flash. When the next firing pulse occurs, it is applied to the lead-in wires of the second lamp 12 via the now closed connect switch 61, whereupon the second lamp 12 flashes and becomes an open circuit between its lead-in wires, with the lamp radiation causing the connect switch 62 to assume a near zero or low resistance. When the next firing pulse occurs, it is applied via the now closed connect switches 61 and 62 to the lead-in wires of the third flashlamp 13, 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. When the flash unit is turned around and the other connector tab 18b attached to the camera socket, the group 58 of lamps that then becomes upper most and farthest away from the camera lens will be in the active circuit and will be flashed in the same manner as has been described. In a preferred embodiment, the lamps 11, etc., are high voltage types requiring about 2,000 volts, for example, at low current for flashing, and they can be fired by impacting or stressing a piezoelectric element in the camera.

The high degree of electrical sensitivity needed in high voltage flashlamps gives rise to distinct problems of inadvertent flashing during handling of the array package. Any static charges on equipment or personnel can cause the lamp to flash. Accordingly, as described in the aforementioned copending application Ser. No. 072,251, filed Sept. 4, 1979), electrostatic protection is provided by the rear housing member 26 in a cost-efficient manner by electrically connecting the conductive coating 42 to the common circuit conductor. By virtue of the present invention, this connection is automatically provided by staple 83, which contacts both the coated channel rear wall and common circuit runs 24 and 25. In this manner, continuous conductive surfaces on rear wall 40 and sidewalls 36 and 38 of channel 30, and on the reflector cavities and front faces of outer flanges 32 and 34, provide a protective electrostatic shield about three sides of the sensitive circuit strip 18 and the lamps 11-16 mounted thereon.

Protection against electrostatic charges about the front face of the unit is provided in a manner following the techniques of U.S. Pat. No. 4,113,424. Cover panel 28 is provided with eight openings 86 distributed throughout the length thereof, as illustrated, and housing member 26 further includes eight metal-coated posts, or projections, 88 which respectively fit into the front face openings 86. Preferably, the conductive reflector projections protrude through the openings 86 in the cover panel beyond the exterior surface thereof, as shown in FIG. 3, so as to assure electrical contact with any charged object such as a user's hand, which may touch the array housing.

As illustrated in FIGS. 1 and 2, projections 88 are symmetrically disposed on the front face of the housing flanges 32 and 34 between reflector cavity segments 11', 11" and 12', 12"; 12', 12" and 13', 13"; 14', 14" and 15', 15", 15" and 16', 16". These projections 88 are integral molded portions of the insulating plastic material of housing 26 which are covered with the continuous conductive reflective coating 42. Accordingly, the conductive projections 88 are connected to the common circuit conductors 24 and 25 via the staple 83.

Although the invention has been described with respect to a specific embodiment, it will be appreciated that modifications and changes may be made by those skilled in the art without departing from the true spirit and scope of the invention. For example, the construction is not limited to linear high voltage arrays. The array may be single ended, with a connector on only one end; the lamps may all be oriented in one direction; and the number of lamps may vary. For example, a higher output lamp array of the double ended type may comprise two lamps of much larger volume positioned in each of the upper and lower groups housed in a package of slightly larger dimensions.