Patent Publication Number: US-3880572-A

Title: Piezoelectric flash lamp ignition

Description:
United States Patent 1 1 Haugsjaa et al.  
 [ 1 PIEZOELECTRIC FLASH LAMP IGNITION [75] Inventors: Paul 0. Haugsjaa, Acton; Daniel C.  
 Casella, South Hamilton. both of Mass.  
 [73] Assignee: GTE&#39;Laboratories Incorporated,  
 Waltham, Mass.  
 [22] Filed: June 17, 1974 [21] Appl. No.: 479,701  
  Related U.S. Application Data [63] Continuation-impart of Ser. No. 330,557, Feb. 8,  
 1973. abandoned.  
 [52] U.S. Cl. 431/98; 310/87, 317/D1G. 11; 431/255 [51] Int. Cl ..H01v 7/00 [58] Field of Search. 431/98, 255; 317/81, DIG. 11; 310/83. 8.7; 240/].3; 354/135 [56] References Cited UNITED STATES PATENTS 2,972,937 2/1961 Suits 431/255 X 3.585.417 6/1971 Hclfen 431/255 X 3.732.058 5/1973 Ort et a1. 3.771.943 11/1973 Schlamp 431/255 Iv (Mk R17 Ml/fl&#39;fl [451 Apr. 29, 1975 FOREIGN PATENTS OR APPLICATIONS l,186 143 4/1970 United Kingdom 310/81 Primary Examiner-William F. ODea Assistant Examiner-Harold Joyce Attorney, Agent, or Firmlrving M. Kriegsman; Bernard L. Sweeney 1 1 ABSTRACT Aphotographic flash lamp igniter utilizing piezoelectric elements as high voltage generating means comprisises two parallel piezoelectric elements, impact caps and mechanical linkage. ln synchronization with the shutter of a camera, striking hammers hit two impact caps which activate two piezoelectric elements arranged in parallel. The electrical energy created by the piezoelectric crystals is transferred efficiently to ignite a photographic flash lamp electrically connected across the piezoelectric elements. However, the net kinetic energy seen by the supporting structure is essentially zero.  
 5 Claims, 1 Drawing Figure PIEZOELECTRIC FLASH LAMP IGNITION CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of our earlier application. Ser. No. 330.557. filed Feb. 8. I973. now abandoned.  
 BACKGROUND OF THE INVENTION This invention relates to piezoelectric voltage generators and. in particular. to a piezoelectric generator for igniting photographic flash lamps.  
  Conventionally. the energy for ignition of photographic flash lamps used in portable photographic equipment is obtained from batteries installed in the flashgun or camera. However. batteries are not entirely satisfactory since they deteriorate with use and time, and must be replaced at relatively frequent intervals. Piezoelectric generators have been proposed as a replacement for batteries since they are capable of producing a large amount of energy, have a life commensurate with the rest of the camera and remain relatively stable in performance without significant loss of voltage or electrical capacity.  
  In one system disclosed by the prior art. a piezoelectric element is mechanically stressed and the electrical energy generated thereby stored in a capacitor. The charge in the capacitor is then discharged into a photographic flash lamp by connecting the capacitor directly across the lamp. This system is disadvantageous in that it requires a capacitor, which must be charged before lamp ignition can take place.  
  Another known method involves using sheets of pi ezoelectric material arranged as a flexible cantilevered beam structure. When the unsupported end of the beam is displaced and released. the beam rebounds momentarily. touching an electrical contact at the point of maximum beam displacement. The piezoelectric material is delivered to the lamp when the beam rebounds and contacts the lamp terminals. This method requires a large, bulky enclosure to permit the movement of the beam.  
  Accordingly, we have invented a piezoelectric flash lamp igniter which does not employ a capacitor or other external storage elements yet transfers energy efficiently into the photographic flash lamp. Furthermore. the present invention is compact and does not require a large container to enclose and activate the piezoelectric elements.  
 SUMMARY OF THE INVENTION In the present invention, two small piezoelectric crystals are arranged end to end and electrically connected in parallel. When a mechanical mechanism such as a shutter release is initiated. two striking members or hammers fall in unison and the force of the impact created thereby is delivered simultaneously to both piezoelectric elements. The hammers strike two impact caps or impact receiving members which contact and distort the piezoelectric crystal elements arranged therebetween. The other end of the piezoelectric crystals are in common relation to an electrode. When the impact receiving member is struck by the hammer in the above manner. the piezoelectric elements are distorted to generate a high voltage between the confronting positive ends of these elements. The thus generated high voltage is transmitted through the common conducting metal plate electrode and a resistor of conductive coupling to an anode terminal in a photographic flash lamp socket. The cathode of said flash lamp socket is connected to a common ground potential; therefore, when the voltage is generated by the piezoelectric crystal. it is delivered immediately through the socket of the flash lamp. thereby igniting the photographic flash lamp. As previously indicated. the sequence is initiated by a mechanical mechanism such as a shutter release. which may be synchronized with the flash lamp ignition for proper photographic exposure. The use of two piezoelectric crystals being struck simultaneously at opposite ends creates no net force to be transferred to the camera body. This avoids shaking the camera and the possibility of blurring the photograph.  
  The features of the present invention which are believed to be novel are set forth with particularity in the attendant claims. The invention. together with further advantages thereof. may best be understood by reference to the following description taken in connection with the drawing.  
 BRIEF DESCRIPTION OF THE DRAWING The FIGURE is a crosssectional view of the flash lamp igniter in accordance with the present invention.  
 PREFERRED EMBODIMENT OF THE INVENTION The present invention will now be described referring to the accompanying drawing in which a preferred embodiment of the piezoelectric photographic flash lamp igniter in accordance with the present invention is illustrated.  
  The piezoelectric ignition system. 15, in accordance with the present invention. is shown in detail in the FIGURE. This system may be located within a camera (not shown) or in a separate unit associated with flash lamp I3 (as shown in the FIGURE). The ignition system includes a pair of piezoelectric elements such as polarized lead-zirconate-titanate ceramic in a horizontally aligned relation in a horizontally extending hollow cylindrically insulative member 18. The pair of piezoelectric elements 16 and 17 are horizontally aligned having the adjacent positive ends thereof facing each other with a conductive metal plate 20 extending through the adjacent wall of the cylindrical member 18 and longitudinally along the outside of cylindrical member I8. The metal plate 29 is electrically connected in series to a conductive connector or ballast resistor 21 which is connected to the anode of the photographic flash lamp l3 by an insulated wire 22. The cathode of the photographic flash lamp 13 is electrically connected to the casing I4. An impact receiving cap 25 is secured to the left side of the left element 16 and the cap is adapted to receive an impact from an impact device which will be described hereinafter. A second impact receiving cap 26 is secured to right side of the right element 17 and the second cap is adapted to receive an impact from an impact device which will be described hereinafter.  
  The impact device may be actuated by an actuating member or a camera shutter release button 11 having a shaft and flanged end 11&#39;. A cylindrical spiral return spring 29 is anchored to the base of the shaft of the bottom II near the flanged end 11&#39;. The other end of spring 29 is mounted to the casing 14, normally urging the release button ll upwardlyv Thus a portion of the release button I1 is normally disposed outside of the casing 14. A right striking member 30 is pivotably supported on the transverse shaft 31 extending between opposite side walls of casing 14 and secured at the opposite ends to the interior of the casing. A tension spring 32 is disposed on the transverse shaft 3] with one end abutting against a laterally extending pin (not shown) on the striking member 30 and the other end secured to the interior of the casing [4 by a transverse pin 35 fixedly mounted on the inside of the casing. Therefore. the right striking member 30 is adapted to pivot about transverse shaft 31 toward and away from the above-mentioned impact receiving member 26. A left striking member 40 is pivotably supported on the transverse shaft 41 extending between opposite side walls of the casing 14 and secured at the opposite ends to the interior of the casing. A tension spring 42 is dis posed on the transverse shaft 41 with one end abutting against a laterally extending pin (not shown) on the striking member 40 and the other end secured to the interior of the casing 14 by a transverse pin 43 fixedly mounted on the inside of the casing. Therefore, the left striking member 40 is adapted to pivot about transverse shaft 41 toward and away from the above-mentioned impact receiving member 25. Two angulated stop arms 50 and 51 having elbows 50&#39; and 51&#39; and fingers 50&#34; and 51&#34; are pivotably supported on transverse shafts 31 and 41 respectively. The outer portion of the elbows 50 and contact transverse tripping pins 57 and 58 respectively which are fixedly mounted on the striking members 30 and 40 respectively.  
  Therefore, when activating member ll is depressed downward, the stop arms are pivoted outwardly forcing the striking members outwardly also. When the member 11 reaches its lower limit of travel, as represented by the dotted position 60, the fingers 50&#34; and 51&#34; no longer are engaged by the lower surface of member ll. Springs 52 and 53 operate to quickly rotate stop arms 50 and 51 back toward the original position. Since the elbows no longer engage the tripping pins, the striking members 30 and 40 are released and fall against the im pact receiving members 26 adn 25, respectively. After the downward pressure is removed from member 11, spring 29 urges the member 11 upward. When the release approaches an upright rest position, the stop arms re-engage their respective tripping pins. In operation, when the shutter release button or actuating member [I is first manually pushed downward in the arrow direction (shown in the FIGURE) against the force of the spring 29, the spring 29 having one end anchored to the inside of the case 14 and the other end thereof anchored to the flanged end of the actuating member, the spring 29 is stretched so as to store the moving or pushing energy of the member 1] in the spring 29. The movement of a member 11 actuates the shutter of a camera (not shown) in a conventional manner as well as synchronously actuating the flash lamp igniter which is described hereinafter. As the member 11 is pushed further in the above arrow direction, the flanged portion thereof forces the pivot arms 50 and 51 about shafts 31 and 41 respectively in the arrow directions (shown in the FIGURE). The elbow portions of the pivot arms 50 and 5] engage stop pins 57 and 58 respectively and thereby force the striking members 30 and 40, respectively, to pivot about shafts 3] and 41, respectively, against the force of tension springs 32 and 42, respectively, until the elbow disengages from stopping pins upon release by member 11 whereupon the striking members 30 and 40 are allowed to rapidly descend inwardly to strike against the impact receiving members 26 and 25, respectively. In the above manner. the piezoelectric elements 16 and 17 are distorted to generate a high voltage between the confronting posi- 5 live ends of these elements. The thus generated high voltage is transmitted through the conductive metal plate 20, resistor or conductive coupling 2], and insulated wire 22 to the anode of photographic flash lamp 13 which is ignited thereby. AS the actuating member It) It is returned to its normal position in the manner as mentioned above, the pivot arms 50 and 51 are also allowed to pivot about transverse shafts 31 and 4] contra to the arrow direction (shown in the FIGURE) to the extent necessary for the member II to return to its normal position.  
  The various features and advantages of the invention are thought to be clear from the foregoing description. Various other features and advantages not specifically enumerated will undoubtedly occur to those versed in the art, as likewise will many variations and mofifications of the preferred embodiment illustrated, all of which may be achieved without departing from the spirit and scope of the invention as defined by the following claims.  
  What is claimed is:  
  l. A piezoelectric photographic flash lamp igniter comprising an outer casing,  
 a socket having a pair of electrodes for receiving a photographic flash lamp therein being attached to and insulated from the outer casing,  
 a piezoelectric high voltage generating device disposed within and attached to the outer casing, the device comprising a pair of substantially identical piezoelectric elements positioned end to end, the abutting ends being ofa like polarity and being commonly electrically connected to a first one of the pair of electrodes, and  
 a pair of conductive impact receiving caps being in mechanical and electrical engagement with the other opposing end of each of the piezoelectric elements, the caps being electrically coupled to the other of the pair of electrodes,  
 means for simultaneously impacting each of the impact receiving caps on the piezoelectric elements with a force which is equal to and in the opposite direction of the force applied to the other impact receiving cap so that a high voltage signal is applied across the photographic flash lamp to cause ignition thereof, and the net kinetic energy transferred to the outer casing is substantially zero, and means for actuating the impacting means.  
  2. A piezoelectric photographic flash lamp igniter according to claim 1, wherein the means for impacting comprises an opposed pair of substantially identical force generating assemblies each of which comprises a shaft affixed to the outer casing,  
 an elongated striking member pivotably positioned 60 on the shaft so as to reach the respective impact receiving cap, means for rotating the striking members away from the impact receiving cap, an impact force storing spring engaging the striking member so that as the striking member is rotated away from the impact receiving cap energy is stored in the spring, and  
 means for releasing the striking member so that it is rapidly counterrotated toward and against the impact receiving cap to cause a high voltage to be applied across the photographic flash lamp.  
  3. A piezoelectric photographic flash lamp igniter according to claim 2. wherein the means for actuating the impacting means comprises an outwardly spring biased. extended release member slidably mounted through the outer casing and having an outwardly flared portion at the internal end forming a cam surface at the internal end thereof. and  
 wherein each striking member has a protuberant generally pointed follower thereon which engages the flared cam surface on the release members so that as the release member is slid inwardly the cam surface forces the striking members to rotate away from the impact receiving caps until the continued inward travel of the release member causes the cam surface-follower engagement to terminate thereby releasing the striking members.  
  4. A piezoelectric flash lamp igniter according to claim 3, wherein the piezoelectric high voltage generating device further includes an insulative hollow cylindrical member in which the pair of piezoelectric elements are arranged with the positive ends thereof abutting each other and having a conductive metal plate disposed therebetween.  
  5. A piezoelectric photographic flash lamp igniter according to claim 4. which further includes a ballast rcsistor connected in series with the piezoelectric elements.