Flash gun for photoflash lamps and piezoelectric ignition energy generating apparatus for use therein

Oct.

Filed ^12,p“^sts ., ENERGY GENERATING ------------May 31, 1953

APPARATUS FOR USE THEREIN

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FIG. 8. FIG. 9.

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RTTOR.NEY.

Oct. 12, 1965 p j_| rixton

FLASH GUN FOR PHOTOFLASH LAMPS AND J ENERGY GENERATING APPARATUS j

Filed May 31, 1963

3,211,069

PIEZOELECTRIC IGNITION

FOR USE THEREIN

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•32

United States Patent Office

3,211,069

Patented Oct. 12, 1965 _ , „ 3,211,069 ^F raOTOFLASH LAMPS AND

ELECTRIC IGNITION ENERGY GENERALING APPARATUS FOR USE THEREIN

Frederick H. Rixton, Livingston, N.J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa. a corporation of Pennsylvania ’

Filed May 31,1963, Ser. No. 284,704

Claims. (CI. 95—11.5)

This invention relates to improvements in flash guns tor flashing photoflash lamps, and more particularly to an improved flash gun having piezoelectric means for generating the energy utilized to ignite the flash lamp.

The need has long existed for obtaining a suitable and satisfactory substitute for a battery as a means for igniting or firing a photoflash lamp in portable photographic equipment. It has been proposed in one prior art patent to employ a hand crank generator to charge a capacitor and to utilize the charge from the capacitor to ignite the photoflash lamp. It has been proposed in another prior art patent to utilize a piezoelectric crystal with electrodes duectly connected to the photoflash lamp and to have a hammer, the operation of which is synchronized with the shutter mechanism of the camera, apply a hard blow to the piezoelectric crystal at the instant the shutter is opened, to thereby provide a synchronized flashing of the lamp. This apparatus, however, has the disadvantage that the mechanical energy required for a trip hammer to activate the piezoelectric crystal produces considerable mechanical shock to the camera with resultant blurring of the picture, this blurring being an inevitable result of the hammer action occurring simultaneously with the opening of the shutter.

The apparatus of the instant invention overcomes these and other disadvantages of the prior art. In summary my invention includes but is not limited to a hand operated lever to compress and stress one or more piezoelectric elements, the voltage or signal generated by the element as it is compressed being stored as a charge in a capacitor. The capacitor is connected by way of a normally open switch to the photoflash lamp, the operation of the switch being synchronized with the camera shutter so that at the instant the shutter is opened the switch is closed and t’- ’ ' flash lamp at the proper instant. It should be noted that in my invention the capacitor is charged prior to the taking of the picture, eliminating movement, and eliminating the mechanical shock and blurring inherent in prior art apparatus employing a piezoelectric generator.

Accordingly, a primary object of my invention is to provide a new and improved flash gun for photoflash lamps.

A further object is to provide a new and improved gun for photoflash lamps employing a piezoelectric generator. ¹

A further object is to provide a new and improved flash gun for flashing photoflash lamps employing a piezoelectric generator in which necessary mechanical movement to generate a voltage in the piezoelectric element results in no mechanical shock to the apparatus and no ' blurring of the picture.

These and other objects will be more clearly apparent hereinafter after a study of the following specification when read in connection with the accompanying draw- 65 ing, in which:

FIGURE 1 is a front elevational view of a flash gun and photoflash lamp according to my invention;

FIG. 2 is a cross-sectional view in a vertical plane through the apparatus of FIG. 1 after 90 degree rotation; 70

FIG. 3 is a cross-sectional view in a horizontal plane along the lines III—-III of FIG. 2;

-I..- C .1. ; ----- --- uuu uu&gt;uu₆ live U1UVHUCM UX IUC ICVCt 1/. At 1116 DOtt fl ^e,^c,^arge °A!^{he ca}Pacitor immediately fires the photo- ⁴⁵ the plastic case 14 as seen in FIG. 1 there is a latch nncn Inmn or -·-» ———x___x ttx if*·· .- - - - .

FIG. 4 is a cross-sectional view in a horizontal plane along lines IV—IV of FIG. 2;

FIG. 5 is a cross-sectional view in a vertical plane of a portion of the apparatus of FIGS. 1 and 2;

FIGS. 6 and 7 are cross-sectional views in a horizontal plane along the lines VI—VI, with the lever-actuated shorting switch in opened -and closed settings;

FIG. 8 is an electrical schematic circuit diagram of the apparatus during the capacitor charging portion of the cycle of operation in which a voltage is generated by the piezoelectric elements as pressure is applied thereto; and FIG. 9 is a schematic electrical circuit diagram of apparatus embodying my invention during the brief period that the photoflash lamp is connected to the capacitor by way of a closed switch and is fired as a result of the charge from the capacitor.

Particular reference is made now to the drawings, in which like reference numerals are used throughout to designate like parts, for a more detailed understanding of the invention, and in particular to FIG. 1 thereof. A reflector 10 having a photoflash bulb or lamp 11 mounted therein is mounted by way of a bracket, not shown in FIG. 1, upon a head portion 13 disposed upon and secured to a flash gun body generally designated 14. The gun body 14 may be generally cylindrical in shape and may be composed of preferably lightweight insulating material having the necessary mechanical strength, for example, a suitable plastic. The plastic case or body 14 has two off-centered! longitudinally extending cavities 30 designated 15 and 16 located therein, FIG. 2. The cavity 15, as will become more fully apparent hereinafter, has disposed therein two piezoelectric elements which are electrically in parallel and mechanically in series, and which are adapted to be compressed together and released simul35 taneously by lever means hereinafter to be described in detail, the hand operated lever being shown at 17. Disposed in the lower cavity 16 is a capacitor and leads interconnecting the electrodes of the piezoelectric elements, the capacitor and cables which run to the photoflash lamp 40 and to the switch on the camera apparatus, not shown in FIG. 2. The aforementioned head portion 13 is secured to body member 14 by screws 18 and 19, the front portion of the head 13 having the cut away section at 20 for permitting free movement of the lever 17. At the bottom of ---------------~ member 21, adaped to be hand released, for securing the lever 17 adjacent the body 14 after the lever has been hand actuated, and retaining the lever in place until the latch 21 is pressed down, releasing the lever. As will appear more fully hereinafter, the compressed piezoelectric elements tend to expand when latch 21 is released, and tend to restore the lever to the position shown in dashed outline in FIG. 2.

Lever 17 has pivotally connected thereo, by any convenient pivot means, a link member 22, the pivoted end of which extends into slot 36 in the lever FIG. 1, and which is provided for purposes to be hereinafter more clearly apparent.

As previously stated, FIG. 2 is a cross-sectional view through the apparatus of FIG. 1. A bracket 12 is secured to the reflector 10, and is secured to head 13 by the bolt or rivet 23. The flash bulb 11 is mounted in a socket 24 which has a two conductor insulated cable 25 connecting the socket of the flash bulb to a double socket or socket region generally designated 26 in the body 14, for purposes which will become hereinafter more clearly apparent.

The heart of the electrical generator consists of a pair of piezoelectric elements which are electrically connected in parallel and are mechanically connected in series to be compressed at the same time and to have the pressures thereon released simultaneously. To this end the

3,211,069 ³aforementioned cavity 15 in insulating body 14 is provided. Disposed in cavity 15 are two similar piezoelectric elements 34 and 35, separated from each other by metallic disc or contact member 33, the metallic disc or contact member 37 being disposed in cavity 15 at the lower end of element 35, and the metallic disc or contact member 40 being disposed in cavity 15 adjacent the upper end of piezoelectric element 34.

The insulating body member 14 is seen, FIG. 5, to have bores 30 and 31 extending longitudinally thereof on either side of cavity 15 in the wall portion, the bores 30 and 31 having disposed therein electrical conductors or rods 29 and 32 respectively. The conductor 32 is electrically connected near the central portion thereof to the metallic contact member or electrode 33. Member 33 may be displaced slightly when the piezoelectric elements are compressed; accordingly, electrical connection between rod 32 and contact plate 33 is by way of spring biased ball 91, spring 88, and screw 90 in threaded bore 89 in rod 32. Screw 90 is inserted through wall aperture 92 covered by plug 93 which may be cemented in place.

The metallic contact plate or electrode 37 does not move an appreciable amount when the piezoelectric elements are compressed; accordingly the contact plate 37 is electrically connected to rod 29 by screw 102 in bore 101 in rod 29, screw 102 having been inserted through wall aperture 103 closed by plug 104. Disposed adjacent the upper end of piezoelectric member 34 is the aforementioned metallic contact plate or electrode 40; plate 40 is displaced downward when the piezoelectric elements are compressed by action of lever 17, and accordingly electrical connection between contact plate 40 and rod 29 is by way of spring biased ball 97, spring 94, and screw 96 in threaded bore 95 in rod 29, screw 96 being inserted through wall aperture 98 sealed by plug 99 which may be cemented in place after the spring tension is adjusted. The purpose of the rod 29 is to electrically connect the plate or electrode 40 to the contact plate or electrode 37, so that the two piezoelectric elements 34 and 35 are electrically in parallel, the contact plate 33 forming one common connection thereto, and the plates or electrodes 37 and 40 connected together forming the other electrical connection thereto.

Disposed on top of electrode 40 is an insulating disc 43 of mica or other suitable insulating material, to electrically insulate electrode 40 from lever 17. Metallic disc 50 is provided to have pressure exerted thereagainst by the protruding hump 27 of lever 17.

As seen in FIG. 5, rods 29 and 32 extend downward in their respective bores 30 and 31 below the level of the lower contact plate 37. They are utilized to provide electrical connections to a storage capacitor located in the lower chamber 16, and in addition rods 29 and 32 are arranged to be short-circuited at a time corresponding to a predetermined position of lever 17 after it is released, to thereby dissipate the charge in the capacitor resulting from electrical energy generated by piezoelectric elements 34 and 35 as they expand when lever 17 is released from latch 21. Depending upon the extent of movement of lever 17, rods 29 and 32 may be momentarily shortcircuited at the moment when, or shortly before, compressing the lever starts to compress the elements, but this momentary short circuit is removed from the capacitor so as not to interfere with the charging thereof.

Two stiff exposed ends 38' and 41' of two insulated conductors 38 and 41 extend into two bores 39 and 42 connected with chamber 16, the bores 39 and 42 extending upwardly through the body 14 of insulating material, and being parallel to and spaced equally from bores 30 and 31 respectively. A bore 58 extends through the body 14 in a horizontal direction and transverse to bores 39 and 42, bore 58 having a member 59 of insulating material movably or slidably disposed therein for purposes to become more clearly apparent hereinafter.

Lead or rod 38' is electrically connected to rod 29 by screw 107 in threaded bore 108 in rod 29, screw 107 being inserted through aperture 109 in the wall of body 14, aperture 109 being closed by plug 110 which may be 5 cemented in place. Lead or rod 41' is electrically connected to rod 32 by screw 112 in threaded bore 113 in rod 32, screw 112 being inserted through aperture 114 in the wall of body 14, aperture 114 being closed by plug 115 which may be cemented in place.

j Q The aforementioned cavity 16 is seen in FIG. 2 to have the lower end closed by a cover member 45 retained in position by set screw 46 in threaded bore 67. In chamber 16 is disposed the capacitor 47, which has two electrical terminals 48 and 49. The aforementioned j 5 socket portion 26 is seen to be adapted to receive the terminals of the plug of the aforementioned cable 25 which connects the apparatus to the flash bulb, and also the two terminal plug of a cable 51 which is connected to the camera and which is terminated in a normally open

2o switch 87 shown in FIGS. 8 and 9, the closing operation of which is synchronized with the operation of the camera shutter by means, not shown. The two terminals of the plug 52 of cable 25 are designated 53 and 54, whereas the two terminals of the plug 55 of cable 51 are designated

56 and 57. Inside the cavity or chamber 16, the terminal 53 has the aforementioned lead or conductor 41 connected thereto, which connects the terminal 53 to the electrode or contact plate 33, and the aforementioned terminal 53 is also connected by way of the insulated por3θ tion of lead 41 to one terminal 48 of the aforementioned capacitor 47. The other terminal 54 of plug 52 is connected by way of a metallic portion 62 of the socket 26 to the upper terminal 56 of plug 55, completing a direct connection between one lead of the cable 25 going to the photoflash lamp and one lead of the cable 51 connected to the camera switch, this portion 62 corresponding to the lead 62' of FIG. 8 hereinafter to be described in more detail. The other terminal 49 of capacitor 47 is connected inside the cavity 16 by way of lead 38 to 40 the aforementioned terminal 57 of plug 55, and from lead 38 by way of rod 29 to electrodes 37 and 40.

Particular reference is made now to FIG. 4, in which a cross-sectional view along the line IV—IV of FIG. 2 is shown. It is seen again that the ball 91 is held against 45 the contact member 33 by pressure of spring 88. After the pressure of spring 88 is adjusted to a desired and satisfactory value, aperture 92 is closed by plug 93, which may be cemented in place.

Particular reference is made now to FIG. 3, a cross50 sectional view looking downward through the line III—III of FIG. 2. The lever 17 is seen to be pivotally mounted for rotary movement about the longitudinal axis of the pivot pin 68, the ends of which extend into bores 69 and 70 in the body portion 14.

In FIG- 2, the lever 17, pivoted at 68, is seen to have the aforementioned downwardly extending hump or pressure portion 27 which is adapted upon clamping the lever 17 to the body 14 to apply pressure to the top of the piezoelectric element 34 through the pressure plate 50, the 60 insulating disc 43, and the electrode 40. Since both element 34 and electrodes 33 and 40 are freely mounted for longitudinal movement with respect to the axis of cavity 15, the pressure is also applied to piezoelectric element 35. The lever 17 may be composed of any suitable 65 material.

Particular reference is made again to FIG. 1, where it is seen that the lower portion of the cover member 45 includes two extended wall portions 75 and 76. Mounted between these two extended wall portions 75 and 76 is a 70 pivot pin 77, FIG. 2, upon which is rotatably mounted the spring biased lock 21. The right-hand end of the spring biased lock lever, as shown in FIG. 2, has a small bore 78 therein to receive a pin 79 for holding in place a biasing spring 80, the upper end of the biasing spring 75 80 being mounted in a suitable bore 81 in the cover mem10

3,211,069 5 ber 45. Disposed on the other side of the pivot pin 77 in a threaded bore 82 is an adjustable set screw 83. In the operation of the locking mechanism, the end 84 of lever 17 forces the left-hand end of the lock lever downward, as seen in FIG. 2, until the catch portion 85 is passed, whereupon the spring 80 forces the catch 21 into locking position.

In understanding the operation of the apparaus, it should be borne in mind that one purpose of the invention is to have a potential or charge readily available in the capacitor 47 to energize the flash bulb 11 in synchronism with the shutter operation of a camera. It should also be recalled that the shutter-synchronized switch 87 shown in FIGS. 8 and 9 is normally open. Assume now by way of description that it is desired to charge the capacitor 47 prior to utilizing or igniting the flash bulb. The lever 17 is grasped and pressed toward the body 14 of the device, causing the pressure portion 27 to press downwardly upon the pressure plate 50 and contact member or electrode. 49. The pressure exerted upon 40 changes the dimensions of the two piezoelectric elements 34 and 35, creating stresses therein, causing the generation of voltages or signals thereacross, as will be readily understood by those skilled in the art. The generation of a potential by a piezoelectric substance upon the application of mechanical forces thereto is well understood and need not be described in detail. The use of two piezoelectric elements electrically connected in parallel and disposed in series mechanically provides an efficient arrangement for increasing the energy available for charging the capacitor 47. For a further discussion of such an arrangement, reference may be had to an article entitled “Piezoelectric Ignition Developed for Small Engines,” by Edwin Crankshaw and R. Arnold, appearing in the S.A.E. Journal, vol 69, August 1961, pages 46-50. The lever, upon reaching the locking position shown in FIG. 2, exerts no additional force thereafter on the piezoelectric members 34 and 35, which remain in their compressed conditions while the lever is latched adjacent the body 14. The signal energy from the two parallel-connected piezoelec- ⁴⁰trio devices 34 and 35 charges the aforementioned capacitor 47, and since no subsequent or immediate relaxation of the pressure on the piezoelectric elements take place, the capacitor does not discharge into the elements although the electrical connections thereto remain intact.

At a suitable time the switch 87, FIGS. 8 and 9 is closed and the charge from capacitor 47 flowing through the switch 87 immediately ignites the lamp 11. When the lever is released after the flash gun has been used, the two piezoelectric elements expand to their previous 50 uncompressed conditions, and this expansion generates a voltage which may be stored momentarily at least in part in capacitor 47. Particular reference is made now to FIGS. 6 and 7 where shorting switch means generally shown for momentarily shorting the capacitor 47 atVpredetermined point in the movement of the lever away from the body, to discharge the capacitor.

FIGS. 6 and 7 are cross-sectional views in a horizontal - _ulc piczuewcirr ^phne along the line VI—VI of FIG. 2, showing the lever 60 said element when the lever and shorting mechanism or shorting switch 44 linked ' ' thereto in unshorted and shorted positions respectively.

In FIG. 6, lever 17 is seen to have pivotally connected thereto one end of the link 22, the link passing into the ing into a slot 119 in the adjacent end of slidable member 59, link 22 being pivotally connected to member 59 by pivot pin 120. Member 59 has a substantially horizontal bore 122 extending thereacross, in which are dis6 lease of lever 17, and it is seen that bore 122 is now substantially aligned with rods or leads 38' and 41', so that an electrical short circuit exists at least momentarily between leads 38' and 41' by way of ball 123, spring 125, and ball 124. This discharges capacitor 47, the terminals of which are directly connected to leads 38' and 41'.

Particular reference is made now to FIG. 9, which shows the electrical circuit as the photoflash lamp is being ignited, and it will be seen that the capacitor 47 is directly connected across the photoflash lamp by way of the switch 87 in the camera, the operation of which is synchronized with the shutter mechanism. Whereas the electrical connections between the capacitor and electrodes of the piezoelectric elements remain intact during this portion of the cycle of operation, it will be understood that the piezoelectric elements have a very high resistance, so that no substantial discharge of the capacitor takes place through the elements. In FIG. 9, shorting switch 44 is shown as being open. Shorting switch 44 is also open during the pressure-applying portion of the cycle • v°K^ra„^tlOn’ ^{and accordi}ngly switch 44 is shown open 1Π rlCr. 8. *

There has been provided then apparatus well suited to accomplish the aforedescribed objects of the inventrnn which are to provide a flash gun for igniting a photoflash lamp, in which the necessity for batteries is dispensed with, and in which piezoelectric generating means are employed while avoiding any mechanical shock to the apparatus at the moment of taking the picture which would result in blurring of the picture.

If desired, the socket portion 26 may be moved to a position further up on the back of the housing 14 so as not to be directly back of the finger grip portion of the lever arm 17.

A number of suitable piezoelectric materials may be employed at 34 and 35, one suitable material being a lead-zirconate-titanate ceramic known in the trade as PZT. Other suitable materials are barium titanate and quartz

A voltage of several hundred to several thousand volts may be developed between the electrodes depending upon the material employed and the pressure resulting from the lever action. The energy developed may be a fraction of a joule.

Whereas the invention has been shown and described with respect to an exemplary embodiment thereof which gives satisfactory results, it should be understood that changes may be made and equivalents substituted without departing from the spirit and scope of the invention