US2513195A - Gear train for kinetographic projectors and similar mechanisms - Google Patents

Description

/HTCHELL T L GEAR TRN FOR KINETOGRAPHIC PROJECTORS AND SIMILAR MECHANISMS Filed Ost. 3.4i 1947 @MET-6E 2@ QS G, A, METCHELL ET AE..

TRAIN FOR KINETUGRAPHC PROJECTORS GEAR AND SIMILAR MECHANISMS 4 Sheets-.Sheet 3 Film1 Oct.

June 2'7"9 1950 G. A. MITCHELL, ET AL GEAR TRAIN FOR KINETOGRAPHIC PROJECTORS AND SIMILAR MECHANISMS 4 Sheets-Sheet 4 Filed Oct. 14, 1947 Patented June 27, 1950 GEAR TRAIN FOR KINETOGRAPHIC PRO- JECTORS AND SIMILAR MECHANISMS George A. Mitchell, Pasadena, and Emanuel C. Manderfeld, Los Angeles, Calif., assignors to Mitchell Camera Corporation, Glendale, Calif., a corporation of Delaware Application October 14, 1947, Serial No. 779,702

2 Claims. l

This invention is concerned generally with machinos for handling flexible film strips, and relates more particularly to a mechanism for driving the various moving parts of motion picture projection machines and the like.

Film is ordinarily fed through such machines by engagement first with a continuously moving pull down sprocket which draws film at a predetermined rate from a supply reel; then with an intermittent mechanism, which may be of claw type but more typically comprises an intermittent sprocket and a mechanism such as a Geneva for intermittently rotating it; and finally with a continuously moving hold back sprocket (sometimes physically the same as the pull. down sprocket) which feeds the film at a predetermined rate to a takeup reel, or to other apparatus such as a sound head. The rates of iilm feed over the two continuously moving sprockets must be equal, and must equal the average rate of film feed over the intermittent sprocket. These conditions are ordinarily satisfied by driving the two continuously moving sprockets and the intermittent mechanism, which in turn drives the intermittent sprocket, from a single power source through a suitable gear train.

An important object of the present invention is to provide an improved gear train for the purpose just outlined. Among the principal char-- acteristics of a preferred form of film feeding gear train in accordance with the invention is the fact that the sprocket driving gears, directly mounted respectively on the shafts of the continuously moving sprockets, and also the driven gear on the intermittent driving shaft, are all directly engaged by a single intermediate gear. Such an arrangement has a number of important advantages, among which are: the relatively small number of working gears, making for smoothness and accuracy of operation and for economy of yconstruction and maintenance; the fact that all working gears, or more accurately all meshing pairs of working gears, can be, and preferably are, provided with hunting teeth, giving longer life and better interchangeability of parts; and the fact that all working gears of the ilm feeding gear train operate in the same plane, lpermitting straightforward, economical mounting of the gears and the use of simple gear types.

In preferred form the invention includes a manual framing adjustment of the intermittent mechanism, by which the longitudinal position of the lm, as it is intermittently drawn past the nlm gate, can be so adjusted that successive picture frames of the lm are momentarily brought to rest in proper registration with the film aperture. The intermittent mechanism is of the Geneva type, with the intermittent sprocket mounted directly on the star cam shaft of the Geneva. The pin cam is mounted on a pin cam shaft which is parallel and eccentricgto the star cam shaft and is driven from the intermittent drive shaft, mentioned above, which is parallel to and coaxial with the star cam shaft. The pin and star shafts, and preferably also the intermittent drive shaft (but the latter is not necessary) are mounted in a unitary intermittent housing which is adjustably mounted on the main frame of the machine for rotation about the common axis of the star cam and drive shafts. The framing adjustment is accomplished by turning the intermittent movement bodily about this axis, thus rotating the intermittent sprocket and modifying the framing as may be required.

An object of the present invention is to provide an improved intermittent gear train for driving the pin cam shaft of the Geneva from the intermittent drive shaft; and, more particularly, to relate the intermittent gear train to the nlm feeding gear train in such a way that all pairs of engaged gears can embody the principle of hunting teeth, while still maintaining a simple overall speed ratio between the driven pin cam shaft and the continuously moving sprockets mentioned above.

The optical projection system by which successive film frames, momentarily positioned at the film aperture, are projected onto the screen generally includes a light source, condensing system and projection lens, lying on a well-defined loptical axis which is substantially normal to the f ing the periods of film motion past the lm aperture the projection light is cut off by one or more shutters, which are ordinarily and preferably rotating disk shutters mounted on a shutter shaft which is parallel to the optical axis, and hence normal to the axes of the sprockets. However, it lies within the purview of cur invention that barrel type shutters may be used, in which event the shutter shaft will lie on an axis parallel to the axes of the sprockets.

The present invention includes, in addition to the film feeding gear train and intermittent gear train, already mentioned, means for driving the shutter shaft in adjustable synchronism with the sprockets. The shutter driving gear train of the invention includes a single intermediate shaft, here referred to as the jack shaft, which is directly geared both to the shutter shaft, on the one hand, and to one of the shafts of the film feeding gear train, on the other, and thus forms a driving connection between them."v One of the gear connections of thejack shaft (either to the shutter shaft or to the nlm driving train) is in the form of a pair of intermeshing helical gears which are relatively axially shiftable .to adjusta bly change their relative phases of rotation. Such a phase-shiftable set of intermeslied helical gears may be used between shaftsthat 'are 'mutually parallel or that lie at an angle'to yeach other.

Hence, if the shutter is of the type having its axis parallel to the sprocket shafts, the mutually shiftable gears can be used'on'parallel 'shafts either to drive the jack shaft or to drive the shutter shaft from the jack shaft. On the other hand, if the shutter shaft-as is at present preferred, lies at right angles to the sprocket axes, the jack shaft can lie parallel either to the shutter shaft or to the sprocket axes; and the relatively shiftable helical gears can then be used to interconnect either a pair of parallel, or a pairv of crossing, shafts.

In the present preferred form, the jack shaft is parallel to the preferred shutter shaft and therefore at right angles to the sprOcKetaXeS; and in that arrangement the axially shiftabyle helical gears are applied between the vparallel shutter and jack shafts, vand the latter is driven from a convenient shaft or gear associatedwith the sprocket driving train. A Xial motion of one helical gear relative to the other results in rela- Y.

tive rotation of the two gears and'ha'sfthe effect of altering the relative timing of the shutter shaft and shutter with respect to other parts'of the' drive, particularly the intermittent mechanism.

The driving Vconnection mentioned abovebetween the jack shaft and anon-parallel shaft is the only instance in the entire gear system vof the preferred form of the "invention in which mutu'- ally engaged working gears have non-'parallel axes. This permits the general 'use lof gears 'of simple types, which are readily mounted and give relatively smooth operation and longs'ervice.'

Since manipulation of the'manual .framing adjustment, by which the yintermittent housing is turned bodily about the axis of the intermittent sprocket, alters the timing vor phase relation b'etween the intermittent vmechanism and 'other parts of the machine, including the shutter shaft, a timing compensating mechanism is provided in the shutter drivingY gear train, by 'which the relative phase relation between shutter and intermittent is made independent of the'fra'ming adjustment of the intermittent. The timingv compensationmechanism preferably makes use oftheA pair of helical gears by' whichthe jack shaft of the shutterdrive is related either to the shaft of? the nlm feed gear train which drives it, or to the shuttershaftitself. nOne of those gears is axially movable 'on its'shaft, as has been described, and its4 axial motion is under the control, by meansof a suitableiinkage', of .ther'otational adjustment of the 'intermittent .mechanism housing. The linkage just referred tois such as to automaticaL ly produce the correct variation in the shutter timing to just compensate for the-change in timingof the intermittent mechanism resulting from any framing 'adjustment of thelatter. The shutterv timing compensation mechanism includes also a trimming adjustment for the shutter timing, as will be described. f v

As in the nlm feeding gear train and intermittent gear train, all the working gears of the shutter drive can be, according to the present invention, and preferably are, arranged with hunting teeth. The gear systems and the shutter synchronizing system are such that this advantage is attained without adding any complications to the gear systems. In fact the present invention has the great advantage of requiring only ten working gears in the entire film and shutter mechanism, including the three groupings described above as the nlm feeding gear train (four gears), the shutter drive gear train (four gears), and the intermittent gear train (two gears). Those ten working gears include six pairs of meshing gears. Only one of the six pairs involves gears not operating in one plane; and all pairs of meshing gears can have hunting teeth. These .and other characteristics of the invention permit simplification of the mechanical design as compared with previous projection machines and lead to superior operation and longer life of the parts.

A clear understanding of the invention, and of further characteristics and advantages of it, will be obtained from the following illustrative example of its embodiment in a typical motion picture projection machine. This description, which is not intended to limit the scope of the invention, is to be read in conjunction with the accompany-A ing drawings, of which:

Fig. 1 is a side elevation, partly cut away, showing a projection machine in accordance with the invention, with ythe'door to the nlm compartment open, the aspect of this view being indicated by line l-I of Fig. 3;

Fig. 2 is a vertical longitudinal section through the gear compartment of the machine, taken as indicated by line 2`2 of Fig. 3;

Fig. 3 is a vertical transverse section taken generally as indicated by lines 3-3 of Fig. 1 and Fig. 2;

Fig. 4 is an enlarged vertical section along the axis of the intermittent movement, taken as indicated byline 4-*4 of Fig. '2;

Fig. 5 is a transverse `section through the intermittent movement, taken as indicated by line 5 5 'of Fig. 4;

Fig. 6 is a section similar to Fig. 5, `but taken on line ,6.-6 of-Fig. 4. 50

Numeral l in the drawings indicates a frame or casing on and in which the various parts and subassemblies of the machine are mounted, and whichk serves also as Aa housing, enclosing the working parts of the machine, Frame ill includes side walls and a central vertical partition I ,5 whichdivides the interior of the frame into a fllmcompartment i6 (Fig. 1) and a'gear compartment l1 (Fig. 2). Access to film compartment I6 is through a door hinged to frame iii at 2l and indicated in open postion at 2t. Access to gear compartment l'i is obtained by removing cover plate '23.

Ihe motion picture film to be projected, indcated 'generally :at 25, is carried on a reel in magazin, from which it is drawn through an away from trap 38 by merely moving the handle 43 of gate control lever 42 to the right in Fig. 1. This motion first rotates lever 42 counterclockwise around its pivoted connection 44 to the gate, lifting lever pin 45 out of side leg 4'! of L-shaped slot 4B and unlatching the gate, and then moves the gate to the right on rails 4|. After threading, the gate is relatched by merely moving handle 45 to the left in Fig. 1, first sliding the gate on rails 4| into closed position and then rotating lever 42 clockwise so that pin 45 enters latch slot 41.

Film trap 38 carries a removable aperture plate 4S in which is located the film aperture 49 (see Fig. 3) of the projection system. The nlm is intermittently drawn past aperture 49 by inter mittent sprocket 50, successive picture frames of the lm being momentarily brought to rest in register with the aperture. Intermittent sprocket clamp 5| is shown supported on the lower end of movable film gate 40. The nlm next passes via, loose film loop 52 to hold back sprocket 54, provided with the usual sprocket clamp 55, from which it is drawn by means not shown through an opening 56 in casing |0 to a takeup reel or to other apparatus such as a conventional sound head.

The projection system includes a light source such as an arc lamp and condensing system mounted in a lamp house indicated schematically in Fig. 1 at 60 and delivering a beam of concentrated light along the optical axis 6| of the projector. The light beam passes into the rear shutter housing |53, where it is intermittently intercepted by rotating rear shutter 65, mounted on shutter shaft G5 (see below). When not intercepted by the shutter, the light passes through several suitable openings in case I0, in sight box 69 and (under operating conditions) in dowser and fire shutter assembly 10, and then through aperture 49 in plate 4S to illuminate the area of film which is framed by film aperture 49. The various parts and apertures mentioned in the immediately preceding sentence are not shown or described in detail, Vas not related directly to the present invention. Light transmitted by the film traverses an opening schematically indicated at 40a in film gate 40 and passes through projection lens l2, which forms an image of the nlm on the screen (not shown). An aperture, indicated at 13, in the front wall of case transmits the light beam from the lens. A. front shutter 15, mounted on shutter shaft 66 in front shutter housing 16, cooperates with rear shutter G in the usual manner. Projection lens 12 is suspended from ways parallel to optical axis 6| and is adjustable for focus under control of handle 1|. The details are not necessary to the present invention.

Rear and front shutters 55 and l5 are separately adjustable on shutter shaft 6B by any suitable means, such, for example as rear and front shutter hubs 51 and 11 which are releasably clamped to shutter shaft 66. The shutters are so set on the shaft as to give the most advantageous timing relation both between the cooperating but distinct action of the separate shutters upon the light beam, and between the combined action of the shutters collectively and that of the intermittent lm moving mechanism. For clarity in. the present description it will be assumed that the two shutters are properly adjusted on their common shaft with respect to each other, and that the shaftor the shutters together on the shaft-are in approximately the correct rotational phase relation to the intermittent mech-v anism. Improved means for achieving nal adu justment of the latter relation, here referred to as the shutter timing, and for maintaining that relation under operating conditions, form a part of the present invention, and are described below.

In the form illustrated the intermittent mechanism is mounted as a unit within a housing 80 (see Figs. 4,5, and 6) which includes a generally cylindrical case 8| and a cover plate 82 which is secured to one face 83 of case 8| as by screws B4 and a single locating pin 85. (See Fig. l.)

Outer cylindrical surface 88 of case 8| is journalecl in circular opening 89 in frame partition |5, and is located axially by flange 90 of cover plate 82, which ts under cooperating flange 9| of retaining ring 92. Intermittent housing 80 is thus rotatable in the frame partition i5, and is removable as a unit in an axial direction to the right in Fig. 4 after removal of retaining ring 82.

Intermittent sprocket 50 is rigidly mounted on star cam shaft 95, which carries also star cam 96 of an intermittent mechanism of the Geneva type, and which is journaled in an axial bore 91 in cover plate 82 on an axis coincident with the axis of rotation of case 8|. The pin cam 98 of the Geneva mechanism is rigidly mounted on pin cam shaft 99, which is journaled in bushing |00. Shaft 99 is adjustable in position to adjust the engagement of gears |05, |05; and cover 82 is also adjustable to adjust the engagement of the Geneva pin with the star, but those features do not enter into the present invention.

Pin cam shaft 99 carries also gear |05 which is engaged and driven by pin cam driving gear |06, mounted rigidly on the inner end of intermittent drive shaft |08. The latter' shaft is journaled (preferably in case 8|) coaxially with star cam shaft 95, and hence coaxially with both intermittent sprocket 50 and journal 89 of intermittent housing 90. The axial position of shaft |08 is defined by gear |06 at the inner end and lock nuts |09, threaded t0 the shaft at |07 at the outer end of its journal |04. The outer end of shaft |08 projects from housing 80 (to the left in Fig. 4) and carries intermittent driving gear H0 and flywheel which are preferably either formed integrally or securely connected together to form a unit, as by force-fitting the flywheel over gear hub ||0a. This unit is removably keyed or splined to shaft |08, as indicated at H2, and is axially secured to the shaft Iby a retaining member ||5. This retaining member, in the form illustrated, is threaded at i7 to the end of shaft |08 in the manner of an ordinary retaining nut, and engages axially transverse surface |||-i of gear ||0, releasably locking the gear and flywheel to the shaft. Further details of the structure and functions of member ||5 and associated parts are described in copending patent application, Ser. No. 779,789, led Oct. 14, 1947, by applicant Emanuel C. Manderfeld.

The purpose of the above described arrangement, insofar as the present invention is concerned, is to allow of rotative adjustment of the intermittent sprocket and the Geneva movement about the axis of the sprocket. To provide for that, it is only necessary that a frame or case (e. g. the case 8|) carry the pin shaft and its gear and cam in such manner that they can be rotated about the axis of the sprocket and the axis of gear |06. Gear |06, or its shaft E03, can therefore be journaled either in the main frame of the mechanism or in the intermittent housing 80; and it `can be driven from the general gear train in any suitable manner. It is, however,

preferably mounted and ,driven ,as Shown v.| facilitate removal .and replacement ,of the Tintermittent mechanism. Features of the mechanism relating ldirectly vto removal Land replacement of the intermittent movement are the subject matter of .the said `copending application, and are not claimed in the present application.

The rotational position ,of intermittent housing 80 in its journal v80 is 4determined by manual adjustment of framing knob |2001 |2-| r`(see Fig. 3). These are rigidly mounted on opposite ends of framing shaft |22, which is journaled as shown in Fig. 3 at |23 and |24 inthe outer wall and in partition |55 of case |0. Framing shaft |22 is linked by framing gear Y L -2 5 and idler |20 to gear sector |21, ,cut in a portion of the periphery of case 8|, as shown particularly in Fig. 5. Rotational adjustment of knob or 2| is transmitted by vsears |25, |26 and sector |21 to the entire Aintermittent unit 00. Thishas the ,effect of adjustably rotating intermittent sprocket 5 0, and changes the longitudinal position in which the lm is momentarily stopped in front of film aperture |59, and is used to correct the lfram-ing of the film when necessary.

Rotational adjustment of intermittent .housing 80, in addition to the framing action just described, carries pin cam shaft $3 and pin driven gear |05 bodily around shaft |08, which carries pin 4cam driving gear |06. This causes gear |05 to roll on gear |06, rotating pin cam 88 with reference to housing 0, ,and hence also with reference to start cam 96 o f the intermittent mechanism. This alters the phase relation of the intermittent with respect to lintermi ttent driving gear ||0. For example, if housing S0 is rotated clockwise in Figs 1 and v 6 to move the ii-lm down,- ward at aperture 49, pin .cam 96 turns clockwise through a corresponding angle with respect to casing 8|. This is opposite v.to its nor-mal operate ing rotation, and therefore retards the beginning of the next engagement with start cam 96. In other Words the phase of the intermittent action has been delayed with respect, for example, to the rotation of intermittent driving gear l0. The shutter action, normally linked in a definite timed relation to gear 0, must be similarly delayed with respect to that gear, if the proper phase relation between the intermittent and .the shutter is to be maintained. Such compensation of the shutter timing is obtained through the shutter ydrive gear train, under vdirect control of the rotational framing motion of intermittent housing 30.

A spur gear sector Aon case 0| engages circular rack teeth -.3| ,on cylindric rack' `bar |32. The rack teeth |3| on bar |32 are ,of spur `form but extend ,circularly around the cylindricbar so that the bar may be rotated withcut aifecting its longitudinal position with relationy to gear sector |30. Rotational motion of housing 48|! pro.- duoes a corresponding longitudinal motion of rack bar |32, which is slidably and rotatably jour.- naled at |33 and |34. One of a pair .ofhelical gears at some point in the gear train which drives shutter shaft ,06 in timed relation to intermittent driving gear ||0 is slidably splined to its shaft. .The sliding motion of rack bar |32 is transmitted to that gear, which is gear |4| in the present instance, and moves that gear axially with respect to the other helical gear (|40) of the pair. That relative axial motion of the h elical gears results in a corresponding relative rotational motion, and therefore rotates shutter ,Shaft 66 with respect to those rafts t9' which it is linked by the helical gears. Since the latter parts include intermittent driving gear 0, the result is seen to be a shutter `phase shift of the required type. A shift in the proper direction and of the proper size to give accurate compensation can be obtained by correct choice of such factors as the hand and angle of the threads of the helical gears, Athe diameter of the fixed helical gear, and the radius of sector |30.

In the present embodiment, the helical gears by which the shutter is .rotationally adjusted constitute the connection between the shutter shaft and parallel jack shaft |42. This location of the helical gears has the advantage that the longitudinal motion of rack bar |32 is parallel to the required direction of motion o f the splined helical gear, and can be transmitted to it directly without unnecessary linkages. Although either one (or both) of the helical gears lmay be axially movable, the preferred arrangement is that illustrated in which helical gear |40 is rigidly mounted on shutter shaft 06 and in engagement with helical gear |l|, which -is rotationally fixed but longitudinally vmovable l on jack shaft |42, being splined tothe shaft at |45. A Xially movable gear MI is embraced by yoke |35, which is longitudinally adjustably fixed on rack bar |32 by axial threads |37, and which transmits the sliding motion of the rack bar directly to the gear. With this arrangement, the shutter is driven by a gear train which acts through jack shaft |42 and includes the `pair of helical gears |40, IM. Shutter shaft 55 extends Y forward `through front shutter housing l0, and carries hand wheel |47, by which the entire gear mechanism can conveniently be turned over by hand.

Generally speaking, if we assume the ratio of the internal intermittent Agears (|05, |06 in the present instance) to be unity, then the angle of retard `of the film movementis equal to the angle through which intermittent casing 8| has been rotated. The corresponding amount of longitudinal shifting of rack bar |32 depends on the pitch diameter or gear sector |30. If the helical angle of the teeth of gears M0 and MI is 45, say, ,then the peripheral shifting ,of gear |40 and shutter shaft 4| will be equal to the longitudinal shift of bar |32. If then the pitch diameter of gear sector |30 is made equal to that of gear |40, the shutter shaft will be moved through an angle equal to the angle of rotation of -intermittent case 8|.

However, as pointed out later in connection with provision of hunting teeth in the gear trains, the ratio at gears |05, |06 is not unity, gear |00 having twenty five teeth and gear |05, twenty two teeth. In that arrangement, the relative retard of the intermittent movement is 25/22 of the angle of framing adjustment of intermittent case 81. That, or any other specific ratio, can be taken care of by correspondingly changing either the pitch diameter of sector |30, or that of gear |40, or by making the helical angle of .the teeth in gears |40, |4| to suit. This last method is preferred because the choice of any helical angle ,does not involve the gear Iratio at |40, 4,| .and leaves that ratio to be set solely by other considerations (see below); and also bee cause it is not necessary to adopt any particular ratio between the pitch `diameters .0f gear |20 and sector |30. For instance in the illustration given, if those two pitch diameters are equal, then the helical angle of gears lt 0, 4|, measured with reference to the axis, is one whose tangent is 25/.22 1i, the pitch diameters. @f seats '3,0 and 9 |40 are not equal, then the adopted pitch angle is one whose tangent is 25/22 multiplied by the ratio of pitch diameter of gear |40 to that of gear sector |30.

Fine adjustment of shutter position (phase) with relation to the phase position of the intermittent movement, during operation, is provided for by rotating the rack bar |32 to screwthreadedly adjust the longitudinal position of yoke |35 and helical gear |4| with relation to the bar. That rotation does not disturb the longitudinal position of the bar with relation to gear sector |30 nor with relation to the phase position of the intermittent movement. It therefore changes the phase relation of the shutter by sliding gear i4! longitudinally and thereby rotating gear |40 a corresponding amount. The bar may be rotatively adjusted by any means which does not interfere with its longitudinal framing movement, and which is not aected in its operation by the longitudinal framing movement. For instance, the end of bar |32, or a cylindric member mounted on it, is provided with straight axial teeth-in effect, long spur gear teeth-as shown at |32a. A rotatable rod |3222, lying at substantially right angles to rod |32, has a screw thread of small pitch, |32c, meshing in the spur gear teeth. The rod projects through partition l5, and at its end which is available in film compartment |6 (see Fig. 1) it has a formation |32d to receive a screw driver or other suitable tool to rotate it.

The principal driving connections of the projector have the main function of driving four cooperating parts in accurate, and, in certain respects, adjustable timed relationship with each other. Those parts are the two continuously driven film feeding sprockets 32 and 54, shutter shaft 66 and pin cam shaft 99 of the Geneva movement which drives intermittent sprocket 50.

One complete rotation of pin cam 08 results in one quarter rotation of intermittent sprocket 50, the sprocket being of such size that one quarter rotation moves the film one frame spacing. Therefore to obtain an average rate of intermittent sprocket rotation equal, say, to the rate of rotation of pull down sprocket 32 (assuming, for example, equal numbers of teeth on the two sprockets) the pin cam 93 of the intermittent mechanism must be driven four times as fast as sprocket 32. This means that the overall gear train connecting sprocket 32 and pin cam shaft 95 must have the simple integral gear ratio of four to one. (If sprockets 32 and 50 have unequal numbers of teeth, the value of the overall gear ratio will vary correspondingly.) The gear ratio of the intermittent gear train itself, comprising gears and |06, is arbitrary, so long as it is properly related to the remainder of the overall drive. Incorporation of a hunting tooth in the action of gears |05 and |06 requires that the respective numbers of teeth of the two gears, and hence also their respective rates of rotation, be incommensurable. This is permissible only if the remainder of the overall gear system is such that intermittent drive shaft |08 can be driven at a rate incommensurable with that of pulldown sprocket S2, and so related to it as to give the required overall integral speed ratio of (in the present instance) four to one. The same requirement applies to the gear train between intermittent drive shaft |08 and holdback sprocket 54. As will be seen, the gear system of the present invention, in addition to being remarkv ably simple, satisfies the conditions just described.

Pulldown sprocket 32 is rigidly mounted on sprocket shaft 00, which is journaled in boss |6| on partition |5 of the machine frame, Sprocket shaft protrudes into gear compartment I1 and carries sprocket driving gear |62 rigidly mounted on the protruding shaft end.

I-Ioldback sprocket 54 is similarly mounted on sprocket shaft |10, which is journaled in partition l5 and also in the outer wall ol' gear compartment I1, and projects through that wall to the exterior of frame case l0, as indicated in Fig. 2, to serve as the initial driving shaft of the mechanism. Sprocket driving gear |12 is rigidly mounted on shaft |10 in gear compartment I1. The two sprocket gears 62 and |12 are preferably in a common plane which also passes through driven gear ||0 on intermittent drive shaft |08. The three gears |62, |12 and ||0, are connected together by the single intermediate gear |15, which is in. direct mesh with all of them. Intermediate gear |15 is shown as an idler gear lying in the common plane of gears |62, |12, and ||0, and rotatably mounted on stud shaft |16 which is mounted at |11 on partition I5 of the frame.

The correct relative speed ratio of the two uniformly moving sprockets 32 and 54 is obtained, according to the invention, by providing the corresponding sprocket driving gears |62 and |12 with respective numbers of teeth in direct proportion to the numbers of peripheral sprocket teeth 34 on the respective sprockets. If, as in the illustrative preferred embodiment, the sprockets have equal numbers of teeth, gears |62 and |12 also have equal numbers of teeth, and are thus constrained by intermediate gear |15 to rotate at equal speeds. |The ratio of the speeds of sprockets 32 and 54 is entirely independent of the number of gear teeth on intermediate gear l15, and that gear can therefore be made incommensurable in numbers of teeth with both sprocket driving gears. For example, in the present preferred embodiment in which sprockets 32 and 54 have equal numbers of sprocket teeth, gears |62 and |12 each have 88 teeth and intermediate gear |15 has 89 teeth, a number which is incommensurable with 88. Hence the hunting tooth principle applies between intermediate gear |15 and both sprocket gears, and yet the sprockets turn at the same speed.

The speed of pin cam shaft 99, relative, say, to that of pulldown sprocket 32, is also independent of the number of teeth on intermediate gear |15. It is completely determined by two ratios, rst, the ratio of the number of teeth on sprocket driving gear |62 to that on pin cam driven gear |05; and second, the ratio between the numbers of teeth on the two gears |06 and ||0 on intermediate drive shaft |58. Neither one of those ratios involves gears which are directly engaged with each other. This makes it possible to choose the actual numbers of teeth of the Various gears in such a way as to maintain simple integral values for the two ratios just defined (leading to the required overall gear ratio of four to one) and yet to make all pairs of interengaged gears mutually incommensurable as to numbers of teeth.

In particular instance, if the two gears |06 and ||0 on intermittent drive shaft |00 have equal numbers of teeth, (the actual number being arbitrary) the second ratio defined above is unity, and the first ratio gives directly the overall gear ratio, which in the present instance must be four to one. Then, with 88 teeth on each of the sprocket driving gears, pin cam driven gear must have 22 teeth. The actual number of teeth on the two intermittent drive shaft gears, |06 and H0, can then be so chosen as to be incommensurable both with the number of teeth on pin cam driven gear |05 and with the number of teeth on intermediate gear |15. In the present embodiment, for example, gears |06 and ll have 25 teeth each, a number which is incommensurable with the 22 teeth of gear |05 and also with the 89V teeth of gear I'li". In this way the hunting tooth principle is applied with respect to all pairs of engaged working gears throughout the film feeding and intermittent gear trains.

The shutter gear train, according to the present invention, includes only one pair of gears in addition to helical gears |40 and |4l', already described. When, as in the present instance, jack shaft |42 is parallel to shutter shaft 66, it is directly drivenby a pair of engaged gears of any suitable type from a shaft at right angles to it. That shaft may be either one of sprocket shafts |60 and |10, intermittent drive shaft |08 or, as in the modification here illustrated, the short hub sleeve which carries intermediate gear |15. As shown, a large bevel gear |80 is formed integrally with intermediate gear |15, and drivingly engages a smaller bevel gear |-8| rigidly mounted on jack shaft |62. This arrangement gives a shutter drive from bevel gear |89 which is in many respects analogous to the intermittent drive already described from intermediate gear to pin cam shaft 99 of the intermittent movement. In particular, the two drives are similarly well adapted for yielding a simple integral overall gear ratio for the ultimate driven element with respect, say, to pulldown sprocket gear |62, and at the same time for introduction throughout the train of a hunting tooth in every pair of engaged gears. These objectives are attained, for ex ample, in the particular system illustrated, by employing 89 teeth on bevel gear |80, 23 teeth on bevel gear |23! which it drives, 23 teeth also on jack shaft helical gear I4 and ZZtee-th on helical gear |453 on shutter shaft 66. Thus, all engaged gear pairs have incommensurable numbers of teeth. The gear ratio between sprocket shaft |60 .and shutter shaft 616 is determined by the tooth ratio of gears |62 andv |40 and the ktooth ratio of gears lill and |8| on jack shaft |42. The latter ratio is commensurate; specifically it is unity inthe illustration given, but need not be so. Thus, in the specific illustration, the overall ratio between the sprocket shaft and the shutter shaft is one to four, the same as between the sprocket shaft and the pin cam shaft 99 of the intermittent movement, and the shutter' shaft makes one revolution for each film-moving operation of the intermittent mechanism. "Throughout this description shutters making one revolution per cycle of film movement (having, in effect, one lm exposing opening) have been assumed. If shutters making less than one revolution per cycle should be used the overall gear ratiov between the intermittent movement shaft 439Y and the shutter shaft Bt will be changed accordingly, but the principles and advantages of the invention apply equally well.

The overall result of the present improved driving connections is to give positive speed re'- vlations between two continuously moving sprockets, the intermediate sprocket, and the shutter, using for that lpurpose a vremarkably small number of Iworking gears, most of which are of a comparatively simple type and are subject to relatively little wear. The life and smoothness of operation of the machine, as well as the interchangeability of parts, are improved by the fact that the gear system is well adapted for the use of hunting teeth in connection with all engaged working gears. And the system, with those advantages, also admits of and includes the' simple type of framing compensation, between the intermittent movement and shutter, that has been described.

We claim:

l. In a motion picture projection machine which includes a :continuously rotatable film feeding sprocket, an intermittent mechanism of the Geneva type driving an intermittently movable sprocket and having a driving shaft on an axis parallel to the axis of the continuously rotatable sprocket and co-axial with the axis of the intermittent sprocket, a housing for the intermittent mechanism mounted to vbe rotatively adjustable bodily about the axis of the intermittent sprocket, and a shutter and a shutter shaft located -on an axis which lies substantially atv right angles to the axes of the two sprockets; driving and control interconnections between the continuously movable sprocket, the intermittent mechanism and the shutter shaft, said interconnections comprising a driving gear in direct driving relation to the continuously moving sprocket, a driving gear for the intermittent mechanism mounted directly on the intermittent mechanism driving shaft, an intermediate gear in direct mesh with each of the two first mentioned gears, said three gears all lying in a single plane, a jack shaft on an axis parallel to the Shutter shaft, intermeshing gears driving the lack shaft from the interemediate gear, a pair of intermeshing helical gears on the shutter shaft and jack shaft, both said gears bei-ng rotatively xed to theirr shafts and vone of said gears being axially movable, a gear sector on the intermittent housing in the plane of its rotative adjustment, a cylindric rack bar mounted for axial movement along `and rotation about an axis parallel to the jack shaft, circular rack teeth on the bar meshing with said gear sector, screw threads on the rack bar, a yoke mounted on the rack bar and engaging said threads so as to be adjustably positioned on' the bar by rotation of the bar, the yoke engaging the axially movable helical gear to impart axial adjustment movement to it, and means for rotatively adjusting the rack bar.

2. In a motion picture projection machine `which includes a continuously rotatable film feeding sprocket and Aan intermittently movable sprocket mounted respectively on parallel shafts, an intermittent housing mounted to be rotatively adjustable about the axis of the intermittent sprocket, an intermittent mechanismv of the Geneva type c-arried by the housing and including a pin cam shaft parallel to and eccentric of the said axis and in driving relation to the intermittent sprocket, and a shutter and a shutter shaft located on an axis substantially at right angles to the sprocket axes; driving and control interconnections between the continuous sprocket, the intermittent mechanism and the rshutter shaft, said interconnections' comprising a sprocket driving gear fixed on the shaft of the ,continuous sprocket, an intermittent mechanism driving shaftr coaxial withY the intermittent mechanism sprocket, an intermittent mechanism driving gear vmounted onl the intermittent mechanism driving shaft, a pair Lf intermeshing gears fixed respectively on the pin cam shaft and on the intermittent mechanism driving shaft, a jack shaft parallel to the shutter shaft, a jack shaft driving gear rotatively fixed to the jack shaft, a pair of intermeshing helical gears mounted respectively on the shutter shaft and on the jack shaft, both said gears being rotatively xed to their shafts and one of said gears being axially movable, means acting by virtue of rotational adjustment of the intermittent housing to axially shift the axially movable helical gear, and two intermediate gears rotatively fixed together and in direct mesh respectively with the jack shaft driving gear and with both the sprocket driving gear and the intermittent mechanism driving gear; the sprocket driving gear, the gear on the pin cam shaft and the gear on the shutter shaft having respective numbers of teeth that are mutually commensurable, the two intermediate gears having respective numbers of teeth that are mutually commensurable and are incommensurable with the rst mentioned group of tooth numbers, and the pair of gears on the jack shaft and the pair of gears on the intermittent mechanism driving shaft having respective numbers of teeth that are mutually commensurable within each pair and are incommensurable with both previously mentioned groups of tooth numbers.

EMANUEL C. MANDERFELD. GEORGE A. MITCHELL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Number OTHER REFERENCES George B. Grant, A Treatise on Gear Wheels,

10th edition, 1904, published by Philadelphia Gear Works Inc., Philadelphia, Penn., page 21.

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