US2587548A

US2587548A - Mechanism for the intermittent driving of cinematographic films

Info

Publication number: US2587548A
Application number: US149503A
Authority: US
Inventors: Thevenaz Jean
Original assignee: Paillard SA
Current assignee: Paillard SA
Priority date: 1949-03-23
Filing date: 1950-03-14
Publication date: 1952-02-26
Anticipated expiration: 1969-02-26

Description

Feb. 26, 1952 J. THEVENAZ MECHANISM FOR THE INTERMITTENT DRIVING OF CINEMATOGRAPHIC FILMS Filed March 14, 1950 INVEN UR a? ATTRNEY Jean evenaz.

Patented Feb. 26, 1952 MECHANISM FOR. THE INTERMITTENT DRIVING OF CINEMATOGRAPHIC FILMS Jean Thvenaz, Yverdon, Switzerland, assignor to Paillard S. A, Sainte Croix, Switzerland, a corporation of Switzerland Application March 14, 1950, Serial No. 149,503 In Switzerland March 23, 1949 Claims.

Mechanisms for the intermittent movement of a cinematographic film are known which are provided with a lever oscillating in a plane perpendicular to the plane of. movement of the film and at the end of which is hinged an arm provided with a claw which, periodically, enters the perforations of the film, moving the latter through the height of an image and is disengaged therefrom for recommencing its operating cycle. The movements of the claw and those of the oscillating lever may each be controlled by a cam.

In some of these mechanisms, especially when the oscillating lever and the claw-carrying arm move in seperate planes the claw is liable to vibrate laterally and move away from its plane of action, which gives rise to a deleterious lateral component in the driving force or the film, to irregular wear of the perforations and to a lack of fixity or to a faulty alignment of the claw, relatively to the perforations of the film.

Further, it is known that for obtaining the maximum luminosity of a cinematographic projector, it is necessary to efiect the movement of the film in accordance with the height of an image, in the shortest possible period of time, in such a manner as to reduce to a minimum the time during which the luminous beam is obturated. In order to avoid premature wear, the performances of a given mechanism are generally limited. by the thickness of cams which it is possi ble to obtain by cutting. In fact, the specific pressures at the point of contact are the lower the larger the profile of the cams.

The present invention has for its subject an intermittent driving mechanism for a cinematographic film provided with a claw co-operating with the perforations of the film and carried by a lever actuated by a control member in an oscillating movement producing the movement of the film. This mechanism tends to remedy the disadvantages referred to by the fact that the member controlling the movement is formed by two cams of identical profile secured in the same angular position on a shaft on opposite sides of a cam controlling the penetration of the. claw into the perforations of the film and by the fact that the thickness of this intermediate cam at least equal to that of the arm carrying the claw.

One form of construction of the mechanism, forming the subject of the invention, is shown diagrammatically and by way of example in the accompanying drawing, wherein:

Fig. 1 shows in a diagrammatic manner a form 2. Fig. 2 is a view in section on the line IIII of Fig. 3.

of construction of the mechanism seen in oblique perspective.

Fig. 3 is a longitudinal section, on the line IIIHI of Fig. 2.

Figs. 4 and 5 are detail views to a larger scale.

In these figures, D and G indicate the uprights of a stationary framework, each provided with a bearing 1, 2 in which turns. a shaft 3, set in continuous rotation by a motor not shown. The

' shaft 3. carries two identical driving cams and 5 located an opposite sidesv of a penetrating cam 62 and in contact with a. shoe 6 secured to an oscillating lever of which the oscillation shaft 8 is secured to the upright G.

At the free end of the oscillating lever l is hinged an arm 9 carrying a double claw it provided for penetrating two successive perforations of the film F. The driving cams l and 5, practically identical, are secured co-axially to the shaft 3- in the same angular position. These cams are spaced from one another and provide between them a groove 5 E with edges parallel to the plane of oscillation of the claw-carrying arm. The

cam 52 has a. thickness at least equal to that oi the arm 9 and constitutes the penetration cam l2 actuating the arm. 9.

In order that the two

cams

4 and 5 constitute a guide for the arm. of the claw, tending to hold the latter in its plane, it is naturally necessary for the effective radii of these two cams, in each radial plane passing through their common axis of rotation, to be always greater than the corresponding effective radii of the penetrating cam 12. ihus a groove i l is created between the two cams 1 and 5 which constitutes a continuous guide for the arm 9 of the claw.

As shown in the drawing, the two

driving cams

4 and 5, hade thick in order to reduce,as far as possible, the value of the specific pressure of contact of the shoe 6, and the cam 42 thinner, are mounted on a section it of the shaft 3 and locked against a shoulder Hi of this shaft by a nut 85. An extension it of the shaft 3 serves as a trunnion and turns in the bearing 2 provided in the upright G of the framework.

The shoe 6 is held in contact with the

driving cams

4 and 5, by a torsion spring ii of which the axis is located along an extension of the pivotal axis 8 of the oscillating lever l. The torsion spring is formed by a spring blade located perpendicularly to the plane of oscillation of the lever 1, and of which one end is secured in a cylindrical boss I8 located in a bore is of the upright D from which it projects. The boss i8 is locked in angular position by a screw 20. en-

gaging with a screw threaded hole of the upright D. Radial recesses 25 provided in the periphery of the boss and into which may be introduced the end of a tool or of a rod, permit of selecting and fixing the angular position of the boss is and, consequently, of selecting and fixing the torsion and thus the initial tension of the spring I1. The end of the blade I? remote from the boss l8, acts on the oscillating lever i. For this purpose, it has an arcuate slope 22 above the end of the axis of oscillation 8 and forming a fork of which one limb Z3 acts on a contact arm 24, and the other 25, on a contact projection 26 diametrically opposite the arm 2% and also secured to the oscillating lever 1. During the mounting, the boss I8 is locked, in an angular position, such that the

branches

23 and 25 of the spring ll apply to the oscillating lever 3 two equal and pposite forces forming acoup1e centred on the axis of oscillation 8 and which tends to hold the lever I in contact with the profile of the cams i and 5.

Underneath the range of contact, the oscillating lever l is provided with a bent tongue El against which bears, by one of its ends, a resilient blade 28 held flexed by a finger 29, and of which the other end 30 acts on a beak 3i secured to the claw-carrying arm 9. By resilient flexing, the end 38 applies to the beak 3! a force which is eccentric relatively to the hinging axis 32 connecting the arm 9 of the claw and the oscillating lever I. This force causes the arm 9 to bear constantly against the penetration cam l2.

On examination of the accompanying drawing, it will be seen that the oscillating lever l and the arm 9 of the claw it have a common plane of symmetry, which is the plane of oscillation of the oscillating lever. reactions acting on the members of the mechanism are located also in this same plane, which contains the return couple generated by the torsion spring H.

The oscillating lever l is secured by rivets 33 on the peripheral flange B t of an anti-friction sleeve 35 turning freely on the axis of rotation 8 fitted with its reinforced part so in the upright G of the framework. A cap 3? screwed into the shaft 8, holds the sleeve 35 on the said shaft.

The profile of the driving cams l and is so determined that the speeds communicated to the oscillating lever land, consequently to the arm 9 of the claw it are progressive and that the oscillations of the oscillating lever are separated by stopping periods. The penetrating cam i2 acts directly on a projection of the dorsal contact 38 of the arm s of the claw of which the movements of penetration into the perforations of the film and of the disengagement from these, are accomplished approximately during the reversal of the direction of movement of the oscillating lever. Further, the portion of the profile of the cam l2 which is in contact with the projection 38 whilst the descending movement of the oscillating lever l for driving the film F is being accomplished for driving the film F, is preferably so provided as to compensate the effect of the arc of circle described by the hinge axis 32 and to act in sucha manner that the claw it describes a practically straight line path.

As regards the transmission of forces it is to be observed that at each descending stroke of the oscillating lever I, the film opposes a resistance to its movement, so that the arm Q of the claw is subjected to a traction force which is converted into a variable force of application of Consequently the forces and 4. the oscillating lever, or more particularly of the shoe 6 against the

driving cams

4 and 5. In other words, these cams apply the variable force necessary for moving the film, whilst the torsion spring i! only supplies the very weak force necessary for holding the lever l and its shoe 6 in contact with the

cams

4 and 5 and for the idle return of the claw l0, disengaged from the perforations of the film F, between two successive feeding strokes.

By reason of the fact that the member controlling the movement of the film is formed by two cams of identical profile secured to the same cam shaft in the same angular position, it is possible to obtain each of these cams, by cutting and to obtain in this manner cams of sufficient precision and at a cost of manufacture much less than that of a cam having a thickness necessitating rectifying operations of its profile, whilst maintaining a specific pressure of the shoe against their profile of a value sufficiently weak to avoid any premature wear. In order to enable the two

cams

4 and 5 to be mounted easily on the cam shaft 3 in the same angular position it suffices to provide their central openings non-circular as shown in the drawing, which engage on a section [3 of a cross section corresponding with the cam shaft 3.

While this present application relates to the structure of the cams and levers, applicants copending application serial No. 149,502 filed March 14, 1956, relates to the combination of the claw arm, actuating lever therefor and the spring structure urging both elements.

I claim:

1. Mechanism for driving intermittently a film having perforations therein and comprising a frame, an arm having adjacent one end claw means for insertion in the film perforations, a lever pivoted to the other end of the arm and fulcrumed on the frame and including a shoe, a rotatable shaft journaled in the frame, a control cam rigid with the shaft engaged by the arm and of a thickness along the shaft axis at least equal to the corresponding thickness of the claw arm, a pair of other cams duplicates of one another one on either side of the control cam and secured to the shaft in the same angular relation and having in every radial plane effective radii longer than the corresponding effective radius of the firm cam and guiding the claw arm.

2. The mechanism according to claim 1 and also comprising a torsion spring to maintain the lever in contact with the other cams.

3. The mechanism according to claim 2 and further comprising a second spring urging the claw arm to engage its cam.

l. The mechanism according to claim 2 and further comprising a blade spring fixed at one of its opposite ends to the lever and at its other end bearing against the claw arm to maintain it in engagement with the first cam.

5. Mechanism for driving intermittently a film having perforations therein and comprising a frame, a claw cooperating with the perforations, an arm carrying the claw, a lever pivoted to the arm and fulcrumed on the frame, a shaft journaled in the frame, a pair of cams of the same profile and fixed to the shaft in the same angular relation and engaged by the lever, a second cam controlling the film penetration of the claw and fixed to the shaft between the pair of cams, the thickness of the penetration controlling cam being at least equal to the thickness of the claw arm, the first two cams having in every radial plane passing through their axis of rotation efiective radii longer than the corresponding radii of the penetration cam whereby to create between these first two cams a groove guiding the claw arm.

' JEAN THEVENAZ REFERENCES CITED The following references are of record in the file of this patent:

6 UNITED STATES PATENTS Number Number Date Name Pink Nov. 16, 1909 Bundick Apr.;7, 1936 Ross Apr. 13, 1937 FOREIGN PATENTS v Country Date Germany Oct.'21, 1927