DE1037265B - Drive of film projectors for demonstrations with different numbers of images per second with correspondingly different numbers of diaphragm blades - Google Patents

Description

GERMAN

As is well known, cine projectors are usually built with two or more projection speeds, For example, to be able to show silent films at 16 frames / sec and sound films at 24 frames / sec.

For known physiological conditions, it is necessary to avoid flickering of the picture, 48 light-dark changes per lake can be achieved. At a presentation speed of 16 images / sec, it is necessary to achieve this required light-dark change a 3-wing shutter at the demonstration speed of 24 frames / sec a 2-wing shutter can be used.

These wing shutters generally sit on the main drive shaft of the film transport mechanism, So run with this in a ratio of 1: 1.

The change from the 2-wing panel to the In known devices, 3-wing diaphragm takes place by replacing the entire diaphragm disc or also through adjustable diaphragms, in which three movable sectors can be distributed so that once a 2-wing screen is created, with two sectors lying on top of each other and the third sector facing each other, or on the other hand, the three sectors are adjusted by 120 ° against each other using a 3-wing screen form.

There are still other arrangements for avoiding flicker have become known to the required Also the number of light-dark changes per see at different demonstration speeds. For example, two or more can be separated running and powered diaphragm blades are used, one of which only covers the Film transport takes over, while the other wing or wings to achieve the flicker-free take over necessary interruptions of the luminous flux. As it is for physiological reasons it is necessary that the light and dark times are equal to each other, bring such arrangements with different orifices at different speeds usually not the desired result the freedom from flicker.

The switching ratio of film projectors, i.e. the ratio of the time in which the film is transported to the time in which the film stands still, is limited by the conditions of the mechanical strength of the film and _{should not fall below V 6} if possible, i.e. symmetrical designed aperture sectors must encompass 60 °.

With 24 frames / sec and a 2-wing shutter, each sector closes the beam path for _{V 144 see, ie V 72} see is dark and V ₇₂ see is light.

In the case of a presentation at 16 images / sec and a 3-wing shutter, each sector closes the drive of film projectors for _{V 96} seconds, ie V _{32 seconds}

Demonstration with different numbers of images per lake. with correspondingly different

Number of diaphragm blades

Applicant:

Ly tax-Werke GmbH,
Freiburg (Breisgau), Egonstr. 35-41

Ernst Leist, Freiburg (Breisgau),
has been named as the inventor

if the image is dark and ¹ ½ a long time it is light. In other words: In the first case the image Ve of the presentation time is dark and ² / e light, in the second case half of the presentation time is dark and half is light.

This means that at a presentation speed of 16 images / sec, the image becomes significantly darker than at the presentation speed of 24 images / sec.

The invention of the novel drive for film projectors for demonstration with different numbers of images / sec with correspondingly different numbers of diaphragm blades aims to eliminate this disadvantage.

The idea on which the invention is based is that in order to achieve the same image brightness at different demonstration speeds, e.g. B. 16 frames / sec or 24 frames / sec between the Drive the wing diaphragm and the drive of the film switching element optionally switchable, the desired Wing aperture number corresponding translations are arranged so that for the drive of the film switching member Means, such as eccentric gears or crank loops, can be switched on, through which also at slower screening speed causes the film to be transported in the same time becomes like the fastest demonstration speed. Through the optional interposition of e.g. two Gear ratios between the diaphragm shaft and drive element, one in a ratio of 1: 1, the other Times in a ratio of 3: 2, it is achieved that the fixed 2-wing shutter always runs at the same speed, namely 24 frames / sec runs, with the drive shaft either also running at 24 revolutions / sec 1: 1 or with 16 per see 3: 2 works.

809 59S / 200

Claims (1)

In the first case the diaphragm makes only one rotation for one image cycle, in the second case IV2 rotations. This also ensures that the engine at both demonstration speeds the same number of revolutions can run, so that practically so a synchronous motor without an intermediate gear or other devices can also be used. Another advantage is that the fan, which is usually coupled to the motor, At the low demonstration speed, it runs at full number of revolutions, which is special in terms of cooling Importance is. Since, in this arrangement, with the gear ratio 3: 2 being used, the diaphragm shaft has a different, higher number of revolutions than the drive shaft, the drive element also requires a longer time for the film transport. As a result, the aperture sectors would have to be larger, and to avoid this, according to the invention, the use of a crank loop or eccentric gearwheel pairs is provided, whereby the film transport is accelerated in such a way that the actual transport of the film in V _{144 even at the projection speed of 16 images per see} see takes place. Since this transport time l> ei 24 images / sec is permissible. it is also permissible for the screening at 16 frames / sec without damaging the film, and it would mean an unnecessary loss of time if one were to leave _{the transport time at V 96 see here.} The inventive design of the novel drive it is achieved that when demonstration with 16 frames / sec with activation of the 3: 2 transmission ratio between aperture and film drive and with the involvement of the means that accelerate the transport in the case of a 3-wing shutter the same image brightness (measured in lumens) is achieved as in the demonstration with 24 images / sec with activation of the transmission ratio 1: 1 between shutter and film drive, but without activation the transport accelerating means T> ei a 2-wing screen. The one described, for example, for 2- and 3-wing panels Arrangement can also be used for other combinations in the number of diaphragm blades or analogously can also be taken so that the diaphragm shaft carries only one sector. In this case the cited and commonly used example of changing through the 2- and 3-wing panel the transmission ratio between the aperture shaft and the film drive in the demonstration with 24 frames / sec and 2-wing screen 2: 1 and in the demonstration with 16 frames / sec and 3-wing screen 3: 1. Even other combinations with two or more different gear ratios are possible. In the drawing, the subject matter of the invention is shown in a schematic arrangement: On the drive shaft 1, the wing panel 2 is attached as well as the gears 9 and 3, with which latter the gear 4 is in engagement, the axis of which is driven in the ratio 3: 2 and thus also the single-tooth clutch 5 moves in the engaged state. This is about the eccentrically designed Gears 6 and 7 of the film transport 8 are driven. Because of the eccentricity of these two gears 6 and 7, the actual transport process in the drive of the film 13 is accelerated. Instead of the arrangement of eccentrically designed gears, the installation of a corresponding one can also be used Kick crank slides. When the clutch 5 is engaged, the panel 2 works as a 3-wing panel. If the drive is to work in the ratio 1: 1, the clutch 5 is switched off, and that on the Drive shaft 1 seated gear 9 drives via the intermediate gear 11 on the axis of the film transport organs 8 arranged gear 10, which then, with the engagement of the clutch 12, the drive directly causes the diaphragm 2 works as a 2-wing diaphragm. P. \ T E N T A X S P P. U C H: Propulsion of film projectors for demonstration with a different number of images per lake with a correspondingly different number of diaphragm blades, characterized in that to achieve the same image brightness with different Demonstration speeds, e.g. B. 16 frames / sec or 24 frames / sec between the drive Wing screen (2) and the drive of the film switching element (8) optionally switchable, the desired Wing aperture number corresponding translations are arranged so that for the drive of the film switching element (8) means, such as eccentric gears (6, 7) or crank loops, can be switched on are, through which the transport process of the film even at a slower projection speed (13) is effected in the same time as the fastest demonstration speed. Considered publications:
French Patent No. 392 148;
U.S. Patent Nos. 744 251, 770 937. 1 sheet of drawings 1 «09 598/200 Ä. 5 «