US1989310A - Safety device to prevent film burning - Google Patents

Description

Jan, 29, 1935. I M. H. FRITZ 1,989,310

SAFETY DEVICE TO PREVENT FILM BURNING Filed March 14, 1932 bwentar Max if.

, Aflorneys Patented Jan. 29, 1935 UNITED STATES;

PATENT OFFICE SAFETY DEVICE TO PREVENT FILM BURNING Max 11. Fritz, Berlin,

,asslgnortothe Application March 14, 1932, Serial No. 598,858 In Germany March 12, 1931 3 Claims. (01. aa-i'n My invention relates to safety devices to prevent film burning.

The object of the present invention is an apparatus which is influenced by the upper film loop, increased if the film band breaks, the loop moving an electric contact, operating a lever, the moving device of which will be released by meansof a band attached to one end of the lever and holding it in neutral position, which band will be touched by the film loop.

This new apparatus obviates all disadvantages of the devices known until now which require too much force in releasing the contacts. Yet, to

prevent any fire, it is necessary that in case of breaking of the film band the electric contacts are released in a period which is very small in comparison with the moving speed of the film band. Therefore all those devices are not useful with which relatively big masses are to be operated, the inertia of which must be overcome.

Fire preventing devices with which-if the upper film loop is increased-a lever and electromagnets are released, to close the fire safety valve are known as well as mercury rocking switches operating further safety devices. But the present invention consists in avoiding moving of heavier masses by nieans of using a lever held in neutral position by a band attached to one end of the lever and touched by the increasing film band.

In the drawing forming a part of this specification, is shown a safety device in accordance with my invention.

In detail, the invention comprises a film loop 1 increasing automatically in case of breaking of the film band or if locked in window 2 or at any other disturbance, to be pressed against the bal-.

ancing band 3 which is attached to balancing lever 4 and to adjustable arm 20, the band being of any material or metal or a thread or wire or the like. At the slightest pressure the highly sensitive balancing lever 4 supported by an axle is moved out of its position and raised against the contact piece 5. The contact piece 5 and the balancing lever 4 are lying in an electric circuit, so that in closin'gthe circuit current passes through the magnet 6, knocking the magnet core against the double acting lever 8. Now the lever 8, supported by an axle, is lifted out of its neutral position, hook of the fire safety valve, slides out of supporting device 9, while the fire safety valves 12 attached to the supporting device by means of a string 11 or the like close the projection and sight openings 13. Furthermore it is possibletousethelefts'ideofthedoubleaeting lever 8 to operate a fire safety valve between the lantern and the projection window. At the same time arm 14 releases lever 16 supported by axle 15, so that nose 17 slides off lever 14 and that mercury switch tubes l8, 19 attached to lever 16 indifferent positions are switched on or off. The lever 18 will be stopped at 23 and 24. The number of the mercury switch tubes may be chosen as to the necessary functions. For instance it may be possible to switch off the projection lantern, the driving motor of the projector and at talkies the talkies apparatus, and switch on the lights of the theatre.

After the disturbance of the film moving is finished, the device is switched back into its normal position by turning button 19. This button 19 is connected to lever 16, and raising it against the action of spring 22, permits the spring 21 to act and draw the lever 8 into its neutral position, as shown in the drawing. -Now, the fire safety valve 12 may be lifted and supporting device 9 attached to hook 10.

I claim:

1. In a safety device for preventing film burning in cinematographic projectors, a pivoted lever, a flexible member stretched between a fixed support and one end of said lever, and normally out of contact with the moving film, and electric means adapted to be energized when the other end of the lever contacts with a stationary contact member, whenever said flexible member is touched by a loop of film, as a result of any disturbance in the movement of said film travelling through the projector.

2. In a safety device for motion picture projectors, a pivoted lever, a flexible member stretched between a stationary support and one end of the lever and normally out of contact with afilm moving in the projector, to hold said lever in a given position, an electric contact adapted to be engaged by the free end of the lever whenever a cinematographic film travelling through the projector touches the flexible member, and an electric circuit including a source and an electro-magnet, said circuit being closed through the lever whenever it touches the electric contact, whereby the electro-magnet is adapted to trip mechanism efifectuating the energization of safety devices actuated electrically.- I

3. A safety device for cinematographic projectors, comprising in combination with such a projector and the film travelling therethrough, a pivoted lever, a flexible member attached to a fixed support and" one end of the lever and normally out of contact with the moving film, said flexible member being disposed adjacent one loop of the film, an electric circuit including a source. an electro-magnet and contacting means adapted to close said circuit through the lever when the 5 same is caused to engage its free end with the contacting means, as a. result of disturbances in the film movement causing the loop to act on the flexible member, and auxiliary electric circuits controlling means comprising a. tripping member acted upon by the electro-magnet and including a plurality of mercury switches adapted to control suitable safety devices, said switches being operated by the tripping member.

MAX H. FRITZ.

Images