US2838304A - Film projector - Google Patents

Description

June 10, 1958 H. BERKENHOFF FILM PROJECTOR Filed Aug. 9,1955

IN VEN TOR. f/savz EflKE/Y/VOFF United States Patent FlLM PRQIECTQR Heinz Fserkenhotf, Koln-Hoiweide, Germany, to Steatit-Ma esia Aktien 'eseilsehaft Lani a l l: 7 S corporation of Germany Application August 9, 1955, Serial No. 527,279

2 Claims. (Cl. 271-2.3)

Subject of the invention is a motion picture projector, particularly a narrow-film projector, having built into its film-feed, devices for compensating jerky feeding of the film. Motion picture projectors of this type, known in the previous art, use sprockets for feeding, the use of which, however, is too costly on narrow-film projectors. The self-elasticity of the film has also been used for feeding heretofore, by looping the film between reel and aperture. For this purpose, a stationary roll, arranged above the aperture, has been used as a means for looping the film. Thereby, however, irregularities, occurring in the film-feeding, proved to have strong and unfavorable reactions on the grapple-claw. Another design provided for the elimination of this disadvantage is a movable roll, mounted on a swing-arm, which, being controlled by a spring, overcame trouble incidences of larger proportions. This arrangement too caused jams on the film reel and affected the grapple-claw in a troublesome way, making the use of reels with long lengths of film impossible.

In accordance with the invention, the above m ntioned disadvantages are, on projectors of this type, being eliminated by providing additional means of film-feeding, which, upon occurrence of irregularities, become eifective and are controlled by the film-feed.

An exemplified embodiment of the invention is shown in the sketch, which shows the film-feeding in a projector.

In accordance with the invention, there are, in addition to the means of compensation known in the previous art as the swinging roll and the elastic film-loop, other means of film-feeding provided, which become effective upon occurrence of irregularities in film-feeding, and are controlled by the film-feeding operation.

According to the sketch, film 1 is guided from the film reel 2, as a loop 3, over rolls 4 and 5, between film-trap 6 and counterpart 7, past aperture 8, to the take-up reel which is not shown in the sketch. The step by step feeding is effected by a grapple-claw 9. In order to compensate these step by step feeding jerks, the film loop 3 wraps around the roll 4- in such a way as not to impair the selfelasticity of the film loop 3 through the roll 4. Thereby, the loop 3, which tends to be springy, swings in the rhythm of the frequency of pictures, and fully compensates the feeding-step jerks. The roll 4 is mounted torsion-free on one end of shaft 1% while a friction plate 11 is, also torsion-free, mounted on the other end of shaft 10. A lining 16 on the roll 4 increases the friction.

A swing-arm 12, having a stationary axis of rot tion 13, supports the shaft It) on its end which is oppo .e to the axis of rotation, whereby the swing-arm 1.2 kept in vertical position by its own w swingarm 12 may be held in its vertical ition by means of a spring 2%. A cable alley 14, which is continuously operated by the grap le motor or driving means 21, is so arranged wi; '1 we 5. a: of the arm 12, that the friction plate in, swung the arm 12, is coupled with the cable pulley The fact that the drive cable 15 is made of rubber increases the friction.

The pull of the film i, effected by claw 5 causes the feeding reel 2 to rotate. e to the weight (particularly when using long films) of the fully loaded feeding reel 2, said rotation is not smooth but jerky. This jerky rotation excites cusslons cted a ainst the forward feed of film Ti, \vh. on the film loop 3 and, on the other hand, throus roll 4, make the swingarm 12 move clockwise out of its vertical inoperative position. Slight jerks are co ensatcd by the effort of swin -arm 12 to return to Heavier jerks, however, would against the cable pulley 1 2-, whit also the roll 4, are made operated as described, pulls f and feeds said film .1 to the Upon compensation of the re-claw without tension. arrn returns to its n Weight.

A particular advantage over devices lillOVr'l'i in the previous art is the possibility of using spools for long lengths of film on projectors built in accordance with the invention. Furthermore, there will. be much less wear and tear of film in these projectors due to the smooth and tension-free feeding of the film to the grapple claw.

I claim:

1. In a motion picture film projects, a compensating device providing for the smooth feeding of film which comprises a friction roll in the film-feeding path, said roll being mounted on a co ..znon shaft with a friction plate, said shaft also being rotatably mounted on a pivotally mounted swing arm; said friction plate being opcratively engageable with driving means upon movement of the axis of the said common shaft responsive to film tension on the said friction roll, and disengageabie therefrom when said film tension is relieved.

2. The device as set forth in claim 1 in which the swing arm is resiliently mounted and spring biased so as to normally hold the friction plate disengaged from the film driving means.

References Cited in the file of this patent UNITED STATES PATENTS 1,258,352 Mehlfelcler Mar. 5, 1918 1,308,354 Heywood July 1, 1919 1,836,613 Oehmichen Dec. 15, 1931 FOREIGN PATENTS 41,247 France Aug. 23, 1932

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