US2153214A - Pressure pad - Google Patents

Description

April 4, 1939. A. w- ToNDRl-:Au .l 2,153,214

' PRESSURE PAD Filed oct. 3, 195e [Nl/ENTOR ALBERT W. To/VDEAU 23 BY A TTORNEY Patented Apr. 4, 1939 UNITED STATES PRESSURE PAD Albert W. Tondreau, Hollywood, Calif., assigner to Warner Bros. Pictures, Inc., New York, N. Y., a corporation of Delaware Application October 3, 1936, Serial No. 103,900

6 Claims.

'This invention relates to a continuous film contact printer and particularly to a pressure pad which maintains the proper contact between the negative and positive lms at a translation point on a sprocket.

An object of the invention is to obtain better contact between films while passing a translation or printing point.

Another object of the invention is to prevent separation of lms while passing over a println sprocket.

A further object of the invention is to maintain constant pressure on illms in contact with one another as they approach and leave a printer sprocket.

A still further object is to prevent sprocket teeth modulation at the translation point on a printer sprocket.

In the usual type of contact printers the negative and positive lms are advanced in contact with one another over a portion of a large sprocket having teeth which enter the perforations of each film simultaneously. The lms are usually advanced from separate supply reels which means that they approach the printing sprocket at diierent angles so that air may become trapped between them thus separating the films from one another at the printing point. 'I'his separation causes blurring and distortion of the print and in the case of film sound tracks, destroys the low frequency components of the sound. Ihe pressure pad of this invention not only prevents this type of distortion but insures a better lm contact when the negative film has shrunk more than usual as in the case of old negatives.

Prior printers of this type usually employ pressure shoes in the form of curved metal blocks having a curvature concentric with that of the sprocket and which are brought substantially in direct contact with the outermost lm. This type of pad, if operated with suillcient pressure to maintain the films in intimate contact, causes abrasion and scratching of the lm while if abrasion is reduced, entrapped air holds the films apart as they pass the printing point. Pad rollers of diierent types have been used but they ride upon the sprocket which gives rise to sprocket teeth distortion.

The present invention utilizes a pad having self aligning and resiliently mounted pressure rollers at the ends thereof which bear upon the lms before they reach the sprocket, the films passing over guides which direct the film tangentially onto and oi of the sprocket. The tangential positioning of these guides with respect to the sprocket permits a smooth approach of the lrns thereon which facilitates the entrance of the sprocket teeth into the perforations oi thesuperimposed lrns, Sprocket teeth distortion is therebyI eliminated. The rollers are freely rotatable so they may adjust themselves with respect to the tangential guides and iilm irregularities and thus maintain a constant pressure on the lms. Air pockets are eliminated by the approach roller and both rollers will cooperate to maintain the two lms tightly wrapped over the sprocket at the translation point.

The detalls of the invention will be better understood by reference to the following description read in conjunction with the accompanying drawing in which;

Fig. 1 is a schematic sketch of the essential portions of a printer embodying the invention.

Fig. 2 is a cross-sectional detailed view of the pressure pad and the printing sprocket.

Fig. 3 is a detailed view showing a cross section of one of the rollers, and

Fig. 4 is a cross sectional view of the pressure pad bracket and portion of the sprocket taken along line 4 4 of Fig. 2.

Referring specifically to Fig. 1, 5 is a supply reel of raw positive stock and 6 is a supply reel of negative lm from which the print is to be made. The two iilrns are advanced over a sprocket 8, around guide rollers 9 and onto a printing sprocket I0, after passing between pressure pad roller I2 and a tangential guide I3. The two lms are maintained in contact on the sprocket I0 until they are taken therefrom bel tween the tangential guide l5 and the pressure pad roller IE, after which they pass around a sprocket I'l to a take-up reel i8 for the positive film and the take-up reel I9 for the negative lm. This type of printer is of the continuous type, the light therefor being supplied from a lamp 2l, which is diffused to the translation point 22, the sprocket IIJ being of the hollow type mounted upon an axle 2D. The lamp 2|, and sprocket l0 are in a light tight housing 26 to prevent the positive stock from receiving light except at the translation point 22 where the printing of the picture and sound track portions of the lms takes place. A pair of adjustable sections 28 and 3l between the sprocket teeth rings control the size of the translation or printing aperture. The lm is maintained upon sprocket I0 by means of the pressure'pad generally indicated at 23 and which is supported upon a bracket 24 pivoted at 25. A handle 21 is used for opening and closing the assembly. The bracket 24 has an extension 29 to which is attached a compression spring 30 for obtaining a certain initial tension of the assembly with respect to the lms.

Referring now to the detailed views of the pressure pad, the bracket 24 has mounted thereon a curved shoe held in position by means of four screws 31. This shoe has a curvature concentric with the sprocket but positioned five or six film thicknesses therefromso there will be no abrasion and forms a light block when the assembly is in printing position. The shoe carries at its ends hollow sleeves 38, each maintained in position by pins 39 about which they pivot. These sleeves accommodate T-headed studs 4I which are encircled with grooves 42, as shown clearly in Fig. 2. By means of these grooves and cooperating pins 43, the studs 4I are maintained longitudinally in sleeves 3B but may rotate therein within limits deiined by pins 52 attached to studs 4I and slots 53 in the sleeves 3B.

Within the T-heads are ball bearings (see Fig. 3) which carry shafts 44 for rollers I2 and I6. The rollers have large diameter end portions which contact the film and are held onto the shafts by respective screws 5D. By permitting the rollers to rotate on studs 4I, they are self aligning.

The film is directed onto the sprocket I0 by means of the tangential guide I3 and directed off of thesprooket by the tangential guide I5. These guidesare iixedly attached to the frame or housing 26 by suitable screws or bolts not shown. It is to be noted `that there is a separation between the films as they approach the guide I3 and with the old type of pad, air was usually trapped therebetween so that they remained separated as they passed the translation point. In this instance, however, rollers I2 bear against the films as they pass over the guide I3 and roll out any entrapped air, thus bringing the films in intimate contact before they arrive at sprocket IIJ. The guide I5 directs the film tangentially off of the sprocket while the rollers I6 cooperating with rollers I2 maintain the two films in intimate contact and tightly wrapped around the sprocket particularly at the translation point 22.

To provide resiliency in the pressure of the rollers I2 and IB on the films, compression springs 5B and 59 each have one end abutting iiattened portions of the sleeves 38 and their other ends abutting screws 6|) and GI, respectively, these screws being maintained in position by nuts 62 and 63, respectively. Adjustment of the tension of the rollers is made by advancing or backing ofi the screws and 6I, thus varying the pressure on the springs 58 and 59 and consequently on the rollers I2 and I6 as they bear against the films. This resilient mounting permits any irregularities of the film, such as splices, to pass between the guides and rollers without damage to the films, while maintaining a constant pressure thereon. The sleeves 38 are limited in their action toward the sprocket when removed therefrom by underlying portions of the shoe 35 upon which they rest.

In operating the above pressure pad, it is only roller I2 having preferably a greater pressure on the film than roller I8.

I claim:

1. In a continuous film contact printing machine having a film advancing sprocket, a lamp and a housing for said sprocket and lamp, the combination of a pair of tapered guides adapted to direct negative and positive films tangentialiy on and off of said sprocket adjacent the translation point, a pair of self-aligning rollers adapted to bear said films against said guides, means for individually predetermining the pressure of each of said rollers on said films, a bracket for mounting said rollers, and means for resiliently exerting a pressure on said bracket.

2. In a continuous contact film printer having a continuous rotatable sprocket adapted to ad- Vance a plurality of films in contact thereover, the outermost film being a positive to be printed and the innermost film a negative, and a lamp for providing printing light for transmission through said negative to said positive, the combination of guides positioned adjacent the circumference of said sprocket for directing said films onto and off of said sprocket tangentially with respect to the circumference thereof, rotatable means for pressing said films against said guides, and means for individually varying the pressure of each of said rotatable means.

3. In a continuous Contact film printer, the combination in accordance with claim 2 in which said last mentioned means comprises adjustable screws having compression springs interposed between them and said rotatable means.

4. In a printer, the combination of means consisting of a sprocket adapted to engage and advance a pair of films in contact past a printing point on the circumference of said sprocket, a guide adjacent said sprocket adapted to direct said films in a path onto said sprocket, said guide terminating in said path in advance of said sprocket, a support, an arm pivoted on said support, a roller mounted on said arm adapted to bear said films against said guide, resilient pressure means between said support and said arm for urging said roller against said films, and means for adjusting the force of said resilient pressure means.

5. In a continuous contact film printer having a continuous rotatable sprocket adapted to adr Vance a plurality of films in contact thereover, the outermost film being a positive to be printed and the innermost nlm a negative, and a lamp for providing printing light for transmission through saidnegatve to said positive, the combination of guides positioned adjacent the circumference of said sprocket for directing said films onto and off of said sprocket tangentially with respect to the circumference thereof, a light block between said guides, a pair of oppositely extending roller mountings projecting beyond said block, means for pivotally securing the inner ends of said mountings to said block, a self-aligning roller at the outer end of one of said mountings for pressing said films against one of said guides, a self-aligning roller at the outer end of the other of said mountings for pressing said films against the other of said guides, and tensioning means for said mountings, said light block having a curved shoe at each side thereof adjacent the opposite rows of sprocket holes in said films, said light block between said shoes being substantially free from frictional engagement with the outermost one of said films.

` said light block in the general direction of the curvature of said shoes, a self-aligning roller on each of said arms, a bracket secured to said block and extending over said slots, a spring barrel in said bracket opening into each of said slots, and a spring for each of said spring barrels.

ALBERT W. TONDREAU.

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