Patent GB-681262-A (GB)
Title: Improvements relating to film carriers for optical projectors
IPC: G03B23/12
Filed: 1949-09-09
Abstract: 681,262. Optical projectors. PULLIN OPTICAL CO., Ltd., and BAUMGARTNER, W. J. Nov. 15, 1950 [Sept. 9, 1949], No. 23435/49. Class 97 (i). A film transporter mechanism for a projector capable of feeding pictures of different sizes, picture by picture, has members at the projection opening adjustable to form a mask to suit the size of picture to be projected, and a series or rotatable cam surfaces rigidly connected together and having different numbers of equally-spaced notches per revolution, the said cam surfaces being connected to the sprockets or other film-feeding means, and a manually-operated member which both adjusts a spring-urged feeler so that it rides on the particular cam surface with notches spaced to correspond to the size of picture to be projected, and also simultaneously adjusts the masking members to suit that size. One embodiment is shown in perpendicular sections. An upper film container 8, Fig. 3, has a hinged portion 16 and is detachable, by removing a pin 12, from a box-shaped member 1 with a threaded aperture 4 for the projection lens. The rear of the member 1 is closed by a plate 5 having a projection aperture in which is mounted a glass pressure plate 46 carried in a frame 47 with a forwardly extending lug 48 at each side. The pressure plate is urged rearwardly by spring blades 49, 50. The co-operating glass plate 38 is carried in a gate member 22 carried on pivot pins of which the upper one 25 engages a hole in a spring blade 26 to allow the gate member to be detached. The edges of the plate 38 are bevelled and the plate is held in a bevelled seating by spring blades, not shown, carried on an apertured plate 32 at the back of the gate. Rotation of a film feed sprocket also rotates a cam 57 to lift a follower 54 held in contact with the cam by a part 53 of the spring blade 50. The follower, in turn, rotates pivoted arms 60 with hooked ends 61 engaging holes in the lugs 48 to relieve pressure between the plates 38, 46. The cam 57 is carried on a shaft 44, Fig. 5, having a rigid knob 65 at one end and, at the other, a knob 66 screw-threaded on to it. The cam is clamped between these knobs and sleeves 144. The sprocket-wheels 43 are carried on shoulders on the knobs 65, 66 and are not clamped when the knobs are tightened. Pins 69, rigid with the shaft, project through slots in the sleeves 144 and anchor springs 67 attached at their other ends to pins 68 projecting from the sprocket-wheels. The springs normally hold the pairs of pins in contact but provide lost motion, when commencing film feed, before the pressure plates have released. The cam 57 has two diametrically opposite notches, 63, extending for about one-third of its length and two others, 64, extending for about two thirds of its length. By shifting the follower 54 axially of the cam 57, the latter can be arranged to produce either two or four detent positions per revolution of the sprocket between which the pressure plates are separated or, by using the plain part of the cam, to separate the plates and allow free sprocket rotation. The follower 54 is carried on a spindle 55, the end 72, Fig. 5, of which bears on a helical cam face 73 on a knob 74 which is rotated to move the follower axially, notches 76 locating the spindle end 72 in the three positions required. An endless blind 78 of thin sheet steel passes round the spindle 75 of the knob 74 and an upper spindle 79 urged upwardly by springs 85 to keep the blind taut. Rollers 80 hold in juxtaposition the two halves of the blind in which are formed apertures, the overlap of which is varied, as the knob 74 is rotated, to mask a picture size to suit the length of film feed determined by the part of the cam 57 which is in use. The film leaving the gate passes into a scroll-shaped guide containing needle rollers 92 and is directed into a container, rotatably supported on rollers, and wound therein leading end outwards. Alternatively, ordinary film spools may be used at top and bottom of the gate.