Patent GB-1272286-A (GB)
Title: Spring-powered preloaded cameras
IPC: G03C3/00
Filed: 1969-04-29
Abstract: 1,272,286. Preloaded cameras. MINNESOTA MINING & MFG. CO. April 29, 1969 [April 30, 1968], No.21876/69. Heading G2A. In a preloaded camera, i.e. one which is sold with the film already loaded therein during manufacture, the film is advanced by spring means which is also already pretensioned during manufacture, so that no tensioning by the operator is required. As shown, the film 24 passes from a supply roll 25 in an enclosure 26 to a take-up spool 28, passing behind two slanted interior walls 30 which hold the film against the back wall of the camera, and so in the focal plane. The shutter is a disc 33 mounted on a fixed pivot 34, and having an arcuate slot. It is biased clockwise by a spring 35 but normally forced anticlockwise by a stronger spring 38, both springs engaging against a projection 36 on disc 33. The shutter is actuated by a slide 44 having a button 18 extending through the camera wall. The slide is biased towards the left in Fig.4 (towards the right in Fig. 3) by a spring 47. When the slide is moved against the spring, a turned-up tab 51 at its end lifts spring 38 away from projection 36, thus allowing spring 35 to rotate disc 33 clockwise. As tab 51 moves clear of the end of spring 38, it snaps back, striking projection 36 sharply and so causing disc 33 to rotate anticlockwise past its rest position so that the arcuate slot becomes aligned with aperture 23, thus allowing an exposure to be made. Spring 35 then restores disc 33 to its rest position. As the slide 44 is retracted to its rest position by spring 47, the take-up spool 28 is rotated to advance the film. It is rotated by means of a torsion spring 55 built into its interior, the spring being tensioned during manufacture of the spool, so that it is already in that condition when sold, and requires no further tensioning by the operator, the camera being of the expendable type. In the tensioned state the spring has the position shown in full lines, and as the tension is relaxed it eventually takes up the position shown in dotted lines. The top end of spring 55 is fixed in the spool cap 54 which is non-rotatable, and the bottom end is held in an opening 57 in the bottom wall of the spool, and rotates with the spool. Stop means normally hold the spool at rest against the influence of spring 55, said means including a lever 59 pivoted by a pin 58 to a fixed plate. The pin passes through a slot 59a in lever 59, so that the lever can slide as well as pivot. At one end of the lever is a post 60 which extends into a segmented track 66 recessed in the bottom of the spool, the track being shaped so as to have three steps 67. The lever is urged clockwise by a spring 62, and in the rest position of Fig.8 the post 60 engages one of the steps 67 and prevents rotation of the spool. When slide 44 is moved so as to actuate the shutter, an inclined edge 68 of the slide engages an upturned end of arm 61 of lever 59 and flexes it until it springs back into a recess 69 in the slide. The slide thus cannot advance any further. As the slide retracts, after an exposure has been made, lever 59 is pivoted anticlockwise, Fig. 8, so that post 60 disengages from step 67. The spool 28 is now free to be rotated by spring 55, so that the film is wound on. Lever 59 is now pulled upwards by spring 62 (position of Fig. 9 (not shown)). Lever arm 61 now disengages from recess 69, so that it is returned to the Fig.8 position, and post 60 engages with the next step 67, so terminating the rotation of spool 28. A plate 81, Fig.5, fixed to the side walls of the spool 28, has an upwardly extending cylindrical projection 82 eccentrically placed with respect to the spool axis. Over this fits a film counter member comprising a circular plate 84 having a cylindrical boss 85 extending downwards, projection 82 fitting slidingly into boss 85. A ring 90, mounted co-axially with the spool axis, has teeth 88 round its internal periphery which engage with teeth 87 round the outside of boss 85. Thus when the spool rotates, the eccentric projection 82 carries the plate 84 round in a circular path, and since teeth 87 and 88 engage, the plate is caused to rotate. Counter numerals on the top surface of the plate thus become visible in succession through an opening 80 in the camera case. Figs. 11-13 (not shown) illustrate an alternative stop and release means for allowing the spool to rotate under its spring loading. Fig. 14 (not shown) illustrates a cartridge, for insertion into a camera, which includes a take-up spool arrangement similar to that described above.