Patent GB-923874-A (GB)
Title: Improvements in or relating to moving picture projectors
IPC: G03B19/18
Filed: 1961-06-22
Abstract: 923,874. Kinematograph apparatus. ERNST LEITZ G.m.b.H. June 22, 1961 [July 1, 1960], No. 22647/61. Class 97 (1). In a moving picture projector adapted to operate from any one of a plurality of A.C. power supplies of different characteristics, the projector having a single phase induction motor, setting means are provided for operation when changing from a power supply of one frequency to a power supply of another frequency, the setting means serving simultaneously for changing the transmission ratio of a driving system arranged between the motor shaft and a film transport mechanism of the projector, changing a secondary winding connection of a supply transformer for the motor and changing the capacitive value of a condenser system of the motor and switching means are provided for changing a primary winding connection of the transformer whereby to allow for differences in voltages of the said power supplies. As shown (Fig. 2) a single phase induction motor 13 is coupled through a V-belt drive 15 to a shaft 14 from which drive is taken in known manner for a take-up spool shaft 10a, a rotary shutter 11 (actually mounted on the shaft), an adjustable claw feed mechanism 18-20 and shafts 6a, 7a of film transport rollers. The particular projector described is adapted for use with A.C. power supplies having any of the following voltage and frequency characteristics: 220v./50 c.p.s. 110v./50 c.p.s. or 117v./60 c.p.s. Automatic setting of the projector to the correct voltage is obtained by a voltage sensitive relay 35 (Fig. 3) connected across the terminals of a connection socket 33 and operating two switches 40, 41 for connecting the socket 33 to the correct terminals in the primary winding of a transformer 34. If the transformer is only intended for use at 110 volts, a suitable series resistor may be connected between conductor 39 and the primary winding and the resistor connected to the primary winding at the point 110. In the first embodiment (Figs. 2, 3 and 6) allowance for change of frequency is made manually by rotating a control shaft 26. To prevent setting of this shaft except when the projector is running, the shaft is provided with a disc 90 having two slots 90a engageable by a spring-urged slide 91 and the slide is provided with pins 91a, 91b engageable and displaceable by switch members 48a, 48b, which set the projector for forward and reverse operation. The switch 48 (Fig. 3) is coupled to switch members 48a and 48b and is closed whenever either of these members is actuated. Part 48e is a release member for the switch 48, cancelling in known manner any previous setting of the members 48a or 48b. Whenever shaft 26 is rotated to set the projector for a different frequency, the following adjustments are made: (i) By way of a cam disc 28a on the shaft 26, a switch 39a is operated to connect the motor 13 to the correct secondary transformer connection (220v. for 60 c.p.s., 180v. for 50 c.p.s.). (ii) By way of a second cam disc 28b on the shaft 26, a switch 29b is operated whereby a condenser 50 is either included (for 50 c.p.s.) or excluded (for 60 c.p.s.) with a condenser 49 in the circuit of the motor 13. (iii) By way of arms 24, 25 fixedly mounted on the shaft 26, the transmission ratio of the V-belt drive 15 is altered. The pulley on the shaft 14 is constructed in two parts, part 21a being fixedly mounted on the shaft 14 and part 21b being axially slidable on pins 22 fixed in the part 21a. When the shaft 26 is set for 60 c.p.s. by means of the engagement between arm 25 and a bevelled hub of part 21b, the part 21b is moved axially inwards to increase the effective diameter of the pulley 21a, 21b. When the projector is set for 50 c.p.s., the arm 25 disengages from the hub of part 21b allowing the effective diameter of the pulley 21a, 21b to decrease and arm 24 brings roller 23 into engagement with the V-belt 15 to take up any slackness therein. In a first and simplified modification (Fig. 4, not shown), adapted for use only with 220v./50 c.p.s. and 117v./60 c.p.s. sources (i.e. voltage and frequency always change together), the voltage sensitive relay 35 is replaced by a switch operatively coupled to the shaft 26. In a second modification (Fig. 5), the projector is automatically set for frequency by an electromagnet 62 coupled to the shaft 26 by a rack-and-pinion coupling (Fig. 6a, not shown) and having a control switch 61a operated by a relay 61 in a frequency sensitive circuit including the relay and a condenser 64. At 50 c.p.s. the circuit is arranged to be inoperative, but at 60 c.p.s. it is energized to close the switch 61a. In a third modification (Fig. 7) in which the projector is adapted for operation at either of two film frame speeds (e.g. 18 or 24 frames per second), the arms 24 and 25 are not directly mounted on the shaft 26 but on a rotatively spring-urged shaft 30, the arm 25<SP>1</SP> being fixedly mounted thereon and the arm 24 being in two parts, part 24<SP>1</SP>a fixedly mounted on the shaft 30 and part 24<SP>1</SP>b rotatably mounted and spring connected to the part 24<SP>1</SP>a. Further, two cam discs 32, 32a are provided on the shaft 26 for controlling the arms 24<SP>1</SP>a and 25<SP>1</SP> respectively and disc 90<SP>1</SP> is provided with four slots for co-operation with the slide 91<SP>1</SP>. By this means four positions of the pulley part 21b relative to part 21a are obtained, the belt 15 being maintained taut in all the positions. In a fourth modification (Fig. 7a) the projector is adapted for operation at either of two film frame speeds in a manner similar to that above, and in addition, automatic means for setting the projector for frequency are included in a manner similar to that provided in the second modification above. In this case, the pinion 80 of the automatic frequency setting mechanism (which mechanism comprises an electromagnet 81 coupled to a frequency sensitive circuit and having an armature in the form of a rack 82, engaged by the pinion 80) is releasably coupled to the shaft 26 through a recess in its hub engageable by a pin 83 on the shaft 26 which is arranged to be slidable and spring-urged. The desired frame speed is set by manually disengaging shaft 26 from pinion 80 and rotating to either of two settings 180 degrees apart. Setting for frequency is then effected automatically. The disc 90 (again provided with four slots) and the four cam discs on shaft 26 are substantially thicker than in the previous embodiment to allow for axial movement of the shaft 26.