International projectionist (Nov-Dec 1933)

December 1933 INTERNATIONAL PROJECTIONIST 17 'AUTOMATIC CHANGE-OVERS George C. Edwards PAST PRESIDENT, AMERICAN PROJECTION SOCIETY THE trickle of ideas for "automatic" change-over devices has swelled into a deluge, with several more "ideas" reaching us recently. One of these devices is so far removed from any semblance of practicability that we can lay it aside for a year or more, to ripen, as it were. Indicative of the lengths to which "inventors" seem willing to go in making "automatic" change-over equipments is an ingenious attempt by a California inventor to coordinate the work of the S.M. and CO. cues of the Standard Release Print. The description of this device reads well, but close inspection reveals it to be a somewhat elaborate electrical and mechanical device, the function of which is to perform a manual operation which at present offers no serious difficulty. Incidentally, the device requires a certain amount of manual adjustment and setting before it will work properly, and it apparently does not provide a means for fader manipulation or arc-striking. Thus, the "automatic" angle may be taken with several grains of salt. Consider the description of this particular device: "The device consists of a pair of trip mechanisms, one for each upper reel, a change-over unit, and the necessary switches controlling the two projectors and their dowsers. A trip mechanism is built into the reel and its hub, so arranged that the reel may be placed in the magazine or removed in the usual manner. This minor change can be easily made by the projectionist. "The trip mechanism does not require any cue marks or change in the film, but utilizes a particularly efficient lever which does not injure the film and which is inserted between convolutions (layers), of the film and moves clear of the film when uncovered. This trip lever mechanically operates a switch located away from the reel. This switch is in series with one arm of the magnetic switch and a lowvoltage magnetic coil located within the change-over unit, there being one magnetic coil connected with each projector. Connecting the switch, the arm of the magnetic switch and the magnetic coil in series, prevents the trip mechanism from functioning unless the projector is in operation. "The change-over unit comprises a small motor which runs continuously and drives a shaft extending back of a panel. Arranged along this shaft are a pair of clutches and controls, one for each contact drum. This unit complete is mounted in' a small cabinet which can be placed anywhere in the projection room. "By action of the trip mechanism on the reel and the switch on the end of the shaft, the magnetic coil is energized, putting into operation the corresponding clutch on the shaft which rotates the contact drum for one complete revolution, whereupon the clutch disengages and the drum stops. After the change-over has been completed, the unit is automatically set for the next operation. "When the contact drum turns in response to the trip mechanism of one projector, it moves clockwise to engage the first contact. This contact operates a locking magnetic switch which closes to start the other projector. The next contact operates a momentary magnetic switch which causes the dowsers to change. Then the last contact is engaged, which opens the locking magnetic switch controlling the first projector. Sufficient time is provided between the engagement of the several contacts to enable the beginning projector to reach its proper speed before operation of the dowsers. Also, the completed film is completely rewound upon the lower reel before its projector is shut off. The time relation between the dowser controlling contact and the other contacts may be readily and quickly varied, if desired. "The projectionist, when rewinding a reel, inserts the trip lever of the trip mechanism at the proper distance from the end of the reel (if S.R.P. cues are used, the lever is placed upon the film at this point), and upon placing the reel in its magazine the trip mechanism is set. The reel may be removed or inserted repeatedly without danger of operating the trip mechanism, because the circuit 'Automatic' change-over unit "International Photographer's" impression of hoiv a cameraman would look if the producers' ideas on codes prevailed which it controls is incomplete unless the projector is in operation. "At any time, without interfering with projection, the automatic change-over device may be disconnected and manual control used, by merely throwing a switch." Now, let us see just what this device is all about. First, the user of this device will require a complete set of reels of the same diameter hub, which must run perfectly true upon the upper magazine spindle shaft. Any reel which shows even a slight wobble is out of the question. Into this reel must be built the lever mechanism, and if the device is to be of any use at all, this job may not be so easily accomplished without special facilities. To work the device the lever must be placed exactly at the correct point when rewinding, and care must be taken to see that there is no creeping or slippage of film, which condition is often encountered in rewinding, especially at the beginning. It is claimed that the insertion of the trip lever cannot in any way injure the film, and that it moves out of the way when uncovered. Immediately arises the question: Where does it move to? In a majority of cases there is less than Y^ inch clearance between the wall of the magazine and the upper reel, and if the reel is the least bit bent, one may expect troubles in profusion. Setting the trip lever still is a manual operation, of course, and the possibility of error in the setting process is recognized by the inventor by providing a switch permitting the cutting out of the apparatus and allowing manual operation in the usual manner. Here is an example of an enormous amount of thought and ingenuity being spent to develop a mechanism, of considerable cost, to perform the work of about five seconds duration, and the device must be supplemented by manual labor, in absolute synchronization. Also, there is the additional disadvantage of not knowing if all the factors for perfect performance are present. As an effective aid to the projectionist, this device at present lacks many features which might make it acceptable.