Tray Attachment for Developing Films
Roller Attached to Tray for Use in Developing a Full-Length Film
An ordinary tray can be used for film development, when there is no tank at hand, by the use of the attachment shown in the sketch. It consists of a strip of sheet metal, or tin, bent to fit under the tray and up on both sides to provide bearings for a roller. The roller is made of hard rubber and should be of such size that its lower surface will be under the developer in the tray. The film is drawn back and forth under this roller.
An Automatic Window Closer
The window closer consists of a weight, A, attached to one end of a cord, B, which runs through several pulleys and has its other end attached to a hook in the center of the window sash, as shown in [Fig. 1]. The weight A is held in an elevated position by a small trigger which is operated with an electromagnet.
The arrangement of the weight and its control is shown in [Fig. 2]. The latch C is held in a horizontal position by an extension on the arm D, which in turn is held by a latch, E. The latch C is mounted on the same supporting shaft as the arm D, and they are connected with a coil spring having the tension in such a direction that it holds the latch C down on the extension of the arm D. When the weight moves up through the box the latch C will rise and allow it to pass down beside it. The latch holding the lower end of the arm D may be released by means of an ordinary vibrating bell arranged so that its clapper will strike the extension F on the latch and thus cause its upper end to move from the engagement with the arm D. A small coil spring is attached to the arm D so that it will be returned to its vertical position when the weight has passed C and thus make it ready for the next operation without any adjustment except raising the weight and setting the clock.
| Fig. 2 | Fig. 1 |
| Fig. 3 |
The Window is Automatically Closed by a Weight at the Time Set on the Alarm Clock When the Key Closes the Electric Circuit, Causing the Magnet to Release the Latch