| Simplex Daylight Loading Developing Tank |
 |
 |
| The following information has been gleamed from studying a Simplex tank purchased for £1 from a local flea market. No instructions accompanied the tank so there remains some uncertainty exactly how the tank was meant to be used, but there is little doubt that the essentials are as stated below. | |
 |
In many respects it resembles a conventional darkroom loading tank, being constructed of black Bakelite with a push-on light tight lid covering a circular chamber containing a conventional plastic spiral (see below, left). A top central funnel allows pouring in developer & fixer and a peripheral spout is provided for solution emptying. But there are two additional features which distinguish the Simplex from more conventional darkroom loading tanks. The most obvious is the side chamber with a screw on light proofing lid, and the second is that two thumb wheels on the side of the main chamber screw into a vertical channel and push against a red rubber strip. |
|
|
The spiral loads from the outside inwards and has no special means to assist film loading into the spiral. Taking the top off the side chamber (a single knurled thumb screw) reveals a chamber into which the film is located complete with its backing paper (see below left). The chamber contains a 'pull out' Bakelite 'tube' with a side slot and a metal spring clip that can be placed around the film (see below). |
||
  |
The sealing tape around the exposed film is torn away and the backing paper unrolled a few inches. The metal clip is then placed around the film, preventing the backing paper from unwinding further (see right). It is important to attach the clip over the film in the way shown with respect to the backing paper. The film, with the clip, is
now placed inside the Bakelite 'tube' (see below) and the whole
then inserted into the side chamber of the tank (see left). The
backing paper is turned back on itself and is led out of the
side chamber as shown. The top screw on plate is now put back
on. |
 |
 |
When the internal chamber is rotated fully clock-wise, a vertical slot in its side wall lines up with the vertical rubber strip (see far left) inside the side channel that was referred to above. When the internal chamber is rotated fully counter-clockwise. the same vertical slot engages with two spring steel strips which connect into the side chamber film compartment (see left). |
|
 |
 |
In order that the entry groove of the film spiral lines up with the spring steel slots connecting with the side chamber, a double row of radially raised dots can be seen on the top face of the spiral. Location ribs in the bottom of the spiral chamber locate with the underside of the spiral to assist the spiral in taking up its correct position i.e. with these dots pointing to the spiral chamber's vertical slot and, initially, the rubber strip (see above, left). When the spiral chamber is then rotated counter-clockwise by 70°, these same radial dots, still pointing to the slot, align with the place where the spring strips are entering from the film compartment. These strips then locate with the entry groove of the spiral. |
 |
The picture to the left shows what happens during the film loading sequence. By not having the spiral inside the tank and without the lid, it is possible to see the film entering the tank via the spring steel strips. In practice, with the spiral inside the tank, the tank lid on, and the spiral rotated fully counter-clockwise, the backing paper is pulled slowly but firmly away from the tank. Inside the side compartment the light sensitive film is eventaully uncovered but this happens at the end where the film is not attached to the backing paper. Hence, as the film comes out from between the turns of backing paper, instead of following the route taken by the backing paper, it is natural stiffness and curl are free to follow the 'tongue' on the steel clip which surrounds the film roll (see above) and to pass through the spring steel strips which are engaged with the spiral. Further pulling on the backing paper 'feeds' the film into the spiral. |
|
| The backing paper is pulled until a resistance at the end shows it has parted company entirely with the film. At this stage there is perhaps 3cm of film not actually in the tank spiral but still between the two spring steel strips leading from the film compartment. However, if the spiral is then turned clockwise, there is sufficient friction from the film already in the spiral to pull the remaining 3cm out from between the spring strips, whereupon it takes up the contour of the outer turn of the spiral. The whole spiral containment chamber can now be turned clock-wise through 70°, sealing off the entry from the film chamber and aligning the slot, through which the film entered, with the red rubber strip (see above). At this stage, the remains of the backing paper can be entirely pulled out from the film chamber. | ||
  |
The rubber strip is then screwed tight against the slot using the two external knurled thumb screws. This seals the internal spiral chamber and effectively turns it into a closed developing tank with a central filling funnel and a peripheral emptying spout, exactly as a conventional darkroom loading tank. | |
|
|
||
The
Simplex daylight loading developing tank was made in Austria
by Friedrich Fisher, Vienna, during the 1930s. It was sized specifically
for developing 120 or 620 size roll films.
The spiral is conventional apart from
the end plates being of fixed separation, specifically for 120
/ 620 film. The two halves are held together by the screw-in
funnel.
In
order to understand how the light sensitive film, wrapped inside
the backing paper, finds its way onto the spiral, its necessary
to understand that the main chamber consists of an external open-base
cylinder inside which is a a closed-base chamber into which fits
the film spiral. The internal chamber can be rotated relative
to the external cylinder (by about 70°) using the large knurled
grip at the base of the main chamber.|
|
|