654,262. Step-by-step conveyers. PAKO CORPORATION. Nov. 27, 1947, No. 31442. Convention date, March 25, 1943. [Class 78 (i)] [Also in Group XX] In apparatus comprising at least one container for film processing liquid and means for supporting and advancing film carrying holders in succession through the liquid, the said means comprise a pair of bars each extending along one of two opposite sides of the container or containers, a second pair of bars each extending adjacent to one of the bars of the first-mentioned pair, teeth formed along the upper'edge of the bars and having edges downwardly inclined in the direction of advance of the films, the teeth of the bars of each pair being in transverse alignment but the teeth of one pair being offset relatively to the teeth of the other pair, and means for causing periodical vertical reciprocation of the pairs of bars relatively to one another so that the holders will be supported alternately by each pair of bars and will slide forwardly on the inclined edges of the teeth during the transfer from one pair of bars to the other so as to be progressively advanced. The periodic vertical reciprocation is preferably provided by cam mechanism which may also cause minor reciprocation at short intervals to agitate the films. Means of known kind, comprising a member movable continuously through a closed path, may be provided to lift the films one at a time from a container and to lower them into the next. Fig. 3. The machine has a base plate 31, a back plate 34, and end plates 32, 33. The containers for the various processing liquids through which the films are to be passed seriatim are placed on the base plate 31. A pair of bars 44 with saw-like teeth are mounted on the end plates and extend on each side of the containers near the tops thereof. A second pair of toothed bars 42 extend adjacent the bars 44 on the side remote from the containers, and extend through openings in the end plates to brackets which are movable vertically on the end plates. Each film F, Fig. 5, e.g. an X-ray film, is supported in a holder 27 of the kind described in U.S.A. Specification 2,410,131, which has horizontally extending supports 27a resting on bars 44 when they are in their upper position and on bars 42 when bars 44 are lowered. Since the teeth of the pairs of bars are offset, each reciprocation of bars 44 moves the holder forward one tooth. The brackets supporting the bars 44 rest on rollers 48, Fig. 1, on levers 50 pivoted at 51 at the rear of back plate 34. Links 61, 62 connect the levers 50 to a lever 64 pivoted at 65 to a plate 66 and carrying a roller 68 which is urged against a cam on a cam-shaft 71. The cam is shaped to cause the bars 44 to move downwards sufficiently far at each revolution to move the holders forward, and also to move up and down several times to agitate the holders without moving them forward. The whole of the driving mechanism is mounted on the rear of back plate 34. Motive power is provided by an electric motor 87, which is geared to a sprocket 69 driving an endless chain 78 passing over sprockets 144, 141, 140, 143, and a large sprocket 77. The shaft of this large sprocket drives the cam-shaft through another chain- and-sprocket drive. The shafts of sprockets 140, 141 extend through plate 34 and carry, in front of the plate, other sprockets driving endless chains 116, 117, Fig. 3, which pass respectively over idler sprockets 122, 118 mounted on the back plate. A bar 90, extending the full length of the machine, is supported by swivel connections 128, 132 on the chains 116, 117 respectively, and thus moves in an oval path. Bar 90 carries several arms 161, Fig. 5, which are normally horizontal but may pivot upward about a point 162 if they meet resistance in their downward travel. Depending arms 163, 164 are shaped to pick up the holders, raise them from one container, and place them in the next. The gearing is such that the bar 90 makes three complete circuits during each revolution of the cam-shaft, but holders are picked up only on one circuit. Brackets 91 attached to bar 90 have shafts 92 on which are freely mounted wheels 93 by which they are guided between vertical standards 97, 98. Counterweights 112 are attached to bar 90 by chains 110 passing over pulleys 105. The sprockets 143, 144, Fig. 1, are carried on a plate 147 which slides horizontally in guides, lever 150 pivoted at one end to plate 66 being linked to slide 147 at the other end. Lever 150 carries, between its ends, a roller 154 urged against a second cam on the cam-shaft 71, this cam being so shaped that once during each revolution lever 150 is rocked, reciprocating slide 147 so that, during the circuit of bar 90 in which holders are picked up, the upward movement of the bar is slowed down to allow time for liquid to drip from the films into the containers, and the downward movement is accelerated. Film holders for processing may be loaded into a magazine at the entry end of the machine, consisting of a pair of plates 190, fixed to the end plate 32 in alignment with bars 42, and plates 192 in alignment with bars 44. Grooved studs 195 on plates 190 extend through slots 192b in plates 192 which are thereby guided for vertical movement. The upper curved edges of the plates have teeth, the teeth of one pair being offset with respect to those of the other pair, so that the vertical movement of plates 192 advances holders supported on the teeth. Levers 240 pivoted to plates 190 have swinging arms depending from a shaft joining their upper ends. Holders are placed on the arms, and levers 240 are moved forward a number of times, so that a holder is placed in each set of teeth. One lever 240 has a spring- urged pawl 257 which engages ratchet teeth on a plate 255 on one plate 192 when the latter is in its lower position, so that levers 240 cannot be moved forward except when plates 192 are raised. Movement of plates 192 is effected by levers 199, 202 (see also Fig. 3), on a shaft 196 journalled in plates 190. Lever 199 is linked by a rod 205 to a lever 207, pivoted at 208 to the plate 66 and having a roller 218 which selectively engages one of a set of three cams on the cam-shaft 71. Each cam has a high point which rocks lever 207 and thus moves plates 192 up and down to advance the holders in the magazine so that each in turn is brought to a position abutting projections 190d on plates 190, from which it is picked up by an arm on the bar 90 and placed in the processing liquid, resting on bars 42, 44. The high points of the cams are spaced 120 degrees apart, and the bar 90 makes three circuits during the time, e.g. one minute, during which the cam-shaft rotates once. Thus by selecting the cam engaged by roller 218, the time of entry of the holder into the processing liquid can be varied by a period of 20 seconds. Further adjustment of the time during which the film -is processed in the first container is obtained by means of a plate sliding vertically on end plate 32 and having extensions 172, Fig. 3, adjacent the bars 42. The holders, guided into the first container by a surface 170, slide down the inclined surfaces of extensions 172, which have three positions ; according to the position chosen the holder is placed in the first, second, or third sets of teeth of the bars 42. The movements of the bars advance the holders through the containers, each holder, on reaching the end of one container, being transferred to the next by the arms on the bar. 90, and finally being removed from the apparatus and placed, preferably, in means for drying the film. The Specification as open to inspection under Sect. 91 also comprises drying apparatus in which two pairs of relatively movable toothed bars, forming extensions of the bars 42, 44, advance the holders delivered from the machine past electric heating elements. This subjectmatter does not appear in the Specification as accepted.