SP Series Trip Assembly

These presses are in print mode when the carriage is at the feed board and remain so unless the lever is shifted to trip. Independent eccentrics on the inside of each carriage side plates are linked to the trip arms. These eccentrics are oiled from the outside at the small holes located above the ring at the base of the hand crank and above the pushrod on the backside of the carriage. Oil with SAE 20 weekly.

After the print stroke is completed, the impression cylinder automatically shifts into trip during the return travel. This is activated by the trip arms contacting the trip rollers on each side at the right end of the press bed. Another pair of trip rollers, behind the ink drum, shifts the cylinder into print mode before the carriage returns to the feed board. If a roller is missing or damaged, the cylinder will not shift. This can jam up the carriage. Trip rollers fit Challenge Series M presses.

When the print/trip lever is set to trip, steel plungers (X-20805) from the sides of the bed project out, which then shifts the cylinder. These assemblies can become clogged if not cleaned and oiled and may jam the carriage.

The position of the trip arms is held by springs. If a spring breaks its trip arm may slip and cause the carriage to jam. Early SP series presses require coil springs while later ones require flat springs. See the table at right.

Coil Spring Replacement

When a coil spring or its shaft breaks, access requires disassembling the tie rods and oscillator before removing one or both side plates. Removing side plates require a bearing extractor [wheel puller] for Cylinder bearings The entire trip spring assembly should then be cleaned and lubricated and the snap rings replaced.

Leaf Spring Replacement

Review Sheet 302 in the SP manual, but ignore the instruction to break the spring loop with a chisel because this may damage dowel “A”. Instead, pry the loop from the dowel with a long 316 tip screwdriver.

To install a replacement spring, insert looped end into the assembly tool then move it over bearing C and under dowel B. To ensure that the folded end of the spring slides under dowel B,   press down using a tool with a right angle, such as long hex key. Strike the assembly tool with a mallet until the loop of the spring snaps onto dowel “A”.

The assembly tool (J-19953), shown on Sheet 302, can be made from a 2 × 60 pica length of printer’s furniture. Place the loop of the spring against the side of the furniture and tap to indent a pattern, then drill a hole with a 38 wood boring bit and then cut to shape. A flat segment of the broken spring can be used to create tension against the top of the loop. Before installing, the trip arm must be in print mode. Insert the spring into the tool. Raise the oscillator and remove the form rollers from the press. From the feed board, insert a long, thin screwdriver behind the side plate against the spring and dowel A, then hit it with a mallet.


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