John Wolff's Web Museum

The Millionaire - Patent variations

A comparison of the production machine, as described in the preceding sections, with Steiger's original patent descriptions shows the extensive contributions made by Engineer Hans W. Egli in preparing the design for commercial manufacture.

The illustrations below are extracts from US Patents 538710 and 558913. The full patents are available on-line from www.uspto.gov.

Steiger's 1892 patent sets out the basic principles of his multiplying machine. The multiplication table, racks, cross-shafts, sliding differentials, and the tens-carry mechanism are all clearly described and illustrated. Three different constructions are shown to illustrate some of the manufacturing possibilities. In one version the multiplier body uses stepped discs rather than plates, assembled into a drum or barrel which is rotated into alignment with the racks. (Stepped or pinned barrels were established technology of the time, and were used as control elements in applications ranging from mechanical organs to Babbage's calculating engines). In another version, Steiger shows stepped plates attached to the ends of the racks, and actuated by a travelling comb which is lifted into alignment by the multiplier lever. Steiger obviously had a thorough understanding of the principles and the possibilities of his machine, but was undecided as to a suitable way to build it.

The 1895 application is concerned primarily with refining the details of one particular design which was to form the basis of the "Millionaire". Some of Steiger's details were used unchanged in the production machine, but a great many more were altered and improved by Hans W Egli as he prepared the design for commercial manufacture. Some of the more significant changes are described below.

• The most obvious external change was to the layout of the control panel. The patent shows the Regulator and the add/subtract cams at the lower left of the machine, with the winding handle mounted externally at the right-hand end of the camshaft. These were moved to the upper right of the panel to provide a more balanced and functional layout, at the cost of an additional pair of bevelled driving gears.
  
• The patent drawing (above) shows two rows of peep-holes for the registers, with a third row between for the straight-line display of the slider settings. This "check dial" used flat numbered strips extending forward from the sliders, passing above the carriage, between adjacent counter and accumulator windows, and appearing in the central row of offset windows. The addition of twirlers on the accumulator dials made it impossible for these strips to pass above the carriage, so they were formed into a loop-and-pulley arrangement as previously described. With the setting strips removed, the openings in the top panel could be widened into slots to provide a less restricted view of the register dials.
   
• The Steiger patent shows the moving carriage supported in mid-air on two round shafts of perhaps 10mm diameter. The carry drum is supported independently on its drive shaft, and is drawn along with the carriage by a half-round yoke. The mechanism has a moving mass of around 6kg, and must be held in close alignment with the differentials and the carry drum. In the production machine the carriage and carry drum are built as a single rigid unit, which is supported on steel rollers running on replaceable steel rails.
  
• All of the cams in the Steiger patent are shown in the conventional form with spring-loaded followers, as in this drawing of the add/subtract cam and the differential rocking shaft. This construction has the disadvantage of requiring relatively strong springs to ensure a positive return, with consequent increases in loadings and wear. The production version replaced all of the plain cams with an enclosed or slotted construction, ensuring a positive movement in both directions without the use of springs.
  
• The most significant internal difference between the patent and the production machine is in the addition of new mechanisms to control over-run in the racks, and the consequent changes to the counter mechanism. In the patent drawings, the counter register has ten-digit numeral wheels and is driven 1:1 from a single cross-shaft and pinion. In multiplication the pinion is drawn forward to engage with the No 1 rack, as previously described. In division, it moves rearward to engage with a "minus one" rack located behind the zero rack, driving the ten-digit numeral wheel in complementary fashion. The overrun gate mechanism does not appear in the patent drawings. When it was added later, the space occupied by the "minus one" rack was re-assigned to the cross-shaft star wheels, and the counter register, drive, and clearing mechanisms were re-designed to suit.
   
• Similar changes were made to control over-run in the tens-carry mechanism. The carry lever latching bar does not appear in the patent, and there are no matching holes in the carry levers. The latching mechanism was added to prevent mis-operation caused by the carry lever moving more than one position when struck by the actuating arm on the register shaft. Likewise, stop pins were added to the bottom rail of the carry lever assembly to limit the travel at the second stage, when the levers are struck by the cam blocks on the carry drum.