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Application Date, Mar, 14, 1919. No. 6400/19
Complete Left, July 17, 1919.


Improvements in Slide Rules.


I, THOMAS JACKSON, of "Dunollie," Scotland Lane, Horsforth, in the County of York, Drawing Material Manufacturer, do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement : -

The object of my invention is to provide a less-expensive method than at present exists, of manufacturing slide rules which shall possess the essential qualities of strength, practical usability, and durability, and at the same time not be liable to the faults of working, distortion, or alteration of length, such as are often caused by atmospheric changes, or by the drying-in, or "seasoning," of the materials commonly used in slide rule construction.

In my invention the body of the slide rule is formed entirely of one piece of thin sheet metal, bent and moulded to the shape shown on the accompanying sheet of drawings in Figure 1, which is an end elevation of the rule body. The sliding tongue or "slide" is formed of similar thin sheet metal, folded 2-ply or 3-ply or as may be needed to secure the necessary stiffness, as shown in Figure 2, which is an end elevation of the slide.

Figures 3 and 4 show respectively front and end elevations of the rule, with the slide in position in the groove or channel which the construction adopted for the rule body provides for it to work in. The faces of the rule body which the the calculating scales are suitably inclined, so that their edges A A lightly touch the slide; incidentally, this inclining of the faces tends to increase the ease and accuracy with which " results " can be read. The central portion of die channel or groove in which the slide works is pressed slightly outward, so as to clear the slide, which thus, bearing only on narrow strips along the edges, and being touched only lightly on its upper surface by the edges A A of the rule body, is free to move easily and smoothly to and fro as required.

Having now particularly described and ascertained the nature of my said invention, and in what manner the same is to be performed, I declare that what I claim is:-

In slide rules, the use of sheet metal bodies of the construction illustrated in Figure 1, in combination with slides constructed of the same, or similar, sheet metal by the process of folding, substantially as illustrated and described herein.

Dated the Twelfth day of March, 1919.


Redhill: Printed for His Majesty's Stationary Office, by Lowe & Malcolmson, Ltd.-1919

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