Patent GB-752022-A (GB)
Title: Improvements in or relating to mechanisms, instruments and machines for drawing, tracing or otherwise generating or defining the locus of a point revolving about a second point which itself is revolving about a third point
IPC: B43L11/00
Filed: 1954-05-27
Abstract: 752,022. Curve-describing instruments. JONES, H. Nov. 12, 1954 [May 27, 1954], No. 15724/54. Class 97 (3). The instrument shown has a bracket A comprising a sleeve bearing b<SP>1</SP> joined by arms c<SP>1</SP> to sleeve bearings d<SP>1</SP>. A horizontal shaft a<SP>1</SP> and a vertical shaft a<SP>2</SP> turn freely in bearings b<SP>1</SP> and d<SP>1</SP> respectively. A bevel gear 2 fast on shaft a<SP>1</SP> engages a bevel gear 1 on shaft a<SP>2</SP>, bearing against one sleeve d<SP>1</SP> and against a distancepiece i bearing against the other sleeve d<SP>1</SP>. A lug on gear 1 engages a groove f on shaft a<SP>2</SP> so that the gear rotates with the shaft but may slide therealong for adjustment, the gear being held in the adjusted position by friction or by a set-screw j<SP>1</SP>. A second bracket B has an arm c<SP>2</SP> joining a bearing sleeve f<SP>2</SP>, in which shaft a<SP>1</SP> turns freely, to a flaring sleeve d<SP>2</SP> for a short vertical shaft a<SP>3</SP>. A bevel gear 3, fast on shaft a<SP>3</SP> engages a bevel gear 4 which rotates with shaft a<SP>1</SP> by reason of a lug engaging a groove f, but which is slidable along the shaft for adjustment, being held in the adjusted, position by friction or by a set-screw j<SP>4</SP>. A shoulder-piece k fixed to or frictionally engaging shaft a<SP>3</SP> below the bearing sleeve d<SP>2</SP> carries two legs l hinged to the shoulder-piece like the legs of a compass. The legs l terminate in drawing points e<SP>2</SP>, and the shaft a<SP>1</SP> has a hard point e<SP>1</SP> at its. lower end. The gearing is such that, when shaft a<SP>1</SP> is rotated about shaft a<SP>2</SP>, the shaft a<SP>3</SP> is rotated in the opposite direction at twice the angular speed. If desired, rotation of shaft a<SP>1</SP> relative to shaft a<SP>2</SP> may be effected by means of a crank. In this case a bracket similar to bracket A is placed on shaft a<SP>2</SP> above bracket A. One bearing sleeve of the second bracket has a lug engaging the groove f in shaft a<SP>2</SP>, while the other surrounds the hub of a bevel gear fast with bracket A. A bevel gear driven by the crank journalled in the second bracket engages the bevel gear fast with bracket A so that bracket A and shaft a<SP>1</SP> may be rotated about shaft a2 on turning the crank. Several horizontal shafts a<SP>1</SP> with vertical shafts a<SP>3</SP> and attachments may be used to draw several curves at once. The shoulder-piece k may carry, instead of legs l, a horizontal bar with adjustable vertical marking bars. To draw a straight line, the point e<SP>1</SP> is set on a fixed point, bracket B is set a distance from shaft a<SP>2</SP>, and bracket A is adjusted along shaft a<SP>2</SP> until the point e<SP>2</SP> of one leg l is set at the same point as point el. On rotation of shaft a<SP>1</SP>, a straight line is drawn. The other point e<SP>2</SP>, if also in contact with the paper, traces a straight line at rightangles to the first. To draw a pair of ellipses, the points e2 are,made to touch the paper at positions separated from point e<SP>1</SP>. Rotation of shaft a<SP>1</SP> about shaft a<SP>2</SP> causes points e<SP>2</SP> to draw a pair of ellipses with their major axes at rightangles. By allowing only one point e<SP>2</SP> to touch the paper, and rotating shafts a<SP>1</SP>, a<SP>2</SP> together about point e<SP>1</SP>, a circle may be drawn.