Patent GB-904750-A (GB)
Title: Improvements in and relating to pencils
IPC: B43K21/08
Filed: 1958-12-29
Abstract: 904,750. Propelling pencils. SCHISCHKAW, K. F. Dec. 29, 1958, No. 41857/58. Class 146 (3) In a mechanical pencil the lead is projected by pressing the tip of the pencil against a surface so that the tip slides inwards in relation to the pencil barrel and backwards in relation to the lead so as to expose the latter, the tip and lead subsequently sliding forward under the influence of gravity to a projected position in relation to the barrel wherein the lead is latched against rearward movement during writing. The lead 11 is held by a split tubular clutch member 15 having a lateral lug 16 and the clutch member 15 is slidable in a guide tube 12 mounted in the rear end of the tip portion 10. The tube 12 is longitudinally slotted at 13 and the lug 16 projects through this slot. An ejector 17 is slidable in the clutch member 15 and a lateral lug 18 thereon projects through an elongated opening 37 in the clutch member and also through the slot 13 in the tube 12. A bowed friction strip 19 is inserted in the tube 12 to the rear of the clutch member and has an ear 20 which also projects through the slot 13. A piece of spirally wound wire 21 is slipped over the guide tube 12 and one end 22 thereof abuts against the lug 18 as it projects from the slot 13. A spiral feed member 23 is slipped over the guide tube 12 and threaded over the wire member 21, the ear 20 and the lugs 16, 18. The continuous helical path 33 of the feed member 23 is smooth on its lower side and serrated on its upper side as at 34, the teeth on the serrated side being shaped to allow the parts 16, 18, 20 to slide downwards (when the pencil is held point down) but to resist any upward movement of these parts. The path 33 has a width somewhat greater than that of the lugs 16, 18 and the ear 20. A cap 24 is fastened to the rear end of the spiral feed member 23 and has a knurled part 25 which is pressed into the bore of the barrel 29 at the rear end thereof so as to prevent the feed member from rotating relatively to the barrel. The guide tube 12 is slidable in an axial bore of the cap 24 and the projecting rear end thereof is fitted with a stop member 27 to limit the forward movement of the tube 12, rearward movement thereof being limited by the abutment of a shoulder 28 on the tip member 10 with the lower end of the feed member 23. When the projecting portion of the lead 11 has been worn away the tip 11 is pressed against a surface so that it slides back into the barrel 29. The lead 11 is prevented from sliding back with it by the engagement of the ear 20 of the friction strip 19 and the lug 16 of the clutch member 15 with the serrated upper side of the path 33, so that as the tip 10 and guide tube 12 slide back in the barrel 29 and spiral feed member 23, the lead 11 is projected relatively thereto. When the tip 10 is raised from the surface the parts 10, 12, 15, 17, 19 will slide downwards as a unit under the influence of gravity into writing position, the parts 16, 18, 20 riding down the path 33 until the stop 27 abuts against the rear end of the cap 24. The spiral wire member 21 also slides down the path 33. The projected lead is prevented from sliding backwards in the course of writing by engagement of the lug 20 with the serrated upper side of the path 33. Rotation of the stop 27 and hence guide tube 12 in one direction serves to eject the lead when the clutch member 15 has reached its most forward position with the lug 16 abutting against a stop 14 on the guide tube 12, and rotation in the other direction retracts the parts 15, 17, 19 to the rear end of the spiral feed tube 23 ready for the insertion of a new lead. A removable rear barrel part which may carry an eraser at its end is fitted over the cap 24 and stop 27.