when the cartridge is pushed onto the coupling portion 6 in the embodiment of fig4 the cartridge 15 is provided with a stepped part 25 onto which a tubular section 26 is pushed the section 26 has a partition wall 28 formed with one or more slits 27 which constitute the weak zones at which the wall is to break in this embodiment the funnel 20 fig2 of the cartridge is replaced with a funnel 30 that is provided on the coupling portion 29 of the propelling mechanism the cap 19 in this embodiment is provided with a cleaning needle 31 for cleaning the lead passage 4 shown in fig1 which extends through the eraser when the cap 19 is in place the eraser 18 may be provided with a hole or bore for this purpose fig6 shows a modified embodiment of the member 23 of fig2 in fig6 this member is replaced by a ring 32 having having one or more inwardly projecting tongues 33 one shown of which one must extend across and beyond the center of the ring 32 so as to overlie and close the channel 21 another such modification is shown in fig7 where a disk 40 is provided with a plurality of slits 41 which form at the center of the disk 40 an annular space 42 one or more one shown webs 44 are integral with or secured e g bonded to the disk 40 and carry a small plate 43 which is located in the space 42 and closes the channel 21 either of the embodiments of fig6 and 7 can be used in fig2 in lieu of the disk 23 fig8 a shows a lead cartridge 35 which is composed.