Improvements in and relating to mechanical printers

925,205. Typewriters. I.B.M. UNITED KINGDOM Ltd. May 16, 1961 [May 25, 1960], No. 18408/60. Class 100 (4). A high-speed printing device in which a web of paper is passed between a plurality of reciprocating hammers and a corresponding plurality of print heads each bearing a character to be printed so that when a print head is raised in the direction of reciprocation of the hammers to a print position the character is printed by the impact of the corresponding hammer. In a high-speed printing device in Fig. 1, the web of paper 1 is' fed continuously across a print head matrix 2, consisting of 120 characters in a line and 39 rows of characters composed of 36 alpha-numeric and 3 special characters, with the web taken from a stack 7 by rollers 3 and 4, fed past a sensing brush 12 and then delivered into a receiving stack 8 by rollers 5 and 6. A carbon ribbon 15, having a rough surface for frictional gripping of the top of the raised print heads is moved across the matrix by rollers 16 and 17 at the speed of the paper web. To prevent misalignment of the printed data, on the fast moving web of paper, the brush 12 senses the start of a new block of data by means of a hole provided at the top right hand corner of each form. Each of the print heads 9 in the matrix 2 is mounted for vertical displacement from a rest position to the printing position, when the character corresponding to that print head is sensed and the character is printed on the paper web by an associated hammer 11. The hammers might be simple rotating cams, arranged in rows corresponding to the character position with adjacent rows having a different phase relationship and firing cyclically at a rate of 6000 times a minute, printing, however, will not take place unless a print head is raised beneath one of the hammers. Assuming that a line QQ1 (Fig. 3), containing the characters D and F in the first and second character positions, respectively, is to be printed the approach of the line QQ1 is sensed by the brush 12 and when the line is at the threshold of the matrix 2 the line of data to be printed on QQ1 is written into a magnetic drum 13 (Fig. 2, not shown), and the reading operation is begun by read heads 14 and switching circuit 10 so that when the line QQ1 passes over the line of print heads D, the head D in the column associated with the first character position is raised into the printing position and a letter D is printed by the hammer 11 on the paper web in the first character position of