Patent GB-993658-A (GB)
Title: Printing hammer assembly
IPC: B41J9/10
Filed: 1964-04-06
Abstract: 993,658. Selective printing. DATA PRODUCTS CORPORATION. April 6, 1964 [May 13, 1963], No. 14026/64. Heading B6F. Typewheel machines; hammer impression arrangements.-A high speed line-by-line selective printer having a continuously rotatable type wheel 10 is provided with a hammer assembly stack 14, Fig. 1, comprising a plurality of hammer assemblies 18, one for each character in a line, each assembly 18 including a magnetic coil 50 mounted on the hammer shank 24 for generating a first magnetic field, a pair of permanent magnets 54, 56 mounted on a base 20 for establishing a second magnetic field to interact with the first magnetic field to move the shank relative to the base, the shank being connected to the base by a pair of resilient support members 26 and 28. The support members 26 and 28 are electrically conductive and extend through sleeves 30 and terminate adjacent a terminal block 38 which includes a plurality of conductors 44 separated by insulative spacers 42 of connector screw block 46 is fixedly mounted adjacent the block 38 to force the terminal portions of the support members 26, 28 into electrical contact with the conductors 44, the support member intermediate their ends are secured in aligned V-notches 32 of base plate 20 by a holding screw block 34. The upper terminal portions of the support members 26, 28 are potted in a rubber or epoxy material 90, Fig. 4, which secures them in receptacles 74 on the lower side of the hammer shank 24, which may be formed of low mass material, e.g. aluminium, either end 70 or 72 being capable of use as an impact tip. The shank 24 has a central opening 76 having secured therein the magnetic coil 50, whose terminals 60, 62 are soldered to the support members 26, 28. Consequently, when an electrical potential is applied across the support members 26, 28, by selectively applying such a potential to the conductors 44, the current flowing through the coil establishes a magnetic field which interacts with the magnetic field of the permanent magnets 54, 56, Fig. 3, encompassing the shank 24 and the coil 50, whereby the shank is impelled towards the type wheel 10. The shank is restored by the resilience of the support members 26, 28 which are coated with a rubber or epoxy film 88 to quickly damp out any vibrations set up by the shank 24 being bounced back against the locating screw 68 in a block 64. To compactly package the hammer assemblies 18 in the assembly stack 14 a first group hammer assemblies 18 is dependently supported from a base plate 22 while a second group is supported on the base plate 20 such that the first and second groups are interleaved. In addition, to space the hammer assemblies very closely the coils 50 are placed at three different points along the shank 24 (Fig. 2, not shown), and the permanent magnet pairs 54, 56 are mounted in three rows on bars 58, Fig. 1. Dust excluders.-The base plates 20, 22 and bars 58 are provided with holes 59 to permit air to flow through the hammer assembly stack 14, Fig. 1, for cooling purposes and the holes permit also the use of pressurized air to exclude dust which may introduce frictional effects.