Browse Prior Art Database

Distributed Mass Hammer Design

IP.com Disclosure Number: IPCOM000081102D
Original Publication Date: 1974-Apr-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 99K

Publishing Venue

IBM

Related People

Mulzet, AP: AUTHOR [+2]

Abstract

Impact printers traditionally use lumped mass hammers which are driven by the armature of an electromagnetic actuator (Fig. 1). The cost of this print mechanism can be reduced by combining the hammer and armature into a single moving piece, which is excited by a magnetic field and strikes an impact surface. The mass of the moving piece must be distributed in such a way that there is sufficient mass to complete the magnet circuit, as well as to provide sufficient impact energy. The resulting distributed mass hammer (Fig. 2) is less rigid than lumped mass hammers, and vibrations of the hammer become a factor.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 3

Distributed Mass Hammer Design

Impact printers traditionally use lumped mass hammers which are driven by the armature of an electromagnetic actuator (Fig. 1). The cost of this print mechanism can be reduced by combining the hammer and armature into a single moving piece, which is excited by a magnetic field and strikes an impact surface. The mass of the moving piece must be distributed in such a way that there is sufficient mass to complete the magnet circuit, as well as to provide sufficient impact energy. The resulting distributed mass hammer (Fig. 2) is less rigid than lumped mass hammers, and vibrations of the hammer become a factor.

In a distributed mass hammer a tendency for a double impact will exist due to the excitation of the first natural frequency, if the period of the first frequency is longer than the contact time of a lumped mass hammer with the same equivalent mass. Double impacts cause smearing or double printing and must be avoided. Double impacts resulting from the excitation of the first natural frequency of the hammer can be avoided, by reducing the excitation of that frequency.

The amplitude of excitation of the first frequency varies with the location of the impact point on the hammer. If the impact point is located at the nodal point of the first frequency, the excitation of that frequency for that beam will be a minimum and double impact will not occur. However, the first nodal point is significantly removed from the most desirable impact point which, from a design and contact time point of view, is the outermost point of the beam.

It is, therefore, necessary to compromise by locating the impact point above the nodal point of the first natural freq...