US 4872027

Patent Overview — US 4,872,027

Title: Printer having identifiable interchangeable heads

Patent number: US4872027A
Application number: US07/116,093
Inventors: William A. Buskirk, Carl J. Landsness, John D. Rhodes
Original assignee: Hewlett Packard Co
Priority/filing date: 1987-11-03
Publication (grant) date: 1989-10-03
Status listed: Expired – Lifetime; anticipated expiration 2007-11-03

Purpose: The invention addresses printers, particularly drop-on-demand dot-matrix types such as thermal inkjet printers, in which printheads are interchangeable. The stated aim is to let a printer identify the type of head mounted on its carriage and reconfigure its control accordingly, enabling different colors and/or differing ink dot densities or sizes. The text notes that single-color printers had not been retrofitted with color heads because of differing printhead body configurations, nozzle spacing and grouping, and control requirements.

Plain-language scope: Each interchangeable head carries a specific code identifying its type. In one embodiment, extra electrical contact pads are provided on the resistor network that fires the head's nozzles; these pads are selectively connected (or not connected) to resistor circuits or circuit traces, forming unique configurations. A connection or lack of connection can yield nine unique connections to identify a head. Types identifiable include single color, multicolor, single drop, multiple drop, differing drop sizes and colors. The printer reads the code and its head identity circuit selects an input to supply instructions to the microprocessor controlling that head. The text also mentions alternative coding means: separate electrical pad configurations, projections or depressions sensed by carriage switches, bar codes read by a reader, or reflective strips detected by light-sensitive devices.

Source: https://patents.google.com/patent/US4872027/en

What the excerpt does not establish: It does not provide full claim language or claim scope, the complete specification, drawing contents, or detailed embodiments. It also does not establish prosecution history, the accuracy of the listed assignee or legal status, or the content of the references mentioned (e.g., the Hewlett-Packard Journal, May 1985).