US 4,461,984 AGranted

Linear motor shuttling system

AssigneeMannesmann Tally Corporation

InventorsC. Gordon Whitaker, James H. Safford

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Abstract

A linear motor shuttling system for shuttling the print head (11) of a dot matrix line printer is disclosed. The print head (11) is supported by a pair of flexures (13, 15) such that the head is free to move back and forth along a print line. One end of the flexure supported print head is attached to the coil (31) of a voice coil linear motor (23). The linear motor (23) is also flexure (27, 29) supported. The linear motor (23) is positioned such that the axis of coil movement is co-axial with the axis of movement of the print head (11). Further, the resonant vibration frequency of the combination of the linear motor and the linear motor flexure support is tuned to the resonant vibration frequency of the combination of the print head and the print head flexure support. A position sensor (51), preferably in the form of a pair of windows (W1, W2) connected to the print head (11) to move therewith and control the light impinging on a pair of differentially connected photovoltaic cells (A, B), produces a signal denoting the actual position of the print head. The actual position signal is compared with a commanded position signal in a control loop and the resultant error signal is used to control the magnitude and polarity of the current applied to the coil of the linear motor and, thus, the position of the print head. The signals produced by the photovoltaic cells (A, B) are also used to control the intensity of the light impinging on the cells so that the sum of the photovoltaic cell signal is a constant.

A linear motor shuttling system suitable for rapidly shuttling a carriage over a short distance, said linear motor shuttling system comprising:

(A) first flexure means for supporting a carriage for rectilinear movement along and axis;
(B) a linear motor, said linear motor including a housing having magnetic means for producing a magnetic field and a coil positioned so as to produce a magnetic field that interacts with the magnetic field produced by said magnetic means when a current flows through said coil, said interaction causing said coil to move in one direction or the other along a linear axis depending upon the polarity and magnitude of current flow through said coil;
(C) second flexure means for supporting said housing of said linear motor such that said linear axis along which said coil moves lies in substantial alignment with the axis along which said carriage is supported for rectilinear movement by said first flexure means;
(D) coupling means for coupling said coil of said linear motor to said carriage such that said movement of said coil in one direction or the other along said linear axis causes said rectilinear movement of said carriage along said axis;
(E) power supply means for supplying power to the coil of said linear motor;
and,
(F) control means connected to said power supply means and the coil of said linear motor for controlling the polarity and magnitude of current flow through said coil, and, thus, the shuttling frequency of said rectilinear carriage movement, said control means including:
(1) position sensing means for continuously sensing the position of said carriage and producing an actual position signal related thereto;
(2) command signal generating means for continuously producing commanded position signals;
(3) comparison means for comparing said actual position signals with said commanded position signals and producing error signals related to the difference therebetween;
and,
(4) current flow control means connected to receive said error signals and control the polarity and magnitude of the current flow through said coil so as to reduce said error signals.

9 more elements

Abstract

Claims16