Printer

Abstract

A printer has a plurality of print hammers displaceable between a rest position and a print position, and respective deformable elastic bodies maintained in a deformed position by each print hammer in its rest position and biasing the print hammer toward its print position. Respective magnetic circuit control means are selectively operable to hold each print hammer in its rest position and to release the print hammer for displacement to the print position by the respective elastic body. Each magnetic circuit control means includes a permanent magnet, a first hammer-hold magnetic circuit including a portion of the respective hammer and a second release magnetic circuit including a release coil operable to release the print hammer from its rest position responsive to a print command signal thereto in a direction to increase the magneto-motive force in the second magnetic circuit with a corresponding decrease in the magneto-motive force in the first magnetic circuit to release the respective print hammer for movement to its print position by the associated elastic body. The second magnetic circuit has a magnetic reluctance greater than that of the first magnetic circuit. The first and second magnetic circuits are connected in parallel with the permanent magnet. In one embodiment of the invention, the greater magnetic reluctance is provided by an adjustable air gap in the second magnetic circuit. In another embodiment of the invention, the two magnetic circuits are connected in parallel with the permanent magnet through a common air gap having a reluctance greater than that of the print hammer portion in the first magnetic circuit.

What is claimed is: 
     
       1. In a printer having respective control means for print hammers which are arranged in a plurality of columns and each of which is displaceable between a rest position and a print position, and having respective deformable elastic bodies maintained in deformed condition by the associated print hammers in the rest position, improved magnetic circuit control means associated with each of said columns for .[.selectively.]. holding each said print hammer at its rest position and .Iadd.selectively .Iaddend.releasing same for displacement to a print position including a permanent magnet .[.common to at least two of said columns.]., a first hammer hold magnetic circuit portion associated with each print hammer including a portion of the associated print hammer and a second release magnetic circuit portion associated with each print hammer including release coil means and means for adjusting the magnetic reluctance of the release magnetic circuit portion said release coil means including means for applying signals thereto, said first and second magnetic circuit portions being connected in parallel with said permanent magnet, each of said magnetic circuit control means being adapted to hold said respective hammers in said rest position and to release said respective hammer upon application of a signal to its release coil means by means of said signal applying means in a direction so as to decrease the magnetomotive force applied to said hammer, the energy stored in the respective deformed body displacing said respective hammer from said rest position to said print position upon said decrease in said magnetomotive force. 
     
     
       2. In a printer as claimed in claim 1, wherein said magnetic reluctance adjusting means is an adjustable air gap. 
     
     
       3. In a printer, the improvement claimed in claim 1, in which said first and second magnetic circuits connected in parallel with said permanent magnet through a common magnetic saturation area of said magnetic circuit control means. 
     
     
       4. In a printer, the improvement claimed in claim 1, including a respective two armed lever for each print hammer having one arm engaging the print hammer and the other arm connected to a spring constituting the deformable elastic body. 
     
     
       5. In a printer, the improvement claimed in claim 4, including means limiting pivoting movement of each lever in a direction toward the print position of the associated print hammer. 
     
     
       6. In a printer, the improvement claimed in claim 4, including cam means selectively engageable with each lever to restore the lever to the rest position of the associated print hammer. 
     
     
       7. In a printer, the improvement which comprises a print hammer displaceable between a rest and print position; an elastic body maintained in deformed position by said print hammer at said rest position; a magnetic circuit control means for selectively holding said hammer at said rest position and releasing same for displacement to said print position including a permanent magnet, a first hammer hold magnetic circuit portion including a portion of said hammer, and a second release magnetic circuit portion including a control coil means, said first and second magnetic circuit portions being connected in parallel through a common reluctance means with said permanent magnet, said common reluctance means having a magnitude greater than the reluctance of said first hammer hold magnetic circuit portion, said magnetic circuit control means being adapted to hold said print hammer at said rest position and to release said print hammer upon the application of a signal to said control coil means in a direction so as to decrease the magnetomotive force applied to said print hammer, the energy stored in said deformed elastic body displacing said print hammer from said rest position to said print position upon said decreased magnetomotive force. 
     
     
       8. In a printer as claimed in claim 7, wherein said common reluctance means is an air gap. .Iadd.9. In a printer as claimed in claim 1, said permanent magnet being common to at least two of said columns. .Iaddend.