US3643594A

US3643594A - Print hammer for high-speed printer

Info

Publication number: US3643594A
Application number: US831460A
Authority: US
Inventors: Roberto Pipitone
Original assignee: Societa Italiana Telecomunicazioni Siemens SpA
Current assignee: Italtel SpA
Priority date: 1968-06-11
Filing date: 1969-06-09
Publication date: 1972-02-22
Anticipated expiration: 1989-02-22
Also published as: FR2010623A1; DE1929481B2; NL6908148A; DE1929481A1; BE730358A

Abstract

An electromagnetically actuated print hammer comprises two rockers independently pivoted on a common axle, one rocker carrying a striker and being urged by spring force against the other rocker which has a long lever arm acting upon the strikercarrying rocker and a short lever arm carrying an armature attractable by an electromagnet; upon energization of the electromagnet, the armature-carrying rocker is arrested before the striker contacts the working surface.

Description

United States Patent Pipitone [4 1 Feb. 22, 1972 154] PRINT HAMMER FOR HIGH-SPEED PRINTER [72] Inventor: Roberto Pipitone, Milan, Italy [73] Assignee: Societa ltaliana Telecomunicazionl Siemens S.p.A., Milan, Italy [22] Filed: June9, 1969 [21] App1.No.: 831,460

[30] Foreign Application Priority Data June 11, 1968 Italy ..17,577

[52] US. Cl. .....101-/93 C [51] Int. Cl ..B4lg 9/38 [58] Field ofSearch ..10l/93 C,93, 297,94; 197/53 [56] References Cited UNITED STATES PATENTS 2,940,385 6/1960 House ..101/93 3,164,085 1/1965 Hawkins ..101/93 3,177,803 4/1965 Antonucci 101/93 3,266,418 8/1966 Russo 101/93 3,349,696 10/1967 Potter.... 101/93 3,385,211 5/1968 Shepard 101/93 3,442,365 5/1969 Ragland et a1. 197/53 3,504,623 4/1970 Staller ..101/93 Primary Examiner-William B. Penn Att0rneyKarl F. Ross [57] ABSTRACT An electromagnetically actuated print hammer comprises two rockers independently pivoted on a common axle, one rocker carrying a striker and being urged by spring force against the other rocker which has a long lever arm acting upon the striker-carrying rocker and a short lever arm carrying an armature attractable by an electromagnet; upon energization of the electromagnet, the armature-carrying rocker is arrested before the striker contacts the working surface.

11 Claims, 2 Drawing Figures PATENTEUFB22 I972 3.643 594 sum 1 or 2 Roberto Pipifone INVENTOR.

WA 6R0 Attorney PRINT HAMMER FOR HIGH-SPEED PRINTER My present invention relates to an electromagnetically actuated print hammer of the type used, for example, in highspeed printers wherein a type carrier, such as a font wheel or ribbon, is continuously rotated so as to present a succession of type faces to a striker whose actuation at the proper instant causes a corresponding imprint to be made on a paper or other recording medium juxtaposed with the type carrier.

In such a system it is essential that the hammer bearing the striker or head be rapidly advanced and retracted, in order to enable correct selection of the desired character in response to a command pulse and to prevent smearing of the character on the recording medium due to excessive contact time between this medium and the rotating type carrier.

The general object of my present invention, therefore, is to provide an improved print hammer which can be rapidly and accurately operated for printing at high speed.

A more specific object is to provide means in such a device for damping the vibrations of the print hammer to allow for a high recurrence rate of the printing strokes.

lt is also an object of my invention to provide a print hammer which, while satisfying the aforestated desiderata, develops sufficient power to work on a self-contained paper of the ribbonless type which required a somewhat sharper hammer blow than a paper to be marked by an ink ribbon.

The invention also aims at providing a print hammer of compact construction and low consumption of electrical energy adapted to realize all the aforestated objects.

In accordance with this invention, I providean improved print hammer including a first rocker carrying an armature and a second rocker carrying a striker, the two rockers being pivotally' mounted on a support for joint swinging, preferably about a common axis, upon attraction of the armature by energization of a confronting electromagnet mounted on the support; the working stroke of the armature-carrying first rocker is limited by one or more abutments which arrest that rocker while the second rocker, carrying the hammer head or striker, continues its swing toward a working surface. Both rockers are restored to normal by resilient means, such as a coil spring, anchored to the second rocker so as harmonically to reverse its motion after its kinetic energy has been spent.

Advantageously, in order to improve the operating efficiency of my device, the first rocker is of reduced mass compared with the striker-carrying second rocker which performs the actual printing operation. To this end, I prefer to make the first rocker of a lightweight material, such as aluminum, and to give it the shape of a yoke formed from two generally parallel levers with long and short arms, the free ends of the long arms being interconnected by a bridge piece while the short arms are spanned by the armature, e.g., a solid strip of soft iron. With both rockers fulcrumed on a common axle parallel to the armature, the long arms of the first rocker may have their widths progressively decreased with increased distances from that axle, i.e., with increasing moment arm, to save mass and weight. The aforementioned bridge piece may carry a boss directly in line with the striker on the adjoining second rocker and may also coact with an adjustable backstop, such as a micrometric screw, which determines the extent of the return swing under the urging of the restoring spring and therefore the effective stroke length of the hammerhead.

The above and other features of my invention will become more fully apparent from the following detailed description of a preferred embodiment, reference being made to the accompanying drawing in which: 1

FIG. 1 is an exploded perspective view of a print hammer according to my invention; and

FIG. 2 is a somewhat diagrammatic cross-sectional view of the assembly of FIG. 1 and associated components of a highspeed printer.

The print hammer shown in the drawing comprises a support 11, illustrated only in part, with a base plate 1 la carrying an electromagnet generally designated 10. A pair of lugs 13 integral with support 11 extend transversely to base plate 11a and have aligned holes 14 traversed by an axle 9 which also passes through holes 2a and 3a of a pair of rockers 2 and 3. Rocker 3 comprises two generally parallel levers 3b which are fulcrumed on axle 9 and which have long arms interconnected at their free end by a bridge piece 3c, the latter bearing a boss 6 normally contacting the free end of rocker 2 which is generally frame-shaped and is also fulcrumed on axle 9. Levers 3b are of the bellcrank type and diminish progressively in width, for the purpose stated above, from fulcrum 9 to bridge piece 3c. The short arms of these levers are spanned by an armature 4 which may consist of soft iron, in contradistinction to the nonmagnetic rocker 3 which is preferably made from a light metal such as aluminum or one of its alloys.

A coil spring 8, anchored to an extension 11b of baseplate lla, engages a tab 2b of rocker 2 so as to urge the latter into contact with boss 6 while tending to hold the bridge3c against a seat formed by the tip of a micrometric screw 7 threaded into the base 11. Screw 7 may be adjusted with the aid of a tool inserted into a slot 7a thereof and may be locked in position by a counternut 7b.

A striker l on the free end of rocker 2 confronts a working surface here provided on a recording medium 15, such as a paper tape, which is drawn by feed rollers 16 past a font wheel 17 carrying a multiplicity of type faces 17a. An ink ribbon 18 is shown interposed between wheel 17 and recording tape 15, this ribbon being drawn in the usual manner from a reel 18a and wound up on a reel 18b. Operating current, designed to drive the striker 1 toward tape 15 for imprinting thereon a character represented by a confronted type face 17a, is supplied to the coil 10a of electromagnet 10 from a pulse generator 19 which receives command signals via a line 20, this pulse generator working into a pair of input leads 21, 22 which are bridged by a damping circuit, consisting of a diode 23 and a resistor 24 in series, connected across coil 10a.

Electromagnet 10 has an E-core 10b which lies in a plane parallel to axle 9 and has three pole faces confronting the armature 4, the center leg of the core being surrounded by the coil 1011. Core 10b is composed of a stack of laminations, each parallel to the plane of E", which preferably consist of ferrosilicon. The core and its coil are advantageously enclosed, at least in part, by a shield of soft iron or the like designed to suppress stray flux.

The short lever arms of the low-inertia rocker 3 terminate, beyond the armature 4, in free extremities 5 which are guided in slots 12 of base plate 11a and form abutments arresting the forward swing of the rocker, upon energization of coil 10a, in a position in which the armature 4 is spaced from the confronting pole faces of core 10b whereas striker l is still separated from the working surface of tape 15. The kinetic energy dissipated upon contact of abutments 5 with the ends of slots 12 is small, however, owing to the reduced mass of driving rocker 3, the working rocker 2 thereupon continuing its swing against the force of restoring spring 8 to translate its own kinetic energy into the formation of an imprint on tape 15. The coaxial mounting of rockers 2 and 3 eliminates any relative motion therebetween as long as they are in contact. Upon recall of the rocker 2 by the spring 8, this rocker reengages the boss 6 of rocker 3 which at that instant is still biased forwardly, albeit at reduced force, by the residual magnetic field of core 1011. This residual field is maintained for a certain period after the disappearance of the short actuating pulse from generator 19 by the flow of inductive current through diode 23 and resistance 24, the length of that period being determined by the time constant of the circuit constituted by resistance 24 and the inductance of coil 10a. Owing to the damping effect of this residual field, vibrations of the movable assembly are minimized and the striker l is retracted with only slight impact preparatorily to its next advance.

The command pulses on line 20 may be generated by a teleprinter or any other conventional system designed to synchronize the occurrence of these pulses with the rotation of font wheel 17 in such a way that the advance of hammerhead 11 coincides with the arrival of a desired type face opposite tape 15. The advance of the tape by the rollers 16 is also correlated with the printing operation in a manner known per se.

If the tape 15 consists of conventional self-contained paper in which a colorant is released by the pressure of a type face, the ribbon 18 will of course be omitted.

It will also be understood that a type carrier may be disposed (e.g., as shown in US. Pat. No. 3,442,365) between the striker 1 and the recording medium 15, the working surface being then the back of the type carrier which is displaced together with the medium against a stationary anvil under the impact of the hammerhead.

I claim:

1. A print hammer comprising a support, a first rocker pivotally mounted on said support, a second rocker pivotally mounted on said support on a common pivotal axle with said first rocker for swinging entrainment thereby, a striker on said second rocker confronting a working surface, resilient means engaging said second rocker for holding same in contact with said first rocker at a location remote from said axle while urging said striker away from said working surface, electromagnetic actuating means on said support, an armature on said first rocker confronting said actuating means for displacement thereby to swing said first rocker in a direction driving said striker toward said printing surface against the force of said resilient means, and abutment means for arresting the swing of said first rocker before said striker contacts said working surface.

2. A pring hammer as defined'in claim 1 wherein said first rocker comprises a pair of generally parallel levers fulcrumed on said axle, said armature spanning said levers.

3. A pring hammer as defined in claim 2 wherein each of said levers has a short arm secured to said armature and a long arm with a free end bearing upon said second rocker.

4. A print hammer as defined in claim 3 wherein said first rocker is of reduced mass compared with said second rocker.

5; A print hammer as defined in claim 4 wherein said first rocker consists of lightweight material and said long arms have a width decreasing with increasing distance from said axle.

6. A print hammer as defined in claim 3 wherein said first rocker further comprises a bridge piece interconnecting the free ends of the long arms of said levers, said bridge piece contacting said second rocker at a location in line with said striker.

7. A print hammer as defined in claim 6, further comprising adjustable backstop means on said support bearing upon said bridge piece for limiting the reverse swing of said first rocker in response to said resilient means.

8. A print hammer as defined in claim 3 wherein said actuating means comprises a coil with an E-core having three pole faces confronting said armature, said core lying in a plane parallel to said axle.

9. A print hammer as defined in claim 8 wherein said core consists of ferrosilicon laminations parallel to said plane, said actuating means further including permeable shield means for said core.

l0.A print hammer as defined in claim 3 wherein the short arms of said levers have free extremities extending beyond said armature and forming part of said abutment means, said support comprising a base carrying said actuating means, said base being provided with guide slots for said short arms, the ends of said guide slots constituting stops for said extremities.

11. A print hammer as defined in claim 1 wherein said actuating means comprises a coil and a damping circuit including a diode and a resistance connected across said coil.

Claims

2. A pring hammer as defined in claim 1 wherein said first rocker comprises a pair of generally parallel levers fulcrumed on said axle, said armature spanning said levers.

5. A print hammer as defined in claim 4 wherein said first rocker consists of lightweight material and said long arms have a width decreasing with increasiNg distance from said axle.

10. A print hammer as defined in claim 3 wherein the short arms of said levers have free extremities extending beyond said armature and forming part of said abutment means, said support comprising a base carrying said actuating means, said base being provided with guide slots for said short arms, the ends of said guide slots constituting stops for said extremities.