EP0034774A1 - Druckhammerbank - Google Patents

Druckhammerbank Download PDF

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Publication number
EP0034774A1
EP0034774A1 EP81101023A EP81101023A EP0034774A1 EP 0034774 A1 EP0034774 A1 EP 0034774A1 EP 81101023 A EP81101023 A EP 81101023A EP 81101023 A EP81101023 A EP 81101023A EP 0034774 A1 EP0034774 A1 EP 0034774A1
Authority
EP
European Patent Office
Prior art keywords
hammer
spring wires
spring
panels
pair
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP81101023A
Other languages
English (en)
French (fr)
Other versions
EP0034774B1 (de
Inventor
Val K. Jezbera
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ricoh Printing Systems America Inc
Original Assignee
Ricoh Printing Systems America Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ricoh Printing Systems America Inc filed Critical Ricoh Printing Systems America Inc
Publication of EP0034774A1 publication Critical patent/EP0034774A1/de
Application granted granted Critical
Publication of EP0034774B1 publication Critical patent/EP0034774B1/de
Expired legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41J—TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS
    • B41J9/00—Hammer-impression mechanisms
    • B41J9/02—Hammers; Arrangements thereof
    • B41J9/127—Mounting of hammers

Definitions

  • the present invention relates to a print hammer for use in a printing mechanism.
  • Such hammer bank assemblies utilize a plurality of print hammers each having a flat, electrically conductive coil disposed in a generally rigid housing or body having an impact tip at one end and supported by a pair of crossed spring wires at the other end.
  • the springs provide electrical contact to the coil, and aid in restoring the hammer to its rest position subsequent to impact.
  • each hammer is situated between a pair of stationarily mounted flat permanent magnets. When a current flows through the coil, the resultant magnetic field interacts with the field of the permanent magnet, resulting in a force which propels the hammer towards the type font and the medium being printed.
  • the basic configuration and operation of such a printing hammer is set forth in U. S. Patent No.
  • Print hammers and hammer bank assemblies of the type disclosed above have proven to be very effective in use, have exhibited high reliability and long lifetime as measured in the number of impact operations between replacement, and have gained widespread acceptance.
  • new designs for hammer bank assemblies require hammers which have an even longer lifetime and which exhibit different operating characteristics than prior art hammers.
  • hammer bank assemblies were designed such that the crossed spring wires were flat and very rigid in the horizontal direction, thus preventing any side to side motion of the hammers. The body of each hammer was located between a pair of magnets, and the rigidity of the crossed spring wires served to keep the body in the correct position between two magnets.
  • a print hammer which utilizes flexible spring members having a round cross section, which reduces friction between the hammers and magnets when they contact one another.
  • a Teflon TM impregnated woven glass tape may be wrapped around the housing of the hammer in order to further reduce friction.
  • the housing of the hammer is designed with a bottom section which is formed so that the, spring wires enter ! it in a substantially perpendicular fashion. This serves to reduce the concentration of stress in the spring wires when the hammer is actuated.
  • the foot section is also designed so that the spring wires enter it substantially perpendicularly, so as to reduce concentration of stress in spring wires.
  • the hammer In order to achieve the maximum deflection of the springs-with minimum stress, the hammer is designed so that the spring wires cross at a point which makes their length above the crossing point unequal to their length below the crossing point.
  • the relative lengths are controlled so that the springs have a relatively constant bending moment along their entire length.
  • weights which surround the wires may be included.
  • hammer bank assemblies having substantially different operational characteristics from those of the prior art may be produced.
  • the use of flexible hammers permits the hammers to be deliberately biased against the magnets. If the magnets are accurately located in the assembly, the hammers will in turn be accurately positioned.
  • FIGURES 1 and 2 A print hammer 10 according to the present invention is shown in FIGURES 1 and 2.
  • the hammer 10 consists of a body or coil housing 12 containing a flat coil 32 (FIGURE 3) sandwiched between a pair of flags 26 and 28 (described below) and embedded in a molding compound such as a structural epoxy.
  • the central portion of the coil housing 12 may have a typical thickness on the order of 0,89 mm.
  • the hammer 10 includes an impact end 14 which has an enlarged thickness, typically on the order of 2,54 mm, and includes a forwardly projecting impact tip 16..
  • the spring wires 20 and 22 are laterally separated from one another so that they do not touch at their apparent crossover location shown at 21 in FIGURE 1. This separation may be seen more clearly in FIGURE 2.
  • the spring wires 20 and 22 pass-through, and are embedded in, a foot member 24 formed of the same molding compound as the coil housing 12.
  • the lower ends 20A and 22A of the spring wires 20 and 22 project below the foot member 24 and are available for electrical connection to the hammer 10.
  • the flags 26 and 28 are punched from thin metal strips.
  • the flags 26 and 28 may be formed of aluminum having a thickness of 0,1 mm.
  • the flag 28 includes an embossed or raised locating portion or core 30 in its central area corresponding in size to the interior 32c of the coil 32, which serves to accurately locate the coil 32 with respect to the flag 28.
  • the inner lead 32A of the coil 32 is connected to the spring wire 20 by means of a flat strip 34.
  • the outer lead 328 is connected directly to the spring wire 22.
  • the lower portion 18 and the foot-section 24 are shaped so that the spring wires 20 and 22 enter them generally perpendicularly.
  • the hammer coil 32 is energized by applying current through the spring wires 20 and 22 and the hammer 10 is impacting the spring wires 20 and 22 will flex a great deal, thus causing the generation of a large amount of stress in spring wires 20 and 22.
  • the concentration of stress in the wire housing junction is greatly reduced. This allows spring of smaller diameter (and therefore lower spring constant) to be used, thus increasing the efficiency of the hammer components.
  • the foot section 24 includes a pair of mounting pegs 36 and 38.
  • the pegs are offset from one another such that the peg 36 is aligned (i.e., coplanar) with the spring wire 20 and the peg 38 is aligned with the spring wire 22.
  • the mounting pegs 36 and 38 are utilized to accurately mount each individual print hammer in a hammer bank assembly.
  • a hammer bank mounting assembly includes a frame having a rear vertical"portion 40, to which a plurality of spaced parallel magnets 41 are secured, and a forwardly-extending horizontal portion 42. Formed in the horizontal portion 42 are a group of front parallel equally-spaced slots 44 and rear parallel equally-spaced slots 46.
  • the front slots 44 are offset with respect to the rear slots 46 by an amount equal to the offset between the mounting pegs 36 and 38 of a hammer.
  • the hammers are mounted in the hammer bank assembly by passing the lower portions 20A and 22A of the spring wires through the slots 46 and 44 respectively, and fitting the pegs 36 in a slot 46 and the tab 38 in a slot 44.
  • the pegs 36 and 38 fit snugly in the slots 46 and 44 and therefore serve to accurately position the hammer within the assembly. Details of the hammer bank assembly are fully described in EUROPEAN Patent application Serial No. 80104704.4.
  • each hammer 10 is mounted so that its body 12 is biased against the side of a magnet 41. Because the spring wires 20 and 22 have a round cross section, they are relatively flexible in the horizontal direction (indicated by arrow 48).
  • spring wires having a substantially square cross-section would also be flexible in the horizontal direction.
  • a known and small amount of friction is created. Since this friction is known, it may be taken into account when designing for the motion of the hammers 10 when they are energized. That is, the motion of the hammers 10 will be predictable and consistent despite the fact that they touch the magnets 41. Because the wires 20 and 22 have a round cross section and are relatively flexible, the amount of friction created is relatively low and thus does not greatly impede the motion of the hammers.
  • a weight 52 is shown attached-to each of the spring wires 20 and 22.
  • the hammer 10 When the hammer 10 is energized, it will move forward and the tip 16 will impact against a paper and cause a character to be printed.
  • the impact tip 16 strikes the paper (and type font located behind the paper), its forward motion halts.
  • the hammer 10 still has a great deal of stored energy.
  • the striking of the paper will cause the pivot point of the hammer to move from the crossing point 21 of the springs 20 and 22 to the impact tip 16.
  • a great deal of energy will be stored in the springs 20 and 22. They will then recoil and oscillate until the hammer 10 returns to rest at ist equilibrium position.
  • the hammer 10 will recoil to such an extent that more stress will be placed on the springs 20 and 22 than during actual impact.
  • the addition of the weights 52 acts to limit the initial amount of recoil and dampen the subsequent oscillations of the springs 20 ' and 22.
  • the addition of the weights 52 to the springs 20 and 22 will not change their spring constants, but will influence their natural frequencies and mass. The recoil mations of the springs 20 and 22 are therefore reduced.
  • Deflection of the springs 20 and 22 can be accomplished either by applying a single force to the spring or by applying a bending moment or combination of both. Although any method will cause the desired amount of deflection at any particular point, the stress which will be placed upon the spring will be vastly different. When a single force is utilized the stress placed upon the spring 20 near the foot 24 will be very high, since the maximum bending will occur- near the foot 24. When a bending moment is utilized however, the maximum stress placed upon the spring 20 at any point will be much lower, since the curvature of the spring 20 will be spread over its length rather than concentrated near the foot 24.
  • the crossing point 21 was located in the middle of the springs and spring deflection was accomplished in a fashion resulting in an uneven distribution of stress in the spring.
  • the springs 20 and 22 are oriented such that deflection is caused by the application solely of a bending moment. This results in lower stress and longer life.
  • the use of a bending moment to cause deflection of the springs 20 and 22 is accomplished by controlling the dimensions of the springs and the position of their crossing point 21 (i.e., the length of the portion of the springs 20 or 22 above the crossing point relative to the length of the portion below the crossing point). Basically, the crossing point is positioned such that the portion below it is longer than the portion above it.
  • the upper portion 20b of the spring 20 is shorter than the lower portion 20c.
  • the control of the crossing point in this manner assures that the spring 20 will be flexed by a bending moment rather than by a single force, thus minimizing stress on the spring 20.
  • the design results in a constant bending moment being applied along the length of the springs, resulting in an even stress distribution along the length of the springs.
  • the present invention is directed to an improved print hammer for use in a hammer bank assembly of a high-speed printer or the like.
  • the hammer includes several new features which enable a significant improvement in performance to be achieved.
  • Crossed spring wires which are used to support the hammer body have a round cross section, thereby rendering the hammer body relatively flexible in the horizontal direction. This permits the hammers to be mounted so that they are biased against the magnets in a hammer bank assembly. This bias creates a known small amount of friction, which may be taken into account in the design of the system.
  • the hammer body and foot member of the hammer are designed so that the spring wires supporting the body are attached to the body and foot in a substantially perpendicular fashion, thereby reducing concentration of stress in the spring wires.
  • the foot includes molded mounting pegs which aid in accurately mounting the hammers in a hammer bank assembly.
  • One of a pair of metal flags, which form the body of the hammer and sandwich a coil, includes a raised mounting surface to aid in accurately locating the coil in the hammer assembly.
  • weights located on the springs are utilized to dampen the recoil motion of the supporting springs after the hammer has impacted against a character.

Landscapes

  • Impact Printers (AREA)
EP19810101023 1980-02-15 1981-02-13 Druckhammerbank Expired EP0034774B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US12206480A 1980-02-15 1980-02-15
US122064 1980-02-15

Publications (2)

Publication Number Publication Date
EP0034774A1 true EP0034774A1 (de) 1981-09-02
EP0034774B1 EP0034774B1 (de) 1983-12-21

Family

ID=22400388

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19810101023 Expired EP0034774B1 (de) 1980-02-15 1981-02-13 Druckhammerbank

Country Status (4)

Country Link
EP (1) EP0034774B1 (de)
JP (1) JPS56129187A (de)
BR (1) BR8100882A (de)
DE (1) DE3161673D1 (de)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3643595A (en) * 1969-06-25 1972-02-22 Data Products Corp Printer hammer bank assembly
GB1359925A (en) * 1971-05-05 1974-07-17 Cii Honeywell Bull Printers
AT324022B (de) * 1971-07-09 1975-08-11 Philips Nv Hammer für eine druckvorrichtung
US3983806A (en) * 1973-12-10 1976-10-05 Data Products Corporation Hammer bank assembly

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3643595A (en) * 1969-06-25 1972-02-22 Data Products Corp Printer hammer bank assembly
GB1359925A (en) * 1971-05-05 1974-07-17 Cii Honeywell Bull Printers
AT324022B (de) * 1971-07-09 1975-08-11 Philips Nv Hammer für eine druckvorrichtung
US3983806A (en) * 1973-12-10 1976-10-05 Data Products Corporation Hammer bank assembly

Also Published As

Publication number Publication date
EP0034774B1 (de) 1983-12-21
JPH029944B2 (de) 1990-03-06
DE3161673D1 (en) 1984-01-26
JPS56129187A (en) 1981-10-09
BR8100882A (pt) 1981-08-25

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