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Multiple Print Hammer Unit

IP.com Disclosure Number: IPCOM000048134D
Original Publication Date: 1981-Dec-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 3 page(s) / 91K

Publishing Venue

IBM

Related People

Hanna, DW: AUTHOR

Abstract

This article describes a multiple print hammer unit which is field replaceable in a bank of like print hammer units in which each print hammer unit is releasably mounted on a stationary hammer bank support structure by a snap-action mechanism.

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Multiple Print Hammer Unit

This article describes a multiple print hammer unit which is field replaceable in a bank of like print hammer units in which each print hammer unit is releasably mounted on a stationary hammer bank support structure by a snap-action mechanism.

As seen in the figures, hammer unit 10 has plural print hammers, such a flexible hammer blade 12 with an impact bar 13 which is several print positions wide. A plurality of such units 10 comprises an entire print hammer bank. A formed spring steel member 14 having four cantilever spring elements 15 is attached to the rear locating surface of the hammer block 16. The purpose of spring member 14 is to hold the hammer unit 10 against the positioning surfaces of a receptacle. The back surface of block 16 has openings 17 which can admit cooling air to the unit. The spring member 14 has over-sized openings 18 that also permit air passage. The spring member 14 has flange 19 that serves as the top of an air duct that channels cooling air into the hammer unit.

Hammer unit 10 includes a printed circuit card 20 that is attached to the rear of hammer block 16 by means of threaded screws 21 and stand-off elements 22. The screws 21 and stand-offs 22 are also used to locate and secure spring member 14. Circuit card 20 is used to distribute electrical driver signals from edge connector 23 (Fig. 2) to hammer coils 24 on block 16. Coils 24 have pins 25 that are soldered on lands on card 20 at assembly. Circuit card 20 could also be used to package the coil driver circuitry in whole or in part thereon or any other electrical components that may require close proximity to the hammer unit. The circuit card also serves as the rear wall of the cooling air duct, the stand-offs 22 providing a space between the hammer unit and the card. The circuit card 20 also serves as a handle for unit 10. The top of card 20, which projects above the hammer unit, has finger holes 26 for manual grasping whereby force to pull or push is applied directly to the circuit card for insertion and withdrawal of the card tab 28 into and out of connector 23.

As seen in Fig. 1, hammer block 16 has spring plungers 27 on opposite sides thereof. The spring plungers function as detents to hold the hammer unit 10 securely in place against its bottom mounting surface, as will be described later.

As seen in Fig. 2, the receptacle for the field replaceable hammer unit comprises identical upright members 30 fixed on base plate 31 to locate and support adjacent hammer units 10 at opposite ends thereof. A flat pad 32 on the front of uprights 30 locates the back mounting surfaces of hammer block 16 near the line of action of hammers 12 where location accuracy is most important. Pads 32 may be ground together after attachment to plate 31 to provide good alignment among the plurality of hammer unit back. Pads 32 are buttressed from behind by a deep web 33 capable of withstanding printing for capable of withstanding printing force...