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Print Hammer Pivot Pin

IP.com Disclosure Number: IPCOM000052327D
Original Publication Date: 1981-Jun-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Lee, HC: AUTHOR

Abstract

An oil-impregnated pivot pin 10 in hole 11 of printer hammer elements 1 is provided with a duct connecting the peak pressure zones of pin 10. The duct connection reduces the peaks of positive and negative pressure produced by the oscillation of the print hammer 12 which cause the oil film around pin 10 to be squeezed axially out of hole 11.

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Print Hammer Pivot Pin

An oil-impregnated pivot pin 10 in hole 11 of printer hammer elements 1 is provided with a duct connecting the peak pressure zones of pin 10. The duct connection reduces the peaks of positive and negative pressure produced by the oscillation of the print hammer 12 which cause the oil film around pin 10 to be squeezed axially out of hole 11.

In the case of print hammers, the hammer elements 12 (Fig. 3) oscillate over a relatively small arc (approximately 2.5 degrees) while exerting cyclic loads on pin 10 in each print cycle. As a result, pin 10 is lubricated by a process of squeeze-film lubrication in contrast to hydrostatic or hydrodynamic lubrication, as in fully rotating devices. Under squeeze-film loading, each of the opposite sides of the pin 10 is alternately subjected to positive and negative pressures (see Fig.
1). For short bearings like those used in print hammers, an axial pressure is inevitable. Therefore, during the positive pressure phase, oil is driven axially outward as well as into the pores of pin 10. During the negative (cavitation) phase, oil is sucked axially inward as well as out of the pores.

If the cyclic load amplitudes are not too high, oil will not be spilled but will just slush back and forth. Under severe loading, oil can be spilled out of the bearing during the positive phase. This spilled oil will not be sucked back into the bearing during the cavitation phase. Instead, more oil will be drawn out of the pores. ...